Epilepsy is a common neurological presentation in dogs and cats, with feline epilepsy estimated to affect up to 2 percent of the general feline population (Stanciu et al., 2017). As with most conditions seen in cats, there is a crossover between the feline and canine patient, but there are some variations that are certainly worth considering.
What is feline epilepsy?
Epilepsy is defined as more than one epileptic seizure. There are different nomenclatures for seizure classification, but following the International Veterinary Epilepsy Task Force proposal for dogs in 2015 and by extrapolation to the feline population, epilepsy can be classified as “idiopathic” or “structural”.
Idiopathic epilepsy relates to cases where the underlying cause has not been identified and/or there is no evidence of structural disease. This therefore includes genetic, suspected genetic and unknown origin. Genetic epilepsy applies when a genetic background has been confirmed, while suspected genetic epilepsy applies when there is a high breed prevalence (over 2 percent) or when there is a high representation of individuals with epilepsy in the same family. In contrast to canine patients, where several breeds with genetic predispositions have been identified, feline patients tend to have a more mixed genetic background. Therefore, the term epilepsy of unknown aetiology is likely more appropriate in most cases.
As the name suggests, structural epilepsy refers to seizure activity secondary to an identifiable structural pathology of the brain. This pathology is confirmed by diagnostic tests, such as advanced imaging, cerebrospinal fluid (CSF) analysis, DNA testing or post-mortem examination.
How do we classify seizure types?
Seizure type can be further classified as focal, generalised, focal with generalisation and non-convulsive seizures. Feline patients can have particular syndromes not generally seen in dogs.
It is important to characterise episodes because the characterisation often correlates with the location of the origin of the epileptic seizures
It is important to characterise episodes because the characterisation often correlates with the location of the origin of the epileptic seizures. For example, the hippocampus is usually the cause of, or is affected by, complex partial cluster seizures.
Complex partial cluster seizures
Complex partial cluster seizures is a syndrome that presents with a specific semiology in cats with orofacial involvement. These cases typically present with salivation, facial twitching, lip smacking, chewing, licking, absence and behavioural changes. Episodes may generalise in some cases. The outcome of complex partial cluster seizures can be good, and therefore treatment should be considered (Pakozdy et al., 2011). The main differential diagnosis to be considered in these cases is feline orofacial pain syndrome.
Feline audiogenic reflex seizures
Another described syndrome in feline patients is feline audiogenic reflex seizures. This is usually seen in older patients, and there is a high incidence in Birman cats. Semiology includes myoclonic seizures commonly followed by generalisation or absence episodes usually triggered by high-frequency sounds. In these cases, a good response to levetiracetam therapy has been seen; however, due to the age distribution, quality of life can be generally affected (Lowrie et al., 2017).
Diagnosing feline epilepsy
History
When taking the clinical history, it is important to try to determine if there are different parts to the episode. This becomes particularly relevant when the episodes are not typical seizures and/or there is a need to determine the most likely nature of the episode described.
Three stages can be identified during an epileptic seizure: pre-ictal, ictus and post-ictal phases. However, in some cases only one or two may be present and often the ictus, or the episode itself, may be the only phase described or identified by the owner. Despite the possibility of the pre- and post-ictal periods not being identified or present, when they are described they can be a valuable tool to clarify the nature of atypical presentations.
- The pre-ictal period refers to any change in the behaviour that precedes an episode; however, this is rarely identified and, if present, is case-dependent, lasting from seconds to days
- The ictus refers to the epileptic seizure itself, and, as mentioned above, it varies depending on the presentation. Autonomic signs such as salivation, urination or defecation can be present alongside motor activity, such as pedalling and jaw chomping
- The final or post-ictal phase also refers to changes in behaviour, but after the seizure has occurred. Behavioural changes can vary from disorientation to increased thirst or hunger. This period is also case-dependent, and its duration is variable
Initial investigations
Once the nature of the episodes is established (based on the differential diagnoses), investigation is then warranted. Basic haematology and biochemistry blood tests should be performed before more specific blood tests, such as bile acid stimulation tests and infectious disease panels, are considered, as these will depend on the initial results and differential diagnoses. Blood pressure, urinalysis and imaging of the thorax/abdomen should also be considered depending on the presentation and differential diagnoses.
