Metrizamide myelography in conjoined lumbosacral nerve roots.

Conjoined lumbosacral nerve roots are a congenital anomaly found at 1% of lumbar disc operations. They are usually present at the L5-S1 level and may or may not be associated with herniated intervertebral discs. Previously it had been thought that the preoperative myelogram was not helpful in diagnosis but using metrizamide myelography the diagnosis should be made more often by observing: (a) an asymmetric subarachnoid space, (b) a common axillary pouch exiting between opposite upper and lower nerve root sheaths, (c) a widened axillary pouch, and (d) two or more individual nerve roots in the axillary pouch.