Conjoined lumbosacral nerve roots. Management of herniated discs and lateral recess stenosis in patients with this anomaly.

Anomalous L-5 and S-1 nerve roots occur infrequently. If not properly recognized, surgery for entrapment disorders may result in serious neural injury because of an improper surgical approach in exposure and in removing the underlying herniated discs. The diagnosis has been made preoperatively since the introduction of water-soluble myelography because of improved filling of the nerve roots. A herniated disc beneath the bifid root causes extreme pain and disability with marked signs of entrapment because of firm fixation of the conjoined root in the lateral recess between the two pedicles. An underlying herniated disc may not be recognized because of the unique anatomical changes. To properly identify the nature of the lesion, wide exposure by hemilaminectomy is preferred, with unroofing of the lateral recesses and wide foraminal decompression. Eight such patients are reported: seven had herniated discs, and one had lateral recess stenosis with superior facet entrapment. With adequate decompression, all patients made a rapid, uneventful recovery.