Afferent limb of the human jaw reflex: electrophysiologic and anatomic study.

Jaw reflexes were recorded before and after neurosurgery of the trigeminal sensory root or the gasserian ganglion in 11 patients with idiopathic trigeminal neuralgia and in 2 patients with orbital malignancies. The reflex was also studied in three patients with unilateral midbrain lesions verified by postmortem findings. Jaw reflex abnormalities appeared in all cases, although there were no clinical or EMG signs of masseter dysfunction. Proprioceptive afferent fibers of the jaw reflex therefore seem to be mediated by the sensory and not the motor root. The afferent limb of the jaw reflex seems to run centrally through the midbrain, probably through the mesencephalic nucleus of the trigeminal nerve.