Seizures

Seizures, fits or convulsions are a relatively common disorder in companion animals, with as many as 5% of dogs and 1 in 200 cats being affected. In this article we review the different forms of seizure, the events and diseases associated with them and common treatments.

Posted: 16 April 2018

Seizures

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How are seizures classified?

They can be classified as being either generalised or partial. Generalised seizures are usually brief, lasting less than 2 minutes, whilst partial seizures may last for longer periods of time.

Generalised seizures

These may be preceded by an aura or period where an animal seems anxious, seeking reassurance from their owner. They then become hyper excitable, followed by developing involuntary running or paddling movements, loss of consciousness with salivation, urination and/or defecation.

Partial seizures

These differ in that they often include involuntary movements, abnormal behaviour, and gastrointestinal signs, but the animal usually remains conscious. They do however have behavioural changes such as aggression and staring.

The post ictal phase

This is the period immediately after a generalised or partial seizure. The animal will often appear exhausted, but may also seem restless, pace constantly, walk in circles and appear disoriented or ‘drunk’. Dogs may appear to be blind, demented, vocal and become polydipsic or polyphagic. This phase may last anything from a few minutes to a day or two.

8 behaviours, events, & diseases linked to seizures

The list of conditions that may be implicated in seizures is extensive, and below is a quick checklist to help you;

  1. Atlant-oaxial subluxation – road traffic accidents and dog fights may result in this devastating injury
  2. Chiari malformation – CKCS with syringomyelia associated episodes
  3. Poisonings – lead, metaldehyde and organophospates
  4. Congenital – conditions such as hydrocephalus
  5. Neoplasia – CNS lesions such as a meningioma or glioma. These are more common in Boxers and Golden Retrievers
  6. Encephalitis – a variety of presentations including necrotising, granulomatous and eosinophilic forms
  7. Metabolic disease – there are numerous disturbances that can trigger seizures, including hypoglycaemia, hypocalcaemia, hyperkalaemia, renal and hepatic failure.
  8. Idiopathic epilepsy - this is a seizure disorder where no underlying cause can be established. It is the most common cause of seizures in dogs, and because of this, we look into it in more detail below.

Idiopathic epilepsy

This form of epilepsy is often called genetic or primary epilepsy. In this form of epilepsy, seizures typically occur in dogs under six years of age, and between one and eight years of age in cats. Animals with idiopathic epilepsy will usually show no neurologic abnormalities between seizures.

Epilepsy may occur in any breed, including cross-bred dogs. Males have a  higher incidence of idiopathic epilepsy than females. An increased frequency of seizures may be seen in females during oestrus or pregnancy – it’s not uncommon for females to have their first seizure when in season.

Making a diagnosis

All animals that have had even one seizure should have a thorough physical and neurologic examination. Blood tests, urinalysis, radiography, ultrasound, and more definitive testing such as an MRI of the brain spinal fluid analysis may be necessary.

What treatment is available?

A wide variety of medications are used to control seizures, the most common being phenobarbitone, primadone and potassium bromide.

Most animals will need at least one of these medications to have a reduction in their seizure activity, while others may require a combination of several. Owners should be made aware that even with the appropriate treatment, some animals may still experience seizures.

If idiopathic epilepsy is diagnosed, the decision on whether or not to start treatment with anticonvulsant medication depends on seizure frequency and severity. For example, an animal that has a seizure once every two months does not really need medication (unless the seizures are excessively long and distressing). If there are more frequent seizures though, the patient should be treated.

Anticonvulsant medication is usually a long-term commitment.  It needs to be given every day at regular intervals and all medications have significant side effects. The aim of treatment is usually to reduce the frequency and severity of seizures. It’s most important to let owners know that epilepsy is not curable. They also need to be informed that all animals on long-term anticonvulsant therapy need regular veterinary reassessment and monitoring. Liver function tests must be carried out as most animals on phenobarbitone can develop elevated ALKP and ALT levels.

Phenobarbitone - the most effective anticonvulsant in dogs is phenobarbitone. A dose of 2-5mg/kg is often used.

Primidone – this drug is metabolised predominantly to phenobarbitone. Sedation and hepatotoxicity, however, is more frequently seen with Primidone than phenobarbitone alone.

Potassium bromide – this is used if seizures are not well controlled with phenobarbitone alone or if the side effects of phenobarbitone are not tolerated. It must be given with food and may take several weeks to reach a stable blood level. It’s not recommended in cats as it can cause pulmonary disease.

Other medications - other anticonvulsants that are used in combination with phenobarbitone include;

  • Gabapentin
  • Levetiracetam
  • Felbamate
  • Pregabalin

Find out more about these treatments >

Remember to prescribe under the rules of the Cascade.

These medicines are not authorised by the Veterinary Medicines Directorate (VMD) for use in dogs/cats/pets. You must explain the ‘prescribing cascade’ in further detail to your client and also explain why the drug is prescribed. Owners should sign a consent form stating that they understand the reasons that the drug is being prescribed and its possible complications, before the treatment is issued.

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