How many types of epileptic seizure are there?
Under the classification of the international expert group IVETF, which is used in veterinary neurology today, there are three types of seizure, depending on where in the brain they start and how far they spread:
- focal seizures, which start in one area of one cerebral hemisphere;
- focal seizures evolving into generalised seizures, which start focally and then spread to both hemispheres;
- generalised seizures, which involve both hemispheres from the start.
You may also have come across the older terms “simple partial seizure” and “complex partial seizure”. Current guidelines recommend no longer using them in animals, because the distinction was based on the level of consciousness, and this cannot be assessed reliably in a dog or a cat.
What does a focal seizure look like?
A focal seizure affects only one part of the body, or only behaviour, and the animal does not necessarily fall over. The signs depend on the area of the brain involved:
- motor signs: twitching of the face, lip or eyelid, repeated head movements, a paw that jerks rhythmically, chewing movements with nothing in the mouth;
- autonomic signs (affecting the functions the animal does not control voluntarily): dilated pupils, heavy drooling, vomiting;
- behavioural signs: a short spell of restlessness, anxiety or fear for no reason, hiding, persistently seeking out the owner.
Focal seizures can last a few seconds and may go unnoticed or be mistaken for something else. In cats, focal seizures with signs in the face are common: drooling, licking, repeated swallowing, twitching of the whiskers or ears. You can read more about these in the article on epilepsy in cats.
What is a focal seizure evolving into a generalised seizure?
It is a seizure that starts as a focal seizure and then spreads to the whole brain. First come the focal signs (restlessness, drooling, twitching of the face, seeking out the owner), then the animal falls, loses consciousness and goes into the convulsive phase. This is the most common type of seizure seen in dogs.
The focal part at the start can be very short. Many owners say they “sensed” a seizure was coming, because the animal changed a few seconds or minutes beforehand. That change is in fact the focal start of the seizure. If you manage to film the first few seconds as well, your vet can identify the type of seizure more easily.
Are the signs before a seizure part of the seizure?
It depends how early they appear. Some animals change hours or even days before a seizure: they are restless, more clingy or more withdrawn. This period is called the prodrome and is not part of the seizure itself. Signs that appear only a few seconds or minutes before the collapse, on the other hand, are considered the focal start of the seizure. The term “aura”, used in people, is no longer recommended in animals.
What does a generalised seizure look like?
In a generalised seizure both sides of the body are involved and, as a rule, the animal loses consciousness (except in myoclonic seizures). The animal may drool and may pass urine or faeces. The forms described are:
| Form | What you see |
|---|---|
| Tonic-clonic | The animal falls and goes rigid (the tonic phase), then makes rhythmic paddling or jerking movements (the clonic phase). This is the best-known form. |
| Tonic | Stiffening of the body and legs, without rhythmic movements. |
| Clonic | Repeated rhythmic jerking, without stiffening beforehand. |
| Myoclonic | Short, sudden jerks, usually on both sides of the body. They can also happen during sleep. |
| Atonic | A sudden loss of muscle tone, and the animal collapses. |
A generalised seizure usually lasts under 5 minutes, most often 1-2 minutes. It is followed by the post-ictal phase, in which the animal may be confused, unsteady on its legs, agitated or very tired, for anything from a few minutes to a few hours.
How do focal seizures differ from generalised seizures?
| Focal seizure | Generalised seizure | |
|---|---|---|
| Where it starts | In one area of one hemisphere | In both hemispheres from the start |
| Part of the body affected | One part of the body, or only behaviour | Both sides of the body |
| Consciousness | May be preserved or altered, hard to assess | Usually lost (exception: myoclonic seizures) |
| Falling | Not necessarily | Usually yes |
| Examples | Twitching of the face, drooling, sudden fear | Stiffening and paddling, collapse |
A neurological consultation tells you where the problem comes from and what to do next.
What are cluster seizures?
Cluster seizures means two or more seizures within 24 hours. The animal may recover in between. Cluster seizures are a sign that the condition needs to be reassessed, and they are one of the criteria for starting or adjusting treatment. If your vet has already given you a treatment plan for situations like this, follow it and let your vet know.
What is status epilepticus and when is it an emergency?
Status epilepticus is a seizure lasting more than 5 minutes, or two or more seizures one after another without the animal fully regaining consciousness in between. It is a life-threatening medical emergency. Go straight to the nearest emergency vet clinic (open now).
Why does the type of seizure matter?
The type of seizure tells the vet where in the brain the problem might be and which investigations are needed. For example, seizures that always affect the same side of the body, or neurological signs that persist between seizures, can suggest a lesion in the brain and justify an MRI. The type of seizure also matters when choosing treatment and when monitoring the response to it.
Some episodes look like seizures but have other causes: fainting due to a heart problem, pain, balance problems. The difference is explained in the article on epileptic seizures and fainting. For a full assessment of the seizures, you can book an epilepsy consultation, and if it is not clear what kind of episodes your pet is having, an EEG recording can help.
Frequently asked questions
My dog twitches in his sleep. Is that a seizure?
Most of the time, no. Movements during sleep, such as running in a dream or whimpering, stop when the dog is called or woken. A seizure does not stop when you call him, and the dog is usually confused afterwards. If you are not sure, film the episode and show it to your vet.
Can the type of seizure change over time?
Yes. An animal may have focal seizures for a while and then seizures that become generalised, or both types. Write every episode in the seizure diary, because these changes help your vet adjust the treatment.
Does a short, mild seizure matter less?
Short focal seizures matter too. They show that there is epileptic activity, and they can be the first step towards generalised seizures. Tell your vet about every episode, even those lasting only a few seconds.
Sources
- Berendt M. et al. 2015, IVETF consensus report on epilepsy definition, classification and terminology in companion animals, BMC Veterinary Research 11:182
- De Risio L. et al. 2015, IVETF consensus proposal: diagnostic approach to epilepsy in dogs, BMC Veterinary Research 11:148
- Podell M. et al. 2016, 2015 ACVIM Small Animal Consensus Statement on Seizure Management in Dogs, Journal of Veterinary Internal Medicine 30(2):477-490
- Hazenfratz M., Taylor S.M. 2018, Recurrent seizures in cats: diagnostic approach, Journal of Feline Medicine and Surgery
This article is for information only and does not replace a veterinary consultation.