Auditory cortical responses in patients with Bell's palsy.

We recorded auditory evoked magnetic responses with a whole-scalp 122-channel SQUID neuromagnetometer in 14 patients with Bell's palsy (9 with left-sided and 5 with right-sided) and in 10 controls. The stimuli were 50-ms 1-kHz tone bursts, delivered first to the left and then to the right ear at interstimulus intervals (ISIs) of 1, 2 and 4 s. In patients, the N100m, the 100-ms response originating in the auditory cortices peaked, on average, 8 ms earlier and the response strengths were, on average, 7 nAm stronger over the contralateral than ipsilateral hemisphere. The response latencies and strengths did not differ significantly from those of controls and there were no significant differences in response latencies and strengths between the stimulation of the affected and healthy side. On average, the response latencies and strengths increased as a function of ISI over both hemispheres both in patients and in controls. These findings suggest that Bell's palsy is an isolated peripheral neuropathy that does not affect the function of the auditory pathways.