title: Incidence of high-frequency hearing loss after microvascular decompression for hemifacial spasm.
abstract: OBJECTIVE
  The primary aim of this study was to evaluate the incidence and discuss the pathogenesis of high-frequency hearing loss (HFHL) after microvascular decompression (MVD) for hemifacial spasm (HFS).
  
  
  METHODS
  Preoperative and postoperative audiogram data and brainstem auditory evoked potentials (BAEPs) from 94 patients who underwent MVD for HFS were analyzed. Pure tone audiometry at 0.25-2 kHz, 4 kHz, and 8 kHz was calculated for all individuals pre- and postoperatively ipsilateral and contralaterally. Intraoperative neurophysiological data were reviewed independently. An HFHL was defined as a change in pure tone audiometry of more than 10 dB at frequencies of 4 and 8 kHz.
  
  
  RESULTS
  The incidence of HFHL was 50.00% and 25.53% ipsilateral and contralateral to the side of surgery, respectively. The incidence of HFHL adjusted for conductive and nonserviceable hearing loss was 26.6% ipsilaterally. The incidence of HFHL at 4 and 8 kHz on the ipsilateral side was 37.23% and 45.74%, respectively, and it was 10.64% and 25.53%, respectively, on the contralateral side. Maximal change in interpeak latency Waves I-V compared with baseline was the only variable significantly different between groups (p < 0.05). Sex, age, and side did not increase the risk of HFHL. Stepwise logistic regression analysis did not find any changes in intraoperative BAEPs to increase the risk of HFHL.
  
  
  CONCLUSIONS
  High-frequency hearing loss occurs in a significant number of patients following MVD surgery for HFS. Drill-induced noise and transient loss of CSF during surgery may impair hearing in the high-frequency ranges on both the ipsilateral and contralateral sides, with the ipsilateral side being more affected. Changes in intraoperative BAEPs during MVD for HFS were not useful in predicting HFHL. Follow-up studies and repeat audiological examinations may be helpful in evaluating the time course and prognosis of HFHL. Prospective studies focusing on decreasing intraoperative noise exposure, as well as auditory shielding devices, will establish causation and allow the team to intervene appropriately to decrease the risk of HFHL.
authors: Department of Neurological Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors: Tingting
authors: T
authors: Ying
authors: Parthasarathy
authors: P
authors: Thirumala
authors: Aalap
authors: A
authors: Shah
authors: Tara
authors: T
authors: Nikonow
authors: Kelley
authors: K
authors: Wichman
authors: Maura
authors: M
authors: Holmes
authors: Barry
authors: B
authors: Hirsch
authors: Yuefang
authors: Y
authors: Chang
authors: Paul
authors: P
authors: Gardner
authors: Miguel
authors: M
authors: Habeych
authors: Donald J
authors: DJ
authors: Crammond
authors: Lois
authors: L
authors: Burkhart
authors: Michael
authors: M
authors: Horowitz
authors: Jeffrey
authors: J
authors: Balzer
mesh_terms: D000328:Adult; D001299:Audiometry; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005260:Female; D006316:Hearing Loss, High-Frequency / Q000453:epidemiology* / Q000209:etiology* / Q000503:physiopathology; D019569:Hemifacial Spasm / Q000601:surgery*; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D061145:Microvascular Decompression Surgery / Q000009:adverse effects* / Q000379:methods*; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome