Preserved Auditory Steady State Response and Envelope-Following Response in Severe Brainstem Dysfunction Highlight...

Area of Science:

• Neuroscience
• Audiology
• Pediatrics

Background:

• Auditory Steady State Response (ASSR) systems are standard for objective pediatric hearing threshold assessment.
• ASSRs in sleeping children are typically of subcortical origin, with the inferior colliculus as a major contributor.
• Severe brainstem dysfunction can impact auditory pathway responses, necessitating sensitive diagnostic tools.

Purpose of the Study:

• To evaluate the sensitivity of ASSR, Auditory Brainstem Response (ABR), and Envelope-Following Response (EFR) in diagnosing severe pediatric brainstem dysfunction.
• To differentiate peripheral (cochlear nerve) from central (brainstem) auditory pathway function using EFRs in sleeping children.
• To compare the diagnostic utility of different objective auditory electrophysiological tests in cases of brainstem dysfunction.

Main Methods:

• Conducted a neurophysiological assessment on 3 sleeping children with severe brainstem dysfunction.
• Utilized standard audiological tests including tympanometry, distortion product otoacoustic emissions, click-evoked ABRs, and ASSRs.
• Recorded EFRs using horizontal (EFR-H) and vertical (EFR-V) channels with a stimulus phase rotation technique to isolate and measure latency and phase-locking.

Main Results:

• Children with brainstem dysfunction showed abnormal ABR central waves but normal cochlear nerve function (ABR wave I, summating potential, cochlear microphonic potential).
• EFR-H recordings indicated normal cochlear nerve function, while EFR-V showed abnormal latencies and phase-locking, suggesting central auditory pathway involvement.
• ASSR audiograms in two cases provided normal or slightly elevated thresholds, failing to detect the underlying brainstem dysfunction, unlike ABR and EFR.

Conclusions:

• ASSR testing lacks sensitivity for severe pediatric brainstem dysfunction, potentially leading to missed diagnoses.
• EFR recordings, particularly EFR-V, demonstrate greater sensitivity in detecting central auditory pathway abnormalities compared to ASSR.
• The Cross-Check Principle, incorporating ABR and EFR alongside or instead of ASSR, is crucial for comprehensive auditory assessment in pediatric cases with suspected brainstem dysfunction.