title: Mid-frequency sensorineural hearing loss: aetiology and prognosis.
abstract: OBJECTIVE
  An audiometric finding of mid-frequency sensorineural hearing loss (MFSNHL), or a U-shaped pattern, is uncommon. The objective of this study is to investigate the aetiology and prognostic significance of MFSNHL.
  
  
  METHODS
  Tertiary academic referral centre-based retrospective case review and review of audiograms to determine the prevalence of this audiometric finding.
  
  
  METHODS
  Patients with a pure tone threshold average at 1, 2, and 4 kHz at least 10 dB greater than the average at 0.5 and 8 kHz were included in this study; 35 patients met these criteria. The mean age of the patients was 34.6 years old (range 4-71 years). Twelve patients (33 per cent) were under 18 years of age. Serial audiograms were obtained for 14 patients. The notes were reviewed for any pertinent otologic history, subsequent diagnoses, management and disease course.
  
  
  RESULTS
  The prevalence of MFSNHL in this practice setting is less than 1 per cent. The average hearing threshold in the mid-frequencies was 44 dB, which was 17 dB and 20 dB lower than at 0.5 Hz and 8 kHz, respectively. The pure tone average (0.5, 1, 2 kHz) was 40 dB. Sixteen patients (44 per cent) required amplification. Of all patients, 22 had hereditary hearing loss, eight had idiopathic hearing loss, and five adults had vestibular schwannomas.
  
  
  CONCLUSIONS
  MFSNHL is an infrequent audiometric finding. The great majority of these cases are of presumed hereditary or idiopathic aetiology, although 22 per cent of adults had vestibular schwannomas. This series presents the causes and prognosis of this audiometric pattern.
authors.affiliation: Department of Otolaryngology--Head and Neck Surgery, Tufts--New England Medical Center, Boston, MA 02111, USA.
authors.forename: R K
authors.initials: RK
authors.lastname: Shah
authors.forename: N H
authors.initials: NH
authors.lastname: Blevins
authors.forename: C S
authors.initials: CS
authors.lastname: Karmody
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001301:Audiometry, Pure-Tone / Q000379:methods; D002648:Child; D002675:Child, Preschool; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000151:congenital / Q000209:etiology* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000150:complications / Q000473:pathology; D009622:Noise / Q000009:adverse effects; D009784:Occupational Diseases / Q000209:etiology; D010375:Pedigree; D011379:Prognosis; D012189:Retrospective Studies; D012684:Sensory Thresholds; D012720:Severity of Illness Index; D013063:Speech Discrimination Tests / Q000379:methods