Auditory evoked magnetic fields in patients with absent brainstem responses due to auditory neuropathy with optic atrophy

Objective: To examine whether auditory evoked fields (AEFs) can be used to objectively evaluate hearing in patients with absent auditory brainstem responses (ABRs) due to auditory neuropathy. Methods: Subjects were 3 patients with auditory neuropathy, 1 male aged 29. years and 2 females aged 18 and 27. years, with absence of click evoked ABRs for bilateral ear stimuli at a level of 105. dB nHL. All patients also had optic atrophy. AEFs were measured with a helmet-shaped magnetoencephalography system for 2.0. kHz tone bursts of 60. ms duration to the unilateral ear. Results: Bihemispherical AEF responses were clearly recorded in all three patients for either left or right ear stimulus. Although the latencies of N100m were severely prolonged and amplitudes were considerably decreased compared to the normal range of N100m responses in our facilities, N100m latency of AEF was shorter in the contralateral hemisphere to the stimulated ear, as usually found in normal subjects, despite the abnormal delay in N100m latency in all conditions. Conclusions: Presence and abnormality of auditory cortical responses can be evaluated by AEFs in patients with auditory neuropathy even under null responses in ABRs. Significance: AEFs are useful to evaluate residual hearing in patients with auditory neuropathy.