From the Guidelines
The Asymmetric Tonic Neck Reflex (ATNR) is indeed present among patients with stroke, although the provided evidence does not directly address its prevalence or management. The evidence provided focuses on the management of spasticity in stroke patients, which is a related but distinct topic 1. Spasticity is defined as velocity-dependent hyperactivity of tonic stretch reflexes and is a common impairment after stroke, resulting in significant pain and functional disturbances 1. While the evidence discusses various treatments for spasticity, including oral medications like tizanidine, baclofen, and dantrolene, it does not specifically mention the ATNR 1.
However, based on general medical knowledge, the ATNR is a primitive reflex that can reemerge following stroke due to damage to the brain's inhibitory mechanisms. When a stroke patient turns their head to one side, the ATNR manifests as extension of the limbs on the face side and flexion of the limbs on the skull side. The presence of ATNR can significantly impact rehabilitation efforts by interfering with normal movement patterns, balance, and functional activities. Clinicians should assess for this reflex during neurological examinations, as its presence may indicate more extensive brain damage and potentially poorer functional outcomes.
Some key points to consider in the management of stroke patients with ATNR include:
- Assessing for the presence of ATNR during neurological examinations
- Understanding the neurophysiological basis of ATNR to explain characteristic posturing and movement limitations during recovery
- Incorporating techniques to inhibit or integrate the ATNR into rehabilitation strategies to improve motor control and functional independence
- Managing spasticity, which is a related but distinct topic, using a stepwise approach that includes positioning, passive stretching, and range of motion exercise, as well as oral medications like tizanidine, baclofen, and dantrolene 1.
From the Research
Presence of ATNR in Stroke Patients
- The asymmetric tonic neck reflex (ATNR) has been found to be present in patients with stroke, as evidenced by studies that investigated the effects of ATNR on movement and motor control in stroke survivors 2, 3, 4.
- A study published in 2009 found that the effect of ATNR is significant in the stroke population when abducting the shoulder at 25% of maximum ability, and that it affects reaching distance especially when shoulder loading in abduction is required 2.
- Another study published in 2012 found that neck rotation modulates flexion synergy torques, indicating an ipsilateral reticulospinal source for impairment in stroke, and that the ATNR is reemerged following stroke 4.
- However, a study published in 1984 found that there is no difference in the intensity of the ATNR between post-cerebrovascular accident (CVA) adults with hemiplegia and neurologically intact adults 3.
Comparison with Healthy Adults
- A study published in 2013 found that the ATNR and symmetric tonic neck reflexes (STNR) can still be evoked in healthy adult subjects, suggesting that these reflexes may still be involved in motor control in adults 5.
- This study used a detailed measurement method to investigate the effects of head angle on elbow angle, and found that the ATNR and STNR are still present in healthy adults 5.