Primitive Reflexes
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Direct answer
Primitive reflexes are automatic, brainstem-mediated movements present at birth that normally fade as the cerebral cortex matures during the first year. The Moro, palmar grasp, rooting, asymmetric tonic neck and parachute reflexes are the classic examples tested in NEET-PG. Their timing, symmetry and persistence are the clinical clues to neurological disease, so each reflex is read against the child's age.
What you must remember
- Moro reflex: present from birth and gone by about 4 to 6 months; the arms abduct and then return to the midline in response to a sudden startle.
- Palmar grasp: present from birth and usually lost by about 5 to 6 months, when voluntary grasp takes over.
- Rooting reflex: the head turns toward a cheek stroke from birth and fades by about 3 to 4 months.
- Asymmetric tonic neck reflex (ATNR): the fencing posture with the limbs extending on the side the head faces, usually gone by about 6 months.
- Parachute reflex: the arms extend when the infant is tilted forward; it appears around 8 to 9 months and persists throughout life.
- Persistence: a Moro, grasp or ATNR still present after about 6 months raises concern for upper motor neuron disease such as cerebral palsy.
- Asymmetry: an unequal Moro suggests a fractured clavicle or humerus, or a brachial plexus palsy such as Erb palsy.
- Absence of parachute: a missing parachute reflex after 9 months indicates cortical or central nervous system disease.
Reading a reflex at the bedside
A 9-month-old boy is brought for a development check, and his parents report that he still grasps and turns his head when touched. The reflexes must be read together rather than one at a time.
- Note the age first: each reflex has a window of appearance and disappearance, so a reflex is abnormal only in relation to the child's age in months.
- Check symmetry: compare the left and right limbs, since an asymmetric Moro or grasp points to a unilateral injury such as a fractured clavicle or brachial plexus palsy.
- Look for persistence: a Moro, palmar grasp or ATNR still present after about 6 months raises concern for cerebral palsy or another upper motor neuron lesion.
- Look for absence: a missing parachute reflex after 9 months, or a bilaterally absent Moro in a newborn, suggests significant brain or neuromuscular disease.
- Correlate with tone and posture: combine the reflex findings with muscle tone, head control and milestones before labelling the child.
Where the exam tries to catch you
Viva and MCQ questions usually ask what a reflex means when it fails to fade or fails to appear.
- Trap: calling a persistent grasp normal because the child is otherwise well. Correct: persistence beyond about 6 months is abnormal and should prompt a neurological check.
- Trap: attributing an asymmetric Moro to a brain disorder first. Correct: a fractured clavicle or brachial plexus injury is the common cause, and the limb should be examined before anything else.
- Trap: expecting the parachute reflex to disappear like the others. Correct: it appears around 8 to 9 months and persists for life, so its absence is the abnormal finding.
Frequently asked questions
At what age should the Moro reflex disappear?
The Moro reflex normally fades by about 4 to 6 months of age. Persistence beyond this age, or an asymmetric response at any age, is abnormal and needs review. The timing of its disappearance is a common MCQ.
Which persisting reflexes suggest cerebral palsy in an infant?
Persistence of the asymmetric tonic neck reflex and the palmar grasp beyond about 6 months suggests cerebral palsy, especially when muscle tone is abnormal. An absent parachute reflex after 9 months adds to that concern. Neurological assessment is then required.
What does an asymmetric Moro reflex suggest in a newborn?
An asymmetric Moro reflex in a newborn suggests unilateral injury, most commonly a fractured clavicle or humerus, or a brachial plexus palsy such as Erb palsy. The affected arm moves less than the normal side. Examining the limb for swelling and crepitus is the next step.
Why is the parachute reflex different from the other primitive reflexes?
The parachute reflex is different because it appears around 8 to 9 months and persists for life, unlike the others, which fade. Its absence after 9 months indicates cortical disease. It is therefore checked as a marker of cerebral maturity rather than as a reflex that should disappear.