Recognizing schwannomatosis and distinguishing it from neurofibromatosis type 1 or 2.
BACKGROUND
Schwannomatosis has become a newly recognized classification of neurofibromatosis. Although the genetic loci are on chromosome 22, it lacks the classic bilateral vestibular schwannomas as seen in NF-2. We present the surgical treatment of 4 patients with schwannomatosis, including a brother and sister.


METHODS
Case 1 presented with multiple progressively enlarging peripheral nerve sheath tumors. Case 4 presented with a trigeminal schwannoma and a vagal nerve schwannoma. Three of 4 patients had spinal intradural, extramedullary nerve sheath tumors. Surgery in all was multistaged and consisted of spinal laminectomies, site-specific explorations, and microsurgical tumor dissection and resection, with intraoperative neurophysiologic monitoring (including somatosensory-evoked and motor-evoked potentials, upper extremity electromyography and intraoperative nerve action potential monitoring, as appropriate).


RESULTS
Intraoperatively the schwannomas had cystic and solid features and in all surgical cases the tumors arose from discrete fascicles of sensory nerve roots or sensory peripheral nerve branches. None of the patients experienced neurologic worsening as a result of their resections. Pathologic analysis of specimens from all cases demonstrated schwannoma.


CONCLUSIONS
Not all patients with multiple schwannomas of cranial nerve, spinal nerve root, or peripheral nerve origin have NF-1 or NF-2. In schwannomatosis, these lesions are present in the absence of cutaneous stigmata, neurofibromas, vestibular schwannomas, or parenchymal brain tumors. Schwannomas in schwannomatosis can be large, cystic, and multiple. However, the predominant nerve involvement seems to be sensory and discrete fascicular in origin, facilitating microsurgical resection with minimal deficit.
Westhout
Franklin D
FD
Department of Neurological Surgery, School of Medicine, University of California Irvine, 101 The City Drive South, Orange, CA 92868, USA.
Mathews
Marlon
M
Paré
Laura S
LS
Armstrong
William B
WB
Tully
Patricia
P
Linskey
Mark E
ME
D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009423:Nervous System Neoplasms / Q000175:diagnosis* / Q000235:genetics; D009442:Neurilemmoma / Q000175:diagnosis* / Q000235:genetics; D017253:Neurofibromatoses / Q000175:diagnosis* / Q000235:genetics