title: Cervical vestibular-evoked myogenic potential in vestibular schwannoma after gamma-knife surgery.
abstract: OBJECTIVE
  Gamma-knife radiosurgery (GKS) for vestibular schwannomas (VSs) has become popular during the last two decades, and a promising tumor control rate has been reported. Therefore, the evaluation and preservation of auditory-vestibular nerve function after GKS have become more and more important in these patients with long-term survival. We have traditionally used pure-tone audiometry (PTA) for evaluation of auditory nerve function, and the caloric test for superior vestibular nerve function. Vestibular-evoked myogenic potential (VEMP) has recently emerged from various neurophysiological examinations for assessment of the integrity of the inferior vestibular nerve function. This novel tool has been established to represent a sacculo-collic reflex. By using these three tools, the auditory-vestibular nerve function of VS patients can be evaluated and monitored before and after GKS.
  
  
  METHODS
  Fourteen patients with unilateral VS that underwent GKS were prospectively recruited. All of them received a battery of auditory-vestibular function tests including PTA, caloric, and cVEMP tests before and after GKS at each time point (1, 6, and 12 months). Our data also included the tumor volumes and their relationship with the PTA, caloric, and cVEMP test results.
  
  
  RESULTS
  The PTA, caloric, and cVEMP tests showed abnormal results before GKS in 85.7%, 78.6% and 78.6% of our VS patients, respectively. The PTA, caloric, and cVEMP results did not show strong correlations between each other. However, there was a tendency that when the tumor grew larger, the auditory-vestibular function deficits became more severe. The PTA and cVEMP test results remained stable during the 1-year follow-up after GKS. However, the caloric test showed transient deterioration at the 6th month follow-up, which then recovered by the 1-year follow-up.
  
  
  CONCLUSIONS
  The combination of these three tests can help us diagnose VS and assess the change in auditory-vestibular nerve function during the post-GKS follow-up period. The results of these three tests were independent for smaller tumors, but all tests may show abnormal findings with larger tumors. Although the study is still ongoing, the preliminary data showed that GKS treatment would not affect the auditory-vestibular nerve function within a 1-year follow-up period.
authors: Department of Otolaryngology, Taipei Veterans General Hospital, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Yi-Fang
authors: YF
authors: Lee
authors: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Cheng-Chia
authors: CC
authors: Lee
authors: Department of Otolaryngology, Taipei Veterans General Hospital, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Mao-Che
authors: MC
authors: Wang
authors: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Kang-Du
authors: KD
authors: Liu
authors: Department of Radiology, Taipei Veterans General Hospital, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Hsiu-Mei
authors: HM
authors: Wu
authors: Department of Radiology, Taipei Veterans General Hospital, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Wan-Yuo
authors: WY
authors: Guo
authors: Department of Otolaryngology, Taipei Veterans General Hospital, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: An-Suey
authors: AS
authors: Shiao
authors: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: David Hung-Chi
authors: DH
authors: Pan
authors: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Wen-Yuh
authors: WY
authors: Chung
authors: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan. Electronic address: doc3379b@gmail.com.
authors: Sanford P C
authors: SP
authors: Hsu
mesh_terms: D000328:Adult; D000368:Aged; D001301:Audiometry, Pure-Tone; D002150:Caloric Tests; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D011446:Prospective Studies; D016634:Radiosurgery / Q000379:methods*; D016896:Treatment Outcome; D047368:Tumor Burden; D058585:Vestibular Evoked Myogenic Potentials / Q000502:physiology*
keywords: Caloric test; Gamma-knife; Radiosurgery; Vestibular evoked myogenic potential; Vestibular schwannoma