Obliterative arachnoiditis complicating lumbar spinal stenosis.

The authors report five patients with spinal stenosis who had a total myelographic block at the level of the obliterated subarachnoid space. Arachnoiditis had not been considered as a primary diagnosis until laminectomy revealed a non-pulsating, thickened dural sac that conformed to the internal configuration of the involved spinal canal. Two patients had stenosis complicated by spondyloarthrosis over multiple lumbar levels, one had a previous spinal fusion, another had degenerative spondylolisthesis, and the fifth had a large midline extruded disc at L2-3 that completely blocked the spinal canal. The dura was opened in two patients, confirming the lesion. Despite obliteration of the subarachnoid space, significant relief for approximately 1 year followed decompressive laminectomy, foraminotomy, and discectomy, with disappearance of neurogenic claudication in three patients. Postoperative erect films showed no caudad passage of contrast. While further observations are required, an awareness of this complication of spinal stenosis is important in the diagnosis and management of such patients and in evaluating their ultimate prognosis.