title: The influence of mutations in the SLC26A4 gene on the temporal bone in a population with enlarged vestibular aqueduct.
abstract: OBJECTIVE
  To correlate genetic and audiometric findings with a detailed radiologic analysis of the temporal bone in patients with enlarged vestibular aqueduct (EVA) to ascertain the contribution of SLC26A4 gene mutations to this phenotype.
  
  
  METHODS
  A retrospective review of patients with EVA identified in a database of pediatric hearing-impaired patients.
  
  
  METHODS
  A tertiary care pediatric referral center.
  
  
  METHODS
  Seventy-one children with EVA and screening results for SLC26A4 mutations.
  
  
  METHODS
  Genetic screening results, audiometric thresholds, and radiographic temporal bone measurements.
  
  
  RESULTS
  Seventy-one children with EVA were screened for SLC26A4 mutations. Mutations were found in 27% of children overall, while only 8% had biallelic mutations. The mean initial pure-tone average (PTA) was 59 dB; the mean final PTA was 67 dB. A bilateral EVA was found in 48 (67%) of the children; a unilateral EVA was found in 23 (33%). Progressive hearing loss (in at least 1 ear) was seen in 29 (41%) of the patients. The strongest genotype-phenotype interaction was seen in children with a bilateral EVA. Among children with SLC26A4 mutations, there was a significantly wider vestibular aqueduct at the midpoint and a wider vestibule width (P < .05) than in children without the mutation. Among patients with a bilateral EVA, children with any SLC26A4 mutation were more likely to have a more severe final PTA (64 dB vs 32 dB), larger midpoint measurement (2.1 vs 1.1 mm), and larger operculum measurement (3.0 vs 2.0 mm) than those without the mutation in their better-hearing ear (P < .05).
  
  
  CONCLUSIONS
  In a population of pediatric patients with an EVA and hearing loss, SLC26A4 mutations are a contributor to the phenotype. Our data suggest that other genetic factors also have important contributions to this phenotype. The presence of an abnormal SLC26A4 allele, even in the heterozygous state, was associated with greater enlargement of the vestibular aqueduct, abnormal development of the vestibule, and possibly a stable hearing outcome.
authors.affiliation: Department of Audiovestibular Medicine, Manchester Royal Infirmary, Manchester, England.
authors.forename: Colm
authors.initials: C
authors.lastname: Madden
authors.forename: Mark
authors.initials: M
authors.lastname: Halsted
authors.forename: Jareen
authors.initials: J
authors.lastname: Meinzen-Derr
authors.forename: Dianna
authors.initials: D
authors.lastname: Bardo
authors.forename: Mark
authors.initials: M
authors.lastname: Boston
authors.forename: Ellis
authors.initials: E
authors.lastname: Arjmand
authors.forename: Carla
authors.initials: C
authors.lastname: Nishimura
authors.forename: Tao
authors.initials: T
authors.lastname: Yang
authors.forename: Corning
authors.initials: C
authors.lastname: Benton
authors.forename: Vijay
authors.initials: V
authors.lastname: Das
authors.forename: Richard
authors.initials: R
authors.lastname: Smith
authors.forename: Daniel
authors.initials: D
authors.lastname: Choo
authors.forename: John
authors.initials: J
authors.lastname: Greinwald
mesh_terms: D000293:Adolescent; D000328:Adult; D001301:Audiometry, Pure-Tone; D002648:Child; D002675:Child, Preschool; D005260:Female; D005838:Genotype; D006319:Hearing Loss, Sensorineural / Q000235:genetics*; D006801:Humans; D007223:Infant; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics*; D009154:Mutation; D010641:Phenotype; D012189:Retrospective Studies; D000076988:Sulfate Transporters; D013701:Temporal Bone / Q000002:abnormalities*; D014723:Vestibular Aqueduct / Q000002:abnormalities*
chemical_list: D026901:Membrane Transport Proteins; C085609:SLC26A4 protein, human; D000076988:Sulfate Transporters