Magnetically elicited blink reflex: an alternative to conventional electrical stimulation.

Magnetically and electrically elicited blink reflexes were studied in 11 normal subjects and in 5 patients with partial peripheral facial nerve palsy. Both methods were able to elicit a reproducible blink reflex. In both groups the latencies of the magnetically elicited reflexes were equal to those that followed electrical stimulation. The magnetic stimulation technique offered 2 advantages over the electrical stimulation: (1) it was less painful and therefore better tolerated and (2) the coil position in the middle of the forehead was sufficient to elicit a bilateral blink reflex because the windings of the stimulation coil excited both supraorbital nerves simultaneously. This bilateral response enables one to reduce the number of stimuli and can be used in the examination of patients that have peripheral facial nerve palsies without the concomitant impairment of the reflex pathway in the brainstem. The magnetic technique can also elicit a blink reflex at stimulation points distant from the supraorbital notch. This finding offers an alternative explanation of the late responses of facial muscles following transcranial magnetic stimulation of the motor cortex.