The Laboklin Expert Panel on Epilepsy

Prof. Volk explained how epileptic seizures can be categorised. Generalised tonic-clonic seizures are most likely to be classified as epileptic. Focal seizures are more difficult to assess. The presence of hypersalivation can be helpful. In the case of syncope, there tends to be a single, brief myoclonus with a rapid recovery. Paroxysmal dyskinesia can resemble epilepsy. Prof. Fischer explained it as a non-epileptic brain disorder that occurs episodically and is triggered by certain stimuli. Patients with dyskinetic seizures remain conscious. They do not salivate or spontaneously defecate or urinate.

Genetic predisposition also plays a major role in idiopathic epilepsy. Prof. Fischer points out that certain breeds, such as Australian Shepherds, Border Collies, German and Belgian Shepherds, Boxers, Beagles, Labrador Retrievers and Cane Corsos, are predisposed. However, due to the complexity of the disease, in which various risk factors may serve as common triggers, genetic tests are not available for these breeds. The situation is different for rare, monogenic epilepsies. For example, genetic tests are available for juvenile myoclonic epilepsy in Rhodesian Ridgebacks and neonatal encephalopathy in Jack Russell Terriers. Prof. Volk also reported on Lafora epilepsy, which is caused by a gene mutation that leads to a storage disease. In this case, visual and acoustic stimuli can trigger epileptic seizures, such as myoclonic seizures. Genetic tests are available for wire-haired Dachshunds, Basset Hounds and Beagles, among others.

When asked whether stress can trigger a seizure, Prof. Volk reports that increased cortisol levels in blood and saliva have been detected in epileptic dogs. He agrees with Prof. Fischer that stress- induced seizures are most likely to occur during the resting phase following a stressful event. However, maintaining a regular daily routine and implementing measures to reduce stress, e.g., during a hospital stay, are more effective than (temporarily) increasing antiepileptic therapy.

Can one seizure trigger another? Prof. Potschka explained that a single classic seizure is unlikely to lead to an increase in seizure frequency. However, the situation may differ with prolonged seizure duration, cluster seizures, or status epilepticus. Prof. Volk defines status epilepticus as a seizure lasting five minutes or more and characterised cluster seizures as the occurrence of more than one seizure within 24 hours. Prof. Bröer answered the question of when to start drug therapy. Dogs with two seizures in six months, cats with two seizures in three to four months, and any patient after status epilepticus or a cluster episode should be treated with an antiepileptic drug. Additionally, animals should be treated if the seizures become longer or more severe, or if they are accompanied by postictal behavioural changes, such as aggression.

In laboratory diagnostics, Prof. Fischer and Prof. Volk placed particular emphasis on haematology and biochemistry. The aim being to exclude other causes of epileptic seizures and to detect any concomitant diseases that may be relevant with regard to therapy with antiepileptic drugs. There are no typical markers for epilepsy in the blood, although CK levels may be elevated for up to two days after a seizure. Further diagnostics, including MRI (and a spinal fluid examination), are used to check for structural changes or inflammatory processes in the brain.

These are particularly important in the case of less typical clinical presentations and in older patients (dogs over six years of age, cats over seven years of age). Prof. Fischer emphasised that it is not necessary to wait until the diagnostic process is complete before starting treatment.

Asked about the role of the intestinal microbiome and diet in epilepsy, Prof. Potschka stated that the metabolites produced by the microorganisms in the intestine (the microbiome) appear to have an influence. Additionally, studies have shown that diet can affect epilepsy and its treatability. Prof. Volk reported that good results with the use of medium-chain triglycerides (MCT) in the diet.

The participants asked about the optimal medication for treating epilepsy. Prof. Bröer reported that imepitoin and phenobarbital have demonstrated relatively similar efficacy in studies. Both can also be combined, allowing for a reduction in the dose of each medication. In patients with cluster seizures, however, phenobarbital is considered the drug of choice. A possible add-on is potassium bromide, which is best administered twice daily with food to minimise potential gastrointestinal side effects.

As part of the monitoring process, the determination of plasma levels for phenobarbital and potassium bromide is used. Prof. Bröer explains that this is useful for phenobarbital from two weeks after the start of therapy, while for potassium bromide, an examination provides meaningful values at the earliest three months after the start of administration. So-called ‘loading dose’ protocols can be used to achieve effective plasma levels more quickly; however, this should be done in a hospital setting due to the increased risk of adverse effects.

Of course, the cat should not be neglected in the discussion. Prof. Volk confirmed that cats do not suffer from seizures more severely than dogs, even if it sometimes appears more dramatic.

Prof. Fischer dismissed the notion of breed defined predispositions, although there seems to be more prevalence British Shorthairs.

Prof. Bröer discussed therapy. Overall, the research situation for cats is less effective than for dogs, but it can generally be said that the response to twice-daily administration of phenobarbital in cats is very good, with cats also experiencing significantly fewer side effects. Imepitoin is also well tolerated by cats and is effective. There is an absolute contraindication for potassium bromide in this species. A special feature in cats is limbic encephalitis. Prof. Volk describes symmetrical, focal seizures that are associated with changes in the MRI in the hippocampus area and findings in the CSF. Typical symptoms include serial seizures, behavioural changes, and non-response to antiepileptic therapy. Steroid therapy, on the other hand, can be effective. The participants wanted to know more about feline audiogenic reflex seizures (often referred to as ‘Burmese epilepsy’).

Prof. Fischer explained that these are myoclonic seizures triggered by violent auditory stimuli, resulting in electric-shock-like twitching, especially in older cats (not only of the Burmese breed).

We would like to thank the experts for sharing their extensive knowledge!

The experts discussed a genetic background and breed predispositions. Genetic tests are now available for some forms of epilepsy, such as Lafora disease in various breeds, juvenile epilepsy in Lagotto Romagnolos, juvenile myoclonic epilepsy in Rhodesian Ridgebacks, and juvenile encephalopathy in Parson and Jack Russell terriers. Other types of seizures can also be caused by changes in certain genes. Examples include movement disorders, such as episodic falling in Cavalier King Charles Spaniels, encephalopathies like necrotising meningoencephalitis in Pugs, storage diseases such as neuronal ceroid lipofuscinosis (which can occur in various breeds), and narcolepsy in Dachshunds, Dobermans, and Labradors. The complete list of these diseases and their symptoms, which can be identified through genetic testing, can be found in our ‘Laboklin Spotlight’ on seizure disorders in dogs.

Click here to acces the Spotlight.

Dr. Jennifer von Luckner,
Dr. Angelika Drensler