Equipment for Ear Examination

Both indirect and direct light sources are used
1. Bull’s eye lamp-indirect light source.
2. Head mirror.
3. Head light-direct light source.
4. Ear specula of various sizes-The largest speculum which can be conveniently inserted into the ear canal should be used.
5. Siegel’s pneumatic speculum.
6. Tuning fork-256, 512, 1024 Hz is preferred to assess the speech frequency.
7. Jobson Horne probe can be used as a cot­ ton wool carrier to clean the discharge from the external auditory canal before examining the tympanic membrane.
8. Tilley’s or Hartmann’s forceps.
9. Eustachian tube catheters.
10. Otoscope-It gives a magnified view of the part to be examined.
11. Suction apparatus-This is one of the important equipment in ENT and is used to remove the secretions from the external ear and helps in proper examination.
12. Microscope-Either attached with ENT equipment unit or separate entity.
13. Otoendoscope.

In examining the ear with a forehead mirror good illumination is necessary. Any fairly powerful lamp such as Bull’s eye lamp will be sufficient.
For direct examination patient is seated sideways in such a way that examiner faces the ear to be examined with a good source of light and direct this light on to the auditory meatus. On completion of the above examination, patients head is tilted lightly opposite from the ear being examined.

The pinna is held between thumb and index finger of left hand when examining right ear and of the right hand when examining the left ear and ear is pulled upwards, backwards, outwards in adults, downwards and laterally in infants and young children. The other three fingers are placed on the temporal region serving as fulcrum. This manipulation will straighten the ear canal to a certain extent and provide a better view in preliminary examination.

In case where canal is wide and follows a straight line, this examination permits examiner to inspect the ear drum without the use of a ear speculum. The following points to be examined during this procedure.

External auditory canal-may show the following abnormalities:
• Narrow canal

(i) Congenital- atresia
(ii) Acquired – scar following trauma, bums, bony tumor like osteomas, etc.
• Wide canal: Patients in whom tympano­ mastoidectomy is done, syphilis, oto­ sclerosis.
• Foreign body: Vegetative and non-vegetative.
• Impacted wax: Hard blackish mass occluding whole of the external auditory canal.
• Tumor: Both benign and malignant.
• Discharge: Profuse and thin discharge usually from middle ear pathology, whereas slight and thick discharge from the external auditory canal.

2. Aural Speculum Examination (Instrument examination)
For this examination a proper and adequate size aural speculum preferably black coated is selected and introduced into the external auditory canal. Aural speculum will help examination of deep meatus and tympanic membrane. Most commonly used speculum is Toynbees and Gruver’s speculum.
Aim of this speculum is to straighten the canal and it should be long enough to reach the deepest obstacle which is at the junction of the bony and cartilaginous canal. Specula are circular with diameters varying between 2 and 7 mm. The speculum used should correspond to the size and permeability of the canal. In rare cases, it may be necessary to fall back upon forced dilatation of the canal to examine the drum. In such cases a dilating speculum can be used the best being Moores instrument. The dilation is extremely painful and should be performed under general anesthesia. When greater precision and details are required a special speculum like seigel’s pneumatic speculum or an endoscopic speculum or otoendoscope or otoscope can be used.

Technique of speculum examination: Patient is placed as per direct examination when the examiner focuses the light from his head mirror or head light on to the auditory meatus. The pinna is held between the middle and ring fingers of the left hand and pulls upwards and backwards. The speculum is held in the right hand and gently introduced into the canal. Once speculum has been introduced it is held in place by the thumb and index finger of the left hand in order to free the right hand for cleaning and probing. The speculum should be introduced with the utmost gentleness with a slow rotatory movement to facilitate its passage. One should not be surprised when the patient coughs while introducing the speculum which is due to irritation of auricular branch of vagus nerve.

3. Palpation of the External Auditory Canal This examination is made directly with finger or with instruments.
• Finger Palpation: Direct digital palpation is done by inserting the tip of the index finger  in to the canal. By this the consistency of these is felt and also the condition of the mandible can be felt.
• Instrumental: The probe or stylet which is preferred and introduced through the speculum which will prevent instruction of examiner’s vision. It helps to determine the consistency, shape and direction of a fistula.

4. Otomicroscopic examination (EUM) is of more precise diagnostic method. When canal is obstructed by secretion or foreign body it is necessary to clean the canal as completely as possible either by dry mopping or suction cleaning under microscopic vision.

Examination of the Tympanic Membrane

To make an effective examination of tympanic membrane it is first necessary to be properly oriented with the normal anatomy of the tympanic membrane. To achieve this, the examiner should first examine the upper part of the drum and look in front of its upper pole for a small yellowish prominence. This is the short or lateral process of malleus. This landmark is particularly important since it is almost always present even when the re t of malleus has disappeared.

From this Prominence (Short or Lateral Process) Originate
1. Anteriorly. A horizontal line, often scarcely perceptible extending to the periphery of the drum. this is the anterior malleolar fold.
2. Posteriorly. A small similar line, but a little longer, this is the posterior fold, or posterior malleolar fold.
3. Inferiorily and posteriorly a whitish bony landmark is seen at an angle of 45° called handle of malleus and its tip is called the umbo. The convexity of the umbo will be directed medially towards middle ear.
. A light reflex can be observed, triangular in shape which is placed anteriorly and inferiorly called Cone of light. The cone of light is always projecting anteroinferiorly in normal tympanic membrane because the tympanic membrane is placed obliquely in the deep part of the external auditory canal.
It is customary to divide the drum topographically into four sectors or quadrants. This is done by drawing an imaginary line horizontally touching the tip of the umbo, and a second line vertically along the long axis of the handle of malleus. The quadrants are known as:
• Anterosuperior quadrant
• Posterosuperior quadrant
• Anteroinferior quadrant
• Posteroinferior quadrant.

After orientation is achieved the tympanic membrane should be examined in relation to:
I. Color.
II. Position.
III. Mobility.
IV. Changes in surface.

I. Color
Normal drum appears grayish white. If this color is changed some pathological condition should exists as follows.
• Congested drum: Indicates an inflammation, e.g. acute otitis media, myringitis bullosa, active otosclerosis, glomus jugularis, excessively crying child, etc. Congestion with yellowish tint is sometimes the sign of an acute suppurative otitis media. In stage of suppuration the congestion may be diffuse or localized. Localized in the handle of the malleus in acute otitis media or in subacute otitis media. Generalized congestion in acute simple or necrotising otitis media.
• Dark grey slate color: This color is an indi­ cation of tubal occlusion. This type of drum does not light up well (Dull appearance).
• A dull white, thickened, cotton-like drum, is found in certain types of sclerosis (senile) or following scarring and changes after otitis media popularly called as chalky white patch or tympanosclerotic patch.
• A dull lusterless occasionally bulging tympanic membrane is seen in secretory otitis media or glue ear.
• A slight vasodilatation of blood vessels caused by the irritation of the canal, or probing with a stylet, should not be confused with a pathological condition. Such congestion may be especially pronounced along the handle of malleus.
• A blue drum is sometimes found when infection is entirely absent. It is seen in transudative type of otitis media, glomus juglare, high jugular bulb, cholesterol granuloma and Van der Hoeve syndrome.
• A dark blue drum is seen in case of hemotympanum following head injury.

II. Position
Normally, the drum inclines downwards and medially. The upper portion is much more closer to the examining eye than it’s lower portion. The drum may change position so that it protrudes outwards towards the examiner or it may be pulled i ward towards the tympanic cavity. The following are the commonly known abnormal position:
Bulging drum: Apparent increase in length of the handle of malleus, decrease in the short process and absence of the cone of light. The bulge may be due to blood (trauma, hemorrhagic otitis media), pus (purulent otitis media), and air following tubal insufflations or tumors.
Retracted drum: Apparent shortenting of the handle of malleus, exaggeration of the prominence of the short process and anterior and posterior malleolar folds and distortion of the cone of light reflex. It may be due to insuff­ icient tubotympanic aeration (eustachian tube dysfunction) or adherence of the drum to the medial wall of the middle ear cavity (atelectatic drum). The retracted tympanic membrane has been classified into four grades depending on the amount of retraction of pars tensa (Sade’s classification).
Grade 1 Mild retraction not touching the long process of incus.
Grade 2 Retracted drum touching the long process of incus.
Grade 3 Retracted drum touching (he promontory.
Grade 4 Drum plastered to the promontory
Retraction of Pars flaccida has been classified into four grades according to Tos’s classification:
Grade 1: Mild attic retraction, without touching the neck of malleus
Grade 2: Attic retraction touching neck of malleus.
Grade 3: Limited outer attic wall erosion with extent beyond 0sseous malleus.
Grade 4: Severe outer attic wall erosion

III. Mobility
Mobility can be examined with the aid of seigle’s pneumatic speculum or by valsalva maneuver. During compression the triangular light reflex changes shape and the handle of malleus moves. If it does not change or move there is evidence of more or less complete loss of mobility of tympanic memebrane
The mobility is decreased or absent in:
• Adhesive otitis media which may be due to adhesion and scars following necrotizing otitis media.
• Ankylosis of the ossicular chain.
• Eustachian tube dysfunction.
Other methods of testing the mobility are by increasing the air pressure inside the middle ear cavity by insufflations of the eustachian tube while at the same time examining the drum through an otoscope which is called as Toynbee’s maneuver. The tympanic membrane also seen moving along with breathing in case of patulous eustachian tube called as hyper mobile tympanic membrane.

IV. Changes in the Surface
In pathological conditions the following changes can occur on the surface of the membrane calcareous deposits (tympanosclerotic patch), scars or thinned out membrane, bullas and perforation.
(a) Calcareous deposits: These look like white plaques of varying sizes and shapes, resembling small pieces of plaster of paris on the drum.
(b) Bulla: Bullas vary in number and are seen by the examiner as grey, reddish or bluish in color, resembling small pearls attached to the surface of the drum.

The location of a perforation is extremely variable. Determination of the exact location is most essential for diagnostic therapeutic and prognostic accuracy. The perforation may be central, attic or marginal.

