Your horse’s gait doesn’t look right. It’s not something you can really put your finger on, but he looks off. Is he lame, or is there something else going on? And how serious is it?
"Most clinicians can intuitively recognize an ataxic gait, but for owners or in subtle cases it can be challenging to distinguish an ataxic horse from a lame horse," explained Caroline Hahn, DVM, MSc, PhD, Dip. ECEIM, ECVN, MRCVS, from the Neuromuscular Disease Laboratory, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Scotland, at the 12th Congress of The World Equine Veterinary Association, held Nov. 2-6 in Hyderabad, India.
That being said, Hahn recommends going back to the basics to truly understand what ataxia is and how to diagnose the cause for ataxia in affected horses.
"Ataxia is a Greek term that means inconsistent," said Hahn. "Ataxic horses are those that are unable to control the rate, range, or force of their movements resulting in an inconsistent gait."
A normally functioning body is able to "sense" how its joints, muscles, and tendons are moving, and where all of the components of the body are in relation to each other. This is called proprioception, and two regions of the brain are responsible for proper proprioception: the forebrain and the cerebellum (at the base of the brain).
According to Hahn, "In order for the information to get to the cerebellum and forebrain the spinal cord has to be intact also, and this is a structure commonly involved in an ataxic patient."
To complicate matters further, damage to the vestibular system (which tells the body where it is in space) and the brainstem can also cause ataxia. Luckily, the "quality" of ataxia and the degree of the inconsistency associated with problems specific areas of the brain and spinal cord vary depending on which structure is affected.
"These subtle differences allow us to identify where the problem is when we are presented with an ataxic horse," noted Hahn. "For example, a horse with spinal cord ataxia due to a lesion in the neck may only show signs in the hind legs if the lesion is mild, and commonly will have large and small steps, step on itself when turning, and be very weak when its tail is pulled while it is walking.
"A horse with an inner ear (vestibular system) lesion on the other hand may have a wide-based stance, take small steps (because it is worried about falling over), and potentially has a head tilt towards the side that has the problem," she continued.
Owners can use these signs as guidelines to help determine whether a horse is ataxic or lame and to better communicate with the veterinarian to ensure the animal receives prompt and accurate treatment.