Multiple schwannomas of bilateral posterior tibial nerves - A case report and review of literature

Introduction: Schwannoma is a type of slow growing benign nerve sheath tumor arising from Schwann cells. Peripherally, they are found in association with the ulnar, sciatic and posterior tibial nerves. Peripheral schwannomas, neurofibromas and malignant PNSTs are collectively grouped as peripheral nerve sheath tumors. Presentation of case: We report a case of a 35-year-old male, without clinical features of NF2, presenting with 2 painful lumps around the ankle, and was incidentally found to have multiple lumps in both lower limbs. MR imaging, surgical excision and histology revealed multiple bilateral posterior tibial nerve schwannomas. Discussion: Schwannomas usually occur as a solitary mass or sometimes multiple. Multiple schwannomas are seen in association with type 2 neurofibromatosis and Schwannomatosis. Schwannomatosis is a separate clinical entity with considerable overlap both in phenotype and presentation with NF2 but that can be distinguished from NF2 based on clinical diagnostic criteria. Peripheral schwannoma is a differential diagnosis for painful lumps with positive Tinel's sign in close association to peripheral nerves, mainly posterior tibial, sciatic and ulnar nerve. Surgical excision can be safely performed with preservation of the nerve using meticulous technique. Conclusion: Schwannomas of the posterior tibial nerve (PTN) and its medial and lateral plantar branch have been described as a cause of tarsal tunnel syndrome and foot pain. Although multiple reports of solitary PTN schwannomas exist, only 4 cases of multiple PTN schwannomas have been reported in literature, with no reports of cases involving bilateral PTN.