Ear-to-ear derivation in short latency brainstem auditory evoked responses

Area of Science:

• Audiology
• Neuroscience
• Electrophysiology

Background:

• Auditory evoked potentials (AEPs) are crucial for assessing auditory pathway function.
• Accurate identification of Wave I in AEPs is essential for diagnosing auditory neuropathy spectrum disorder.
• Conventional electrode montages may present challenges in consistently identifying Wave I.

Purpose of the Study:

• To evaluate the utility of an ipsilateral to contralateral earlobe (Ai-Ac) derivation in auditory evoked potential (AEP) recordings.
• To compare the Ai-Ac derivation with conventional scalp-to-ear derivations (Cz-Ai and Cz-Ac) for Wave I identification.
• To determine if the Ai-Ac derivation enhances the detection of Wave I in individuals with normal hearing and hearing loss.

Main Methods:

• Auditory evoked potentials were recorded from 12 normal-hearing volunteers and 36 patients with hearing loss.
• Electrode derivations included scalp to ipsilateral ear (Cz-Ai), scalp to contralateral ear (Cz-Ac), and ipsilateral to contralateral earlobe (Ai-Ac).
• Latency and amplitude of Wave I were analyzed across different derivations.

Main Results:

• Wave I latency in the Ai-Ac derivation was identical to Cz-Ai in normal subjects.
• Wave I amplitude was smaller in Ai-Ac compared to Cz-Ai (0.21 +/- 0.1 vs. 0.30 +/- 0.13 microV, p < 0.005).
• Striking and consistent phase-reversals of Wave I were observed between Cz-Ai and Ai-Ac derivations across all participants, aiding identification.

Conclusions:

• The Ai-Ac derivation, when added to conventional montages, shows potential for improving Wave I identification in AEPs.
• This enhanced identification of Wave I can aid in the diagnosis of auditory pathway disorders.
• The findings support the integration of the Ai-Ac derivation for more robust AEP analysis.