Sciatic neuropathy at the popliteal fossa: clinical, ultrasonographic and computed tomographic diagnosis.

A 22-year-old female had been suffering from sciatica-like pain in the left leg for four years. Clinical findings strongly directed further investigations to the popliteal fossa. Ultrasonography located a hypoechogenic mass in the upper lateral popliteal space. Guided by these data, computerized tomography (CT) with vertical reconstructions made the tentative diagnosis of a common peroneal nerve tumor, which was confirmed at operation. Microscopic examination showed a neurinoma of the mixed neurilemmoma-neurofibroma type. In the presence of atypical features of sciatica, a high index of suspicion seems advisable. Emphasis is laid on the complementary contribution of ultrasonography and CT in this type of ill-defined lower limb pain.