A nurse is assessing a 3-day-old newborn. Which finding would indicate a normal primitive reflex?
The nurse observes the newborn's reflexes during a routine assessment.
1When the nurse strokes the sole of the foot from heel to toe, the toes fan out and the big toe extends upward.✓ 정답
2When the nurse claps hands loudly near the newborn, the infant extends arms and legs then brings them back to midline.
3When the nurse places a finger in the newborn's palm, the infant grasps the finger tightly.
4When the nurse turns the newborn's head to one side, the arm and leg on that side extend while the opposite limbs flex.
해설
The Babinski reflex (toes fan out and big toe extends when sole is stroked) is normal in newborns. Other options describe Moro (2), grasp (3), and tonic neck (4) reflexes.
This question tests your ability to differentiate between normal and abnormal newborn reflexes. The key is to identify the expected response for a specific primitive reflex in a neurologically intact 3-day-old infant. The correct answer describes the Babinski reflex, a normal finding in infants up to about 12-24 months of age due to an immature central nervous system.
Why Option 1 is Correct
Option 1 accurately describes a normal Babinski reflex. The expected response when stroking the lateral sole of a newborn's foot from heel to toe is dorsiflexion of the great toe and fanning of the other toes. The provided source explains the physiological basis for this [1]. In the newborn, the pyramidal tract is not yet fully myelinated, meaning it does not exert the same inhibitory control over spinal motoneurons as it does in an older child or adult. Therefore, a primitive flexion synergy is brisk and involves all muscles that shorten the leg. The toe "extensors" are part of this synergy because their contraction also contributes to shortening the leg, making them physiological flexors in this context [1]. The upward movement of the big toe is a component of this mass flexion response, not a sign of upper motor neuron damage as it would be in an adult.
Why the Other Options are Incorrect
Option 2: This describes the Moro reflex. While the Moro reflex is normal in a newborn, the description is incomplete and could be misinterpreted. A complete Moro reflex involves symmetric abduction and extension of the arms, fanning of the fingers, and then a return to midline with the arms coming together in an embrace-like motion, often followed by crying. The description of extending and bringing back the arms and legs is too vague and does not capture the characteristic "embrace" motion of the arms, making Option 1 a more precise and unequivocal description of a normal reflex.
Option 3: This describes the palmar grasp reflex. While a tight grasp is normal, the description is a general observation. The Babinski reflex description in Option 1 is a highly specific, objective neurological sign with a clear developmental rationale tied to corticospinal tract maturation, making it a more definitive indicator of a normal primitive reflex in the context of this question.
Option 4: This describes the asymmetric tonic neck reflex (ATNR), often called the "fencer's pose." While ATNR is a normal primitive reflex, it should not be obligatory. If the infant is stuck in this posture, it could indicate a neurological problem. The Babinski reflex is a more straightforward, consistently present, and easily elicited sign of a normal, immature nervous system in a 3-day-old, without the clinical caveats associated with ATNR.
Clinical Application and NCLEX Insight
For the NCLEX, you must know the timeline for the Babinski reflex. It is a normal finding in infants until the corticospinal tract matures, typically around 12-24 months of age. After this age, a positive Babinski sign (great toe dorsiflexion and toe fanning) is abnormal and indicates an upper motor neuron lesion. The underlying mechanism, as the source highlights, is the maturation of the pyramidal tract gaining control over spinal reflexes, which causes the toe "extensors" to disengage from the primitive flexion synergy. The toes then respond with plantar flexion, a segmental reflex, instead of the mass extension response [1]. This pathophysiological link between an anatomical finding and a clinical sign is a high-yield concept for the examination.
References (research sources)
[1]
The Babinski reflex.Research articlevan Gijn J. (1995) · DOI: 10.1136/pgmj.71.841.645
Clinical Assessment of the Babinski Reflex in Newborns
Correct Technique
Use a firm but gentle stimulus, such as the blunt end of a reflex hammer or your fingernail.
Stroke the lateral aspect of the sole, starting at the heel and moving upward toward the little toe, then curve medially across the metatarsal heads.
Avoid deep or painful stimulation that could cause a withdrawal response, which may mask the reflex.
Ensure the infant is in a quiet, relaxed state; crying or active movement can interfere with the assessment.
Expected vs. Abnormal Findings
Normal (0-24 months): Dorsiflexion of the great toe and fanning of the other toes. This is a normal primitive response due to an immature corticospinal tract.
Equivocal: No response or a plantar flexion response can be normal variants but warrant documentation and follow-up if asymmetric.
Abnormal: Absence of the reflex unilaterally may indicate a peripheral nerve injury or lower motor neuron lesion. Persistence beyond 2 years suggests a central nervous system lesion.
Key Distinction: In adults, the same stimulus producing great toe extension (upgoing toe) is an abnormal upper motor neuron sign (positive Babinski sign). In infants, it is the expected physiological response.
Documentation and Parent Education
Document the response as "Babinski reflex present and symmetric" or note any asymmetry or absence.
Reassure parents that the toe fanning is a normal sign of a healthy, developing nervous system and is not painful.
Explain that this reflex will disappear as the baby grows and the nervous system matures, typically by the time they start walking.
If the reflex is absent or asymmetric, notify the pediatric provider for further neurological evaluation.
Integration with Complete Neurological Exam
Always assess primitive reflexes bilaterally to compare symmetry.
Pair the Babinski assessment with other newborn reflexes: Moro, rooting, sucking, palmar grasp, plantar grasp, and ATNR.
Consider the infant's gestational age; preterm infants may have incomplete or diminished reflexes.
Serial examinations are valuable; a reflex that changes from present to absent or vice versa on one side is a significant finding requiring immediate investigation.
Babinski Reflex — A primitive reflex elicited by stroking the lateral sole of the foot from heel to toe, resulting in dorsiflexion of the great toe and fanning of the other toes; normal in infants up to 12-24 months due to incomplete myelination of the pyramidal tract.
Moro Reflex — A startle reflex triggered by a loud noise or sudden movement, characterized by symmetric arm extension and abduction with hand opening, followed by arm flexion and adduction back to the midline.
Palmar Grasp Reflex — A primitive reflex where the infant's fingers close tightly around an object placed in the palm; it appears in utero and persists until about 4-6 months of age.
Asymmetric Tonic Neck Reflex (ATNR) — A primitive reflex where turning the infant's head to one side causes extension of the arm and leg on that side and flexion of the opposite limbs, often described as the 'fencer' position.