The palmomental reflex consists of contraction of the mentalis muscle induced by stroking the ipsilateral palm with a blunt object. It may indicate damage to the contralateral paracentral cortex or its connections, but since it is observed in about one quarter of normal adults and is very common in the normal elderly, and may occur in other conditions, both its sensitivity and specificity are low. It may be considered a frontal release sign or primitive reflex, but is less specific than the grasp reflex. Induction of the reflex by stimulation of areas other than the palm is more likely to be associated with cerebral damage.
Owen G, Mulley GP. The palmomental reflex: a useful clinical sign? Journal of Neurology, Neurosurgery and Psychiatry 2002; 73: 113-115