The effects of simulated hearing loss on the auditory brainstem response components

Standard neurodiagnostic ABR has a high over-referral rate to rule out acoustic neuromas due to the increased latency in individuals with sensory cochlear hearing loss. Existing correction factors take into account the degree of hearing loss but unlike the present study, previous research has not taken into account the configuration of hearing loss.; White noise was spectrally shaped to simulate a high frequency notched hearing loss and a relatively flat hearing loss. Spectrally shaped noise was presented ipsilaterally during the measurement of standard neurodiagnostic ABR. The presence of simulated hearing loss resembled the presence of actual hearing loss on the standard neurodiagnostic ABR components. The higher the intensity of spectrally shaped noise present, the greater the shift in absolute latency, interpeak latency, and interaural latency difference of ABR component waves. There were not significant differences in wave I latency, which led to significantly increased interpeak latencies I-III and I-V. Spectrally shaped notched noise compared to spectrally shaped flat noise, showed significantly longer absolute latency of wave V and interaural latency difference. When a high frequency notched hearing loss was present, interaural latency difference of wave V correlated with pure tone thresholds at 2000 and 4000 Hz. The correlation increased with an increase in frequency in the presence of a simulated high frequency notched hearing loss. When a flat hearing loss was present, interaural latency difference of wave V also correlated with pure tone thresholds at 2000 and 4000 Hz. These results lead to the development of updated and more accurate latency correction factors. It is recommended that all degrees and configurations of sensorineural hearing loss warrant the use of correction factors when operating standard neurodiagnostic ABR. One set correction factor may not sufficiently account for varying hearing loss configurations. A correction factor specifically for flat hearing loss and one specifically for notched hearing loss, as developed from this study, may help to improve the predictive accuracy of standard neurodiagnostic ABR.