A stimulus to the thenar area of the hand causes a reflex contraction ipsilaterally of the orbicularis oris and mentalis muscles.
Incidence from neonatal period to age 20 ranges between 3.3-20%.
After the age of 20 years the incidence increases approximately 10% per decade.
Symmetrical reflex can be found in individuals with no neurological or mental disease process and is not considered a pathological sign.
Asymmetrical reflex is considered a significant neurological finding of the central or peripheral nervous system.