title: Long-term results for trigeminal schwannomas treated with gamma knife surgery.
abstract: OBJECTIVE
  Surgical resection is considered the desirable curative treatment for trigeminal schwannomas. However, complete resection without any complications remains challenging. During the last several decades, stereotactic radiosurgery (SRS) has emerged as a minimally invasive treatment modality. Information regarding long-term outcomes of SRS for patients harboring trigeminal schwannomas is limited because of the rarity of this tumor. The aim of this study was to evaluate long-term tumor control and functional outcomes in patients harboring trigeminal schwannomas treated with SRS, specifically with gamma knife surgery (GKS).
  
  
  METHODS
  Fifty-three patients harboring trigeminal schwannomas treated with GKS were evaluated. Of these, 2 patients (4%) had partial irradiation of the tumor, and 34 patients (64%) underwent GKS as the initial treatment. The median tumor volume was 6.0 cm(3). The median maximum and marginal doses were 28 Gy and 14 Gy, respectively.
  
  
  RESULTS
  The median follow-up period was 98 months. On the last follow-up image, 7 patients (13%) had tumor enlargement, including the 2 patients who had partial treatment. Excluding the 2 patients who had partial treatment, the actuarial 5- and 10-year progression-free survival (PFS) rates were 90% and 82%, respectively. Patients with tumors compressing the brainstem with deviation of the fourth ventricle had significantly lower PFS rates. If those patients with tumors compressing the brainstem with deviation of the fourth ventricle are excluded, the actuarial 5- and 10-year PFS rates increased to 95% and 90%, respectively. Ten percent of patients had worsened facial numbness or pain in spite of no tumor progression, indicating adverse radiation effect.
  
  
  CONCLUSIONS
  GKS can be an acceptable alternative to surgical resection in patients with trigeminal schwannomas. However, large tumors that compress the brainstem with deviation of the fourth ventricle should be surgically removed first and then treated with GKS when necessary.
authors.affiliation: Department of Neurosurgery, Gamma Knife Center, Komaki City Hospital, Komaki, Japan. Electronic address: h-toshi@komakihp.gr.jp.
authors.forename: Toshinori
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Takenori
authors.initials: T
authors.lastname: Kato
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Iizuka
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kida
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001933:Brain Stem; D003251:Constriction, Pathologic / Q000150:complications / Q000601:surgery; D003390:Cranial Nerve Neoplasms / Q000150:complications / Q000473:pathology / Q000601:surgery*; D018450:Disease Progression; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D005720:Gamma Rays / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000150:complications / Q000473:pathology / Q000601:surgery*; D016634:Radiosurgery / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D016879:Salvage Therapy / Q000379:methods; D013997:Time Factors; D017211:Treatment Failure; D016896:Treatment Outcome; D020433:Trigeminal Nerve Diseases / Q000150:complications / Q000473:pathology / Q000601:surgery*; D047368:Tumor Burden; D055815:Young Adult