title: Relation of distortion product otoacoustic emission with tinnitus.
abstract: OBJECTIVE
  To investigate cochlear outer hair cell function based on distortion product otoacoustic emission (DPOAE) in patients with tinnitus.
  
  
  METHODS
  This is a case control study.
  
  
  METHODS
  The subjects are patients who attended the Otorhinolaryngology Clinic in Hospital Universiti Kebangsaan Malaysia over a period of 19 months from April 2005 until October 2006. All patients underwent a full ENT assessment and had tympanometry, pure tone audiometry, and DPOAE tests. The UKM Research and Ethics Committee reviewed and approved the study proposal prior to commencement of this study.
  
  
  RESULTS
  The study population included 49 patients. They consisted of 16 patients (32 ears) with tinnitus and reduced hearing, 13 patients (26 ears) with tinnitus and normal hearing, 7 patients (13 ears) without tinnitus with reduced hearing, and 13 patients (26 ears) without tinnitus with normal hearing. Statistical analysis showed significant differences (P = .00) of mean DPOAE levels between the four groups of patients.
  
  
  CONCLUSIONS
  Our results suggest that reduced outer hair cell activity, as detected by reduced DPOAE levels, may manifest as tinnitus even before there is a shift on hearing threshold. We also postulate that further reduction of cochlear outer hair cell activity, as shown by further reduced DPOAE levels, may actually terminate the source of tinnitus.
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Faculty of Medicine. Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia. mazitaami@yahoo.com
authors.forename: Mazita
authors.initials: M
authors.lastname: Ami
authors.forename: Asma
authors.initials: A
authors.lastname: Abdullah
authors.forename: Mahamad A
authors.initials: MA
authors.lastname: Awang
authors.forename: Borhan
authors.initials: B
authors.lastname: Liyab
authors.forename: Lokman
authors.initials: L
authors.lastname: Saim
mesh_terms: D000158:Acoustic Impedance Tests; D000328:Adult; D000368:Aged; D001301:Audiometry, Pure-Tone; D001307:Auditory Perception / Q000502:physiology*; D001309:Auditory Threshold / Q000502:physiology*; D001844:Bone Conduction / Q000502:physiology; D016022:Case-Control Studies; D002908:Chronic Disease; D003051:Cochlea / Q000503:physiopathology*; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D018072:Hair Cells, Auditory, Outer / Q000502:physiology*; D006309:Hearing / Q000502:physiology; D034381:Hearing Loss / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D014012:Tinnitus / Q000503:physiopathology*