It refers to inflammation of the arachnoid membrane leading to fibrous thickening and adhesion formation which compresses upon the spinal nerve roots. Cysts may form containing cerebrospinal fluid. Rarely the adhesion bound down the spinal cord.
Arachnoiditis usually follows operation on the spinal cord or after instillation of radio graphic dyes (Myodil) antibiotics or chemicals into sub arachnoid space. It may follow meningococcal infection, lymphocytic choriomeningits, syphilis or spinal trauma. Tuberculous pachymeningitis may occur as a result of spread of infection from tuberculous osteitis.
It is a slow growing process. In period spread over months to years, the cyst or contracting membrane puts pressure on the cord and nerve roots. In acute cases there may be slight fever.
Bilateral asymmetrical limb pain in the distribution of nerve roots is the most important feature.Although adhesive arachnoiditis interferes with the functioning of the spinal cord, signs of cord compression may develop late.
Root pains may be predominant. Muscular wasting may occur corresponding to the site of compression. The tract signs are limited to gradual increasing spasticity of the limbs with level of sensory loss.
Root compression may produce reflex loss and these radicular symptoms are prominent feature of arachnoiditis though arachnoiditis may not be commonly responsible for cord compression.
Typical clinical picture of root pains and pain in lumbar region shall be suggestive of spinal arachnoiditis especially when there is history of either fever or spinal surgery. Lumbar puncture may reveal partial or complete obstruction. Myelography will show typical ‘Candle on end’ appearances.
Surgical treatment is the main line of approach. Laminectomy is performed and if a cyst is present there it is removed. Many times there, are multiple cysts which have to be tackled.
If adhesion are present these may be carefully removed and nerve roots separated. In some cases there may be exacerbation of symptoms as the whole process may recur and progress due to formation of adhesion.