MIDDLE EAR
Direct examination of the middle ear is not possible under normal conditions. Only a small area can be observed through the perforated or thin drum, i.e. a part of the incus, a shadow of the round window niche and in case the drum is extremely thin the chorda tympani nerve is seen.

In case of large central perforation labyrinthine wall, promontory and ossicle may be seen. The stapes may also be seen in posterosuperior perforations.
Changes in the tympanic membrane may give us an indication as to the condition of the middle ear cavity and its contents. All these parts may however be hidden by granulations or polyp arising from the middle ear.

Instrumental Examination
A blunt probe or stylet is used to test the softness of the granulation tissue, point of origin of the polyp, resistance of the promontory, denuded bone in an osteitic area and orifice of a fistula.

Eustachian Tube
It is a communication canal between the middle ear and the pharynx. It maintains the equilibrium between the pressure of the middle ear and the atmosphere. Any obstruction whether partly or complete causes a reabsorption of air from the middle ear with consequent retraction of the drum as a result of a higher atmospheric pressure. Due to its deep-seated anatomical location, the eustachian tube can only be examined indirectly with the help of several instruments and various methods. To test eustachian tube patency it is necessary to insufflate air into the eustachian tube by various methods such as:
• Val salva maneuver
• Toynbee maneuver
• Politzerization
• Catheterization
• Frenzel’s maneuver (nasopharyngeal pressure test).
Tuning Fork Tests
The commonly performed tests are Rinne Weber and absolute bone conduction tests. The commonly used tuning fork tests are of the frequencies of 256. 512 1024. The details of the technique have been described under the chapter of hearing evaluation.
Fistula Test
It is done by applying intermittent pressure over the tragus. or by seigelization with an pneumatic speculum. Ask the patient to look straight ahead, and check for nystagmus directed towards the opposite side. The patient may complain of vertigo. (Details are given in examination of the labyrinthine function).

Facial Nerve
It is important to differentiate between upper motor neuron palsy and lower motor neuron palsy by asking the patient to show various facial expressions like:
• Frowning (wrinkling of the forehead)
• Movement of the eyelids (closing of the eyes)
• Smiling or showing the teeth (angle of the mouth).
• Loss of nasolabial fold.

Examination of the Eye

Inspection of the eye may reveal features such as hypertelorism or coloboma associated with congenital hearing disorder syndrome. The presence of blue sclera (osteogenesis imperfecta) and interstitial keratitis (congenital syphilis, Cogan’s disease) should be noted.
On fundoscopy, papilloedema may be seen in space occupying lesions such as cerebellopontine angle tumors, temporal lobe abscess, otitic hydrocephalus. Eye movements for nystagmus should be observed. The absence of corneal reflex is usually a late sign of acoustic neuroma.

Examination of Other Cranial Nerves

Paralysis of the VI nerve may be associated with lesions in the petrous apex. e.g. (Gradenigo’s syndrome). The involvement of last four cranial nerves are frequently associated with stage 3 malignant otitis externa and advanced glomus jugulare tumor. Loss of corneal reflex is seen in acoustic neuroma.

Examination of the Nose and Throat

A full examination of the nose and throat must always be carried out to rule out rhinitis, sinusitis, pharyngitis, tonsillitis, nasopharyngitis, etc.
Functional Examination of Hearing Plethora of clinical tests of hearing were introduced in the 19th century and, although, the majority have been superseded by more sensitive and reliable audiometric tests, some knowledge of these clinical tests is of value.

Clinical tests of auditory function may be divided into four types:

1. Finger friction test: Rubbing or snapping of the forefinger and thumb is a test commonly employed by neurologists, for screening for both threshold of hearing deficits and sound localization.
2.Lever pocket watch test: With the introduction of the Quartz watch, lever pocket watch tests, have become obsolete, although for many years they were a valuable tool in audiometric screening in the absence of more sophisticated equipment.
3. Speech test: Speech test can be done in any of the following ways. However, free field speech test is most popular. These are
a) Freefield speech test by whisper.conversation
(b) Recorded voice test (c) Speech audiometry.
(d) Monitored speech through a closed circuit. In this the patient must be 20 feet from the examiner.
Requirements for Speech Test
• Testing room should be reasonably quiet.
• The eye must be shielded to prevent lip reading.
• The ear under test is directed towards the examiner.
• The non-test ear is blocked by assistant’s index finger on tragus.
• Speech test material should be spondee and phonetically balanced, example:
“Black Bird”, “night tight”, etc.
• Whisper test should be done with whisper with residual air after an ordinary expiration.
• Speech materials if audible at a distance of 20 feet are considered to be normal.
• Despite these precautions, great care must be exercised in using clinical speech tests to assess auditory thresholds.
4. Tuning fork tests: The most clinical information may be obtained using tuning forks that vibrate naturally at 256,512, 1024 and 2048 Hz. These are the frequencies commonly used in clinical practice.

The following precaution should be taken:
1. The test should be performed in a quiet room.
2. The prong should be struck sharply against some resistance, e.g. Elastic object like, hard rubber, thenar eminence, and femoral condyle.
3. The prong should be struck at a point about one-third of its length from the free end, thus keeping overtones to a minimum and producing a pure tone.

The following tuning fork tests are commonly used in practice.
• Rinne’s test
• Weber’s test
• Absolute bone conduction test (Modified Schwabach’s test).
Rinne’s Test
In this test the vibrating tuning fork is kept over the mastoid and when the patient indicates that the sound has stopped, the tuning fork is placed 2.5 cm in front of the external auditory canal . Rinne is said to be positive if the patient still hears the sound and negative if the sound is not heard. Alternatively, the vibrating tuning fork is placed in front of the external canal and on the mastoid intermittently and the patient is asked to indicate with which the hearing is better.

In cases with severe unilateral sensorineural deafness, the vibrating tuning fork may be heard when placed on the ipsilateral mastoid but not in front of the ear. This is due to trans- mission of the vibrations to the healthy ear and is referred to as a ‘false Rinne negative’ and it may be differentiated from a true negative by masking the non test ear with Barany’s noise box.
Weber’s Test
This test is performed in conjunction with the Rinne test and is of particular value in cases similar tuning forks (512) struck with moderate intensity and held at 25cms from each ear. Malingeer will say that he hears in the normal ear only. The fork on the deaf side is advanced by 3 inches towards the ear. Patient who is malingering deafness will deny hearing the sound at all.
2. Chimani Moos test: A modification of the Weber test to detect non-organic hearing loss. If a tuning fork is placed on the forehead the malingerer states that he hears the sound in his good ear (simulating a sensor neural deafness). If the meatus of the good ear is occluded, the truly deaf patient still hears the sound in the occluded ear but the malingerer may deny that he hears the tuning fork at all.
Others tests being: Teal test and Lombard test.

POINTS TO REMEMBER
1. Tragal tenderness can be elucidated in case of furunculosis of external ear .
2. The site for eliciting the mastoid tenderness is over the cymba concha, midpoint of posterior border of the mastoid and tip of the mastoid.
3. False negative Rinne is seen in severe sensor neural hearing loss.
4. Tuning fork tests are done for subjective assessment of hearing.
5. Gelle s test is an excellent method of determining the functioning of the ossicular chain and especially the stapes.
6. Toynbees maneuver is done to test the mobility of the tympanic membrane.

Hyper mobile tympanic membrane can be seen in patulous eustachian tube.

History taking and careful clinical examination is very much essential to establish a proper diagnosis. No amount of present day sophisticated investigations can replace thorough history taking and careful clinical examination.

History taking for ear diseases can be described under the following headings:
• Chief complaints
• History of presenting symptoms
• Past history
• Family history
• Personal history
• Treatment history
• General examination
• Local examination
• Systemic examination
• Provisional diagnosis
• Differential diagnosis.

Chief Complaints

Common Symptoms of Ear Diseases
• Discharge
• Hearing impairment
• Otalgia (pain in the ear)
• Tinnitus
• Vertigo
• Itching
• Blocked sensation
• Feeling of fullness
• Autophonia
• Neuro-otological symptoms like:

(a) Fever
(b) Headache
(c) Stiffness of neck (d) Facial nerve palsy (e) Vomiting
(f) Diplopia
(g) Cervicofacial pain
• Swelling and deformity.

HISTORY OF PRESENTING ILLNESS

All the above mentioned symptoms have to be analyzed under the following heading. Pertinent questions have to be asked, to know how did the disease start and what is the duration? How has it progressed up to this moment? Whether onset is sudden or gradual? All these questions should be asked strictly and impartially, without the influence of a preconceived idea which may tend to mislead the patient from the beginning. These questions lead to a thorough investigation of the patient’s hereditary and medical history.

Discharge from the Ear

Onset
Sudden: ASOM Gradual: CSOM
Duration
Long duration
Short duration
Intermittent
Type of Discharge Watery discharge
Serosanguinous
Mucoidal
Mucopurulent
Purulent
Chronic suppurative otitis media, Eczematous otitis extema
Acute suppurative otitis media, Ruptured furuncu­ losis
Tubotympanic type of chronic suppurative otitis media
CSF otorrhea, otitis extema (eczematous)
Fungal infection, diffuse otitis extema
CSOM tubotympanic type, fungal infection, granular myringitis
CSOM (tubotympanic), secondary infection in CSOM, tuberculous otitis media (painless otorrhea) Furunculosis, mastoiditis, Malignant otitis externa, Atticoantral type of CSOM.
Consistency of the Discharge
Viscid and tenacious discharge in tubotympanic disease.
Odor
Odorless: Allergic otitis extema, CSOM (tubo­ tympanic).
Foul smelling (Fishy smell): Atticoantral disease.
Quantity
Profuse Scanty
Tubotympanic, Atticoantral.

History Taking and Clinical Examination Associated Conditions

• Discharge increases with cold, head bath, pharyngitis and tonsillitis, enlarged adenoids seen in tubotympanic type of CSOM.

