Epilepsy (seizures)
We know how much distress and anxiety seizures (convulsions) can cause in dogs and cats. Throughout the brain, chemical and electrical signals are sent between cells. Seizures are not diseases in themselves but a sign of abnormal brain function (imbalance between excitation and inhibition messengers).
There are several types of epileptic seizures, the most common being generalized tonic-clonic seizures (also called grand mal seizures). Involuntary movements, urination, salivation, and defecation are signs of this type of seizure. A partial epileptic seizure affects only part of the body and can be difficult to distinguish from a non-epileptic seizure (such as a movement disorder or paroxysmal dyskinesia). Signs include muscle spasms or tremors, abnormal sensations, or hallucinations. It is common for pets to act disoriented and confused after a seizure, but they do not feel pain during one. The term epilepsy refers to repeated seizures that are caused by abnormal brain activity. An abnormality in the brain causes it. In cases where the seizures occur due to problems elsewhere in the body, for example, a low sugar level, this is not referred to as epilepsy.
What happens during a fit?
Occasionally, pets will act in a certain way in anticipation of a fit, which an owner will learn to recognise as a sign that a fit is about to commence. Their natural behaviour is to seek out the company of their owners and sit beside them. During a fit, a pet becomes unconscious. It is impossible for them to hear or respond to people. It is common for pets to fall onto their sides and run with their legs. There are times when they will cry out and may lose control of their bowels or bladders. Fits usually last between 1 and 3 minutes – it is good to encourage an owner to make a note of the time when the fit starts and ends because it often seems like they last longer than they do. A pet’s behaviour changes temporarily after a fit. The pet may just get up and continue doing what he or she was doing, while others may appear dazed and confused for up to 24 hours afterwards. The behaviour of pets often follows a set pattern after every fit – such as asking to go out to the bathroom in the garden or getting a drink of water. Once a pet has had several fits, an owner may well notice a pattern of behaviour that is typical of them.
When will fits occur?
Pets typically have epileptic fits when they are relaxed and resting quietly. Fits rarely occur during exercise. It’s common for pets to experience fits in the evenings or at night, and a pattern will develop that an owner will recognise as their own.
Is a fit harmful?
Pets rarely injure themselves during fits. They may bite their tongue occasionally and there may appear to be a lot of blood, but it is unlikely to be serious. It is possible for the brain itself to be damaged if a fit extends beyond 10 minutes.
What causes epilepsy?
There are two types of seizures: intracranial and extracranial. Intracranial seizures occur inside the brain, while extracranial seizures happen outside the brain. The extra-cranial causes of seizures include intoxication and blood disorders, including kidney, liver, low sugar or thyroid disorders. Epileptic seizures of this type are also called reactive seizures.
Epilepsy caused by intracranial causes can be divided into idiopathic and symptomatic categories. Symptomatic epilepsy occurs when the brain is affected by an identifiable disease. The disease might be caused by a brain tumour, an inflammation or infection of the brain (encephalitis), a brain malformation, a stroke, or head trauma. In addition to epileptic seizures, other signs of brain disease may also be present (circling, blindness, wobbling, restlessness, and sleepiness).
A dog with idiopathic epilepsy is most likely to be a young dog (6 months to 6 years of age) who is normally healthy and active between seizures. Veterinary researchers have rarely been able to identify the gene responsible for idiopathic epilepsy in individual breeds; however, there are several breeds with a higher ‘familial’ risk of epilepsy. The majority of epilepsies are polygenic, involving mutations in multiple genes. As a result, unlike ‘recessively’ inherited genetic diseases, breeding to prevent epilepsy is very difficult and primary epilepsy can occur in any pet, regardless of the breed, regardless of the number of generations and litters.
How do I diagnose epilepsy?
Blood tests or a history of exposure to toxins are used to diagnose extracranial causes of epileptic seizures. The diagnosis of symptomatic epilepsy requires MRI or CT scans of the brain as well as tests on the fluid surrounding the brain (CSF analysis). Epilepsy can be classified as idiopathic (or primary) when an underlying cause cannot be identified. Epilepsy caused by idiopathic causes cannot be diagnosed with a single test. We call it a ‘diagnosis of exclusion’ since multiple tests are required to rule out any other cause (blood tests, urine tests, brain imaging, and spinal fluid analysis).
Can epilepsy be treated?
Animals with epilepsy are born with the condition and cannot be cured. Idiopathic epilepsy is a chronic and progressive disease that requires management. The majority of epileptic dogs and cats can, however, lead a very happy and healthy life. It is rare for an animal to have one seizure and never have another. Seizures that occur more than once are likely to occur more frequently or more severely in the future.
Even after treatment, epileptic animals are likely to suffer intermittent seizures. Treatment may result in complete remission, but our goal is to reduce seizures by 50%. There should also be a reduction in the severity of seizures. Approximately 25–33% of dogs with epilepsy require more than one medication to control their signs.
Some evidence suggests that earlier treatment in dogs leads to better outcomes. In most cases, epilepsy should be treated if it occurs more than twice within a six-month period, but this is very dependent on each individual pet. Epilepsy treatment is likely to be continued for life, so making the decision to begin treatment should be carefully considered. There are also the following indications for starting treatment:
- Seizures that are severe or clustered (e.g. more than one in a day), regardless of frequency
- Seizures are becoming more frequent or severe
- Seizures have been linked to an underlying brain disease
What drugs can be used to treat epilepsy?
Epilepsy in pets can be treated with a variety of anti-epileptic drugs (AEDs). The decision on how to best treat a pet’s seizures is based on several factors, including type and number of seizures, licensing, formulation, and price.
Phenobarbital (commonly referred to as Epiphen and Soliphen) and Imepitoin (commonly referred to as Pexion) are both approved for the treatment of idiopathic epilepsy in dogs. In dogs with refractory epilepsy, potassium bromide (marketed as Epilease and Libromide) is approved for use. There are also AEDs licensed for use in people but not in dogs (such as Levetiracetam, Zonisamide, and Gabapentin). The use of these medications in dogs for epilepsy is only recommended in special circumstances. Cats usually receive Phenobarbital or Levetiracetam as their first line of treatment. A high risk of potentially life-threatening side effects makes potassium bromide unsuitable for cats.
Side effects are common with most AEDs. The severity of these side effects should decrease over the course of the first four weeks of treatment. There are a number of common dose-dependent side effects, including increased thirst and hunger (resulting in urination and weight gain), lethargy, panting, hyperexcitability, and possibly wobbly gait. There may be side effects associated with medications and so it is important to make an owner aware of these.
How do you monitor response to treatment?
There are several factors that determine whether medical or surgical treatment is recommended for this condition. Seizure diaries are extremely important. An owner should record the date, number, duration, appearance/severity of seizure(s), whether there was a precipitating cause, and whether abnormal behaviour appeared after the seizure (post-ictal period). These diaries will help assess whether treatment is working. It will also help the owners de-emotionalise the seizure experience if they know what to do when one occurs.
During treatment, an owner may need to visit your practice occasionally. There are some AEDs that will be processed or metabolised by the liver. As metabolism increases with time, higher dosages may be required to maintain the same blood concentration of the drug. Every few months, it is important to perform blood tests to determine the concentration of the AED in the blood alongside the liver’s function. Depending on the individual’s response to treatment, this may need to be done more frequently.
A cluster seizure is when there are more than two seizures within 24 hours. Pets with status epilepticus do not recover between seizures (i.e. go back to normal within 30 minutes) or have seizures lasting longer than 5 minutes. It may not be necessary to change medications immediately in the case of clusters, but we should keep track of the events.