Sciatic Nerve Intraneural Hematoma.

Intraneural hematomas are an uncommon cause of a focal mononeuropathy. When they do occur, it is usually in the setting of inherited or iatrogenic coagulopathies or as a consequence of injections targeting nerves. We report a man aged 68 years on warfarin therapy for a prior pulmonary embolism who presented with a 6-month history of progressive weakness of knee flexion and ankle movement, excruciating pain, and dense numbness in his posterior left thigh and below the knee, consistent with a severe high sciatic palsy. Imaging depicted a contiguous cystic mass of mixed T1 and T2 intensities involving the left sciatic nerve in the thigh, which was radiologically interpreted as a hip arthroplasty-associated pseudotumor. The patient underwent surgical exploration, which revealed a thick hemorrhagic pseudocompartment within the sciatic nerve. The histopathologic diagnosis was consistent with chronic hemorrhage. These impressive lesions should be included in the differential diagnosis of nerve masses.