Hearing Impairment (Deafness) Onset

• Sudden: Impacted wax, vascular or viral deafness, acoustic trauma
• Gradual: Presbyacusis, acoustic neuroma, otosclerosis, noise induced hearing loss
• Unilateral: CSOM, mumps, Herpes Zoster oticus, acoustic neuroma, etc.
• Bilateral: Presbyacusis, Meniere’s disease, otosclerosis, noise induced hearing loss
• Progressive: Meniere’s disease, presbyacusis, otosclerosis, acoustic neuroma, tympano­ sclerosis
• Fluctuating: Meniere’s disease, perilymph leak.
Autophony (Hearing his own voice louder in the ear) Secretory otitis media.
Paracusis willis
• Hearing better in noisy place-otosclerosis, whereas hearing better in a quiet place – suf­fering from SN loss.
Diplacusis
• Differences in the pitch of the tone in dif­ferent ear is found in Meniere’s disease.
Recruitment
• A relativel y small increase in intensity of the auditory stimulus may cause frank discomfort to the listener as seen in cochlear pathology.

Otalgia (Pain in the Ear)

Pain in the ear may be because of the local and referred causes. Whenever the patient complains of pain the following questions should be asked in the history of presenting symptoms.
Onset

• Sudden: e.g. furunculosis, acute otitis media, trauma like otitic barotraumas
• Gradual: otitis extema secondary to CSOM, malignancy, malignant otitis externa

Duration
• Short duration: ASOM, perichondritis of ear pmna
• Long duration: Malignancy

Nature of the Pain
• Dull: eczematous otitis externa, secretory otitis media, impacted wax
• Sharp: furunculosis, otitic barotrauma
• Throbbing pain: ASOM

Relieving Factors
• Pain relieves with discharge from the ear­ acute suppurative otitis media (ASOM)

Aggravating Factors
• Pain increasing on swallowing-ASOM.
• Pain increasing on yawning and chewing­ furunculosis arising from anterior canal wall
• Pain increasing on pulling the pinna and pressing the tragus-otitis externa.

Radiating Pain
Furuncle arising from anterior wall, pain radiates to preauricular region and posterior wall to the mastoid region.

Referred Pain (Otalgia)
• Referred pain to the ear is because of nerve supply from 5th, 9th and 10th cranial nerves and C2,3 to the ear.
Referred pain via 5th nerve
• Dental: Caries tooth, impacted molar, malocclusion
• Oral cavity: Benign or malignant ulcerative lesion
• Temporomandibular joint disorders like Costen syndrome, T.M joint arthritis.
Referred pain via 9th nerve

• Base of tongue malignancy
• Oropharynx-Acute tonsillitis, peritonsillar abscess, benign or malignant ulcers of the soft palate or tonsils.
• Elongated styloid process also known as Eagles syndrome.
Referred pain via 10th nerve

• Ulcerative lesions of vallecula, epiglottis, larynx or laryngopharynx.
Referred pain via C2, C3

• Cervical spondylosis, caries spine.
Symptoms associated with Otalgia
• Tinnitus-Acoustic neuroma
• Itching-Otomycosis

Tinnitus

It is the name given to the symptom of noises in the head or ear. It is very common and sometimes may be the only symptom. It may be regarded as a sign of irritation to the cochlea or central auditory pathway. Tinnitus should be clinically evaluated as follows:
Duration of Tinnitus
• Short: Middle ear pathology.
• Long: Meniere’s disease, acoustic neuroma, palatal myoclonus, glomus jugulare, patent cochlear duct, ototoxicity.

Types of Tinnitus
• Subjective type
• Objective type
Subjective type: Sounds like ringing, whistling or roaring is heard by the patient without the presence of such a sound. This can also be psychogenic and functional in origin, apart from diseases like Meniere’s, ototoxicity, etc.

Objective type: This is heard not only by the patient but also by the examiner, e.g. palatal myoclonus, patulous eustachian tube, vascu­lar bruit, arteriovenous malformation, etc.
Nature
• Continuous: Otosclerosis, acoustic neu­roma, acute noise trauma.
• Intermittent and fluctuant: Meniere’s disease.
• Pulsatile: Glomus tumors, strychnine poiso­ning.
• Relieving factors: By putting pressure at the side of the neck in vascular causes.
• Aggravating factors: By smoking­ cochlear pathology, ototoxicity. Yawning and blowing-eustachian dysfunction.

Vertigo

Sensation of rotation of surrounding environment with respect to person. Vertigo without loss of consciousness is mainly of peripheral origin-BPPV, labrynthitis. Vertigo with loss of hearing is seen in Meniere’s disease, acoustic neuroma, bacterial labrynthitis. Vertigo with loss of consciousness is mainly because of central pathology.

Past History

History of similar illness in the past.
Past history of drug intake, especially in sensorineural hearing loss and bronchial asthma. Following are the commonly associated past illnesses that can cause ear diseases.
• Diabetes mellitus
• Allergy and bronchial asthma
• Hypertension
• Tuberculosis
• Syphilis
• Childhood diseases
• Radiation
• Bleeding condition
• Connective tissue disorder
• Hyperthyroidism

Family History

History of consanguineous marriage causes high incidence of deaf-mutism and other congenital disorders. Otosclerosis runs in the family.
Personal History
• Occupation
• Diet
• Personal hygiene
• Smoking and alcohol
• Loss of weight
• Pan chewing Treatment History

Any past medication and surgery should be inquired for better planning of the treatment.

Semicircular canals-Sense of head rotation.
Otolith organs-Stimulated by gravity and linear acceleration of the head.

Physiologically, the vestibular labyrinth transduces mechanical energy (linear and angular) into electrical activity (nerve action potential) which is interpreted by the brain to allow conscious awareness of the position and movement. Transduction and coding-common to both maculae and cristae.

Mechanical event is bending of hair cells.
When the macula surface is tilted, otoliths slide down carrying gelatinous membrane and attached cilia. On head rotation, the endolymph pushes the cupula which carries cilia with it.

Bioelectric Events

There is a constant resting or tonic discharge in many of the afferent fibers from the receptors. Bending the cilia modulates the discharge. On bending of the stereocilia towards the kinocilium depolarization with increase in impulse frequency while bending away from the kinocilium causes hyper polarization with decrease in impulse frequency. Thus, membrane deformation of hair shearing surface alters its electrical conductance.

Reflex Responses Distributes as Follows:

1. Superior vestibular nucleus: Receives impulses from cristae of semicircular canal and cerebellum.
2. Lateral vestibular nucleus: Receives impulses from macula of utricle and cerebellum.
3. Medial vestibular nucleus: Input from cristae and cerebellum.
4. Descending vestibular nucleus receives the impulses from macula of utricle and saccule.

Efferent Activity

Vestibular nuclei connect with five main systems.
1. Oculomotor nuclei by way of MLF and multisynaptic connections in reticular formation.
2. Motor part of spinal cord by reticulospinal,vestibulospinal and inferior part of MLF.
3. Cerebellum.
4. Autonomic nervous system.
5. Cerebral cortex by multisynaptic pathways.

Functions of Vestibular Nuclei

1. Superior nucleus: Control of semicircular canal-ocular reflex.
2. Lateral nucleus: Vestibulospinal activity.
3. Medial nucleus: Co-ordinating eye, head and neck movements through medial longitudinal bundle.
4. Descending nucleus: Mainly to cerebellum and recticular formations.
5. Subjective awareness is by vestibulocortical projections.

Functions of Utricle and Saccule

Utricle and saccule respond to the slightest tilt and to fine acceleration of the head. Such a movement results in compensatory ocular reflexes where by the visual axis is fixed when the head is deviated slightly.
Macula of the saccule is at right angles to the macula of the utricle and may serve linear acceleration.

Functions of Semicircular Ducts

They respond to angular acceleration. The horizontal pair are for rotation about a vertical axis. Posterior and superior canals respond to tipping displacement of the head about a horizontal axis.
Movements of endolymph within the ducts stimulate cristae causing reflex nystagmus. The slow component is vestibular and the fast component cerebral. In clinical practice, nystagmus is named in the direction of the fast component.

Postural Reflexes

Labyrinthine reflexes maintain the posture.
1. Static reflexes: It is the postural reaction at rest. Together with reflexes from muscles, joints and others. They include the following labyrinthine (utricular) reflexes:
• Tonic labyrinthine reflexes-with effect on the limbs, neck, trunk and eyes.
• Labyrinthine righting reflexes

Restore the body to normal position when it is brought to rest in abnormal position.
2. Kinetic reflexes: Postural reactions of the body during movement.
• Angular as in movement of rotation in any plane.
• Progressive as in movement in a straight line.
In general, kinetic reflexes bring the body into normal stance while it is maintained by activation of various static reflexes.

Vestibular Physiology

Saccule and utricle are known as static labyrinth whereas semicircular canals are known as dynamic labyrinth because it is associated with kinetic balance.
Saccular macula responds to the tilting movement of the head, i.e. if the head is tilted to the right side, the right saccular macula will get stimulated whereas the left saccular macula will remain static. The utricular macula responds to forward and backward movement of the head. The cristae of the semicircular canals respond to turning of the head, i.e. angular acceleration.

The bending of hair cells towards the kinocilium causes depolarization with increase in impulse frequency, whereas bending towards the steriola will produce less stimulation due to hyper polarization. The hair cells of the utricle and saccule are divided by an arbitrary line called striola. The bending of utricular hair cells away from striola causes hyper stimulation due to depolarization whereas the bending of saccular hair cells towards the striola causes decrease stimulation.

Bending of hair cells of the cristae towards utricle (ampullofugal) movement in the lateral semicircular canal causes hypo stimulation. However, some authors believe that the ampullofugal movement in the lateral semicircular canal causes hyper stimulation whereas ampullopetal movement in the vertical semicircular canal causes less stimulation.
Fibers, both afferent and efferent, form a plexus of unmyelinated fibers from which myelinated fibers arise and go to the bipolar cells in Scarpa’s ganglion of the internal auditory canal.

