[Trismus, trigeminal motor dyssynergy with brain stem lesions (author's transl)]

Paradox activity of masticatory muscles was observed clinically and electromyographically in 4 patients with brain steem lesions who had trismus. There was no activity in the elevators of the jaw on the side affected during voluntary biting, as if the muscles were paralyzed. There was strong activity of the elevators on the side of the trismus on opening the mouth, inactivity on the unaffected side, or inverse activity appeared on both sides. In view of the trigeminal anesthesia on the side of paradox activation, and the absence of pyramidal signs, a stretch reflex mechanism and abolition of inhibition can not be the only basis for these phenomena; so, a disturbance of bilateral synergism, in the sense of an internuclear lesion, is postulated. In one case of motor and sensory paralysis after the extirpation of a meningioma of the cerebellopontine angle, intensive paradox activity was observed, without trismus.