Overview
Primitive reflexes are central nervous system reflexes that occur normally in infants in response to particular stimuli. As the infant develops, these reflexes are suppressed by the frontal lobe and disappear within the first year of life. They may recur in adults with brain injuries or certain types of dementia.
These primitive reflexes are likely to have helped infant survival in early humans in the distant past.
Frontal release signs
A frontal release sign describes the re-emergence of primitive reflexes suggesting disorders affecting the frontal lobes. These disorders reduce primitive reflex inhibition and ‘release’ them, resulting in their re-emergence.
Clinical Significance of Primitive Reflexes
When primitive reflexes are suppressed, they are described as ‘integrated’. If primitive reflexes are not integrated and persist, they can suggest disorders such as cerebral palsy and learning difficulties.
Absent primitive reflexes suggest neurological dysfunction.
Moro Reflex
Overview
The Moro reflex is elicited by simulating a sense of falling in the infant. Quickly tipping back the infant into a supine position leads to:
- Abduction of the shoulder and extension of the elbow (they reach out) followed by
- Immediate flexion of the upper limbs and an audible cry
It is thought that the Moro reflex is thought to be a survival mechanism to help the infant cling to their mother if they lose balance.
Clinical significance
The Moro reflex evaluates the central nervous system, therefore an abnormal Moro reflex can suggest a problem with the brain or spinal cord.
Sucking Reflex
Overview
The sucking reflex is elicited when placing a finger in the mouth causing the neonate to suck. This is associated with the infant’s coordination of breathing and swallowing.
Clinical significance
An abnormal reflex can suggest neurological immaturity in newborn infants or dysfunction in the basal ganglia or brainstem.
Rooting Reflex
Overview
Stroking the infant’s cheek or mouth causes them to turn their head to the stimulus and assists in breastfeeding. It helps the newborn find the source of food.
Clinical significance
An abnormal rooting reflex may suggest cerebral palsy. An absent abnormal rooting reflex may suggest trigeminal nerve dysfunction if the infant cannot feel the stimulus on their cheek.
Grasp Reflex
Overview
The palmar grasp reflex can be elicited if a finger is placed in the infant’s palm. This causes the infant to grasp the finger. Its role in survival is not entirely known.
Clinical significance
A weak grasp reflex suggests peripheral nerve damage and its persistence suggests cerebral palsy.
Stepping Reflex
Overview
Despite infants not being able to support their own weight, the stepping reflex is elicited by holding the infant upright and lowering them until their feet touch a surface. Once the soles of the feet touch the surface, they will attempt to walk.
Clinical significance
Persistence of the stepping reflex can suggest cerebral palsy.
