Infantile reflexes

Alternative names:

primitive reflexes; reflexes in infants

Definition:

A reflex is an involuntary muscular response to a sensory stimulus. Certain sensations are known to produce specific muscular responses. The presence and strength of a reflex is an important indication of neurological development and function. Many of the infantile reflexes disappear as the infant matures, though some remain throughout adulthood.

Considerations:

Infantile reflexes are tested and observed by the medical team to evaluate neurological function and development. Absent or abnormal reflexes in an infant, persistence of a reflex past the age where the reflex is normally lost, or redevelopment of an infantile reflex in an older child or adult may suggest significant central nervous system, nerve trunk, or peripheral nerve problems.

Examples of reflexes that persist into adulthood are:

• blinking (corneal) reflex (blinks before eyes are touched or when sudden bright light appears)
• sneeze reflex (sneezes when nasal passages irritated)
• gag reflex (gags when throat or back of mouth stimulated)
• yawn reflex (yawns when needs additional oxygen)
• cough reflex (coughs when airway stimulated)

Infantile reflexes (normal in infants, abnormal in all others):

• Moro response
• tonic neck reflex
• grasp reflex
• rooting reflex
• sucking reflex (sucks when area around mouth stimulated)
• startle reflex (pulling arms and legs inward after loud noise)
• step reflex (stepping motions when sole of foot touches hard surface)
• crawl reflex (crawling motions when placed on abdomen)
• parachute reflex

The Moro response is elicited by lying an infant on the back. Support the upper body weight of the supine infant by the arms (not lifting the infant off the surface) then release the arms suddenly. The infant responds by throwing the arms outward, clenching the fist, appearing startled, then relaxing back to a normal rest position.

The tonic neck reflex is elicited when the head of a relaxed child, lying supine, is rotated to the side. The arm toward which the infant is facing extends straight away from the body with the hand partially open while the arm on the side away from the face is flexed and the fist is clenched tightly. Reversing the direction in which the face is turned reverses the position. The tonic neck positions is often described as the fencer's position because it resembles the stance of a fencer.

The grasp reflex is elicited by placing a finger on the infant's open palm. The hand will close around the finger. Attempting to remove the finger causes the grip to tighten. Newborn infants have strong grasps and can almost be lifted from the examination table if both hands are used.

The rooting reflex is elicited by stroking the cheek. The infant will turn toward the side that was stroked and begin to make sucking motions with its mouth.

The parachute reflex occurs in the slightly older infant and is elicited by holding the child upright then rotating the body quickly face forward (as if falling). The arms are reflexively extended as if to break a fall even though this reflex appears long before walking.

The presence of an infantile reflex after the age at which the reflex normally disappears can be a sign of brain damage or damage to the nervous system.

Common causes:

Abnormal presence of infantile reflexes can occur in adults with:

• stroke
• brain damage from trauma

Note: There may be other causes of persistence of infantile reflexes. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as location, quality, time course, aggravating factors, relieving factors, and associated complaints. Use the Symptom Analysis option to explore the possible explanations for persistent infantile reflexes, occurring alone or in combination with other problems.

Update Date: 02/09/00
Updated by: J. Gordon Lambert, MD, Associate Medical Director, Utah Health Informatics and adam.com editorial