title: Auditory brainstem responses for click and CE-chirp stimuli in individuals with and without occupational noise exposure.
abstract: BACKGROUND
  Encoding of CE-chirp and click stimuli in auditory system was studied using auditory brainstem responses (ABRs) among individuals with and without noise exposure.
  
  
  METHODS
  The study consisted of two groups. Group 1 (experimental group) consisted of 20 (40 ears) individuals exposed to occupational noise with hearing thresholds within 25 dB HL. They were further divided into three subgroups based on duration of noise exposure (0-5 years of exposure-T1, 5-10 years of exposure-T2, and >10 years of exposure-T3). Group 2 (control group) consisted of 20 individuals (40 ears). Absolute latency and amplitude of waves I, III, and V were compared between the two groups for both click and CE-chirp stimuli. T1, T2, and T3 groups were compared for the same parameters to see the effect of noise exposure duration on CE-chirp and click ABR.
  
  
  RESULTS
  In Click ABR, while both the parameters for wave III were significantly poorer for the experimental group, wave V showed a significant decline in terms of amplitude only. There was no significant difference obtained for any of the parameters for wave I. In CE-Chirp ABR, the latencies for all three waves were significantly prolonged in the experimental group. However, there was a significant decrease in terms of amplitude in only wave V for the same group.
  
  
  CONCLUSIONS
  Compared to click evoked ABR, CE-Chirp ABR was found to be more sensitive in comparison of latency parameters in individuals with occupational noise exposure. Monitoring of early pathological changes at the brainstem level can be studied effectively by using CE-Chirp stimulus in comparison to click stimulus.
  
  
  CONCLUSIONS
  This study indicates that ABR's obtained with CE-chirp stimuli serves as an effective tool to identify the early pathological changes due to occupational noise exposure when compared to click evoked ABR.
authors.affiliation: All India Institute of Speech and Hearing, Mysuru, Karnataka, India.
authors.forename: Zeena Venkatacheluvaiah
authors.initials: ZV
authors.lastname: Pushpalatha
authors.affiliation: All India Institute of Speech and Hearing, Mysuru, Karnataka, India.
authors.forename: Sreeraj
authors.initials: S
authors.lastname: Konadath
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D006317:Hearing Loss, Noise-Induced / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009623:Noise, Occupational; D009784:Occupational Diseases / Q000175:diagnosis / Q000503:physiopathology*; D016273:Occupational Exposure; D055815:Young Adult