An unusual bifurcation of sciatic nerve deep to Piriformis: Case report with review of literature

Abstract

Sciatic nerve, the thickest nerve in the body, is formed in the pelvis from the sacral plexus. It is comprised of both anterior and posterior divisions of fourth lumbar to third sacral spinal nerves [1]. Having left the pelvis through the greater sciatic foramen, it courses beneath the piriformis and enters the gluteal region. Then it travels over the gamelli, obturator internus and quadratus femoris and descends vertically midway between greater trochanter and ischial tuberosity [1]. During its course in the posterior compartment of the thigh, it divides into tibial and common peroneal nerves. This division is observed to occur usually a hands breath above the knee joint [1]. However, numerous variations have been reported with regard to its course and divisions. Clinical consequences such as entrapment syndromes and failure of regional nerve blocks are known to be associated with variant courses and divisions [2, 3]. Bilateral division of the sciatic nerve deep to the piriformis muscle and a variant course of its common peroneal branch seen on a cadaver is discussed.