The glabellar reflex, also known as the nasopalpebral reflex or the blink reflex, involves blinking in response to tapping on the forehead skin [1][3]. The afferent limb is the trigeminal nerve, which senses stimuli applied to the glabella region between the eyebrows [2][4]. The efferent response travels via the facial nerve to cause bilateral contraction of the orbicularis oculi muscles, closing the eyelids [1][5].

In healthy people, blinking stops after the first few taps as habituation occurs [1]. Persistent reflex blinking beyond 4-5 taps is abnormal and indicates dysfunction like Parkinson’s disease or frontal lobe lesions [1][3]. The reflex may disappear when Parkinson’s patients are treated with levodopa [4][6]. Light trigeminal stimulation anywhere on the face can evoke a blink but the forehead is most sensitive [2]. Overall, the glabellar reflex demonstrates brainstem circuits mediating responses to facial tactile stimuli.