title: [Audiologic features of mitochondrial DNA A3243G mutation and its correlation with mutation rate].
abstract: OBJECTIVE
  To summarize the clinical audiologic features of patients with mitochondrial DNA (mtDNA) A3243G mutation and explore the lesion location of hearing loss so as to examine its correlation with the related syndrome.
  
  
  METHODS
  A total of 44 patients with mtDNA A3243G mutation from 2009-2011 were studied. Audiological evaluations consisted of measurements of pure-tone and speech audiometry, tympanometry, distortion-product otoacoustic emissions and auditory brainstem response. We investigated a possible correlation between the degree of hearing loss and gender, age and mutation rate.
  
  
  RESULTS
  (1) Pure tone test was performed in 41 patients and showed normal hearing or symmetrical sensorineural hearing loss. Pure tone audiogram (PTA) showed high-frequency loss and descending curve in a majority of patients. There were 75 ears with hearing loss in 82 ears (91.46%), 22 ears with abnormal speech audiometry in 26 ears, 77 ears with abnormal distortion product otoacoustic emissions (DPOAE)testing in 86 ears, including 5 ears with normal PTA, 31 ears with abnormal electrocochleography in 75 ears, 25 ears with abnormal auditory brainstem response (ABR) in 82 ears. The abnormal ABR showed elevated threshold in 10 ears, delayed interpeak latencies of wave I-V in 2 ears and disappearance of wave V before wave I in 1 ear. In addition, there were 2 ears with speech audiometry abnormal but with normal ABR. (2) The correlation between the severity of hearing and gender did not reach statistical significance, nor the severity of hearing and mutation ratio. Age could influence the hearing of A3243G-induced MELAS.
  
  
  CONCLUSIONS
  The predominant lesions of mtDNA A3243G is at cochlea and retrocochlear sites. Significant variations in clinical manifestation of hearing are the prominent features in patient with A3243G mutation. There was no correlation between the degree of hearing loss and mutation load. However, hearing impairment is the most common symptom of A3243G mutation.
authors.affiliation: Department of Otolaryngology, Head & Neck Surgery, Peking University First Hospital, Beijing 100034, China.
authors.forename: Jun-fang
authors.initials: JF
authors.lastname: Xue
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Yi-nan
authors.initials: YN
authors.lastname: Ma
authors.forename: Dan-hua
authors.initials: DH
authors.lastname: Zhao
authors.forename: Ji-bo
authors.initials: JB
authors.lastname: Duan
authors.forename: Zhao-xia
authors.initials: ZX
authors.lastname: Wang
authors.forename: Yu
authors.initials: Y
authors.lastname: Qi
authors.forename: Yu-he
authors.initials: YH
authors.lastname: Liu
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D004272:DNA, Mitochondrial / Q000235:genetics*; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis / Q000235:genetics*; D006320:Hearing Tests; D006801:Humans; D008297:Male; D008875:Middle Aged; D059645:Mutation Rate; D055815:Young Adult
chemical_list: D004272:DNA, Mitochondrial