Schwannomas of the sciatic nerve: A rare and neglected diagnosis. A review of the literature with two illustrative cases

Objective: Schwannomas of the sciatic nerve, which is the largest nerve of the human body, are very rare accounting for ≤ 1% of all schwannomas. They often may raise confusion with other more common causes of sciatica, such as lumbar degenerative and inflammatory diseases or spinal tumors, which may often lead to a late correct diagnosis. Patients and methods: We present two cases of sciatic nerve schwannomas that were recently treated at our Institution, and we review the pertinent English literature on this topic over the last 15 years, yielding twenty three cases to analyze. Results: Even if sciatic nerve schwannomas are a rare occurrence, a thorough clinical and radiological evaluation of the sciatic nerve should be considered whenever a sciatic pain is not otherwise explained. A positive Tinel sign and a palpable mass along the course of the sciatic nerve may be strong clues to achieve the diagnosis. Combined morphological and advanced functional MRI imaging may help to differentiate benign from malignant peripheral nerve sheath tumors, avoiding unnecessary preoperative biopsy. Conclusions: A standard microsurgical technique guided by ultrasound and neurophysiologic monitoring, allows in most of the cases a safe removal of the tumor and very satisfactory post-operative results for the patients.