Basic haematology and biochemistry blood tests should be performed before more specific blood tests […] are considered, as these will depend on the initial results and differential diagnoses
Advanced imaging
Once the initial tests are done, advanced imaging should then be considered. Evidence shows that if your feline patient is below five years old and there are no abnormalities in the neurological examination, it is unlikely that a structural lesion will be identified (Raimondi et al., 2017). Yet if the patient is over five years old, the likelihood of finding structural disease increases by 14 percent every year.
The identification of abnormalities in a neurological examination should raise the suspicion of structural disease. In these cases, advanced imaging and cerebrospinal fluid analysis may help establish the underlying cause, which may or may not require more specific treatment on top of anti-epileptic drugs.
Identification of abnormalities in a neurological examination should raise the suspicion of structural disease. In these cases, advanced imaging and cerebrospinal fluid analysis may help establish the underlying cause
Treatment for feline epilepsy
There is no consensus on when to start anti-epileptic treatment in feline and canine patients. However, some guidelines suggest treatment be started if and when structural disease is identified and in cases of status epilepticus or recurrent cluster seizures (Berendt et al., 2015; Charalambous et al., 2018). Guidelines for the occurrence of single episodes and what frequency should warrant medication initiation are available but must be tailored to the individual case.
Seizure frequency, severity and owner compliance will influence the decision process. Generally speaking, cats are more challenging to medicate, and in cases where they are frequently outdoors, the timing for administration can be extremely challenging to follow. Based on the increased challenge that feline patients can present, it is paramount to understand which medications are available and their dosing, side effects, monitoring and costs.
The most-used options to treat feline epilepsy are phenobarbitone, levetiracetam and zonisamide. Imepitoin can also be used and is well tolerated in healthy cats, but its efficacy is still to be proven (Engel et al., 2017). Potassium bromide is no longer used in cats due to the possibility of causing eosinophilic bronchopneumonia and death. Oral diazepam can lead to hepatic necrosis; therefore, it should also not be considered as a first-line medication, if at all.
Ultimately, when choosing the right prescription for each case, it is important to consider:
- The owner’s ability to administer the medication and, therefore, the frequency of administration. (Phenobarbitone is twice, sometimes three times, daily; levetiracetam is three times, sometimes twice, daily; and zonisamide is once or twice daily)
- The use of tablets versus a liquid formulation (phenobarbitone, levetiracetam and zonisamide have a liquid formulation). It is essential to remember that it can be difficult to judge how much the patient takes when using a liquid formulation, but it might be the only way to medicate in certain cases
- If there is a need to perform blood testing (if phenobarbitone is being considered)
Quality of life in feline epilepsy cases: an ethical dilemma
More and more frequently owners are emphasising their perception of quality of life in relation to different pathologies, both for the patient and for themselves. In cases of epilepsy, this has been explored in more length in dogs; however, a recent study evaluated at length how quality of life and burden of care are perceived by cat owners (Szelecsenyi et al., 2017).
More and more frequently owners are emphasising their perception of quality of life in relation to different pathologies, both for the patient and for themselves
As part of the study, questionnaires filled out by owners from 22 countries were evaluated. Controlled seizures, no side effects and early onset (younger than five years) were related to a significantly higher quality of life. The owners’ burden of care was less when associated with age (better in older owners), duration of epilepsy greater than eight years, controlled seizures and cases where owners felt supported by their vets. The latter highlights the impact and importance of veterinary professionals when it comes to the management, compliance and support in feline epilepsy cases. Moreover, a better cat–owner relationship was associated with a lower burden of care and a better quality of life.
Prognosis
Prognosis is generally good in cases of epilepsy of unknown aetiology. According to one study, seizure semiology and seizure type does not appear to be associated with survival, response to treatment and outcome (Szelecsenyi et al., 2017). Time of diagnosis and remission were highly associated with positive outcomes in this study. However, the time of diagnosis was difficult to interpret as the older the diagnosis, the shorter the survival time, which can probably be explained by ageing itself. Remission did, however, result in a better outcome.
It is interesting to see that the remission rates reported in different studies suggest epilepsy has a better overall outcome in cats than in dogs
It is interesting to see that the remission rates reported in different studies suggest epilepsy has a better overall outcome in cats than in dogs.
