Neuronland: NeuroTeach 19 - Glabellar reflex

Glabellar reflex (Myerson's sign)!!!

"the preliminary note on a new cranial reflex"

British doctor Walker Overend (1858–1926)

2) Glossary

Glabellar reflex, Habituation, Myerson’s sign, Primitive reflex

3) History

1896, Dr. Walker Overend - first report 1901, Dr. Daniel J. McCarthy - published a 2nd report without acknowledging Overend 1944, Dr. Abraham Myerson - observed, mainly, in PD 1954, Dr. Doshay - called Myerson’s sign

4) Pathophysiology

poorly understood, probably partially related to the blink reflex Afferent: V CN (supraorbital nerve) Efferent: VII CN (orbicularis oculi muscle) moderated by - cortical areas, especially the frontal lobe - subcortical areas, especially basal ganglia

5) Clinical use

a)may present healthy pts & infants b)inc prevalence w/ age c) disease severity d)differentiate PD from ET (Nuuttila 2021) - sensitivity 78.3% & specificity 36.2% e)reverse after levodopa in PD (Klawans 1969) - 50% - no reverse: dementia & severe PD

6) Definition

“unable to resist blinking when tapped repetitively on the glabella” How many times to tap till be abnormal? The magic number is “five” based in pediatric studies (Zametkin et al 1979)

7) Glabellar reflex – features

“unable to resist blinking when tapped repetitively on the glabella” - primitive reflex - aka Myerson's sign - PD and dementia, severity?

8) Glabellar reflex