Polyradiculopathies from schwannomatosis.

We describe a case of schwannomatosis presenting as radicular pain and numbness in multiple radicular nerve distributions. There were multiple peripheral nerve tumors detected by magnetic resonance imaging (MRI) at the left vestibular nerve, cauda equina, right radial nerve, thoracic paraspinal nerve, and brachial plexi. Several resected tumors have features of schwannomas, including hypercellular Antoni A areas, hypocellular Antoni B areas, Verocay bodies, and hyalinized blood vessels. The specimens are also positive for immunohistochemical staining for INI1 with diffuse nuclear staining. The findings are consistent with sporadic form of schwannomatosis. This case highlights the importance of using MRI and INI1 immunohistochemistry to differentiate familial schwannomatosis, neurofibromatosis 2 (NF2)-associated schwannomatosis, and sporadic schwannomatosis.