title: Cerebellar retraction and hearing loss after microvascular decompression for hemifacial spasm.
abstract: BACKGROUND
  This retrospective study evaluated the length of cerebellar retraction and the changes of intraoperative brainstem auditory evoked potential (BAEP) during microvascular decompression (MVD), and assessed the predictive value of the hearing loss as a prognostic indicator for the treatment outcome of hemifacial spasm (HFS).
  
  
  METHODS
  This series included 1,518 consecutive patients affected with HFS who underwent MVD, during which BAEP was monitored. Patients were divided into two groups based on whether hearing loss occurred following decompression or not. Each patient underwent a similar procedure performed by one neurosurgeon. The two patients groups were matched with regard to sex, age, and degree of spasm.
  
  
  RESULTS
  Among the 1,518 patients, 106 (6.98 %) displayed functional hearing changes. Hearing loss was permanent in 12 patients (0.79 %). Of the 1,412 patients with stationary hearing compared with preoperative audiometry, 96 patients were selected who were individually matched with respect to sex, age, and degree of spasm. BAEP changed immediately after cerebellar retraction in 7 of 12 hearing-loss patients, suggesting the importance of retraction on hearing outcomes. The distance from the cerebellar surface of the petrous temporal bone to the neurovascular compression point was measured. The median distance of cerebellar retraction in the hearing-loss group was 13.77 mm, which was longer than the median distance in the control group.
  
  
  CONCLUSIONS
  Preoperative measurement of the cerebellar retraction distance can be a valuable clue to predict and prevent postoperative hearing loss in MVD for HFS.
authors.affiliation: Department of Neurosurgery, Samsung Medical Center, School of Medicine, Sungkyunkwan University, 81 Irwon-ro, Gangnam-gu, Seoul, 135-710, Korea.
authors.forename: Min Ho
authors.initials: MH
authors.lastname: Lee
authors.forename: Hyun Seok
authors.initials: HS
authors.lastname: Lee
authors.forename: Tae Keun
authors.initials: TK
authors.lastname: Jee
authors.forename: Kyung Il
authors.initials: KI
authors.lastname: Jo
authors.forename: Doo-Sik
authors.initials: DS
authors.lastname: Kong
authors.forename: Jeong A
authors.initials: JA
authors.lastname: Lee
authors.forename: Kwan
authors.initials: K
authors.lastname: Park
mesh_terms: D000328:Adult; D000368:Aged; D002531:Cerebellum / Q000601:surgery; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D034381:Hearing Loss / Q000175:diagnosis* / Q000209:etiology; D019569:Hemifacial Spasm / Q000601:surgery*; D006801:Humans; D008297:Male; D061145:Microvascular Decompression Surgery / Q000009:adverse effects* / Q000379:methods; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D011379:Prognosis; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult