Glabellar reflex (also known as the "glabellar tap sign") (Glabella) is a reflex. It is elicited by repetitive tapping on the forehead. Subjects blink in response to the first several taps. If the blinking persists, this is known as Myerson's sign and is abnormal and a sign of frontal release; it is often seen in people who have Parkinson's disease.
The afferent sensory signals are transmitted by the trigeminal nerve, and the efferent signals come back to orbicularis oculi muscle via the facial nerve, which in turn reflexively contracts causing blinking.
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- Vreeling, Fred W; Verhey, Frans R J; Houx, Peter J; Jolles, Jellemer (1993). "Primitive reflexes in Parkinson's disease" (PDF). Journal of Neurology, Neurosurgery, and Psychiatry. 56: 1323–1326. doi:10.1136/jnnp.56.12.1323.