Suggested pathological basis of "redundant nerve root syndrome" of the cauda equina.

A clinical entity described as "redundant nerve root syndrome" of the cauda equina is reviewed. Eighteen reported cases with typical gross features are analyzed. Considerable speculation has existed regarding the pathogenesis of this syndrome, chiefly because the involved nerve root was not biopsied in the majority of instances. In one reported case, when the redundant root was examined histologically, a plexiform neurofibroma was found to be the cause of the thickening and redundancy of the nerve. In the case presented here, the enlarged nerve roots were part of a malignant plexiform neurofibroma with a short clinical course, and the tumor led to the death of the patient. It is suggested that biopsy of the involved nerve root is crucial in establishing the definitive diagnosis.