The Asymmetrical tonic neck reflex (ATNR) is a primitive reflex that is found in new born babies and normally remains until around 6 months. It emerges in utero at around 18 weeks after conception and is usually identified and seen within the first 3 months after birth. The reflex is initiated when the head is turned to the left or the right whilst the baby lies on its back. The turning of the head causes the arm and the leg on one side to extend, whilst the limbs on the opposite side flex. If the head turns to the right, the right arm and leg will automatically extend whilst the left arm and leg both flex. It is often called the "fencing" reflex due to this pattern.      

The purpose of the ATNR is to provide stimulation for developing muscle tone and the vestibular system whilst in the womb before birth. It also assist with the birthing process by inhibiting limb movement and slowing it down so that the baby uses a "corkscrew" movement through the birth passage. ATNR helps with eye-hand co-ordination and serves as a precursor to this skill. A retained ATNR can have a significant impact on a child's development and it is often thought to have a major effect on the child's physical, cognitive, social and emotional progress, thus affecting their ability to function well in school. The retained reflex will continue to influence limb movement every time the head is turned and will have physical influences that impact on all other areas.

The retained ATNR prevents a baby from developing certain physical cross pattern movements such as rolling over, crawling and later marching using alternative leg and arm. As they grow older the child may have atypical movement patterns and may draw circles backwards, clap downwards, use one hand more than the other whilst clapping, or may be very single handed in most activities. A strongly retained reflex in the legs can also affect balance as the child looks from left to right. Walking, running and other physical activities can be uncoordinated and the child could have difficulty with symmetrical movements of the hands and feet.  A strongly retained ATNR may eventually cause physical problems in the child's bone development. It may affect joints as well as the skeletal structure. It is often seen in children with scoliosis (curving of the spine).

When assessing and identifying a child with a retained ATNR, therapists will look for key features that indicate the child has retained the reflex. It may be mild and difficult to detect, or strong and obvious. If the child displays three or more of the following symptoms, further investigations should be conducted:

• Difficulty with visual tracking and crossing the mid-line.
• Difficulty with reading and following a line of text. Easily losing their place when reading. Difficulty reading small print.
• Listening skills and attention skills are difficult to develop.   
• Difficulty with binocular vision so that images are blurred. Double vision as two eyes can't work together well.
• Poor handwriting and difficulty copying written script. Tight pencil grip.
• Difficulty with spellings.
• Poor eye-hand coordination.
• Difficulty with bilateral coordination.
• Poor sense of direction.
• Difficulty catching and throwing balls. Often using one hand to throw.  
• Poor gross motor coordination and balance.
• Difficulty with swimming, especially breast stroke.
• The child finds it hard to tell their left from right.
• Poor short term memory and difficulty following verbal instructions.
• Impulsive and emotionally immature for their age.

Asymmetrical Tonic Neck Reflex