title: Reduction in high-frequency hearing loss following technical modifications to microvascular decompression for hemifacial spasm.
abstract: OBJECTIVE
  Microvascular decompression is a safe and effective procedure to treat hemifacial spasm, but the operation poses some risk to the patient's hearing. While severe sensorineural hearing loss across all frequencies occurs at a low rate in experienced hands, a recent study suggests that as many as one-half of patients who undergo this procedure may experience ipsilateral high-frequency hearing loss (HFHL), and as many as one-quarter may experience contralateral HFHL. While it has been suggested that drill-related noise may account for this finding, this study was designed to examine the effect of a number of techniques designed to protect the vestibulocochlear nerve from operative manipulation on the incidence of HFHL.
  
  
  METHODS
  Pure-tone audiometry was performed both preoperatively and postoperatively on 67 patients who underwent microvascular decompression for hemifacial spasm during the study period. A change of greater than 10 dB at either 4 kHz or 8 kHz was considered to be HFHL. Additionally, the authors analyzed intraoperative brainstem auditory evoked potentials from this patient cohort.
  
  
  RESULTS
  The incidence of ipsilateral HFHL in this cohort was 7.4%, while the incidence of contralateral HFHL was 4.5%. One patient (1.5%; also included in the HFHL group) experienced an ipsilateral nonserviceable hearing loss.
  
  
  CONCLUSIONS
  The reduced incidence of HFHL in this study suggests that technical modifications including performing the procedure without the use of fixed retraction may greatly reduce, but not eliminate, the occurrence of HFHL following microvascular decompression for hemifacial spasm.
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Parthasarathy
authors.initials: P
authors.lastname: Thirumala
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Frederickson
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Balzer
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Donald
authors.initials: D
authors.lastname: Crammond
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Miguel E
authors.initials: ME
authors.lastname: Habeych
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Yue-Fang
authors.initials: YF
authors.lastname: Chang
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Raymond F
authors.initials: RF
authors.lastname: Sekula
mesh_terms: D005260:Female; D006316:Hearing Loss, High-Frequency / Q000209:etiology* / Q000517:prevention & control*; D019569:Hemifacial Spasm / Q000601:surgery*; D006801:Humans; D008297:Male; D061145:Microvascular Decompression Surgery / Q000009:adverse effects* / Q000379:methods*; D008875:Middle Aged; D012189:Retrospective Studies
keywords: BAEP = brainstem auditory evoked potential; HFHL = high-frequency hearing loss; HFS = hemifacial spasm; MVD = microvascular decompression; SNHL = sensorineural hearing loss; SPL = sound pressure level; hearing loss; hemifacial spasm; microvascular decompression; surgical technique