title: The prevalence of "incidental" acoustic neuroma.
abstract: OBJECTIVE
  To estimate the prevalence of "incidental" acoustic neuromas (ANs) in the population at large.
  
  
  METHODS
  An intracranial magnetic resonance imaging (MRI) database of 46 414 patients presenting to the University of California, San Francisco (UCSF), without known audiovestibular complaints was searched retrospectively from July 1995 to February 2003. Seventy percent of these MRIs included gadolinium, and none was specifically targeted through the internal auditory canal. A medical chart review of 688 patients with acoustic neuromas presenting to UCSF between 1980 and 1999 was searched for sex distribution.
  
  
  METHODS
  Tertiary care university medical center.
  
  
  RESULTS
  Eight patients with incidental AN were discovered. This figure suggests that undiagnosed ANs may be present in at least 0.02% of the population. Three patients were found to have audiovestibular symptoms on inquiry after diagnosis. Audiometry revealed asymmetry at 4 kHz in only 3 of 7 patients, with an otherwise symmetric audiogram in the remaining patients. Tumor size in this population ranged from 3 to 28 mm. Incidental ANs were more common in men, but ANs were more common in women overall.
  
  
  CONCLUSIONS
  The prevalence of incidental AN appears to be roughly 2 in 10,000 people. This figure indicates that AN may be less prevalent than suggested in previously reported temporal bone studies and more prevalent than suggested by epidemiologic studies.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, USA.
authors.forename: Doris
authors.initials: D
authors.lastname: Lin
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Hegarty
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Fischbein
authors.forename: Robert K
authors.initials: RK
authors.lastname: Jackler
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002140:California / Q000453:epidemiology; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000175:diagnosis* / Q000453:epidemiology*; D015995:Prevalence; D011379:Prognosis; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution; D015996:Survival Rate