Neurology Service


This information is not meant to be a substitute for veterinary care. Always follow the instructions provided by your veterinarian.

A seizure is defined as a paroxysmal, transitory disturbance of brain function that has a sudden onset, ceases spontaneously, and has a tendency to recur. Generalized seizures affect the entire body. Most commonly, animals will fall to the side, make paddling movements with the limbs; they will often will urinate, salivate and defecate during the episodes. Generalized seizures usually last from several seconds to upwards of a couple minutes. Focal seizures remain localized to one body region and are usually shorter in duration, lasting a couple seconds. Seizures may start focal and then become generalized. 
After the veterinarian is convinced that a seizure disorder is present, the most important question to be answered is whether the seizure is the result of primary brain disease (intracranial disease), or the result of a disturbance outside the brain (extracranial disease), The most common intracranial causes of seizures include: structural disease including hydrocephalus, head trauma, inflammatory brain disease (encephalitis), strokes and neoplasia (brain cancer). The most common causes of extracranial diseases that cause secondary brain signs include: toxins and metabolic diseases. Metabolic diseases include: low blood sugar (hypoglycemia), high blood sugar (hyperglycemia), liver disease, kidney disease, electrolyte disturbances, toxins (poisons), anemia.

Idiopathic epilepsy

Idiopathic epilepsy is another common cause of seizures in dogs and less commonly in cats. It is by definition, seizures of unknown cause. These episodes are thought to be due to "mal-wiring" within the brain. Idiopathic epilepsy is seen in dogs between the ages of 6 months and 6 years of age. It is more common in certain breeds: border collies, Australian Shepherds, Labrador retrievers, beagles, Belgian Tervurens, collies and German shepherds. That being said, seizures can occur in any breed of dog or cat. To search for the cause of seizures, a systemic work up is performed (physical and neurologic exam, blood work, blood pressure, sometimes chest x-rays, specific liver function test including bile acid testing). Once an extra-cranial cause of seizures is ruled out, then the brain is imaged using either a CT scan or an MRI. Following brain imaging, a cerebrospinal fluid (CSF) tap is performed in order to look for encephalitis. If an underlying disease can be found, then primary treatment for that disease may help to make the seizures stop. If the seizures are recurrent, anticonvulsant medications are often given. The choice of medication depends upon the characteristics of the individual animal's problem. Some of the more commonly used anticonvulsants are listed below. It is important to remember that once an anticonvulsant is initiated, it should not be changed without veterinary assistance. Most animals with idiopathic epilepsy will require anticonvulsant medication for the rest of their life.

Drugs Used to Treat Seizures

  • Phenobarbital is the most commonly used anticonvulsants in veterinary medicine because it is effective and also inexpensive. Side effects include: sedation, incoordination and rear limb weakness, , increased drinking, urination and appetite. With high dosages or prolonged use, phenobarbital can cause damage to the liver. Paradoxically, some animals given phenobarbital may become restless and excitable. If any of these signs are observed, occurs, consult your veterinarian for assistance. For best results, this drug needs to be given consistently (every day) at least twice daily. This drug should not be altered without veterinary consultation.
  • Potassium Bromide is another effective first-line seizure medication used in veterinary medicine. Due to its lack of metabolism it is the ideal anticonvulsant for patients with liver disease. Side effects include: sedation, incoordination, limb weakness and vomiting. Pancreatitis has also been described as a possible complication. If any of these signs are observed, occurs, consult your veterinarian for assistance.
  • Levetiracetam (Keppra) is a newer anti-convulsant for use in veterinary medicine. It is also not liver metabolized making it safe in patients with liver disease. It is to be given three times daily. Side effects are rare and include sedation and incoordination.
  • Zonisamide (Zonegram) is a newer anti-convulsant for use in veterinary medicine. It, like phenobarbital, is metabolized by the liver. It is a sulfonamide medication and can therefore cause dry eye, decreases in white and red blood cells. It can also cause liver disease and sedation and incoordination.
  • Diazepam (Valium) is a medication to be given on an emergency basis to halt an active seizure in dogs and cats because its effects are very short acting. Thus, this medication is not used on a daily basis. Side effects include drowsiness, lethargy, and depression and liver disease.

This information was made possible by funds from the Neurology Endowment at Washington State University.

Washington State University assumes no liability for injury to you or your pet incurred by following these descriptions or procedures.

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