From the Research
The Asymmetrical Tonic Neck Reflex (ATNR) manifests on both sides of the body, not just one side, and its presence can be observed in individuals of all ages, including adults. When the head is turned to one side, the arm and leg on the face side extend while the limbs on the skull side flex. This primitive reflex is normal in infants up to about 4-6 months of age and should naturally integrate (disappear) as the central nervous system matures. However, research has shown that ATNR can still be present in adults, as demonstrated by a study published in 2013 1, which found that the reflex can be evoked in healthy adult subjects. ATNR is bilateral in nature, meaning it affects both sides of the body in a predictable pattern depending on head position. If ATNR persists beyond the expected developmental timeframe, it may interfere with activities requiring crossing the midline, crawling, and coordination. The reflex exists to help develop muscle tone and early eye-hand coordination in infants, but its persistence can indicate neurological immaturity. Assessment of ATNR involves observing the child's response when the head is turned to both the right and left sides to evaluate the reflex pattern on each side of the body.
Some key points to consider when assessing ATNR include:
- The reflex is normally present in infants and should integrate by 4-6 months of age
- Persistence of ATNR beyond the expected developmental timeframe may indicate neurological immaturity
- ATNR can still be present in adults, as demonstrated by recent research 1
- Assessment of ATNR involves observing the individual's response to head rotation, which can help evaluate the reflex pattern on each side of the body.
It's worth noting that while some studies have investigated the presence of ATNR in specific populations, such as individuals with functional neurological disorders 2 or stroke survivors 3, the most recent and highest-quality study on the topic of ATNR manifestation is the 2013 study published in Neuroscience Letters 1. Additionally, a 2021 guide to cranial nerve testing for musculoskeletal clinicians highlights the importance of neurological examination in musculoskeletal practice, including the assessment of reflexes like ATNR 4.