title: Spinal accessory schwannoma mimicking a tumor of the fourth ventricle: case report.
abstract: OBJECTIVE
  Spinal accessory schwannomas unassociated with neurofibromatosis are very rare, and only 30 cases have been reported in the literature. To our knowledge, this is the first report of a spinal accessory schwannoma mimicking a tumor of the fourth ventricle.
  
  
  METHODS
  A 50-year-old man presented with neck pain after being involved in a motor vehicle accident. There were no neurological deficits, but a computed tomographic scan revealed a large hypodense mass with punctuate calcifications in the fourth ventricle. The tumor exhibited low intensity on the T1-weighted magnetic resonance imaging scan and high intensity on the T2-weighted scan, and it showed inhomogeneous contrast enhancement.
  
  
  METHODS
  The tumor was totally removed by a bilateral suboccipital craniectomy and C1 laminectomy. Dissection of the surgical specimen revealed that the tumor had originated from the left spinal accessory nerve. Histopathological examination confirmed the diagnosis of schwannoma. The patient experienced transient postoperative cerebellar ataxia but recovered completely.
  
  
  CONCLUSIONS
  Intracisternal-type spinal accessory schwannomas sometimes mimic a tumor of the fourth ventricle. Total surgical resection can be achieved with good outcome.
authors.affiliation: Department of Neurological Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan. Ryukurokaw@aol.com
authors.forename: Ryu
authors.initials: R
authors.lastname: Kurokawa
authors.forename: Masanao
authors.initials: M
authors.lastname: Tabuse
authors.forename: Kazunari
authors.initials: K
authors.lastname: Yoshida
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kawase
mesh_terms: D020436:Accessory Nerve Diseases / Q000473:pathology*; D002551:Cerebral Ventricle Neoplasms / Q000473:pathology*; D003390:Cranial Nerve Neoplasms / Q000473:pathology*; D003937:Diagnosis, Differential; D020546:Fourth Ventricle / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000473:pathology*