An unusual variation in the formation and termination of the sciatic nerve - a case report

Abstract

The sciatic nerve (SN) presented with unusual patterns in which five smaller fibers instead of one or two nerves at the level of the Piriformis muscle. Those five fibers measured 7.5 cm from their origin to where they joined to form the SN. The SN terminated in the popliteal fossa by giving rise to three terminal branches: the tibial nerve, the common peroneal nerve, and another unusual nerve that supplied the medial head of the gastrocnemius. This case is unusual because the SN presents with different positional variations of its two components in relation to the piriformis muscle but not five fibers; in addition, the SN normally bifurcates instead of trifurcating when it reaches in the popliteal fossa. The case presented a Type A pattern of SN to the piriformis muscle. This type of pattern has been documented to be the most common in some parts of Africa. Some authors have reported two patterns of trifurcation of the SN. One is a pattern where the SN gave rise to the tibial, superficial, and deep peroneal nerves at the popliteal fossa, and another is a trifurcation pattern where it gave rise to the tibial, common peroneal, and sural nerves. The case is different as it presents an unusual unreported pattern where the SN trifurcates by giving rise to the tibial, common peroneal, and nerve that supplies the medial head of the gastrocnemius muscle. The current variation has never been reported elsewhere.