There are few things more distressing than witnessing a cat in the throes of a seizure. Fortunately, feline seizure disorders are much less common compared to the canine population, but when they do occur, treatment may be challenging.
The terminology regarding seizures can be confusing. Seizures (sometimes called convulsions or fits) result from a sudden, uncontrolled surge in the electrical activity of the brain.
If we can find no discernible reason for the seizure, we call this primary or idiopathic epilepsy. Idiopathic epilepsy is a common inherited disorder in dogs but is rarely diagnosed in cats.
Secondary epilepsy is characterized by seizures that have some identifiable, underlying cause, such as inflammation, trauma or cancer. Secondary epilepsy is more common in cats compared to dogs.
Trying to prove that a cat has primary (idiopathic) epilepsy can be difficult. Affected cats will test normal on physical and neurological examination, including sophisticated tests such as CT scan and/or MRI. The diagnosis is reached by excluding all other causes of seizures. Metabolic disorders (liver disease, for example), toxicities (likelead or insecticides), infectious diseases (such as feline leukemia virus, feline immunodeficiency virus, feline infectious peritonitis and toxoplasmosis), brain tumors and parasitic disorders of the brain are all potential causes of seizures in cats.
Seizures can also be characterized by type.
Generalized seizures affect the entire body and are what we typically picture when we think about epilepsy: the cat falling on her side, losing consciousness, gnashing her teeth, salivating, paddling all four limbs and sometimes urinating and/or defecating. This is often referred to as a grand mal seizure. Partial or focal seizures arise from a more localized area ofthe brain and may affect an isolated body part or parts.
To distinguish whether a cat has primary versus secondary epilepsy, your veterinarian will take a thorough history and perform a comprehensive physical exam and neurologic exam, including a funduscopic exam (evaluation of both retinas). A complete blood count, serum biochemistry panel, urinalysis and evaluation for infectious disease should be performed. If the neurologic examination reveals any deficits, additional procedures, such as a spinal tap and advanced imaging tests (CT scan or MRI) are advised. Consultation with a board-certified veterinary neurologist may be warranted, as many of these tests will need to be performed at a referral center.
Treatment of seizure disorders should be aimed at the underlying cause, if possible. For example, if liver disease has led to seizures, treatment of the liver disease may reduce or eliminate the seizures. In most cases, however, either an underlying cause cannot be identified (primary epilepsy), or the cause may not be treatable (for example, some brain tumors). In these cases, anticonvulsant medications may be warranted. The general consensus regarding anticonvulsant therapy is that it should be administered if seizures occur more frequently than once a month, if the cat begins to have cluster seizures (a few seizures within a short period of time) or if the owner strongly desires to treat the seizures regardless of the frequency.
Complete elimination of the seizures is not a realistic goal. The goal is to decrease the frequency of the seizures, reduce their severity and improve the quality of life for both the cat and the owner. Phenobarbital remains the first-choice anticonvulsant in cats. It is effective and generally considered safe; however, cats may occasionally experience adverse effects such as sedation, increased appetite (resulting in weight gain), or excessive thirst and urination.
For cats who do not tolerate or respond well to phenobarbital, diazepam (Valium) is usually the second choice of most veterinarians. Unlike epileptic dogs that become refractory to treatment with diazepam over time, epileptic cats remain responsive to the drug, and seizures become fairly well-controlled. Adverse effects in some cats include unacceptable sedation and increased appetite and weight gain. Several reports have also documented severe liver toxicity in a few cats receiving diazepam.
Although most cats respond to phenobarbital and/or diazepam, a few cats show a poor response, necessitating the use of alternative medications. Levetiracetam (brand name Keppra) and zonisamide (brand name Zonegran) are newer anticonvulsants that have shown positive effects in treating feline seizures. I have personally treated several cats with these newer drugs, and all have responded well. Often, these medications are given in addition to the phenobarbital and/or diazepam. Once the seizures come under control, it may be possible to slowly and carefully wean the cat off of the initial medications, maintaining control solely with the new drug. Treatment with anticonvulsant drugs is a lifelong commitment.
Seizure disorders in cats remain a challenge for most veterinarians and cat owners. Fortunately, most cats respond nicely to medication, and newer medications have increased our options for treatment of this frustrating condition.
If you witness your cat having a seizure, don’t panic. Do the following: