Auditory evoked magnetic fields in children with functional hearing loss

ObjectivesAbnormal cortical responses in patients with functional hearing loss were evaluated by magnetoencephalography, which can better separate bihemispherical activity than electroencephalography.MethodsAuditory evoked fields in response to 1 kHz or 2 kHz tone bursts at 80 dB sound pressure level were measured by a helmet-shaped magnetoencephalography system in 22 patients with functional hearing loss (18 females, mean age 13.2 years) as well as 5 control subjects under 10 years old. Waveform, latency, and equivalent current dipole of N100m responses were used to evaluate activity in the bilateral auditory cortices.ResultsAbnormal N100m of the contralateral response to the stimulated ear, either absence or delayed latency in comparison to normal adult subjects, was found in 6 of the 7 patients with functional hearing loss aged 9 years or younger, but in only 3 of the 15 patients aged 10 years or older. However, such abnormalities were also observed in younger control subjects.ConclusionAuditory evoked field may be applied to objectively evaluate cortical auditory function in patients with functional hearing loss, but the normal findings for young children have not yet been established.