Dementia may be defined as a chronic organic disorder which is characterized by deterioration in mental functions, primarily affecting thought and memory and secondarily in abnormalities of personality, higher cortical functions and conduct. Dementia is a disorder which is gradual in onset and has a progressive course.
With the increase in age span, the prevalence of dementia has also increased. It has been classified as presenile when it occurs before the age of 65 and senile after that age. But this distinction is arbitary since most cases merge with each other. An incidence of 1-2% in elderly people is reported.
Dementia is an important feature in number of neurological disorders. Depending on the age of onset it may be presenile or senile. There are over 70 different causes of dementia the most common ones being Alzheimer ‘s disease, multiinfart, psychiatric disorders (pseudodementia) alcohol and drug toxicity.
It may result from cortical disease or from diseases of subcortical structures such as basal ganglia, thalamus and deep white matter. In western world Alzheimers accounts for 50-90% cases of dementia and cerebral infarction contributes to intellectual loss in 13-15% of cases.
The earliest symptom is deterioration in the faculty ofjudgement, intelligence and behaviour. Loss of memory is the most important and this is especially so to start with events of recent past and later on that of remote events. Besides memory there is failure of comprehension leading to disorientation in time and space.
Loss of higher control leads to emotional instability. Patients behaviors suffers most. Behavior is out of tune with his character and social state. Patient may suffer from delusions of grandiose.
As the disease progresses patient becomes careless in his personal habits. Speech may suffer and it may appear meaningless and ends in isolated words or phrases. Agnosia and Apraxia may develop. Depending on the underlying cause, focal neurological defects may be seen.
It is based on clinical features.
Common forms of dementias
It is a progressive disease characterized by disturbances of intellectual functions and deterioration of cognitive functions. There is memory loss and disorientation in time and space.
Patient becomes careless and is unable to look after his dress and conduct. Speech becomes slurred and aphasic syndromes appear (constructional apraxia). Patient is unable to recognize friends and relatives. Hallucinations, delusions and symptoms of paraonia appear. There is difficulty in understanding complex commands. Seizures may occur.
As the movements become stereotyped, sucking reflex is elicitable. Preterminally patient looses weight, does not take interest in surroundings is confined to bed and is uncommunicative.
Alzheimers is a disease of middle age and the onset of disease is between 40-65 years of age. Pathologically there is diffuse degeneration of the cerebral cortex (Frontal, Parietal and temporal regions) involving all its layers. The brain is atrophic while the ventricles are dilated. Basal ganglia and cerebellum are not affected.
Histologically there are neurofibrillary tangles and profusion of senile plaques in the cortex. An abnormal phosphorylated form of micro tubule protein, called ‘tau’, is a major component of these intraneural fibrillary tangles.
Diagnosis is mainly clinical. CT scan and MRI shall show cortical atrophy. Average course of the disease is from 5-13 years. Terminally patient dies of intercurrent pulmonary infections.
Showing Diagnostic criteria for dementia
1. Impaired short and long term memory,
2. Other cognitive disturbances must be present.
3. Impaired abstract thinking.
4. Impaired judgement
5. Personality changes
6. Other cognitive defects (Aphasia, Apraxia, agnosia, constructional impairment).
7. Impairment which significantly interferes with occupational or social functions.
8. Delirium excluded as the sole aetiology.
9. An organic disorder is etiological related or no functional disturbances such as major depression is etiologically related.
(Adapted from Ou, B.R. (1996).
Causes Of Dementia
1 Primary dementia
(a) Alzheimer’s disease
(b) Picks disease
(c) Frontal lobe degeneration
2. Dementia due to vascular causes (a) Cerebral arterior sclerosis
(b) Multi-infarct dementia
3. Chronic infections of CNS
(b) Human immunodeficiency disease (HIV)
(c) Slow viral infections (subacute scierosing panencephalitis, subacute spongiform encephalopathy)
(d) Tubercular meningitis
(t) Fungal and protozoal infection
(g) Whipple’s disease
(h) Demyelenating disorders (multiple sclerosis, progressive multifocal leukoencepholopathy)
4. Degenerative disorders
(a) Hereditary ataxias
(b) Huntigton’s chorea
(c) Parkinson’s disease
5. Epilepsy. Tuberose sclerosis
6. Intracranial tumors
7. Acute head injury
8. Endocrine disorders
(b) Adrenal insufficiency
(c) Cushing’s syndrome
(d Hypo- and hyperparathyroidism 9. Defeciency stats
(a) Thiamine deficiency (ben-ben)
(b) Pellagra (nicotinic acid deficiency)
(c) Vitamin 812 deficiency
10. Toxic damage to the brain
(a) Alcoholic dementia
(b) Lead, mercury, manganese poisoning
(c) Drugs and narcotic poisoning
(d) Dementia following dialysis
11. Psychiatric disorders
(b) Korsakoff’s psychosis
12. Metabolic disorders
(a) Cardiopulmonary hypoxia
(b) Chronic renal failure
(c) Chronic liver cell failure.
