Electromyographic evidence of inferior gluteal nerve compromise: an early representation of recurrent colorectal carcinoma.

Lumbosacral or primary buttock pain and cutaneous anesthesia in the distribution of the posterior femoral cutaneous nerve were the initial symptoms in 5 patients later proven to have extensions of previously resected colorectal malignancy. The initial electromyographic impression of an inferior gluteal nerve mononeuropathy associated with recurrent neoplasia was confirmed by a positive colon biopsy in 1 case and widespread pelvic metastasis demonstrated at laparotomy in the 4 remaining cases. Four of the 5 patients also had increased levels of carcinoembryonic antigen. Roentgenographs and other laboratory data were otherwise normal in all 5 cases. Entrapment of the inferior gluteal nerve and the accompanying posterior femoral cutaneous nerves is facilitated by its medial, intrapelvic fixation at its origin from the sciatic nerve and the crowding effect of the piriformis muscle above, the dorsal rim of the sciatic notch behind and the inferior gluteal vessels and nodes below. The demonstration of hypestesia over the inferior lateral buttock and a concomitant history of colorectal malignancy should alter the examiner to the possible presence of an inferior gluteal nerve neuropathy.