The glabella tap reflex is characterized by persistent blinking in response to repeated light tapping on the forehead between the eyebrows. Normally, blinking diminishes after a few taps (habituation). Persistence of the reflex, known as Myerson’s sign, indicates neurological dysfunction, particularly in Parkinson’s disease, presenile dementia, or frontal lobe lesions.

Pathophysiology

• The reflex involves facial nerve (cranial nerve VII) stimulation and central processing in the brainstem and frontal lobes.

• Normally, the blink response habituates after a few taps due to inhibitory cortical input.

• Persistent blinking reflects failure of cortical inhibition, commonly due to:

  • Basal ganglia dysfunction in Parkinson’s disease

  • Frontal lobe pathology from tumors, trauma, or degenerative disease

  • Diffuse cortical or subcortical lesions impairing inhibitory control

Examination Technique

1. Patient positioning: Have the patient sit comfortably, facing the examiner.

2. Reflex elicitation: Lightly tap the glabella (forehead between the eyebrows) several times.

3. Observation: Monitor the blink response. Normally, blinking stops after 2–3 taps. Persistence beyond this indicates a positive reflex.

4. Documentation: Record presence, duration, and laterality of the reflex.

Clinical Features

Differential Diagnosis

Pediatric considerations

Rarely tested in children; persistence may reflect frontal lobe dysfunction or developmental delay.

Geriatric considerations

• Useful in screening for Parkinsonism or early dementia.

• Persistent reflex may correlate with frontal lobe atrophy or degenerative disease.

Limitations

• Reflex persistence is not specific; requires correlation with clinical context.

• Patient cooperation and attention can influence results.

• May be absent in early Parkinson’s disease or subtle frontal lesions.

Patient counseling

• Explain that the reflex is a neurological sign, not a disease itself.

• Emphasize the importance of further neurological evaluation to identify underlying causes.

• Discuss monitoring for cognitive or motor changes if indicated.

Conclusion

The glabella tap reflex is a simple bedside test for detecting impaired cortical inhibition, often associated with Parkinson’s disease, dementia, or frontal lobe pathology. Persistent blinking beyond a few taps is a clinically significant finding that warrants further neurological assessment.

References

1. Myerson R. Glabellar reflex in Parkinsonism. Arch Neurol. 1952;67:8–15.

2. Jankovic J. Parkinson’s disease: Clinical features and diagnosis. J Neurol Neurosurg Psychiatry. 2008;79:368–376.

3. Ropper AH, Samuels MA. Adams and Victor’s Principles of Neurology. 11th ed. New York: McGraw-Hill; 2021.

4. Kumar A, et al. Frontal lobe dysfunction and primitive reflexes in dementia. Neurol India. 2015;63(1):33–39.