Interdural cyst of the lumbosacral region.

The purpose of this report is to call attention to the clinical, myelographic, and computed tomographic appearance of a very rare type of dural cyst within the lumbosacral spinal canal. We report this condition in three unrelated boys who presented with symptoms of cauda equina compression. Our experience suggests that these cysts are congenital in origin. Anatomically, the cyst wall consisted of a dura-like layer without arachnoid. There was a small ventral defect allowing incomplete communication with the compressed subarachnoid space. Cerebrospinal fluid-like fluid accumulated within the interdural cyst as a result of this communication. Treatment consisted of obliteration of the point of entry between cyst and subarachnoid space in all cases and partial cyst wall excision in one case. After operation, the two patients who had presented with long-standing sphincter disturbance had partial improvement in function and the child with a pain syndrome was completely relieved of symptoms.