La audiometría por vía ósea mediante potenciales evocados auditivos de estado estable a multifrecuencia: estudio en sujetos normooyentes

Here we examine the clinical usefulness of multiple auditory steady state responses to estimate the frequency specific thresholds to bone and air conduction stimuli and the air-bone gap. For this purpose was studied a group of normal hearing children (30 ears) with ages between 7-15 years. For each child the audiometric thresholds to bone- and air- conduction stimuli were determined behaviorally (pure tones) and with multiple auditory steady state responses (four carrier tones (0.5, 1, 2 and 4KHz) modulated in amplitude at rates of 104, 108, 111 and 115 respectively). All Multiple auditory steady state responses were obtained with the AUDIX V system. The acoustic stimuli were presented simultaneously through B71 bone vibrator placed at the mastoid or insert phones at variable intensities (Air Conduction 50-10 dB HL; Bone Conduction 40-10 dB HL). The thresholds differences were between 7-9 dB for bone conduction and 8-13 dB for air conduction. Significant correlations were found between physiological and behavioural thresholds for bone conduction stimuli at all test frequencies (r=0.70). Physiological airbone gap was almost equivalent to the behavioral estimate at each explored frequency (differences between 0-4 dB). The value of the correlation coefficient to air bone gap with all frequency collapsed was 0.61. In conclusion the MSSR technique can accurately evaluate both Bone Conducted and Air Conducted thresholds in normal hearing children thus contributing to obtain an objective estimate of the air bone gap.