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How to elicit Glabellar tap?

The glabellar tap is a primitive reflex where the eyes shut if an individual is tapped lightly between the eyebrows. This reflex may normally be overcome rapidly - i.e. the individual soon fails to blink, usually less than five taps.
In those patient with frontal release signs the reflex cannot be overcome, and they continue to blink for as long as the examiner cares to keep tapping. A similar response is also seen with late parkinsonism.
Other names of glabellar tap

  • Orbicularis oculi reflex 
  • Glabellar reflex
  • Nasopalpebral reflex
How to elicit glabellar tap?
The glabellar reflex is elicited by repeatedly tapping the patient between the eyebrows (the glabella area), causing them to blink.
Normally, the adult patient will habituates to this stimulus hence  normal indivual will blink in response to the first two or three taps only. Thereafter he or she will adapts to it and blinking ceases
If blinking persists,that is considered  abnormal in adults.
The examiner  stand on the side of the patient and softly tap the glabellar area with a reflex hammer or finger from above (as it will avoid eliciting the blink reflex to threat).
Response: narrowing of the palpebral fissure by contraction of the orbicularis oculi muscle(possibly bilaterally)

Afferent is both 5th and 7th nerve 
Efferent - 7th CN. 
Center is pons.
Clinical significance
There are primitive reflexes that are normal in infants, but they disappear with brain maturation allowing inhibition, and they reappear  in disorders that affect the frontal lobes.Hence called as “released”reflex . Like most primitive reflexes.The glabellar reflex probably has evolutionary/adaptive advantage in infant apes, protecting the eyes from threat.
Exaggerated glabellar tap is seen in supranuclear lesions of the corticopontine pathway and in extrapyramidal diseases
It is a sign of frontal, diffuse, or extrapyramidal disease
  • Normally after a few contractions, the response ceases, 
  • In bilateral  UMN lesion and in Parkinsonism the response persists. 
  • In LMN lesion the normal response is absent. 
  • Persistent glabellar tap response is called Myersons sign.