Otolith Physiology

Otoliths are stretch receptors. When a tangential force, regardless of its origin is applied over the macula, the otoconia slide over the surface of the sensory epithelium stimulating the hair cells. The position of otoliths changes whenever the head position is changed or during head displacement with a component of linear acceleration.
The Dynamics of the otoliths is comparable to those of a low pass filter i.e., displacement due to linear acceleration is greater for lower frequencies, including stimulation with constant acceleration, than for higher frequencies.

The nerve fibers innervating the macular organs are sensitive to changes in position of the head. Each fiber has a preferred direction of tilt to which it responds maximally. Thus the movements of head are appreciated along a vector in a three dimensional space. The mechanical deformation of the hair bearing surface alters its electrical conductance. The endolymph has a +40mV potential compared to the -5Om V in the substance of sensory epithelium. Electrical modulation of the resting discharge arises when electrical current leaks from the top of the cell membrane.

Saccules are affected by lateral tilt of the head. When head is tilted to right, macula of right saccule hangs downwards – pulls on its macula and maximal stimulation is produced. Whereas the macula of the left saccule points upwards, rests on its macula producing minimal stimulation.
Ventral/dorsal deflection of the head affects macula of utricle when the head is straight, macula of the utricle points upwards producing minimal stimulation. Forward or backward bending makes the macula pendant, pulling on the macula producing maximal stimulation.

A tilt of as little as 2.50 stimulates the appropriate macula. The frequency of the impulse generated by the hair cells is directly related to the strength of the stimulation. They show little adaptation.

Mode of Action of Semicircular Canals

Effective stimulus to each semicircular canal is rotation of head in the plane of its canal.
When the head starts to rotate, e.g.: to the right, the endolymph in the semicircular canals, which lie at right angles to the axis of rotation tends to lag behind the movement and it moves to the left initially.
With regard to the flow of the endolymph, the left ampulla is Leading and the right one Trailing.

Rotation to right-endolymph moves to left. After the initial inertia is overcome, endolymph no longer lags behind the movement of head. It flows in the same direction.
Cupula swings back because of its elasticity, to its normal position, as long as the movement exists in the same velocity and direction and resting discharge is resumed. When the movement ceases, the endolymph tends to continue to rotate and cupula is displaced in the opposite direction and hair cells are bent in that direction. Swinging in a particular direction in any canal increases the stimulus while in the opposite direction decreases the stimuli. Thus in any movement there is an increase in frequency of impulse in one ampula and decrease in its opposite side ampulla.

This combination of increased and decreased stimuli forms the basis of interpretation of the direction of the movement. Accordingly in the above example-when the movement ceases, since the chain of events occur in a way opposite to that at the start, a subjective impression of motion in the reversed direction occurs. Finally the cupula regains the resting potential and sense of movement ceases.The various impulses produced by the hair cells are transmitted to the vestibular nucleus via vestibular fibers. The vestibular system has diffuse connections with central nervous system like with ocular nuclei complex, anterior horn cells of spinal cord, cerebellum, and higher centers in the brain.

Ewalds Law
The vestibular physiology was well clarified by Ewald’s experiments. He came out with three major observations.
1. Head and eye movement always occur in the plane of the canal being stimulated and in the direction of the endolymph flow.
2. In the horizontal canal, ampullopetal endolymph flow causes a greater response than ampullofugal flow.
3. In the vertical canals ampullofugal flow causes greater response than ampullopetal flow.

Vestibular Tract

Some salient features and points to ponder.
1. Vestibular nuclear complex occupies the dorsolateral region of the rostral medulla and caudal pons.
2. Vestibular nuclear complex-Afferent­ efferent connections.
3. Reflex responses:

Stimulation of the vestibular sensory epithelium causes Two reflex responses.
1. Vestibulo-ocular reflexes a means by which humans stabilize gaze so that image can be fixed on the fovea of the retina during head movement.
2. Vestibulospinal reflex to maintain the normal posture of the head, trunk and limbs.

Vestibulo-ocular Reflex

Utriculopetal stimulus in one labyrinth is matched by an equal but opposite, utriculofugal displacement in the functionally paired canal of the other ear. Accordingly the lateral canals form one pair while the posterior canal pair with the opposite side superior canal.
Taking as an example – utriculopetal deviation of the cupula of the right horizontal canal, occurs with an utriculofugal movement of the cupula of the left horizontal canal.

This results in an increase in the firing rate of the right afferent nerve and an equal but opposite response in the left afferent nerve. The right afferent information exerts an excitatory influence on the agonist muscles and an inhibitory influence on the antagonist muscles. The left afferent information reduces the excitatory influence on the antagonist muscles and dis-inhibits the agonist muscles. This results in contraction of the left lateral rectus and the right medial rectus muscles producing deviation of the eyes to the left.

If the stimulus is large, such that the compensatory movement cannot be obtained within the confines of the orbit, a fast movement in the opposite direction occurs. This fast movement is central, initiated and mediated by the reticular formation, cutting off the incoming flow from the vestibular nucleus and reticular activating neurons directing the ocular muscle nuclei to return the eyeballs to the point of gaze at which the slow component began.

• Helmhotz’s place theory (1883): postulated that the basilar membrane acts as a series of tuned resonators similar to a piano string. Each pitch would cause resonant vibration of the basilar membrane which is particular to its own place. Thus, the frequency was analyzed. High frequency waves excite the basal region and low frequency the apical region.

• Rutherford’s frequency/Telephone theory (1886): Proposed that all frequencies activate the entire length of the basilar membrane along with the hair cells. He postulated that the frequency of the signal is represented by the rate of firing of the auditory nerve fibers. He believed that all vibrations are portrayed by the nerve impulses to the brain without complex vibrations in the cochlea.
• Wever’s volley resonance theory (1949):

Combines both the place and telephone theories postulating that:
• High frequencies (5000 Hz) are perceived in the basal turn;
• Low frequencies (1000 Hz) stimulate nerve action potential equal to frequency stimulation;
• Intermediate frequencies (1000-5000 Hz) are represented in the nerve by asynchronous discharges which then combine actively to represent the frequency of stimulus.

• Von Bekesy’s travelling wave theory (1960) This Wave begins from the base and moves towards the apex. Traveling wave is independent of frequency. The region of maximum displacement varies according to frequency. High pitched sounds causes a short traveling wave not beyond the basal turn. Low frequency stimuli cause maximum displacement near the apex.

Middle frequency changes occur in between these two. It is now known that the basilar membrane is much more sharply tuned for frequency filtering. The basilar membrane becomes less selective in tuning at high stimulating intensities due to non linearity of its response. The sharp tuning and non – linearity is due to an active mechanical amplifier which uses biological energy to boost the membrane vibration.

MECHANISMS OF HEARING

Mechanisms of hearing can be broadly divided into:
1. Mechanical conduction of sound.
2. Transduction of mechanical energy to electrical impulses.
3. Conduction of electrical impulses to brain.

Mechanical Conduction of Sound (Acoustic Transformer)

A sound wave, on arriving at the boundary of its supporting medium, may be reflected or absorbed by the material of which the boundary is constructed. For example, if the medium is air and the boundary is water, 99.9 percent of the sound energy is reflected. The resistance to the passage of sound through a medium is its acoustic resistance or impedance. A similar situation exists in the ear when air conducted sound has to travel to cochlear fluids. So to compensate this loss of sound energy, nature has made middle ear to convert sound of greater amplitude, but lesser force, to that of lesser amplitude and greater force. This function of middle ear is called impedance matching.
The major contributors to the human acoustic transformer are the pinna, external auditory canal, and the middle ear sound conduction system.

Pinna
The pinna, because of their location and shape, serve to gather sound arriving from an arc of 135° relative to the direction of the head. This pattern rejects sound arriving from the ear and serves to determine the origin of the sound. The hom­ shaped conchea then acts like a megaphone to concentrate the sound at the entrance of the auditory canal. This action increases sound pressure as much as 6 dB (2 times).

External Auditory Canal
Acting in concert with the effect of the pinna, can increase sound pressure at the tympanic membrane by 15 to 22 dB at 4000 Hz.

Middle Ear Transformer Mechanism
The transformer system of middle ear can be divided into three stages:
1. That provided by the eardrum (catenary lever.
2. That provided by the ossicles (ossicular lever).
3. Provided by the difference in surface area between the tympanic membrane and the stapes footplate (hydraulic lever).
1. Catenary lever
Helmholtz was first to propose a concept of a catenary lever to the action of the tympanic membrane. A familiar example of this type of lever is tennis net. The tighter a tennis net is stretched, the greater the force exerted on the posts holding it. Because the bony annulus is immobile, sound energy applied to the tympanic membrane is amplified at its central attachment, the malleus. It is estimated that even though the curvature of the tympanic membrane is variable, the catenary lever provides at least a two times (2x) gain in sound pressure at the malleus. Forces exerted on the stretched curved fibers of the tympanic membrane are amplified at its point of attachment, the annular bone and the malleus handle. The annular bone is immobile, so that the malleus is the recipient of this magnified energy, directing it into the ossicular chain for transmission to the perilymphatic fluid.
2. Ossicular lever
Handle of malleus is 1.3 times longer than long process of the incus, providing a mechanical advantage of 1.3. The catenary and ossicular levers, acting in concert provide an advantage of 2.3.
3. Hydraulic lever
Helmholtz’s third concept of impedance matching is referred as areal ratio. The effective vibratory area of tympanic membrane is 55 mm sq. whereas foot plate area is 3.2 mm sq. Hence effective areal ratio is 14: 1. This is a mechanical advantage provided by tympanic membrane. The product of areal ratio into lever ratio is known as transformer ratio. i.e., 14 x 1.3 = 18: 1.
Phase difference
In normal ear, sound pressure waves never reach the oval window and round window in the same phase, due to presence of tympanic membrane, middle ear and air cushions. If air waves reach round window and the oval window at the same time it cancel the effect of sound waves leading to stasis of perilymph. This reciprocal action at oval window and round window is called as phase difference. Therefore, loss of this phase difference (due to large perforation) may lead to deafness. However in normal case sound wave reaches oval window earlier than round window which is also an added advantage of hearing.

