Frontal release signs are primitive reflexes 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 be ...

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 reflex which usually signifies damage to the frontal lobe of the opposite side. The glabellar reflex or "glabellar tap" is present in individuals with extrapyramidal disorders 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 beco ...

. 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

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: 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 ...

: 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: May protect eyes in certain situations.

References

{{reflist Symptoms and signs: Nervous system Reflexes Frontal lobe