Ataxia explained

Why might a horse become weak, wobbly or unable to stand? Dr Philip Ivens MRCVS discusses potential causes

- Dr Philip Ivens

ATAXIA refers to incoordination, which can affect one or more of the limbs and also the neck and body. While this complex condition can result from problems with the vestibular apparatus in the inner ear, or in a part of the brain called the cerebellum, ataxia often arises due to an issue in the spinal cord.

Spinal ataxia occurs when there is a lack of information coming up the horse’s spinal cord to tell his brain where his body parts are in space and the state of muscle contraction at any one time. Ataxia is therefore not painful for the horse; rather, he has no sense of the position and movement of affected areas.

The hallmark of ataxia is inconsistency. Most orthopaedic lamenesses are consistently repeatable in any one gait, or on a particular surface, but with ataxia, the gait changes all the time. A leg might swing out to the side or under the body; a joint might overflex, or a foot scuffor drag.

If he trips, an ataxic horse may be slow to correct himself and potentially fall. His trunk, neck or both might sway. He may tread on himself, or struggle to turn or instead of crossing his legs underneath as he does turn, he stays rooted to the spot, pivoting while his legs eventually catch up.

A grading system can document the severity of the problem, starting with a zero for normal strength and coordination. Grade one applies to a horse who walks normally in a straight line, but shows a slight deficit when walking on tight circles or with his head extended. He may also sway when pulled by the tail.