Transduction Function of the Cochlea

What is Transduction?
It is the conversion of mechanical energy of movement of sound to electrical energy, which is followed by electrical event in the cochlear nerve. Many theories have been put forward while exploring the mehanics and mode of encoding in the cochlea which have been modified with the present day knowledge.

When the stapes is pressed onto the oval window, pressure is exerted to the perilymph in scala vestibuli which is transferred to the scala media. This causes downward movement of the basilar membrane exerting pressure in the scala tympani. This is transmitted in turn to the round window which bulges into the middle ear. When the stapes and oval window move out, there is an upward movement of the basilar membrane. The elastic tension built up in the basilar fibers initiates a wave which travels towards the helicotrema. This wave is comparable to the movement of a pressure wave along the arterial walls.

Each wave is weak at the onset but becomes stronger as it reaches its natural resonant frequency.
High frequency waves travel a short distance and die. Low frequency waves travel a long distance and die. This is because the energy in the wave is completely dissipated. The nature of interaction between the membrane and the fluids is complicated and many theories were put forward based on experimental findings and hypothesis.
• Transduction by Hair Cells
Many theories were put forward regarding transduction by the hair cells. It is obvious now that auditory nerve endings are not only stimulated electrically but also by chemical transmitters.

Major steps involved in transduction are:

• The Basilar Membrane and the organ of Corti move up and down with sound stimulus. This causes a shearing action between the tectorial membrane and the reticular lamina causing the stereocilia to bend sideways.
• This bending of the hair bundles opens the channel to allow K+ to flow into the hair cell, resulting in depolarization.
• Depolarization spreads to the lower part of the cell causing Ca + channels to open.
• Ca+ causes transmitter vesicles to fuse with the basal part of the cell membrane. This fusion releases transmitter substance.
• The transmitter substance i.e. amino acid glutamate diffuses across the synaptic cleft to initiate action potential in the auditory nerve fiber.

Electrical responses of cochlear hair cells Using microelectrodes, four gross potentials have been extensively studied,
• Endocochlear potential: In relation to the perilymph, the endolymph in the scala media has a positive potential of +80mV and a high K+ concentration. This is known as endocochlear potential. It is dependent on adequate oxygen and is produced by stria vascularis. When the K+ is driven into the cell by this big potential gradient, large voltage is given triggering the natural impulses.
• Cochlear microphonics: Described by Wever and Bray are generated by the outer hair cells at the apical region. It produces the AC current wave form of stimulating sound and represents the K+ flow through the outer hair cells. Cochlear rnicrophonics is absent in any part of the cochlea where outer hair cells are damaged.
• Summating potential: It is a DC potential that follows the envelope of stimulating sound. Several origins have been cited; probably arising from inner hair cells with a small contribution from outer hair cells, this is a rectified derivative of sound signal.
• Auditory nerve action potential: It is neural discharge in the auditory nerve produced at the presence of stimulus. Each fiber has optimum stimulus frequency for which the threshold is lowest. Amplitude increases while latency decreases with intensity over 40 to 50 dB range.

Conduction of Electrical Impulses to the Brain

Physiology of the cerebral cortex

Area of auditory pathway to the cerebral cortex is illustrated as primary auditory cortex excited by medial body.
Secondary auditory cortex excited secondarily by impulses from primary auditory cortex, thalamic area adjacent to medial body.
Sound frequency perception in the primary auditory cortex

Six different tonotopic maps have been found in both the primary and secondary auditory cortex. Low frequency sounds are located anteriorly and high frequency sounds posterior. One of the large maps in the primary auditory cortex discriminates the sound frequency; another map detects direction of sound.

It starts in the 3rd week of the intrauterine life and is completed by the 16th week of the intrauterine life.
Membranous labyrinth develops from the otic capsule. This differentiates into various structures, like sensory end organ of hearing and equilibrium.
Bony labyrinth develops from the otic capsule.

This is a mesenchymal condensation surrounding the membranous labyrinth. Soon this is converted into cartilage. Between the cartilage and the labyrinth is loose periotic tissue. This tissue disappears around the utricle and saccule to form the vestibule. It also disappears around the semi­ circular ducts to form the semicircular canals.
In the cochlea two spaces are formed on either side of the cochlear duct known as scala vestibuli and scala tympani.

Anatomy

The inner ear is well protected and lies inside the petrous temporal bone, between the medial wall ‘ of the middle ear and the internal auditory canal. It is composed of:
1. The bony labyrinth has a central part called bony vestibule which is connected anteriorly to the bony cochlea and posteriorly to the three bony semicircular canals.
2. The membranous labyrinth has the same named structures as the bony labyrinth which floats on the perilymph and itself has endolymph .

Anatomy of the Bony Labyrinth
Divided into 3 parts:
(a) Bony vestibule
(b) Semicircular canals.
(c) Cochlea
(a) Bony Vestibule

(a)Vestibule is the central part of the bony labyrinth and is compared to a standard aspirin tablet (5 mm). It lies between the medial wall of the middle ear and lateral to the internal acoustic meatus, anterior to the semicircular canal and posterior to the cochlea.
On the lateral wall of the vestibule there is a bean-shaped opening called fenestra vestibulae (oval window) occupied by the footplate of the stapes and surrounded by annular ligament. On the front half of the medial wall there is a marked depression called spherical recess. This is a space for saccule. This wall is perforated by minute holes called maculae cribrosa media for passage of the inferior vestibular nerve filaments. Behind is another depression called the elliptical recess containing utricle. The two are separated by a crest, the anterior end being the estibu1ar pyramid.

Vestibular crest splits posteriorly to enclose the cochlear recess for cochlear nerve filaments. The pyramid and elliptical recess are perforated by small holes called macula cribrosa superior also called Mike’s dot, (It is an important landmark in translabyrinthine approach) for nerves to utricle and ampulla of superior and lateral semicircular canals respectively. Below the elliptical recess, there is a diverticulum called aqueduct of vestibule plugged in life by the endo- lymphatic duct and one or two small veins.

(b) Semicircular Canals:

They are three in number:

1. Superior
2. Posterior or vertical
3. Lateral semicircular canals.

Each occupies two-thirds of a circle and is unequal in length. The diameter is 0.8 mm. All three canals show dilatation at one end called ampulla containing vestibular sensory epithelium.
Superior semicircular canals length 15 to 20 mm lies transverse to the bony axis of the petrous portion of temporal bone. Anterolateral end is ampullated and opens in the upper lateral part of the vestibule. The other end fuses with the superior limb of the posterior vertical canal to form crus commune, 4 mm length, which opens in the medial part of the vestibule.
The lateral semicircular canal projects as a rounded bulge into aditus and antrum of the middle ear cleft It is 12 to 15 mm long, lies at an angle of 30° to the horizontal plane. The ampullary end opens into the upper part of the vestibule, posterior end into the lower part below the orifice of the crus commune.

Anatomy of the Ear I 23 Posterior semicircular canal 18 to 22 mm long lies parallel and very close to the posterior surface of the petrous portion of the temporal bone. Lower ampullated limb opens into the lower part of the vestibule and the upper limb joins the crus commune. The angle formed by three semicircular canal is solid angle, whereas the triangle bounded by the bony labyrinth anteriorly, sigmoid sinus posteriorly and dura superiorly is known as Trautman’s triangle, which is a weakest part.

(c) Cochlea

Cochlea resembles a common snail. It forms the anterior portion of the bony labyrinth.
It is 5 mm from base to apex and 9 mm around its base, length of the tube is 30 mm. It is a hollow tube having 2 and three-fourth turns around a conical central axis called ‘modiolus’. The base of modiolus is directive toward internal auditory meatus and is perforated for the passage of cochlear nerve. The apex lies medial to tensor tympani muscle (internal carotid artery).

The osseous spiral lamina winds around modiolus and along the basilar membrane, it separates the scala media (cochlear duct) from scala tympani. Within this bony canal lies the membranous cochlear duct. There are three longitudinal channels within the cochlea: scala vestibuli above, scala tympani below and scala media in between. Scala vestibuli communicates with scala tympani at the apex of the cochlea called helicotrema.

Scala vestibuli is in continuity with the vestibule at the oval window closed by the stapes footplate. Scala tympani is separated from the tympanic cavity by the secondary tympani membrane at the fenestra cochlea. Central perforation leads to a foramen central in the body of modiolus, where nerves for the apex are accommodated. The nerve for the first turn and 3/4th of the cochlear tube pass through the peripheral tractus spiralis foraminosa. At once the nerves pair off towards the margin of ganglion and from here nerves communicate via the osseous spiral lamina with the organ of corti.

Anatomy of the Membranous Labyrinth
The membranous labyrinth can be broadly divided into three parts based on physiology:
1. Membranous vestibular labyrinth
2. Membranous semicircular canal
3. Membranous cochlear labyrinth
The membranous labyrinth contains endolymph and the specialized vestibular and cochlear receptors. It lies within the bony labyrinth, floating on the perilymph.

1. Membranous Vestibular Labyrinth It consists of:
• Saccule
• Utricle
• The endolymphatic duct and sac.
Saccule is connected to the cochlear labyrinth by the membranous cochlear reuniens. Saccule and utricle are connected to each other indirectly by the endolymphatic duct. Saccule occupies the spherical recess in the bony vestibule and it contains specialized vestibular epithelium. Utricle is bigger in size than the saccule and occupies the elliptical recess of the bony vestibule. The three semicircular canals open into the posterior wall of the utricle by five openings. Anteriorly, it connects to the saccule indirectly via the endolymphatic duct. It also contains specialized vestibular receptor organs.
Vestibular Receptor Organs
• Macula
• Cristae Macula
Vestibular receptor organs of the saccule and utricle are called macula. Macula of the saccule lies vertically in the medial surface of the saccule, whereas in the utricle it lies horizontally. These specialized vestibular receptor organs are composed of hair cells, supporting cells and gelatinous mass.
This gelatinous mass is composed of muco­ polysaccharides thought to be secreted by the supporting cells. Macular gelatinous mass contains additional materials made up of calcium carbonate crystals known as otolith or statoconia. Hence, the gelatinous mass is sometimes known as statoconial membrane.

