A Linear Variant of Segmental Schwannomatosis Localized to the Upper Extremity.

Schwannomas represent benign peripheral nerve sheath tumors. Their phenotypic presentations in schwannomatosis and segmental schwannomatosis have been well described. To date, however, cases of schwannomatosis or multiple schwannomas localized to a single nerve fascicle have been limited in the literature.  In this study, we identify a case of a 48 year-old non-neurofibromatosis male who presented with symptomatic schwannomas localized to a single nerve fascicle of the upper extremity. Intraoperative exploration revealed four schwannomas arising from a 15-cm segment of ulnar nerve fascicle. Surgical excision was successful, without neurological deficit or recurrence.  This study identifies a case of schwannomatosis localized to a single nerve fascicle that may represent a linear variant of segmental schwannomatosis. The presentation may represent a temporary linear appearance in progression to "nonlinear" segmental variant; however, a molecularly distinct subset of schwannomas cannot be excluded.