Tonic labyrinthine reflex

The tonic labyrinthine reflex (TLR) is a primitive reflex found in newborn humans. With this reflex, tilting the head back while lying on the back causes the back to stiffen and even arch backwards, causes the legs to straighten, stiffen, and push together, causes the toes to point, causes the arms to bend at the elbows and wrists, and causes the hands to become fisted or the fingers to curl. The presence of this reflex beyond the newborn stage is also referred to as abnormal extension pattern or extensor tone.

The presence of the TLR as well as other primitive reflexes such as the asymmetrical tonic neck reflex (ATNR) beyond the first months of life may indicate that the child has developmental delays and/or neurological abnormalities. For example, in people with cerebral palsy, the reflexes may persist and even be more pronounced. As abnornal reflexes, both the tonic labyrinthine reflex and the asymmetrical tonic neck reflex can cause problems for the growing child. The TLR and ATNR both hinder functional activities such as rolling, bringing the hands togheter, or even bringing the hands to the mouth. Over time, both the TLR and ATNR can cause serious damage to the growing child's joints and bones, causing the head of the thighbone to partially slip out of the hip socket (subluxation) or completely move out of the hip socket (dislocation).

Source
Sieglinde Martin MS PT, Teaching Motor Skills to Children with Cerebral Palsy and Similar Movement Disorders: A Guide for Parents and Professionals (Woodbine House, 2006), ISBN 1-89062-772-0, and ISBN 978-1890627720.