The human jaw jerk: electrophysiologic methods to measure the latency, normal values, and changes in multiple sclerosis.

The reflex contraction of the masseter muscles to the stretch imposed by a tap on the chin is a monosynaptic reflex. This reflex contraction of the master muscles was present in all control subjects but commonly absent in definite multiple sclerosis (MS) patients. In a few MS patients the latency was prolonged. Abnormalities in the jaw jerk, however, were less frequent than with the blink reflex responses to supraorbital nerve stimulation or …