Glabellar reflex is a primitive 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.
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 reflexly contracts causing blinking.
Glabellar reflex is often seen in patients with Parkinson's Disease.