2. Membranous Semicircular Canal
Cristae ampullaris: The membranous semicircular canal occupies the bony semicircular canals. It opens through the five openings into the posterior wall of the utricle. One end of each semicircular canal gets dilated before entering the utricle. The dilated part is filled in the ampullary end of the bony semicircular canal. It accommodates the specialized vestibular epithelium known as cristae. This cristae also has hair cells, supporting cells and gelatinous mass. The gelatinous mass in the cristae is dome shaped hence called cupula.
The hair cells are of two types:
Type 1 are flask shaped with nerve chalice; Type I cells are predominantly seen in the summit of the cristae.
Type 2 are cylindrical with no nerve chalice. Type 2 cells are found more towards the periphery in the cristae.
The hair cells consist of one kinocilium which is tall and prominent; many small cilia (60-110) known as steriocilia which are smaller than the kinocilium. The kinocilium in the macula are not uniformly arranged. A curve line called striola divides each macula into medial and lateral halves.

3. Membranous Cochlea
Cochlear duct (scala media): It occupies mid pertion of the cochlear canal and is triangular in cross section. Floor is formed by basilar membrane, roof by Reissner’s membrane and lateral wall by stria vascularis and bony wall of cochlea. Basilar membrane supports organ of corti, containing the sound receptors.
The thin area of basilar membrane in its inner part is called Zona Areuata, thicker outer part is Zona Peetinata.

Organ of corti is spread like a ribbon along the entire basilar membrane. It consists of the tunnel of corti which is composed of two rows of rods of inner and outer hair cells. It forms a triangle with the basilar membrane and contains cortilymph. There is one row of hair cells on the inner whereas outer row has 3 or 4 rows of hair cells. Inner rods are 3500 and outer rods are 12000. Rods are expanded like a cap on top. Sensory cells arranged in two groups as inner and outer hair cells. In the fetus and newborn, there are 3500 inner hair cells and 13000 outer hair cells. As age advances there is generalized reduction in the number of hair cells. Hair cells are supported by pillar cells, Deiter’s cells and Hensen’s cells. The tips of the outer hair cells are attached to the under surface of tectorial membrane.

Tectorial membrane: It consists of a gelatinous matrix with delicate fibers, it e organ of corti. The shearing force between the hair cells and tectorial produce stimulus to hair cells.
Lateral wall ‘stria vascularis’: It is thought to play an active role in the maintance of the ionic composition and electrical potential of the endolymph.
Roof formed by Reissner’s membrane.

Blood Supply of Inner Ear
Internal auditory artery arises from the anterior inferior cerebellar artery (AICA). It accompanies the facial and vestibulocochlear nerves in the internal acoustic meatus and usually divides into three branches to supply the inner ear:
• Anterior vestibular artery to supply the macula of utricle and crista of superior and lateral semicircular canals
• Vestibulocochlear branch to supply the posterior semicircular canal
• Cochlear branch to supply the cochlea.

AUDITORY PATHWAY
First order neurons are located in the spiral ganglion and are bipolar. Peripheral processes innervate the organ of Corti and central processes terminate in the dorsal and ventral cochlear nuclei.
Second order neurons lie in the dorsal and ventral cochlear nuclei. Most of the axons cross over in the trapezoid body and terminate in the superior olivary nucleus. Many end in the trapezoid body or lateral lemniscus and some remain uncrossed.
Third order neurons lie in the superior olivary nucleus. The axons cross from lateral lemniscus and reach the inferior colliculus.
Fourth order neurons lie in the inferior colliculus. Their axons pass through the inferior brachium to reach the medial geniculate body (some fibers directly reach the medial geniculate body).
Fifth order neuron lie in medial geniculate body. Their axons form auditory radiation which passed through the part of the internal capsule to reach auditory area in the temporal lobe.

Vestibular Pathway
Vestibular receptors are the macula of the saccule and utricle and the cristae of the ampullae. They are innervated by the peripheral processes of bipolar neurons of the vestibular ganglion which is situated in the internal acoustic meatus. The central processes form the vestibular nerve which ends in the vestibular nuclei.

The entire middle ear cleft is lined by columnar ciliated and pavement epithelium. It is an exten­ sion of the respiratory mucous membrane from nasopharynx. The middle ear cleft consists of:
1. Eustachian tube
2. Tympanic cavity
3. Mastoid antrum
4. Aditus ad antrum
5. Mastoid air cells.

EUSTACHIAN TUBE

Eustachian tube connects tympanic cavity to nasopharynx, it is approximately 3.75 em long in average adult. It is directed upward, backward from lower opening in the lateral wall of naso­ pharynx, towards the upper opening in anterior wall of tympanic cavity. Whereas it is directed downward, forward medially from the tympanic cavity. The nasopharyngeal opening lies behind posterior end of inferior turbinate. Tympanic opening is higher than the pharyngeal opening. Tube is more horizontal and relatively wider, shorter in infants and young children.

The upper or poster lateral one-third is bony whereas lower or anteriomedial two third is cartilaginous. It is widest in entrance to tympanic cavity and narrow at its lower end, where tube is flattened at a diameter of 2 mm. Tubal tonsils are seen near the pharyngeal end of the tube which may at times cause Eustachian tube obstruction because of hypertrophy.
There is also presence of fibro fatty tissue related to membranous part of cartilaginous tube specially in the region of nasopharynx which is known as Ostmann’s pad of fat. This keeps the ET tube closed, thereby protecting the tube from nasopharyngeal reflux.

The fossa of Rosenmuller which lies behind the nasopharyngeal orifice is normally packed with small but well organized lymph nodes. It is the most common site for nasopharyngeal malignancy.

Blood Supply of Eustachian tube

Arterial supply: Ascending pharyngeal and middle meningeal artery and also from artery of pterygoid canal.

Venous Drainage: Pterygoid plexus.

Functions of Eustachian Tube

1. Ventilation of middle ear cleft-It plays a major role in equalizing middle ear pressure with atmospheric pressure.
2. Prevents reflux of nasopharyngeal secretion.
3. Clearance of middle ear secretions.

TYMPANIC CAVITY (the middle ear)

The tympanic cavity lies between the external and inner ear and shaped like a biconcave disc. The vertical and anteroposterior diameters are 15 mm, while the transverse diameter is 6 mm at the upper part, 2 mm at the center and 4 mm at the lower part.It is a six sided cavity with a roof, floor, anterior, posterior, medial and lateral walls. The tympanic cavity is divided into three parts:
• Epitympanum
• Mesotympanum
• Hypotympanum
Epitympanum (attic)
It is situated above the malleolar folds of the tympanic membrane. It contains the head of the malleus, incudomalleolar joint and body and short process of the incus. It connects the mastoid antrum via the aditus poster superiorly.

Mesotympanum
It is situated medial to the pars tensa of the tympanic membrane.

Hypotympanumi

It is situated below the level of the tympanic membrane.
Anterior mesotympanum and hypotympanum are lined by columnar ciliated epithelium. The posterior mesotympanum, aditus and mastoid area are lined by pavement epithelium.
Lateral Wall

It is formed by the tympanic membrane and partly by a portion of squamous part of the temporal bone. This wall separates the middle ear from external ear.
Medial Wall

It separates the middle ear from the inner ear. It has several important structures:
a) Promontory i the most prominent and bulging part of the medial wall formed by the basal turn of the cochlea.
(b) Bony Lateral Semicircular Canal lays poster superior to the promontory above the oval window.
(c) Oval Window (Fenestra vestibuli) lies between the middle ear and the scala vestibuli of the cochlea. It is closed by the footplate of stapes and the annular ligament.
(d) Round Window (Fenestra cochlea) is situated below and behind the promontory. The niche of the round window is directed posteriorly. It is closed by the secondary tympanic membrane and separates the middle ear from the scala tympani of cochlea.
(e) Facial Nerve runs in the bony fallopian canal above the oval window.
Anterior Wall

Anterior wall separates middle ear cavity from internal carotid artery. There are various structures passing through the anterior wall to the tympanic cavity. They are as follows:
(a) Canal for chorda tympani nerve (b) Canal for tensor tympani muscle (c) Eustachian tube
(d) Anterior malleolar ligament (e) Anterior tympanic artery
Posterior Wall

The upper part of the posterior wall shows the opening of aditus, which leads backwards from the posterior epitympanum to the mastoid antrum. Below the aditus there is a triangular bony projection known as processus pyramidalis through the apex of which is transmitted the stapedius tendon. The vertical portion of facial nerve courses down the posterior wall to its exit in the stylomastoid foramen.

• Facial recess (Suprapyramidal recess) and sinus tympani (Infrapyramidal recess)
Two recesses extend posteriorly from the mesotympanum that are often impossible to visualize directly. These spaces, the facial recess and sinus tympani, are the most com­ mon location for cholesteatoma persistence after ear surgery. The sinus tympani lies between the facial nerve and the medial wall of the mesotympanum and is very difficult to access surgically. The facial recess (suprapyramidal) is lateral to the facial nerve, bounded by the fossa incudis superiorly and the chorda tympani nerve inferiorly, posterosuperior meatal wall laterally and pyramid medially. It may be directly accessed via a posterior tympano­ torny approach, through the mastoid (posterior tympanotomy or facial recess approach).

