The glabellar reflex, also known as the "glabellar tap sign", is a

primitive reflex Primitive reflexes are reflex actions originating in the central nervous system that are exhibited by normal infants, but not neurologically intact adults, in response to particular stimuli. These reflexes are suppressed by the development of the f ...

elicited by repetitive tapping of the the smooth part of the forehead above the nose and between the eyebrows. Subjects respond to the first several taps by

blinking Blinking is a bodily function; it is a semi-autonomic rapid closing of the eyelid. A single blink is determined by the forceful closing of the eyelid or inactivation of the levator palpebrae superioris and the activation of the palpebral portio ...

; if tapping were to then be made to persist, in cognitively intact individuals this would lead to habituation and consequent suppression of blinking. If instead the blinking were to persist along with the tapping, this is known as

Myerson's sign Myerson's sign or glabellar tap sign is a clinical physical examination finding in which a patient is unable to resist blinking when tapped repetitively on the glabella, the area above the nose and between the eyebrows. It is often referred to as t ...

, and is abnormal and a sign of frontal release; it is often seen in people who have

Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...

. The afferent sensory signals are transmitted by the

trigeminal nerve In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewin ...

to the brain stem; the

efferent Efferent may refer to: Anatomical structures Meaning 'conveying away from a center': *Efferent arterioles, conveying blood away from the Bowman's capsule in the kidney *Efferent nerve fiber, carries nerve impulses away from the central nervous sy ...

signals go to the

orbicularis oculi muscle The orbicularis oculi is a muscle in the face that closes the eyelids. It arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short ...

via the

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of tas ...

, causing the muscle to reflexively contract, yielding blinking. This reflex was first identified by Walker Overend.

References

{{Medical-stub Reflexes

See also

References