Developmental (Primitive) Reflexes in Pediatrics

Key Concepts

• Origin: Mediated by brainstem and spinal cord; inhibited by maturing cortex as myelination progresses
• Significance:
  • Absent at expected appearance → lower motor neuron or spinal injury
  • Persistent beyond expected disappearance → upper motor neuron injury (cerebral palsy, TBI, developmental delay)
  • Asymmetry at any age → suspect focal neurological lesion (brachial plexus injury, hemiplegia, etc.)

Primitive Reflexes: Appearance & Disappearance

Individual Reflex Descriptions

1. Moro Reflex (Startle Reflex)

• Stimulus: Sudden drop of the head relative to the body (semi-reclined, then allow head to drop slightly), or sudden loud noise
• Response:
  1. Abduction and extension of arms with opening of hands (symmetric)
  2. Followed by adduction (embracing) and flexion
  3. Often accompanied by crying
• Appears: 28 weeks GA
• Gone by: 5–6 months
• Clinical notes:
  • Asymmetric Moro → suspect brachial plexus injury (Erb's palsy), clavicle fracture, or hemiplegia
  • Absent Moro → severe CNS depression, diffuse motor disorder
  • Persistent beyond 6 months → suspect cerebral palsy

2. Palmar Grasp Reflex

• Stimulus: Pressure on the palm (place finger from ulnar side)
• Response: Flexion of all fingers, gripping the examiner's finger
• Appears: 28 weeks GA
• Gone by: 2–3 months
• Clinical notes:
  • Asymmetric grasp → contralateral hemisphere lesion or ipsilateral peripheral nerve injury
  • Persistence beyond 4–5 months → upper motor neuron pathology
  • The plantar grasp (Babinski's related response) is a separate but analogous reflex in the foot

3. Rooting Reflex

• Stimulus: Stroke the corner of the mouth or cheek
• Response: Turning of head toward the stimulus, mouth opens — facilitates breastfeeding
• Appears: 32 weeks GA
• Gone by: ~1 month (awake); may persist during sleep for several months
• Clinical notes:
  • Absent in premature infants < 32 weeks — important for feeding decisions
  • Persistence in adults = frontal lobe release sign

4. Asymmetric Tonic Neck Reflex (ATNR) — "Fencer Posture"

• Stimulus: Rotation of the head to one side while the infant is supine
• Response: Extension of the arm and leg on the face (chin) side; flexion of the arm and leg on the skull (occiput) side
• Appears: 35 weeks GA
• Gone by: 6–7 months
• Clinical notes:
  • Should never be obligatory (infant should be able to break the posture)
  • Obligatory ATNR at any age or persistence beyond 7 months → cerebral palsy strongly suspected
  • Interferes with midline hand activity, rolling, and feeding if persistent

5. Parachute Reflex

• Stimulus: Sudden downward thrust while holding infant in ventral suspension (face-down, horizontal)
• Response: Extension and abduction of arms and hands, as if to break a fall — "protective extension"
• Appears: 7–8 months
• Persists: For life — this is a protective postural reflex, not a primitive one that needs to disappear
• Clinical notes:
  • Absence after 10–12 months → suspect motor pathway abnormality
  • Asymmetry suggests hemiplegia on the non-responsive side

6. Plantar (Babinski) Reflex

• Stimulus: Stroke lateral sole from heel to ball of foot
• Response in infants: Upgoing (extensor) big toe with fan-out of other toes — normal in infants
• Response in older children/adults: Downgoing (flexor) toes — upgoing is pathological
• Transition: Becomes flexor by ~12–18 months (when walking begins and corticospinal tract matures)
• Clinical notes:
  • Upgoing Babinski after 18–24 months → UMN pathology (pyramidal tract lesion)

7. Sucking Reflex

• Stimulus: Touch to lips or oral cavity
• Response: Rhythmic sucking movements
• Appears: ~28 weeks GA (weak); strong by 34 weeks
• Gone by: Replaced by voluntary sucking; primitive form disappears ~4 months
• Clinical notes: Critical for feeding. Absent or weak sucking in term neonates → brainstem dysfunction, hypotonia, or birth asphyxia

