Dogs and cats can seizure for a number of reasons. Cats are much less likely to develop epilepsy than dogs. The term epilepsy is often used to describe seizure activity but it says little about the cause of the problem. There are many reasons for seizures and there are different types of epilepsy. I'll start with some broad definitions.- Seizures are periods of uncontrolled electrical activity in the brain (convulsions).
- status epilepticus is repeated or prolonged seizure activity.
- Epilepsy is a disorder characterised by recurring seizures that originate from the brain.
- Idiopathic Epilepsy is epilepsy of unknown cause with no evidence of any damaged structural areas within the brain. (genetic?) The term idiopathic means unknown cause. When vets say "epilepsy" then this is the type we are referring to!
- Symptomatic Epilepsy is a syndrome where the seizures are a result of identifiable, structural brain lesions (like a tumour).
We divide the causes of seizures in two areas, those involving the brain and those caused by something outside the brain.
Intracranial (brain) causes:
- Degenerative encephalopathy
- Cell storage diseases
- Cancer, either primary or due to spread from elsewhere
- Viral infections (distemper)
- Fungal infections
- Protozoal infections (Neospora, Toxoplasma)
- Meningitis or Encephalitis
- Trauma
- Stroke (cerebrovascular accident)
- Idiopathic epipilepsy (probably genetic)
Extracranial (body) causes:
- Low blood sugar (hypoglycaemia)
- Low blood calcium (hypocalcaemia)
- Acute renal failure (kidney failure)
- Hepatic encephalopathy (liver disease)
- Hypoxia (lack of oxygen in blood)
- Poisons
If we do not find any abnormalities on the blood tests and examination then we generally assume that the causes of seizures that relate to areas outside the brain have been ruled out. The next step in diagnosis is an MRI scan. This allows us to rule out structural brain lesions like areas of cancer or scarring in the brain. If structural disease is ruled out then we diagnose idiopathic epilepsy.
So epilepsy (idiopathic) is a diagnosis that is made by excluding the other causes of seizure activity only after a thorough assessment has been carried out.
When we consider a diagnosis of idiopathic epilepsy the most important factors we look at are the age of onset and the pattern of seizures. With idiopathic epilepsy the first seizure occurs between 6 months and 5 years of age. Dogs that start to seizure outside this age range often have an identifiable cause. If they have more than 2 seizures in the first week at the onset of the problem then idiopathic epilepsy is less likely but still possible.
Severe seizures or seizures that come on repeatedly one after the other are medical emergencies. Should your pet seizure then prevent it from injuring itself on surrounding objects. Keep a record of how long the seizure lasts and if possible taking video footage helps your vet see how severe the seizure is.
There are effective treatments for most dogs. Once treatment starts it is lifelong and the drugs can cause liver damage in the long term. We select patients for treatment based on how severe the seizures are and how frequently they occur.
A dog that has a history of seizures should never be allowed to swim as there is a real risk of drowning.
There are some excellent resources available including a Canine Epilepsy site and a site that shows the genetic diseases of different dog breeds. Click here to find the links.
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