The asymmetrical tonic neck reflex in normal full-term infants.

Area of Science:

• Pediatric neurology
• Developmental pediatrics
• Infant motor development

Background:

• The asymmetrical tonic neck reflex (ATNR) is a primitive reflex crucial for early motor development.
• Understanding the ATNR's presence and pattern in healthy infants is essential for developmental assessments.

Purpose of the Study:

• To investigate the presence and characteristics of the asymmetrical tonic neck reflex in normal infants aged 1 to 12 weeks.
• To document the temporal pattern of the ATNR in both upper and lower limbs during early infancy.

Main Methods:

• Longitudinal observation of 12 healthy infants over the first 12 weeks of life.
• Seven observational visits including the first, second, and every other week thereafter.
• Videotaping of spontaneous supine behavior to record reflex responses in arms and legs.

Main Results:

• The asymmetrical tonic neck reflex was consistently observed in infants' arms throughout the study period, peaking at 6 weeks.
• The reflex was present in the legs, with the longest duration noted at the first week.
• Differential limb movement patterns were observed, with the 'face' side showing more movement than the 'skull' side in both arms and legs at specific time points.

Conclusions:

• The asymmetrical tonic neck reflex is a verifiable component of normal infant posture and movement within the first 12 weeks.
• The manifestation and temporal pattern of the ATNR differ between the arms and legs during early development.