Comparison of multiple auditory steady-state responses (80 versus 40 Hz) and slow cortical potentials for threshold estimation in hearing-impaired adults

Abstract

This study evaluated the use of multiple auditory steady-state responses (ASSRs) and slow cortical potentials (SCPs) to estimate behavioural audiograms in adults for compensation cases. Two groups of 23 subjects were assessed using either 80 Hz or 40 Hz multiple simultaneous tones with carrier frequencies of 0.5, 1.0, 2.0, and 4.0 kHz. SCP thresholds for 0.5, 1.0, and 2.0 kHz were obtained for both groups. Mean evoked potential thresholds (dB HL) minus behavioural pure-tone thresholds (dB HL) difference scores were 5–17 dB for the 80 Hz group, 1–14 dB for the 40 Hz group, and 20–22 dB for the SCPs. Thresholds for 40 Hz ASSR were significantly closer to behavioural thresholds than were 80 Hz or SCP thresholds. SCP and 40 Hz ASSR audiogram estimates were obtained more quickly than the 80 Hz ASSR. Multiple 40 Hz ASSR is the method of choice for evoked potential threshold estimation in adults.

Sumario

Este estudio evaluó el uso de las respuestas auditivas múltiples de estado estable (ASSR) y de los potenciales corticales lentos (SCP) para estimar en casos de compensación, los audiogramas comportamentales de adultos. Se realizaron pruebas en dos grupos de 23 sujetos utilizando tonos múltiples simultáneos a 80 ó 40 Hz con frecuencias portadoras de 500, 1000, 2000 y 4000 Hz. Se obtuvieron umbrales SCP para 500, 1000 y 2000 Hz en ambos grupos. Los umbrales promedio de potenciales evocados (dBHL) menos las respuestas tonales comportamentales se ubicaron entre 5 y 17dB para el grupo de 80 Hz, de 1 a 40 dB para el grupo de 40 Hz y de 20 a 22 dB para los SCP. Los umbrales de las ASSR de 40 Hz estuvieron significativamente mas cercanos a los umbrales comportamentales que los de 80 Hz o los umbrales SCP. Los SCP y las ASSR-40 Hz se obtuvieron más rápido que las ASSR-80 Hz. Las ASSR múltiples de 40 Hz son el método de elección para la estimación de umbrales con potenciales evocados en adultos.

• Multiple auditory steady-state response
• Slow cortical potential
• Sensorineural hearing impairment
• Threshold

Notes

¹We carried out a pilot study of one subject with a 3 Hz separation and found an approximately 33% decrease in four frequencies compared to one carrier frequency with rates from 36 Hz (0.5 kHz) to 45 Hz (4 kHz). Thus four stimuli are more efficient than a single stimulus.

²The bracketing technique was used for threshold estimation with the exception of one subject at one frequency, where the intensity 10 dB below the response was not tested. In this case, threshold was estimated at the lowest recorded intensity rather than the intensity below (which was not recorded) based upon the borderline amplitude (63 nV) and p-value (p=.012) of the recorded response.

³If a 10 dB step size had been utilized for the SCP, the mean difference scores would have changed no more than 1 dB (larger), with a 1–2 dB larger standard deviation. This was estimated by alternately adding or subtracting 5 dB to each SCP threshold that was not at a 10 dB step. This small change is similar to that reported by Luts and Wouters (2004).

⁴Use of the 5 dB step size was estimated to require approximately two to three minutes extra testing for the SCP. However, this is offset by an equal amount by the 15–20% extra time required for the SCP to change frequencies and ears, and to manipulate waveforms, etc. The estimate for the SCP for two ears is thus approximately 30 minutes (2×14.9 minutes).