Background: Cyclical sciatica due to implantation of endometrial tissue in the sciatic nerve in the region of the sciatic notch is a very unusual cause of sciatica. It occurs in women of childbearing age, as episodes of pain in the distribution of the sciatic nerve, which present in a cyclic manner and coincide with menstruation. If it is not treated, a sensomotor mononeuropathy of the sciatic nerve develops.

Methods: The patient had complained of right-sided sciatic pain from the age of 36 years. Over the years a motor deficit had slowly and progressively appeared causing foot drop. The painful crises were related to her menstrual periods. At the age of 44 years a pyramidal muscle syndrome was diagnosed and treated surgically. This was followed by increase in the crises of sciatic pain. A year later, she started to have sciatic pain on the left side, which was similar to that of the right side. The clinical, imaging and electrophysiological findings are reported. The patient improved. She is still being treated with depot medroxyprogesterone and her pain has disappeared.

Conclusions: Cyclical sciatica due to endometriosis is little known and may lead to permanent disability. Computerized axial tomography of the pelvis using contrast material is very useful for diagnosis. The use of depot medroxyprogesterone seems to be a satisfactory treatment in some patients.