• Sinus tympani (Infrapyramidal recess): The niche of two labyrinthine windows communicates at the posterior extremity with the deep recess which is known as sinus tympani. Laterally it is separated from the facial recess by the pyramid.
Floor

It is formed by a thin plate of bone which separates the middle ear from the bulb of the intemaljugular vein lodged in the jugular fossa. In the presence of a bony dehiscence in this area the jugular bulb may come into the middle ear to become a content of it.
Roof

The roof of the middle ear is separated from the middle cranial fossa by a thin plate of bone known as tegmen tympani and tegmen antri.
Ventilatory Anatomy
Normally the middle ear cleft is well ventilated. The air comes through the eustachian tube from the nasopharynx to the anterior mesotympanum. From here the air column goes up to the anterior epitympanum via the isthmus tympanic anticus and then goes backward to the posterior epitympanum. Part of this air passes through the aditus to ventilate the mastoid air cells and part of it comes down via isthmus tympanic posticus to ventilate the posterior mesotympanum. In a well pneumatized mastoid, ventilation of the posterior mesotympanum takes place also through the posterior wall. From the posterior mesotympanum, air percolates to the hypotympanum. Disorder of this ventilatory anatomy has a great bearing in the etiopathogenesis of various inflammatory diseases of the middle ear.

Contents of the Middle Ear

(a) Ossicles
Three tiny bones which conduct the sound from the ear drum to the oval window.
• Malleus (hammer) is the largest and lateral most ossicle measuring 8 mm in length. It has a head, neck, handle and anterior and lateral processes. The head is situated in the epitympanum. A lateral (short) process projects laterally from the neck while the handle is firmly fixed to the pars tensa of the ear drum.
• Incus (anvil) has a body, short process and long process. The body articulates with the head of malleus in the attic and the short process projects into the attic. The long process project downwards behind the handle of malleus, running parallel to it and articulates with the head of the stapes via the lenticular process.
• Stapes (stirrup) is the smallest ossicle mea­ suring about 3.5 mm and consists of head, neck, footplate and anterior and posterior crura. The footplate of stapes is held to the oval window by the annular ligament.
(b) Muscles

• The tensor tympani and stapedius muscles decrease the movement of the ossicles.
• The tensor tympani is inserted to the neck of malleus. First arch muscle supplied by branch of mandibular nerve
• The stapedius is inserted to the neck of the stapes. Second arch muscle supplied by branch of facial nerve, i.e. nerve to stapedius.
(c) Mucosal folds and ligaments-keep the ossicles in place.

(d) Nerves

• Chorda tympani is a branch of the facial nerve which carries the sense of taste. It enters the middle ear cavity from the posterior wall, runs forwards and lateral to the incus and medial to the malleus, escaping out through the anterior wall.
• The tympanic plexus lies on the promontory.
It is formed by tympanic branch of glossopharyngeal nerve and sympathetic fibers from the plexus around the internal carotid artery. It also carries the secretomotor to the parotid gland. Tympanic plexus innervates the medial surface of tympanic membrane, tympanic cavity, mastoid air cells and bony eustachian tube. Tympanic branch of glo sopharyngeal nerve can be sectioned in middle ear for treating the Frey’s syndrome.
(e)Vessels: Plexus of vessels of stylomastoid artery and from caroticotympanic artery.

Mastoid

The mastoid consists of three parts
1. Aditus ad antrum is a short canal connecting the epitympanum with the mastoid antrum. The short process of incus lies on its floor. The facial nerve runs in its canal in the floor, while the lateral semicircular canal lies in the medial wall. The bone lateral to the aditus appears like a bridge during ear operations.

2. Mastoid antrum is the largest air cell in the mastoid bone. The antrum is an important landmark in the surgery of the mastoid bone, and is always present.
• Anteriorly, the antrum receives the aditus. The facial nerve also lies anterior to the antrum.
• Medially, it is related to the horizontall po terior semicircular canal.
• Roof is formed by the tegmen antri.
• Lateral wall is formed by the cortex of the mastoid bone which lies medial to the suprameatal triangle. Its thickness can be upto 15 mm or 1.5 cm.
Mac Ewen’s (Suprameatal) triangle-It forms bony surface marking of the antrum. It is bounded by temporal line of supramastoid crest and posterosuperior bony meatal wall and the line drawn connecting the supprameatal crest and the bony meatal wall.
Posteroinferiorly, the antrum communicates with numerous mastoid air cells. Sinodural angle (Citelli’s angle) Angle between tegmen antri and sigmoid sinus.

3. Mastoid air cells are variable in number, size and distribution. They communicate with the mastoid antrum.
There are three types of mastoid process: (a) Cellular, with large and numerous air cells.
(b) Diploic, with small and less numerous air cells.
(c) Sclerotic, with air cells practically absent.
• The cellular mastoid account in about 80% of subjects and is considered to be normal. The diploic and sclerotic types may be due to the blockage of the eustachian tube. The air cells are located mainly in petromastoid and squamous parts of the temporal bone.

Development of Mastoid

Mastoid develops from squamous and petrous bone. The persistent petrosquamosallamina (bony plate)-the Korner’s Septum, is surgically important as it may cause difficulty in locating the antrum. It divides mastoid air cells into medial and lateral group. Mastoid antrum lies medial to the septum which may be difficult to reach or may lead to incomplete removal of disease during mastoidectomy. So to reach antrum, Korner’s septum has to be removed.

Development of mastoid process depends entirely on development of sternocleidomastoid muscle. Hence, its development does not begin until the end of first year of life, when the infants begin to hold their head erect. It does not form a definite elevation until the end of the second year and achieves its definite size only at puberty. So there is no actual mastoid process at birth and mastoid portion of temporal bone remains flat and stylomastoid foramen remains in surface of mastoid process. The facial nerve will be lying very superficial and may be injured in conven­ tional postauricular mastoid incision. So to avoid injury to the nerve, postauricular incision has to be done more horizontally.

Relations of the Middle Ear

External ear lies lateral to the ear drum.
Temporal lobe of the brain and meninges are above the antrum, aditus and epitympanum. The tegmen plate separates the middle ear cleft from the structures in the middle cranial fossa.
Cerebellum is posteromedial to the mastoid air cells.
Inner ear is medial to the antrum, aditus and tympanum.

Horizontal semicircular canal is an important landmark which lies posterosuperior to the facial nerve.
Fifth and sixth cranial nerves lie close to the apex of the petrous pyramid.
Facial nerve-The horizontal part runs downward in the medial wall of the tympanum.

The vertical part runs downward behind the tympanum and in front of the mastoid cells and emerges out through the stylomastoid foramen. Lateral sinus is posterior to the mastoid cells. Jugular bulb is in close contact with the floor of the tympanum.
Internal carotid artery is anterior to the tympanum.

Blood Supply
The blood supply of middle ear is from the branches of:
• Middle meningeal artery
• Maxillary artery
• Ascending pharyngeal artery
• Stylomastoid branch of the posterior auricular artery.

 Nerve Supply
Sensory: Tympanic branch of the ninth cranial nerve (Jacobson’s nerve) supplies through the tympanic plexus.
Motor: Tensor tympani muscle is supplied by the mandibular division of the trigeminal nerve and the stapedius muscle is supplied by the facial nerve.

Lymphatic Drainage
The lymphatics drain to the preauricular and the retropharyngeal lymph nodes.

Ear is divided into three parts:
1. External ear
2. Middle ear
3. Inner ear
It consists of pinna and external auditory canal. Pinna develops from six tubercles around the 1s1 branchial cleft whereas external auditory canal develops from the 1st branchial cleft.
External auditory canal is the only cul-de­ sac in the body lined by skin.

Pinna or Auricle
Pinna (or auricle) is the prominent part of the external ear composed of a single sheet of yellow elastic cartilage covered by fat, subcutaneous tissue and skin. It has two surfaces-medial (cranial) and lateral. The lateral surface is concave with folds and hollows. The medial surface is convex. The most prominent outer fold is called the helix and the fold in front is the anti­ helix. In front of the anti-helix is a hollow called cavum conchae.

Cavum concha leads inwards to the external auditory canal. Anterior to the cavum conchae there is a small cartilaginous projection known as tragus. In the upper part of the cavum conchae, in front of the anti-helix, there is a triangular space known as fossa triangularis. There is also a boat shaped space in between the upper part of helix and anti-helix known as scaphoid fossa.

The whole of the pinna is composed of a single sheet of cartilage except in the lobule and in the space between the cress of the helix and tragus. This space is called incisura terminalis. Since this area is devoid of cartilage, otologists can safely give an incision here for procedures in the ear to avoid postoperative perichondritis. The skin lining on the lateral or outer surface of the pinna is firmly adherent to the perichondrium of the cartilage with minimal or no subcutaneous tissue. Hence, the outer surface of the pinna is more prone to frost bite. In the cranial surface there is more subcutaneous tissue and the skin is loosely adherent to the underlying cartilage. Cysts like sebaceous cyst are commonly seen on this surface. The cartilage of the pinna extends medially to form the cartilaginous part of the external auditory canal.

External Auditory Meatus
External auditory meatus is S-shaped and approximately 2.5 cm in length. It has two parts – the outer one-third is cartilaginous and inner two third is bony. The cartilaginous part is a continuation of the auricular cartilage. It is firmly attached to the bony part by fibrous tissue. In infants, the cartilaginous meatus may remain collapsed because of the non development of the bony part. Hence, to examine the deeper part of the meatus in an infant, one has to either pull the pinna upward or downward.
It has fissure known as fissure of Santorini from where infection from mastoid and parotid can pass into each other.

The external auditory canal is directed first inward, backward and upward and then goes forward, downward and medially. Isthmus is the narrowest part of the canal lying medial to the junction of bony and cartilaginous parts, nearly 5 mm lateral to the tympanic membrane. To examine the deeper part of the EAC in adult one has to pull the pinna upward, outward and laterally. The roof and posterior wall of the external auditory canal are shorter than the floor and anterior wall. Thus, the tympanic membrane fits obliquely in the deeper end of the canal.
The anterior wall goes sharply forward to the tympanic membrane to form a blind pouch known as the anterior recess. Examination of this area is likely to be missed on routine otoscopic examination unless one takes care. This may be a common site for foreign body impaction lodgement.

Bony part in anteroinferior area has a deficiency known as foramen of Huschke. It persists till age of four.
Skin lining of the external auditory canal has its own peculiarity. The cartilaginous part has both epidermis and dermis whereas the deeper bony part has only the epidermal layer. Furunculosis, therefore, occurs more commonly in the outer part of the canal.

