142 - Posterior Femoral Cutaneous Nerve Block: Subgluteal Approach

Abstract

Clunealgia is caused by compression of the posterior femoral cutaneous nerve and its branches, the perineal and inferior cluneal nerves. The posterior femoral cutaneous nerve is often entrapped along with the sciatic nerve by the piriformis muscle as the nerves both pass through the sciatic notch. When the sciatic nerve is entrapped by the piriformis muscle, it is called piriformis syndrome, and when the posterior femoral cutaneous nerve is entrapped by the piriformis muscle, it is called clunealgia. Clunealgia manifests clinically as pain, numbness, and paresthesias in the distribution inferior posterior buttocks and posterior thigh, with the portions of the posterior labia and scrotum sometimes affected. The symptoms of entrapment of clunealgia usually begin after direct trauma to the posterior femoral cutaneous nerve as it passes through the sciatic notch or along its downward path. Prolonged sitting or repeated pressure on the nerve and its branches may cause the symptoms of clunealgia. Rarely, pathologic elements including occult tumors, aneurysms of the inferior gluteal artery, and ganglion cysts in this anatomic area can also compress the posterior femoral cutaneous nerve, as well as the sciatic nerve as it passes through the sciatic notch, and produce symptoms. Piriformis muscle anomalies or abnormalities of the posterior femoral cutaneous nerve can also result in compression of the nerve, as can acute injury to the nerve as it passes through, over, or under the piriformis muscle.