How does the jaw jerk reflex help in localizing lesions in patients with hypereflexia?

Conclusion: The jaw jek is reflex that involves the contraction of master and temporalis muscles when the patient jaw is tapped. The afferent limb travels via the mandibular branch of the trigeminal nerve to the mesencephalic nucleus to the trigeminal nerve. The efferent limb arises from the motor nucleus of the trigemimal nerve and also travel via the mandibular branch.The jaw jek is exaggerated with bilateral lesions above the trigeminal nerve in the pons but will not affect by lesions below it in the spinal cord.This help in patients who have hyperreflexia in all four limbs because an exaggerated jaw jerk reflex suggests that the lesion is above the level of the spinal cord( high brain stem or brain ).

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