Relation
It is closely related to the temporomandibular joint and parotid gland anteriorly. Mastoid antrum and mastoid air cells are the posterior relations.

Nerve Supply
Nerve supply of pinna
Greater auricular nerve is common to lower one­ third of both the surfaces. Upper two-third of the medial surface is supplied by the lesser occipital nerve and the upper two-third of the lateral surface is supplied by the auriculotemporal nerve.
Nerve supply of external auditory canal
The anterior wall, floor and contiguous portion of the tympanic membrane are supplied by the auriculotemporal nerve. Rest of the canal and posterior part of the tympanic membrane are attached to the handle of malleus. When light is reflected over the tympanic membrane, the anteroinferior part is the most illuminated part in the pars tensa.
2. Pars flaccida (Shrapnell’s membrane; attic) is a triangular area above the malleolar folds which is thin and devoid of fibrous tissue and annulus. It fits into the notch of Rivinus.
The ear drum measures approximately 10 mm in vertical diameter and 5 mm in horizontal diameter. It is oval in shape and placed obliquely at an angle of 55 degrees with the floor of the meatus. The inner surface is convex. The point of its greatest curvature is called umbo which corresponds to the tip of the handle of malleus on the inner surface.

Blood Supply
The outer surface of the tympanic membrane is supplied by mandibular artery whose origin is not known and also by the deep auricular branch of the maxillary artery.
The inner surface of the tympanic membrane is supplied by the following arteries
• Anterior tympanic branch of the maxillary artery.
• Posterior tympanic branch of stylomastoid artery.
• Inferior tympanic artery, a branch from the ascending pharyngeal artery.
• Arteria nutricia incudomallea, a twig from the middle meningeal artery.

Venous Drainage
The external jugular vein provides drainage for the outer surface. The inner surface is drained b; the transverse sinus and the venous plexus located around the Eustachian tube.

Nerve Supply
The outer surface is supplied by the auriculotem­ poral nerve in the anterior half and tympani branch of vagus in the posterior half. Tympani plexus supplies the inner surface.

Ear has a very complex source of development. The sound conductive apparatus develops from the branchial apparatus whereas the sound perceptive apparatus develops from the ectodermal otocyst (pars otica). Because of this dual source of origin the developmental anomaly that produced commonly affects either the sound conductive system which includes anomaly of the external and/or the middle ear or the sound perceptive apparatus which includes the labyrinth. Both these anomalies rarely coexist because of different source of origin.
Development of the External Ear
This develops around the first branchial cleft.
The Pinna
Around 6th week of intrauterine life six hillocks or ‘tubercles of His’ appear around the first branchial cleft. The first tubercle is derived from the first branchial arch and the rest from the 2nd branchial arch. Some authors believe that the first 3 tubercles develop from the first arch and the rest from the 2nd arch.
Structures derived from Various Hillocks
1. Tragus
2. Crus of the helix
3. Helix
4. Antihelix
5. Scapha and the antitragus
6. Earlobule
The ear takes definitive form by the end of third month of intrauterine life. Defective fusion of the tubercles gives rise to preauricular sinus and failure of the development of the hillocks causes anotia. Defective development of 4th tubercle can cause absence of antihelix leading to ‘bat ear’ deformity.

External Auditory Canal
This develops around the first branchial cleft as an invagination into a funnel-shaped pit to form a primary external auditory canal. Subsequent medial growth with a solid core of ectoderm leads to formation of a meatal plate called the secondary external auditory canal. Between 8th and 10th week of IUL, the solid core of epithelium undergoes canalization forming the definitive external auditory canal.
Anomalies of the External Auditory Canal
1. Complete atresia
2. Shallow depression
3. Changes in the curvature of the canal
4. Stenosis
Development of Tympanomastoid Cavity and Eustachian Tube
Around 3rd week of IUL the first pharyngeal pouch develops which is phylogenetic ally the aquatic gill apparatus. This out pouching of the first pharyngeal pouch gives rise to two components namely:
1. The proximal narrow part which forms the eustachian tube.
2. The distal dilated part which gives rise to the developing middle ear cleft and is known as the tubotympanic recess. This forms the definitive tympanic cavity by progressively and systematically invaginating into the adjacent mesenchyme.
Towards the later part of the fetal life a diverticulum appears from the tubotympanic recess which subsequently forms the mastoid antrum. This antrum is about 3 mm thickness at birth and it increases 1 mm every year till it reaches the adult size of 15 mm thickness.

Development of Ossicles
Anson in 1959 described the details of the development of the ossicles. The first arch cartilage (Meckel’s cartilage) forms the head of the malleus and the body of the incus. The second arch forms the manubrium (handle) of the malleus and the long process of the incus and the crurae of the stapes. These sources of development confirm the various developmental anomalies involving the ossicles as encountered during surgery. The foot plate of the stapes develops from three sources namely:
1. The outer periosteal layer of the otic capsule.
2. Middle enchondral layer from the otic capsule.
3. Inner endosteal layer is same as the endosteum of the bony labyrinth and develops from the periotic mesoderm.

Development of Middle Ear Spaces and Folds
The envelopment of the ossicles by the mucous membrane lining of the tubotympanic recess occurs between 3-7 months. This mucous lining while encircling the ossicles form numerous folds and spaces as follows

COMPARTMENT AND FOLDS OF THE TYMPANIC CAVITY
1. Attic compartments
2. Compartment of mesotympanum
Anterior malleolar fold
• Neck of malleus to ant. margin of tympanic sulcus.
Posterior malleolar fold
• Neck of malleus to post margin of tympanic sulcus.
Tensor Tympani fold
Tensor tympani tendon

Prussak’s Space
It is a potential space which may be the first to involve during the extension of cholesteatoma, it is bounded by:
• Laterally by shrapnell’s membrane (Pars flacida)
• Medially by the neck of malleus
• Superiorly by fibers of lateral malleolar fold
• Inferiorly lateral process of malleus

Development of the Inner Ear
The inner ear develops from the otic capsule (pars otica). Initially a thickening appears in the ectoderm of the hindbrain known as otic placode. It later invaginates forming otic cyst which is also known as otic capsule. Subsequent differentiation of this otic cyst leads to formation of membranous labyrinth. The mesoderm surrounding the otic capsule forms the bony labyrinth which attains the adult size at around 4th week of fetal life.

POINTS TO REMEMBER

1. The sound conducting apparatus develops from the branchial apparatus, whereas the sound perceptive apparatus from the ectodermal otocyst.
2. The pinna develops from the six hillocks around the 1st branchial cleft.
3. Defective fusion of tubercles gives rise to pre-auricular sinus.
4. The outpouching of the 1st pharyngeal pouch gives rise to a proximal narrow part that forms the eustachian tube and distal dilated part that forms the middle ear cavity.
5. Prussak’s space is a potential space lateral to the sharpnell’s membrane and medially by the neck muscles that can be involved during the extension of cholesteatoma.

Aetiopathology

Sjogrens syndrome  is a disease which primarily affects women in the age group of forty and fifty years. The main defect is lymphocytic proliferation and immune complex deposition.

Patients with primary form have increased frequency of HLA-B8, HLA DRW 3 and MT-2 antigens. They also develop an immune complex vasculitis.

Activation of mono nuclear cells results in involvement of glandular structures while oligoclonal B cell activation produces increased levels of circulating immune complexes which produce auto antibodies like rheumatoid factor, SSA (anti RO) and SSB (antiLa). These are associated with a more serious profile of the disease.

Clinical features

The most common presentation of Sjogrens syndrome is dry eyes and dry mouth. The former are due to atrophy of lachrymal glands while the latter is due to atrophy of the salivary glands.

This dryness may extend to other mucosal areas like respiratory tract (Presistent dry cough) and female genital tract. Other manifestations include immune complex glomerulonephritis. Raynauds syndrome, nonthrombocytopenic purpura, vasculitis, sensory polyneuropathy, pseudolymphoma etc.

Cases of Sjogren syndrome who have only dry eyes and dry mouth are known as ‘Sicca syndrome’ and these patients do not have rheumatid arthritis but are associated with other auto immune disorder like SLE, polymyositis, Hashimoto’s thyroiditis, poly arteritis nodosa.

Primary form of the disease has mainly kerato conjunctivitis sicca and has presence of anti-RO and anti-LA/SSB with frequency of HLA-B8-DR3 antigens while in secondary form of disease there is evidence of under lying connective tissue disease with HLA-DR 4 positivity. Rheumatid arthritis may be associated with this form.

Diagnosis

Sjogrens syndrome is based on the presence of thy eyes, dry mouth and presence of anti nuclear antibodies. Schirmer‘s test is an important and simple test. Here a standard strip of filter paper is placed on the inside of lower eye lid.

If it does not get wet in 5 minutes, the test is positive. Further staining of conjunctiva by Rose Bengal dye may show a punctuate or filamentary keratitis.

A lip biopsy may be done to study antinuclear antibodies which are found in 70% of cases. Besides this anti RO (SSA) antibodies are also found in equally higher percentage of cases of sjogrens syndrome.

Treatment

There is no satisfactory treatment for Sjogrens syndrome available. Treatment mainly is directed towards symptomatic relief. For dry eyes artificial tears (0.5% hydroxymethyl cellulose) for dry mouth, oral soothing gels and vaginal gels for dryness in vagina.

Salivary secretions are stimulated by the use of lemon drops. Besides this special precautions should be taken about oral hygiene as these people are likely to suffer from dental caries.

Systemic medications include glucocorticoids which are successful in the management of severe form of disease (glomerulonephritis, vasculitis, pseudolymphoma, pneumonitis).

Other drugs which are of benefit include drugs like methotrexate, azathioprine, cyclophosphamide and chloroq,uine. Gold salts which were used earlier are now discarded. Main aim of treatment is directed towards amelioration of symptoms.

Prognosis

Cases of primary sjogrens syndrome carry good prognosis and but for some disability due to dryness, otherwise life expectancy is not affected. Prognosis in secondary form of disease depends on the type of complications they are suffering from.