Seizures in Horses

Key Takeaways

Seizures are characterized by uncontrolled muscle movement and spasming, which may affect a horse’s entire body or be localized to a smaller group of muscles. 

• Seizures are rare in horses, but have a variety of causes including injuries, infections, toxicoses, metabolic imbalances, or disorders affecting the brain

• People and animals in the immediate area of a seizing horse may be at risk of physical injury

• Diagnostics for seizures include a physical examination, diagnostic imaging, bloodwork, and neurological exam

• Treatment depends on the underlying cause

A Closer Look: What are Seizures in Horses?

Seizures are rare in horses, and often indicate severe physical or neurological distress.

A horse experiencing a generalized seizure may be unable to stand, and move their legs uncontrollably. During an episode they may defecate or urinate, and have difficulty breathing. Generalized seizure activity is typically associated with a poorer prognosis. 

In a partial or localized seizure, uncontrollable muscle movement is limited to part of the body, such as in their face or a leg.  

People or animals around a seizing horse may be at risk of injury due to the animal’s uncontrollable movement. It is essential to not approach or attempt to restrain a seizing horse.

Any horse presenting with this symptom requires immediate medical attention.

Keeping a detailed history of a horse’s seizures including the frequency and duration of seizure activity, a description of the seizure, and the behavior between seizures is integral to a timely diagnosis.

Possible Causes

Seizures may be caused by:

• Disturbances in electrolytes, blood sugar levels, or oxygen levels, particularly in foals

• Liver or kidney disease

• Masses in the brain, such as from tumors or bacterial infections causing abscesses

• Toxicoses, such as poison hemlock toxicosis

• Drug reactions, particularly when drugs are accidentally injected into the carotid artery

• Traumatic injuries, such as skull fractures

• Viral infections, such as equine encephalitis

• Fungal infections

• Bacterial infections, such as meningitis

• Sepsis, particularly in foals

• Neurological conditions, such as epilepsy

Risk Factors

Seizures vary in severity based on the location of seizure activity in the body and the duration of the seizure.

Seizures can last up to several minutes, and may occur several times depending on the underlying cause. Repeated seizure activity usually indicates more serious and potentially life-threatening conditions. 

In rare cases, seizure activity is continuous and does not stop, indicating a life-threatening condition called status epilepticus. Status epilepticus is rare in horses, but is has a grave prognosis.

Testing and Diagnosis

Veterinary diagnostics include;

• Physical examination

• Neurological examination

• Diagnostic imaging, including X-rays of the skull 

• Bloodwork

• Cerebrospinal fluid analysis (spinal tap)

• Electrical encephalogram (EEG) 

• Urinalysis

Treatments vary and target the underlying cause, including antibiotics, surgery, and anti-seizure medication. Horses that are experiencing seizures often require hospitalization.

Similar symptoms

Seizures could be mistaken for

• Colic

• Collapse 

• Loss of consciousness

• Severe muscle tremors

• Muscular rigidity due to tetanus

Associated Symptoms

Symptoms which present alongside seizures include:

• Uncoordinated movement (ataxia)

• Collapse

• Lethargy

• Circling

• Head pressing against objects or walls

• Abrasions or scrapes on the body from a previous seizure event