Ataxia: Is my horse demonstrating signs of neurologic deficits?

Over the past several months our practice has aided in the diagnosis, treatment, and management of several patients with neurologic disorders.  Horses with neurologic deficits can be dangerous to themselves, other horses, humans and surrounding property.  They can be extremely reactive and unpredictable so the identification of neurologic disease in horses is imperative on the part of the owner, barn manager, rider and trainers in order to secure the patient in a safe place and to avoid injury to horse and human alike. 

Ataxia is demonstrated by poor voluntary muscle control.  Ataxic horses will stumble, stagger, wobble and present an overall presentation comparable to an intoxicated human.  Unlike humans, many horses with neurologic deficits will appear normal when standing due to the intrinsic mechanism of the stay apparatus.  This series of muscles, ligaments and bones enables the horse to sleep standing up without utilization of energy.  As such, an ataxic horse can often stand quietly until asked to perform a voluntary movement.

The severity of the clinical presentation of an ataxic patient is dependent upon the chronicity of the disease process, the severity of the injury to the central nervous system and the specific systems involved in the disease process.  Below are several videos detailing different stages of neurologic symptoms in equine patients.  The purpose of this blog is to educate clients on common presentations of neurologic deficits to enable early identification in the field.  Click on the images to view the videos.

Example one: Mild Sidewinder – this is a general term for a horse who physically cannot move their front and hindlimbs in the same tracks.  Notice here how this patient’s haunches deviate to the right but he is still able to walk in a specific direction without stumbling or falling.  This horse is in minimal distress but a thorough work up of his ataxia is required to ascertain the potential progression and severity of his neurologic disorder. 

Example Two: Severe Sidewinder – notice here that this horse’s haunches are moving around his front end almost without his consent.  He does not have control over his intentional, voluntary movements and he cannot ambulate in a normal fashion.  While he can stand quietly, his hind end appears weak and the first few steps out of standing position demonstrate the most instability. 

Video courtesy Dr. Amber Bowen, V.I.P. Equine Services

Example Three: Moderate Ataxia – note here that initially, this horse looks fairly normal, but, when he shakes his head, he stumbles and struggles to maintain his balance.  He makes large movements to accommodate for his lack of neurologic competence.

Example Four: Severe Ataxia –   this horse has little to no control over his own body.  He struggles to remain standing and is forced into unintentional voluntary movement by the malfunctioning aspects of his central nervous system.  These patients are incredibly unpredictable and extremely dangerous as they cannot demonstrate normal avoidance behavior to avoid collisions.  They also usually demonstrate abnormal, hyperreactive responses to innocuous audio, visual and mechanical stimuli. 

Recumbence is the most severe form of neurologic deficiency  These horses cannot stand and often thrash, paddle and tremor on the ground.  They may flop about like a fish out of water and they have very little to no control over their limbs, trunk, neck or head.  Humane euthanasia is usually the only kind option available to these patients. 

Stringhalt is a neuromuscular deficit that results in involuntary exaggerated upward movement of one or both of the hindlimbs.  It is usually most pronounced at the walk and while backing.  The movement lessens in the trot and is almost always absent in the canter.  This is not known to be a painful disorder in horses and the horse can remain serviceably sound and rideable in most situations. 

Video courtesy UC Davis Center for Equine Health

Neurologic disorders in horses are always complex and require in-depth analysis and neurologic testing to attempt to determine the etiology.  Prognosis is always dependent upon etiology and progression. 

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