8. Stepping (Walking) Reflex

• Stimulus: Hold infant upright with feet touching flat surface; tilt forward slightly
• Response: Alternating stepping movements
• Appears: Birth
• Gone by: ~2 months (disappears before voluntary walking at ~12 months)
• Significance: Not a precursor to walking; disappears as cortex develops

9. Galant Reflex (Trunk Incurvation)

• Stimulus: Infant prone or held ventral; stroke paravertebral skin from shoulder to buttock on one side
• Response: Lateral flexion (incurvation) of trunk toward the stimulated side
• Appears: 32 weeks GA
• Gone by: 4–6 months
• Clinical notes: Asymmetry or absence suggests spinal cord injury

Tendon Reflex Rating Scale (Deep Tendon Reflexes)

Segmental Localization of DTRs

Upper vs. Lower Motor Neuron: Key Distinctions

Clinical Pearls

1. Always test reflexes bilaterally — asymmetry is more significant than overall hypo/hyperreflexia
2. Obligatory ATNR (cannot break the fencer posture) is always abnormal at any age
3. Absent Moro at birth in a term neonate → urgent evaluation; consider birth asphyxia, cervical cord injury, or severe generalized hypotonia
4. Parachute reflex is unique — it appears late and is permanent; failure to appear by 12 months is a red flag
5. In cerebral palsy, primitive reflexes persist, protective reflexes (parachute, righting) are absent or asymmetric, and DTRs are brisk
6. The Galant reflex persistence beyond 6 months has been associated (controversially) with learning difficulties

Spinal Cord Level of Developmental (Primitive) Reflexes

"This repertoire of movements depends on reflexes organized mainly at the spinal and brainstem levels." — Adams & Victor's Principles of Neurology, 12th ed.

Neuraxis Hierarchy of Primitive Reflexes

Reflex-by-Reflex Neural Level

Spinal Cord Level

The Galant reflex absence or asymmetry is one of the best indicators of thoracolumbar spinal cord injury in neonates.

Lower Brainstem Level (Medulla / Pons)

Upper Brainstem Level (Midbrain)

Diencephalon / Emerging Cortical Level

Why Reflexes Disappear: Cortical Inhibition

• Babinski sign (upgoing toe) is normal in infants — corticospinal inhibition is incomplete
• Persistence of spinal/brainstem-level reflexes (e.g., ATNR, Moro, grasp beyond expected ages) → indicates failure of cortical inhibition → UMN pathology (cerebral palsy, periventricular leukomalacia)
• Brain death abolishes all brainstem reflexes but spinal cord reflexes are preserved (e.g., withdrawal to plantar stimulation can still occur in brain death)

Clinical Localization Summary

Hierarchical Maturation Sequence (Bottom-Up)

SPINAL CORD       → Active from ~20-28 weeks GA
     ↓ inhibited by...
BRAINSTEM (lower) → Active from ~28-32 weeks GA
     ↓ inhibited by...
MIDBRAIN          → Active from ~35 weeks GA
     ↓ inhibited by...
DIENCEPHALON      → Active ~birth–3 months
     ↓ inhibited by...
CORTEX            → Matures 0–24 months; takes over voluntary control

How to Elicit Spinal Cord-Level Developmental Reflexes: Technique & Procedure

General Setup Before Testing

• State: Infant should be alert but calm — not crying or feeding. Crying increases tone and suppresses reflexes.
• Temperature: Warm room; cold suppresses responses.
• Timing: Test between feeds (not immediately post-feed or hungry).
• Position: Each reflex requires a specific starting position (detailed below).
• Symmetry: Always test both sides and compare.
• Documentation: Note presence/absence, symmetry, and quality (brisk, sluggish, obligatory).

Spinal Cord-Level Reflexes — Step-by-Step

1. Galant Reflex (Trunk Incurvation Reflex)

Hold infant in ventral/prone suspension — face-down, supported under the chest/abdomen with one hand, free in the air.

1. With a finger or blunt instrument (fingernail tip), stroke the paravertebral skin in a line from the shoulder (thoracic region) down to the sacrum/buttock on one side.
2. Keep the stroke 1–2 cm lateral to the spine.
3. Repeat on the opposite side.

