Moro reflex

The Moro reflex in a four-day-old infant: 1) the reflex is initiated by pulling the infant up from the floor and then releasing him; 2) he spreads his arms; 3) he pulls his arms in; 4) he cries (10 seconds)

The Moro reflex, which is distinct from the startle reflex, is one of the infantile reflexes. It may be observed in incomplete form in premature birth after the 28th week of gestation, and is usually present in complete form by week 34 (third trimester). It is normally present in all infants/newborns up to 4 or 5 months of age, and its absence indicates a profound disorder of the motor system. An absent or inadequate Moro response on one side is found in infants with hemiplegia, brachial plexus palsy, or a fractured clavicle. Persistence of the Moro response beyond 4 or 5 months of age is noted only in infants with severe neurological defects. It was discovered and first described by Austrian pediatrician Ernst Moro (1874-1951).

This reflex is a response to a sudden loss of support, when the infant feels like it is falling. It is believed to be the only unlearned fear in human newborns^{[citation needed]}. The primary significance of this reflex is in evaluating integration of the central nervous system (CNS), and it involves 3 distinct components:

1. spreading out the arms (abduction)
2. unspreading the arms (adduction)
3. crying (usually)

Absence of any component (except crying) or any asymmetry in the movements is abnormal, as is persistence of the reflex in older infants, children and adults. However, in individuals with cerebral palsy, persistence and exacerbation of this reflex is common.

References

1. Adams and Victor's Neurology, Chapter 28. Normal Development and Deviations in Development of the Nervous System

External links

• Medline Plus: Moro reflex
• Video of the Moro Reflex from the University of Utah (Google Video)
• Pathologic Moro Reflex in an adult following acute demyelinating lesion of unknown origin in medulla oblongata (Neurology)