title: Provisional stimulus level corrections for low frequency bone-conduction ABR in babies under three months corrected age.
abstract: OBJECTIVE
  To estimate bone-conduction stimulus level corrections by testing the auditory brainstem response (ABR) of normally-hearing newborns. The stimuli used were low frequency tone pips calibrated to reference levels derived from ISO 389 values.
  
  
  METHODS
  Tone pips were presented via supra-aural earphones and a B71 Radioear bone vibrator at 0.5 or 1 kHz. ABR thresholds from both transducers were compared at each frequency.
  
  
  METHODS
  twenty-seven newborn hearing screening referrals (33 ears) who passed an ABR discharge criterion at 4 kHz.
  
  
  RESULTS
  Median air- and bone-conduction ABR threshold differences were 30 dB at 0.5 kHz and 20 dB at 1 kHz.
  
  
  CONCLUSIONS
  The 0.5 kHz data from this study and previous studies were compared. Previous studies suggested lower figures for the bone-conduction stimulus level correction. Likely sources of this discrepancy are discussed. The average 0.5 kHz bone-conduction correction value for infants < 3 months old is about 28 dB. The correction for 1 kHz is 20 dB. We recommend that calibration reference levels used in this study be adopted and that appropriate corrections be applied to bone conduction ABR thresholds in infants < 3 months old before calculation of any air-bone gap and subsequent clinical interpretation.
authors: * Audiology Department, Hearing Centre, Croydon University Hospital , Croydon , UK.
authors: Inga
authors: I
authors: Ferm
authors: Guy
authors: G
authors: Lightfoot
authors: John
authors: J
authors: Stevens
mesh_terms: D000161:Acoustic Stimulation / Q000592:standards; D000367:Age Factors; D001309:Auditory Threshold; D001844:Bone Conduction; D002138:Calibration; D016057:Evoked Potentials, Auditory, Brain Stem; D006320:Hearing Tests / Q000592:standards; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015997:Neonatal Screening / Q000379:methods* / Q000592:standards; D011237:Predictive Value of Tests; D012015:Reference Standards