Picks disease (Circumscribed cortical atrophy)
It resembles Alzheimers and generally begins at the age of 50-60 years. Females are affected more than males. There is circumscribed frontotemporal lobe atrophy involving the three cortical layers. Senile plaques and intraneural fibrils are absent.
Clinically patient presents with personality changes, progressive dementia (Personality and emotional changes, lack of restraint, poor social conduct). At first patient is voluble, euphoric with involvement of abstract intellectual functions. Later patient becomes apathetic, mentally dull and speech is reduced to a few stereotyped words and phrases. Treminally patient becomes bed ridden and looses weight.
It is as a result of multiple infarcts in the brain due to vascular cause. The onset of the disease is sudden and there is often previous history of stroke. There is fluctuation in clinical course of the disease.
Hypertension and history of transient, ischemic attacks is elicitable. There may be localizing signs depending on which part of the brain is involved in stroke / infarct (sensory/motor aphasia, constructional apraxia Hemiparesis). There is relative preservation of personality and emotional liability.
Multi in fact dementia can result from all type of cerebral vascular disease. The infarcts may be of lacunar variety, embolic or thrombotic variety. Repeated infarcts in the cortical or subcortical areas may cause intra and inter hemispheric disconnections. This may be responsible for the production of dementia.
Chronic infections. Chronic infections of the CNS due to fungal, bacterial tubercular or syplilis may be important causes of cerebral involvement with resultant neurological deficit and cognitive impairment. Toxoplasmosis can produce a fulminating meningo-encephalitis with delirium stupor and seizures.
Human immuno deficiency virus infection is an important cause of dementia in young adults. It consists of intellectual decline, impaired speech, personality and behavior disturbances. Slow virus infections in children and young adults (subacute sclerosing panencephalitis), cause dementia and are an important cause.
Neoplasia and Mass lesions
Primary or secondary brain tumors especially in the frontal and temporal lobe, particularly the slow growing are known to produce dementia syndrome (amnesia, confusion, personality disorders). Frontal meningiomas are the most important to consider.
Cases with chronic subdural haematoma due to a minor trauma, often forgotten, may present with cognitive or personality changes. Malignancy arising outside nervous system may progressively cause psychiatric disturbances (metastatic or paraneoplastic encephalitis). Diagnosis is made by CT/MRI.
Collagen vascular disease
Diffuse CNS involvement (delirium, seizures, psychosis) may result due to collagen disorders (SLE, Temporal arteritis, Rheumatoid vasculitis, sarcoidosis).
Hypothyroidism is the most important cause of dementia in elderly people. The changes include irritability, hallucinations, paranoia and diminished attention.
Thyrotoxicosis produces irritability, lethargy or depression and may be an apathetic state.
Various nutritional deficiency states ranging from Thiamine, Nicotinic acid, Folate and Vit B12 deficiency. Produce various states of confusion, delirium and dementia.
Intoxicants may produce confusional states and these include various forms of substances abused. Alcohol is an important toxic substance. Chronic alcoholism leads to intellectual impairment, and dementia (Korsakoffs psychosis).
Various drugs especially in elderly are known to produce all types of psychiatric disorders ranging from confusional states to dementia. The commonly used drugs in this are tricyclic anti-depressants, lithium, Bromides, Neuroleptics, Bromocriptine, anticholinergic agents, diuretics, methyldopa and propanolol. Dementia in this group is reversible if the drug is with drawn.
Psychiatric disorders producing dementia. This group includes depressive dementia (pseudo dementia) schizophrenia mania etc.
In all cases of dementia, neuropsychological tests be done to exclude other causes responsible for psychiatric disturbances and to document intellectual decline. Blood counts, serum electrolytes, Blood sugar, Blood urea. Thyroid function tests (T3, T4, TSH) X-ray chest (PA view) be done in every cases.
EEG is an important test. It may show features to support the diagnosis of Alzheimers disease.
CSF exam may be done to exclude any inflammatory disease.
CTIMRI are important to diagnose cortical atrophy, ventricular dilatation and to exclude any intracranial pathology (Tumour I Secondaries).
Regional cerebral blood flow studies may be useful in differentiating between frontal lobe dementias and Alzheimers disease. Brain Biopsy is rarely done except when a treatable tumour is suspected.
In a small percentage of cases of dementia a treatable cause is operative. A mildly dementic patient may lead a normal life. But severety dementic patients, require careful management. Many suffer from sleeplessness and shall require some type of sedative I tranquilizer. Care should be taken of nutritional needs, electrolyte disturbancs and bladder functions. Therapeutics shall vary as per the aetiology of dementia.