Frontal release signs are
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 are suppressed by the development of the f ...
traditionally held to be a sign of disorders that affect the
frontal lobe
The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere (in front of the parietal lobe and the temporal lobe). It is parted from the parietal lobe by a groove betwe ...
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.
One
reflex
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus.
Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...
thought to have good localizing value is the
palmar grasp
Palmar grasp reflex (or grasp reflex) is a primitive and involuntary reflex found in infants of humans and most primates. When an object, such as an adult finger, is placed in an infant's palm, the infant's fingers reflexively grasp the object. ...
reflex which usually signifies damage to the frontal lobe of the opposite side.
The
glabellar reflex The glabellar reflex, also known as the "glabellar tap sign", is a primitive reflex elicited by repetitive tapping of the the smooth part of the forehead above the nose and between the eyebrows. Subjects respond to the first several taps by blink ...
or "glabellar tap" is present in individuals with
extrapyramidal disorder
Movement disorder refers to any clinical syndrome with either an excess of movement or a paucity of voluntary and involuntary movements, unrelated to weakness or spasticity. Movement disorders are synonymous with basal ganglia or extrapyramidal d ...
s such as
Parkinson's disease
Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...
.
These reflexes are believed to be "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
The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere (in front of the parietal lobe and the temporal lobe). It is parted from the parietal lobe by a groove betwe ...
s) exert an inhibitory effect, thus causing the reflex to disappear. When disease processes disrupt these inhibitory pathways, the reflex is "released" from inhibition and can be elicited once again, hence the term "frontal release sign".
Some frontal release signs and their role in infancy:
*
Palmar grasp
Palmar grasp reflex (or grasp reflex) is a primitive and involuntary reflex found in infants of humans and most primates. When an object, such as an adult finger, is placed in an infant's palm, the infant's fingers reflexively grasp the object. ...
: Baby naturally grabs objects placed in palm.
*
Palmomental reflex The palmomental reflex (PMR) or Marinesco-Radovici Sign or Kinn reflex or Marinesco 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 t ...
: stroking on the
thenar eminence
The thenar eminence is the mound formed at the base of the thumb on the palm of the hand by the intrinsic group of muscles of the thumb. The skin overlying this region is the area stimulated when trying to elicit a palmomental reflex. The word ...
of the hand causes contraction of mentalis muscles of the chin.
*
Rooting reflex
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 are suppressed by the development of the f ...
: Baby finds breast to suckle.
*
Sucking reflex
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 are suppressed by the development of the f ...
: Baby sucks breast / bottle / teat to get milk.
*
Snout reflex The Snout reflex (also orbicularis oris reflex) or a "Pout" 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.
This reflex ...
: Involved in suckling.
*
Glabellar reflex The glabellar reflex, also known as the "glabellar tap sign", is a primitive reflex elicited by repetitive tapping of the the smooth part of the forehead above the nose and between the eyebrows. Subjects respond to the first several taps by blink ...
: May protect eyes in certain situations.
References
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Symptoms and signs: Nervous system
Reflexes
Frontal lobe