[Reflex response of the masseter muscle after percussion of the chin and electrical stimulation of the upper lip in patients with central motor disorders].

In 23 patients with central motor disorders (spastic hemiparesis, pseudobulbar syndrome and parkinsonism) reflex responses in both masseters were evoked during their relaxation and contraction by percussion with a reflex hammer on the chin and by electric stimulation of the upper lip. For recording of the reflex responses the electromyographic method was used. On the side of the spastic hemiparesis, as compared with the finding on the non-paretic side, the author found changes in the short-, medium and late-latency excitation and inhibition segments of the reflex response. In patients with parkinsonism the medium-latency portion of the reflex response after percussion of the chin from above as well as from below was satisfactory. The late latency excitation response after percussion of the chin from below was greater than its corresponding part evoked by percussion of the chin from above. In patients with the pseudobulbar syndrome the inhibitory parts of the reflex responses after percussion of the chin were weak. The results of the examination provided thus more detailed information on disorders of supranuclear control of masseter muscles.