MASSETER INHIBITORY REFLEX THRESHOLD - A NOVEL TECHNIQUE FOR ELECTROPHYSIOLOGICAL INVESTIGATION OF TRIGEMINAL NERVE LESIONS

The masseter inhibitory reflex was investigated in 60 healthy voluntee rs, in 38 patients with trigeminal nerve branch lesions in the majorit y due to dental surgery, and in 9 patients with facial sensory loss an d weakness caused by brain hemisphere lesions. The reflex threshold (T R) was almost symmetric both in normal subjects and in the patients wi th hemisphere lesions. In peripheral trigeminal hypaesthesia, elevatio n of TR on the lesioned side proved the most sensitive electrophysiolo gical parameter. There was, moreover, some correspondence between the degree of sensory loss in hypaesthesic skin areas and elevation of TR, and recovery from the lesion was associated with TR normalization. Su pratentorial lesions, in contrast, may influence the reflex pattern ra ther than reflex excitability.