Primitive Reflexes

Overview

• Reflexes normally present in infants.
• Disappear progressively as child develops.
• Mediated by brainstem and spinal cord.
• Suppression occurs via maturation of higher cortical centers.
• Appearance and disappearance follow specific developmental timelines.
• Essential component of neonatal and infant neurological examination.
• Provide crucial information regarding central nervous system (CNS) integrity.
• Absence, asymmetry, or persistence beyond expected age signifies CNS dysfunction.

Prerequisites for Testing

• Infant must be alert (State 3-5: eyes open, responsive).
• Infant must not be irritable.
• Minimum 2 hours post-feeding.
• Head positioned in midline during assessment to prevent tone alteration.

Chronology of Primitive Reflexes

Specific Reflexes: Elicitation and Interpretation

1. Moro Reflex

• Elicitation Method 1: Support infant in semierect position. Allow head to fall backward onto examiner's hand.
• Elicitation Method 2: Support head in midline with one hand, back with the other. Raise infant to 45°. Let head fall through 10°. Repeat three times.
• Normal Response:
  • Phase 1 (Abduction and Extension): The infant abruptly abducts and extends the arms, spreading them outward. The hands open, and the fingers flare, typically with the thumb and Index finger forming a distinct "C" shape.
  • Phase 2 (Adduction and Flexion): The infant then brings the arms back toward the midline in a smooth, clasping, or embracing motion, often flexing the arms over the chest.
• Clinical Nuances:
  • Absent in term newborn: Ominous sign. Suggests significant diffuse CNS dysfunction.
  • Asymmetric response: Indicates local pathology. Fractured clavicle, brachial plexus injury, or hemiparesis.
  • Abnormal Moro: Constitutes a neonatal neurological alarm sign.

2. Palmar Grasp and Traction Response

• Elicitation: Place Index finger into infant's open palm. Gently press palmar surface. Avoid touching dorsal surface.
• Normal Response: Forced grasp of examiner's finger.
• Traction Component: By 37 weeks gestation, grasp is strong enough to lift infant from bed with gentle traction.
• Clinical Nuances:
  • Tests distal power.
  • Asymmetry suggests unilateral weakness or lower motor neuron lesion.
  • Persistence beyond 6 months indicates spasticity or upper motor neuron (UMN) lesion.

3. Asymmetric Tonic Neck Reflex (ATNR)

• Elicitation: Infant in supine position. Manually rotate infant's head to one side.
• Normal Response: "Fencing posture". Extension of arm and leg on the side to which face is rotated. Flexion of contralateral arm and leg.
• Clinical Nuances:
  • Visible movement may be absent; change in muscle tone is sufficient.
  • Obligatory ATNR: Infant becomes stuck in fencing posture. Always abnormal. Implies severe CNS disorder.
  • Persistent ATNR beyond 6 months strongly suggests Cerebral Palsy.

4. Rooting and Sucking Reflexes

• Elicitation (Rooting): Touch corner of lips or cheek.
• Normal Response (Rooting): Infant moves lips to suck or root in direction of stimulus.
• Elicitation (Sucking): Place clean little finger into mouth with pulp facing upwards. Touch center of lips.
• Normal Response (Sucking): Note frequency, strength, and stripping action during finger removal.
• Clinical Nuances:
  • Absent oral reflexes constitute a neonatal neurological alarm sign.
  • Essential for feeding evaluation. Poor suck indicates bulbar dysfunction or encephalopathy.

5. Parachute Reflex

• Elicitation: Hold infant's trunk securely. Suddenly lower infant face down as if falling.
• Normal Response: Arms spontaneously extend to break the fall.
• Clinical Nuances:
  • Postural/protective reflex, not strictly a primitive disappearing reflex.
  • Prerequisite to independent walking.
  • Absence beyond 10-12 months indicates abnormal developmental reflexes and motor delay.

Clinical Significance and Pathology

Indicators of CNS Depression

• Hypoxic-Ischemic Encephalopathy (HIE): Primitive reflexes are depressed or absent. Moderate HIE: Poor suck. Severe HIE: Unable to suck.
• General CNS Insult: Apathy, floppiness, and absent Moro/suck reflexes are critical alarm signs of early brain damage.

Indicators of Cerebral Palsy (CP)

• Persistence: Persistence of primitive reflexes (e.g., ATNR, Moro, Rooting) beyond typical disappearance age is a hallmark clinical feature of CP.
• Delayed Postural Reflexes: Absence of parachute and Landau reflexes further supports CP diagnosis.
• Prognostic Value: Persistent primitive reflexes beyond 2 years of age predict a poor neuromotor outcome and non-ambulatory status in CP.

Differential Diagnosis via Reflexes