DOES DEGENERATIVE DISEASE OF THE LUMBAR SPINE CAUSE ARACHNOIDITIS - AMAGNETIC-RESONANCE STUDY AND REVIEW OF THE LITERATURE

The magnetic resonance appearances in 165 patients with symptoms sugge stive of degenerative lumbar spine disease were reviewed. The aim of t he study was to evaluate the relationship between abnormalities of ner ve root distribution and degenerative disease of the lumbar spine in t he absence of other known risk factors for arachnoiditis. Central clum ping of nerve roots was present in 16 patients (9.7%) and was associat ed with spinal stenosis at one of the affected levels in all (p < 0.00 1). Spinal stenosis was present in 44 patients giving an incidence of abnormal nerve root distribution of 36% in this group. Nerve root clum ping occurred in association with pure spinal stenosis (10 cases), ste nosis secondary to disc prolapse (four cases) and degenerative spondyl olisthesis (two cases). Nerve root clumping was confined to one verteb ral level in nine cases and extended over two to four levels in seven. In five of the latter spinal stenosis was present at multiple levels. The appearance of nerve root clumping described here may result entir ely from mechanical apposition of nerve roots but is indistinguishable from the central pattern of nerve root adhesions which occurs in adhe sive lumbar arachnoiditis. No abnormalities of nerve root distribution were seen in association with any indicator of degenerative disk dise ase in the absence of stenosis. We have been unable to demonstrate the previously reported relationship between lumbar disk degeneration and arachnoiditis and discuss this with a critical review of the literatu re. Abnormal central clumping of nerve roots as described in arachnoid itis may occur in association with spinal stenosis in the absence of o ther risk factors although the cause for this appearance remains unexp lained. Arachnoiditis-like changes extending over more than one verteb ral level are rare (7%) except in the presence of spinal stenosis at m ultiple levels (29%). Awareness of this appearance may avoid a possibl y incorrect diagnosis of arachnoiditis in the presence of a treatable stenosis.