The trunk curves laterally toward the stimulated side — the pelvis swings to that side (concavity toward stimulus).

• Absent unilaterally → ipsilateral spinal cord lesion (T2–S1), rib fracture
• Absent bilaterally → transverse spinal cord injury, severe hypotonia
• Persistent beyond 6 months → associated with UMN pathology

2. Stepping Reflex (Walking Reflex)

Hold infant upright in vertical suspension — grasp under the axillae, face forward, supporting the head.

1. Lower the infant so the soles of the feet (especially the ball/hallucal area) touch a flat firm surface.
2. Tilt the infant slightly forward (~10–15°).
3. Observe for 5–10 seconds.

Infant makes alternating reciprocal stepping movements, lifting each foot and placing it forward.

• Asymmetric stepping → contralateral spinal cord injury, brachial plexus injury (if combined with arm asymmetry), or hemiplegia
• No stepping in term neonate → lumbar cord dysfunction, severe hypotonia

3. Crossed Extensor Reflex

Infant supine or prone; one leg held in full extension.

1. Hold one leg fully extended at the knee.
2. Apply a noxious stimulus to the sole of the extended (held) foot — firm plantar pressure or pin-prick equivalent.
3. Observe the opposite (free) leg.

1. Flexion of contralateral limb (withdrawal)
2. Adduction of contralateral limb
3. Extension of contralateral limb (attempts to push away from the stimulus)

• Absent → bilateral spinal cord dysfunction or severe CNS depression
• Persistence beyond 9 months → UMN spasticity / cerebral palsy
• Exaggerated → hyperreflexic state, UMN lesion

4. Plantar Grasp Reflex

Infant supine or held in ventral suspension; legs relaxed.

1. Apply firm pressure with your finger to the plantar surface just below the toes (ball of foot / hallucal area).
2. Do not stimulate the entire sole (that would elicit Babinski, not grasp).

Plantar flexion of all toes, curling and gripping the examiner's finger.

5. Flexor Withdrawal Reflex

Infant supine, legs relaxed.

1. Apply a sharp or noxious stimulus (firm pinprick equivalent) to the sole or dorsum of the foot.
2. Observe the ipsilateral leg.

Rapid flexion (withdrawal) of the stimulated limb — hip and knee flex, foot dorsiflexes.

• Absent → ipsilateral lower motor neuron lesion (lumbar plexus, spinal cord)
• Exaggerated or mass reflex (whole body flexion) → severe UMN lesion (spinal cord transection)

6. Anal Wink Reflex

Infant prone or in lateral decubitus; buttocks exposed.

1. Use a pin or cotton swab to gently stroke or prick the perianal skin at the anal verge.
2. Observe the external anal sphincter.

Visible contraction (wink/pucker) of the external anal sphincter.

• Absent → S3–S5 cord or cauda equina lesion — important in suspected spinal cord injury, spinal dysraphism (spina bifida)

Brainstem-Level Reflexes (Tested in Same Session)

7. Moro Reflex

Infant supine, head supported in midline by examiner's hand.

1. Support infant's head and upper body at ~30° with both hands.
2. Suddenly lower the head ~3 cm (allow controlled drop) relative to the body, then catch.

1. Infant supine on padded surface.
2. Examiner strikes the surface with both palms simultaneously beside infant's head.

1. Extension and abduction of arms — elbows straighten, arms spread wide, hands open
2. Adduction and flexion — arms "embrace" back to midline
3. Often followed by crying

• Asymmetric → fracture clavicle, brachial plexus injury (Erb's palsy on affected side), hemiplegia
• Absent bilaterally → severe CNS depression, birth asphyxia, cervical cord injury
• Persistent beyond 6 months → cerebral palsy

8. Palmar Grasp Reflex

Infant supine; arm relaxed.

1. Do not touch the dorsum of the hand (this inhibits the response).
2. Approach from the ulnar side and place your finger across the infant's palm.
3. Apply gentle pressure to the palm.

All four fingers flex and grip around the examiner's finger; grip is strong enough that infant can be partially lifted (do not fully suspend — safety risk).

9. Rooting Reflex

Infant supine, head midline, not sucking.

