Frontal release sign
Encyclopedia
Frontal release signs are primitive reflexes
traditionally held to be a sign of disorders that affect the frontal lobe
s. 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 lobe
s) 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:
Primitive reflexes
Primitive reflexes are reflex actions originating in the central nervous system that are exhibited by normal infants but not neurologically intact adults, in response to particular stimuli. These reflexes disappear or are inhibited by the frontal lobes as a child moves through normal child...
traditionally held to be a sign of disorders that affect the frontal lobe
Frontal lobe
The frontal lobe is an area in the brain of humans and other mammals, located at the front of each cerebral hemisphere and positioned anterior to the parietal lobe and superior and anterior to the temporal lobes...
s. 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
Reflex
A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...
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
Glabellar reflex
Glabellar reflex is a primitive reflex. It is elicited by repetitive tapping on the forehead. Subjects blink in response to the first several taps...
or "glabellar tap" is also present in individuals with extrapyramidal disorders such as Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
.
Conceptually, these reflexes are "hard-wired" before birth and are therefore able to be elicited in the newborn. As the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
matures, certain areas (usually within the frontal lobe
Frontal lobe
The frontal lobe is an area in the brain of humans and other mammals, located at the front of each cerebral hemisphere and positioned anterior to the parietal lobe and superior and anterior to the temporal lobes...
s) 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
Palmomental reflex
The palmomental reflex is a primitive reflex consisting of a twitch of the chin muscle elicited by stroking a specific part of the palm. It is present in infancy and disappears as the brain matures during childhood but may reappear due to processes that disrupt the normal cortical inhibitory...
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 reflexPalmomental reflexThe palmomental reflex is a primitive reflex consisting of a twitch of the chin muscle elicited by stroking a specific part of the palm. It is present in infancy and disappears as the brain matures during childhood but may reappear due to processes that disrupt the normal cortical inhibitory...
:- unknown. - Rooting reflex:- Baby finds breast to suckle.
- Sucking reflex:- Baby sucks breast / bottle teat to get milk.
- Snout reflexSnout reflexThe Snout reflex is a pouting or pursing of the lips that is elicited by light tapping of the closed lips near the midline. The contraction of the muscles causes the mouth to resemble a snout....
:- Involved in suckling. - Glabellar reflexGlabellar reflexGlabellar reflex is a primitive reflex. It is elicited by repetitive tapping on the forehead. Subjects blink in response to the first several taps...
:- May protect eyes in certain situations.