Epileptic seizures and epilepsy

If you have witnessed your cat having a seizure (convulsion), you will know how frightening it can be. If your cat has had more than one seizure it may be that he (she) is epileptic. There are medications that can control seizures, allowing your cat to live a more normal life.

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A seizure (also known as a fit) is a short event with an abrupt start and end. The term seizure can relate to a problem in the nervous system (epileptic seizure, narcolepsy/cataplexy, acute balance loss) or a disease in another organ (eg heart disease causing syncope). The term paroxystic event is usually used to describe seizures of uncertain origin.

An epileptic seizure is not a disease in itself but the sign of abnormal brain function. Many types of epileptic seizure are described in humans, dogs and cats. The most common type is the generalized tonic-clonic epileptic seizure (also known as grand mal seizures). Partial epileptic seizures affect only part of the body and are much more difficult to differentiate from non-epileptic seizure (particularly movement disorders).

Epilepsy means repeated epileptic seizures due to abnormal activity in the brain. It is caused by an abnormality in the brain itself. If the seizures occur because of a problem elsewhere in the body, for example a low sugar level, this is not epilepsy.

Epileptic seizures can be caused by problems inside the brain (intra-cranial causes) or outside the brain (extra-cranial causes).

Extra-cranial causes of seizures include intoxication and metabolic diseases. In these cases, the brain is perfectly healthy but reacts to a toxin or a change in the blood make-up (usually caused by liver or kidney disease, salt imbalance, low sugar level, or an under-active thyroid gland). This type of seizure is also described as reactive epileptic seizures. Diagnosis of extra-cranial causes of epileptic seizures is based on blood tests or a known history of access to a toxin.

Intra-cranial causes are divided into primary and secondary epilepsy. In secondary epilepsy, the epileptic seizures are a sign of a disease in the brain.  This disease might be a brain tumor, an inflammation or infection of the brain (encephalitis), a brain malformation, a recent or previous stroke or head trauma. Epileptic seizures may be the only sign of illness or there may be other signs (circling, blindness, wobbliness, restlessness and/or sleepiness). To confirm a diagnosis of secondary epilepsy an underlying brain disease must be identified using MRI or CT-scans of the brain and tests on the fluid surrounding the brain (CSF analysis) (see fact sheet neurodiagnostic test).

In primary epilepsy (also known as idiopathic epilepsy), there is no disease in the brain but the epileptic seizures are caused by a functional problem (an imbalance in the messengers in the brain).

Primary epilepsy is the most common cause of epileptic seizures in young adult cats, although not as common as in dogs. The number of seizures each cat has is extremely variable between individual cats (from many seizures a day to a seizure every few months). Animals with primary epilepsy are typically normal in between seizures.

The diagnosis of primary epilepsy can only be made by excluding all other causes and results of all investigations (blood test, MRI scan or CT-scan of the brain and CSF analysis) will come back normal.

Primary epilepsy is the most likely cause of seizures if your cat:
1) has its first seizure at a young adult age
2) is normal between the seizures.

Identification of the exact cause of the epileptic seizures is essential in choosing an appropriate treatment to control them.