1. Stroke the corner of the mouth or cheek with a finger, moving from commissure toward the cheek.
2. Can also stroke the upper or lower lip.

Infant turns head toward the stimulus, opens mouth, and makes sucking movements.

10. ATNR — "Fencer Reflex"

Infant supine, relaxed, arms at sides.

1. Gently rotate head 45–90° to one side, hold for 5–10 seconds.
2. Observe limbs on both sides.
3. Repeat to the opposite side.

• Chin side: arm and leg extend
• Occiput side: arm and leg flex (fencer pose)

Summary Table: Technique at a Glance

Tips for Accurate Elicitation

1. Warm hands before touching the infant — cold suppresses responses
2. Test Galant first when infant is calm in prone suspension, before other stimuli cause crying
3. For Moro, always support the head — never let it fall freely; the 3 cm drop is sufficient
4. ATNR must not be obligatory — if infant cannot escape the posture within 30 seconds, it is pathological
5. Repeated stimulation fatigues spinal reflexes — test each reflex once or twice only
6. Note the quality: sluggish response may be as significant as absent

Galant Reflex — Why It Exists & Its Physiology

What Is It?

Why Does It Exist? (Functional Purpose)

1. Birth Canal Navigation (Primary "Why")

This is why it is also called a phylogenetically primitive reflex — it is homologous to the trunk-bending locomotion seen in fish and reptiles, controlled entirely by the spinal cord without cortical input.

2. Early Locomotion Contribution

Neurophysiology — The Reflex Arc

STIMULUS (cutaneous stroke, paravertebral skin)
         ↓
  Cutaneous mechanoreceptors
  (skin of back, T2–S1 dermatomes)
         ↓
  Primary afferent fibers (Aβ / Aδ)
  → enter ipsilateral dorsal horn of spinal cord
         ↓
  Spinal interneurons
  (dorsal horn → intermediate zone, ipsilateral)
         ↓
  Ipsilateral ventral horn motor neurons
  → innervate ipsilateral trunk muscles
  (erector spinae, obliques, quadratus lumborum)
         ↓
RESPONSE: Ipsilateral trunk muscles contract
→ Lateral flexion toward the stimulus

Key Points:

• Entirely spinal — no brainstem or cortex needed
• Ipsilateral arc — stimulus and response are on the same side (unlike crossed extensor which crosses)
• Segmental — works through multiple thoracolumbar segments simultaneously (T2–S1)
• Cutaneous trigger — activated by skin mechanoreceptors (touch/pressure), not proprioceptors

Why Does It Disappear? (Cortical Inhibition)

Cortical motor areas
      ↓ (via corticospinal tract, progressively myelinating)
Inhibitory interneurons in spinal cord
      ↓
Suppress the spontaneous spinal reflex arc
      ↓
Galant reflex extinguishes by 2–6 months

• The cortex actively inhibits spinal cord reflex circuits as it matures
• This is the same mechanism by which Babinski sign converts from extensor (normal in infants) to flexor (normal in adults), and why the Moro, ATNR, grasp all disappear on schedule

Myelin Timeline (Corticospinal Tract):

Why Persistence Is Pathological

• Cerebral palsy (UMN pathology, failure of cortical inhibition)
• Learning difficulties / dyspraxia (controversial — some researchers claim persistent Galant interferes with trunk stability needed for sitting and writing)
• Postural control problems — because the unchecked reflex causes involuntary trunk twisting when clothing touches the back or when sitting in a chair

Why Asymmetry or Absence Is Pathological

Absent unilaterally:

• The spinal reflex arc is interrupted on that side
• Suggests: ipsilateral spinal cord injury (T2–S1), thoracic vertebral fracture, spinal cord hemorrhage, or nerve root avulsion
• Clinically important in birth trauma — if one side of back was compressed/injured during delivery

Absent bilaterally in a term neonate:

• Suggests transverse spinal cord lesion (e.g., spinal cord ischemia, transverse myelitis, diastematomyelia)
• OR severe generalized hypotonia affecting motor neuron output (e.g., SMA type 1, birth asphyxia with cord involvement)

Analogy to Understand the Physiology

Summary