[Sciatica secondary to extrapelvic endometriosis affecting the piriformis muscle. Case report]

We present a case report of symptomatic compression of the right sciatic nerve notch, secondary to piriformis muscle endometriosis, as well as a literature review.

We report the case of a 29-year-old woman with 2-year evolution of right chronic sciatica. During the first year, symptoms were episodic and associated with menstruation. During the second year, sciatica was constant and associated with gait disorder due to sciatic musculature weakness. Mononeuropathy was proved by a neurophysiological study, with MRI and PET studies revealing a mass in the sciatic notch and regional pathological increase in metabolic activity. Surgical treatment was performed in order to release the nerve and obtain a histological sample.

The patient was treated by a transgluteal approach, with external neurolysis of the sciatic nerve and resection of an old-blood cyst at the level of the piriformis muscle. This was subsequently reported as endometriosis by histological examination. The sciatica was resolved after surgery.

Extrapelvic sciatic nerve compression by adjacent endometriosis is very infrequent. Muscle denervation and lack of a histological diagnosis led to surgical exploration of the compression area in order to release the nerve, resect the cause of compression and obtain a definitive diagnosis. The procedure improved all symptoms.