The 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

Snout

The snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...

.

This 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:...

 is tested in a neurological exam and if present, is a sign of brain damage

Brain damage

"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...

. Along with the "suck" and 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...

es, snout is considered a frontal release sign

Frontal release sign

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...

. These reflexes are normally inhibited by 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...

 activity in the brain, but can be "released" from inhibition if the frontal lobes are damaged. They are normally present in infancy, however, and up until about one year of age, leading to the hypothesis that they are primitive or archaic reflexes.

Frontal release signs are seen in disorders that affect the frontal lobes, such as dementia

Dementia

Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...

s, metabolic encephalopathies

Encephalopathy

Encephalopathy means disorder or disease of the brain. In modern usage, encephalopathy does not refer to a single disease, but rather to a syndrome of global brain dysfunction; this syndrome can be caused by many different illnesses.-Terminology:...

, closed head injuries

Closed head injury

Closed head injuries are a type of Traumatic Brain Injury in which the skull and dura mater remain intact. Closed head injuries are the leading cause of death in children under 4 years old and the most common cause of physical disability and cognitive impairment in young people...

, and hydrocephalus

Hydrocephalus

Hydrocephalus , also known as "water in the brain," is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head,...

. All of these disorders produce diffuse cerebral damage, usually involving many areas and systems in addition to the frontal lobes and pyramidal system, so the frontal release signs are not sufficient for a diagnosis.