Frontal release sign
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Frontal release signs are primitive reflexes traditionally held to be a sign of disorders that affect the frontal lobes. The appearance of such signs reflects the area of brain dysfunction rather than a specific disorder which may be diffuse such as a dementia, or localised such as a tumor.
The only reflex thought to have good localizing value is the palmar grasp reflex which usually signifies damage to the frontal lobe of the opposite side. The glabellar reflex or "glabellar tap" is also present in individuals with extrapyramidal disorders such as Parkinson's disease.
Conceptually, these reflexes are "hard-wired" before birth and are therefore able to be elicited in the newborn. As the brain matures, certain areas (usually within the frontal lobes) exert an inhibitory effect thus causing the reflex to disappear. When disease processes disrupt these inhibitory pathways the reflex is "released" from its inhibitory shackles and elicitable once again, hence the term "frontal release sign".
Whilst the evolutionary value of some of these reflexes is clear, the role in infancy of the palmomental reflex remains a mystery and therefore may be a phylogenetic remnant.
Some frontal release signs and their role in infancy:
- Palmar grasp:- Baby naturally grabs objects.
- Palmomental reflex:- unknown.
- Rooting reflex:- Baby finds breast to suckle.
- Sucking reflex:- Baby sucks breast / bottle teat to get milk.
- Snout reflex:- Involved in suckling.
- Glabellar reflex:- May protect eyes in certain situations.
