A review of the pharmacology and clinical applications of levetiracetam in dogs and cats

OBJECTIVE

To review and summarize the pharmacology of the antiepileptic drug (AED), levetiracetam (LEV), and to discuss its clinical utility in dogs and cats.

DATA SOURCES

Veterinary and human peer-reviewed medical literature and the authors' clinical experience.

SUMMARY

LEV is an AED with mechanisms of action distinct from those of other AEDs. In people and small animals, LEV exhibits linear kinetics, excellent oral bioavailability, and minimal drug-drug interactions. Serious side effects are rarely reported in any species. LEV use is gaining favor for treating epilepsy in small animals and may have wider clinical applications in patients with portosystemic shunts, neuroglycopenia, and traumatic brain injury. In people, LEV may improve cognitive function in patients with dementia.

CONCLUSION

LEV is a well-tolerated AED with well-documented efficacy in human patients. Although its use is becoming more common in veterinary medicine, its role as a first-line monotherapy in small animal epileptics remains to be determined. This review of the human and animal literature regarding LEV describes its role in epileptic people and animals as well as in other disease states and provides recommendations for clinical usage.

Once-a-day oral treatment with phenobarbital in cats with presumptive idiopathic epilepsy

OBJECTIVES

Phenobarbital (PB) q12h is the most common treatment recommendation for cats with recurrent epileptic seizures. Medicating cats may be challenging and result in decreased quality of life for both cat and owner. The aim of this retrospective study was to evaluate treatment with oral PB q24h in cats with presumptive idiopathic epilepsy.

METHODS

Nine cats with presumptive idiopathic epilepsy, receiving oral PB q24h, were included in a retrospective descriptive study.

RESULTS

Seizure remission was achieved in 88% (8/9) of the cats and good seizure control in 12% (1/9) of the cats, treated with a mean dose of oral PB of 2.6 mg/kg q24h (range 1.4-3.8 mg/kg). No cats required an increase of their PB frequency at any time during a mean follow-up period of 3.5 years (range 1.1-8.0 years). No cats displayed side effects or issues with compliance at the last recorded follow-up.

CONCLUSIONS AND RELEVANCE

Once-a-day administration of PB for feline epilepsy was safe and resulted in satisfactory seizure control for the nine cats included in this study. The results of this study justify exploring this topic further in larger prospective studies.

Perception of challenges in management of neurological cases in the emergency room

OBJECTIVE

To investigate emergency clinicians' comfort level in assessing neurological emergencies and to identify opportunities to foster enhanced training of clinical neurology in the emergency room.

DESIGN

Internet-based survey.

SETTING

University teaching hospitals and private referral centers.

SUBJECTS

One hundred and ninety-two emergency and critical care specialists and resident trainees (ECC) and 104 neurology specialists and resident trainees (NEUR) in clinical practice.

INTERVENTIONS

An internet-based survey was distributed via veterinary professional organizations' listserves and message boards and responses were collected between March and April 2020. ECC completed a survey evaluating stress levels associated with neurological emergencies, confidence with neurological examinations, and neuroanatomical localization. NEUR completed a similar survey to report their perception of their ECC colleagues' confidence in the assessment of neurological cases. Chi-square and Mann-Whitney U-tests were used to compare categorical responses and confidence scores between groups. P < 0.002 was considered significant.

MEASUREMENTS AND MAIN RESULTS

Fifty-two percent of ECC found neurological emergencies slightly challenging, whereas 85% of NEUR found them moderately to extremely challenging for ECC (P < 0.0001). ECC's median self-reported confidence score in performing a neurologic examination on a scale of 0-100 was 75 (interquartile range [IQR], 27), while NEUR reported a median ECC confidence of 44 (IQR, 25; P < 0.0001). Median self-reported ECC confidence in localizing intracranial, spinal, and neuromuscular disease was 67 (IQR, 40), 88 (IQR, 21), and 60 (IQR, 37), respectively, which was significantly higher than median NEUR-reported ECC confidence of 35 (IQR, 38), 51 (IQR, 31), and 18 (IQR, 20), respectively (all P < 0.0001). Following case transfer, 34% of ECC received NEUR feedback in >75% of cases.

CONCLUSIONS

Noticeable discrepancies between ECC and NEUR perceptions of ECC clinical confidence were seen, while no firm evidence of neurophobia could be inferred. Improvements in interdepartmental communication and teaching of clinical neurology may be warranted.

Temporal lobe epilepsy in cats

In recent years there has been increased attention to the proposed entity of feline temporal lobe epilepsy (TLE). Epileptic discharges in certain parts of the temporal lobe elicit very similar semiology, which justifies grouping these epilepsies under one name. Furthermore, feline TLE patients tend to have histopathological changes within the temporal lobe, usually in the hippocampus. The initial aetiology is likely to be different but may result in hippocampal necrosis and later hippocampal sclerosis. The aim of this article was not only to summarise the clinical features and the possible aetiology, but also being work to place TLE within the veterinary epilepsy classification. Epilepsies in cats, similar to dogs, are classified based on the aetiology into idiopathic epilepsy, structural epilepsy and unknown cause. TLE seems to be outside of this classification, as it is not an aetiologic category, but a syndrome, associated with a topographic affiliation to a certain anatomical brain structure. Magnetic resonance imaging, histopathologic aspects and current medical therapeutic considerations will be summarised, and emerging surgical options are discussed.

Neurosurgery in feline epilepsy, including clinicopathology of feline epilepsy syndromes

Feline epilepsy is treated with antiseizure medications, which achieves fair to good seizure control. However, a small subset of feline patients with drug-resistant epilepsy requires alternative therapies. Furthermore, approximately 50 % of cats with epileptic seizures are diagnosed with structural epilepsy with or without hippocampal abnormality and may respond to surgical intervention. The presence of hippocampal pathology and intracranial tumors is a key point to consider for surgical treatment. This review describes feline epilepsy syndrome and epilepsy-related pathology, and discusses the indications for and availability of neurosurgery, including lesionectomy, temporal lobectomy with hippocampectomy, and corpus callosotomy, for cats with different epilepsy types.

[Magnetic resonance imaging findings in 143 epileptic cats]

OBJECTIVE

Epilepsy is one of the more common chronic neurological diseases in cats in which MRI plays a key role in the diagnostic work-up. Hippocampal MRI changes are common in cats, however it is unclear whether these changes represent the reason or the consequence of the disease.The goal of the present study was the retrospective analysis of the MRI findings in a large cohort of epileptic cats.

MATERIAL AND METHODS

In total, 143 cats of 3 age groups (< 1 year, 1-6 years, and > 6 years) were included in the study. MRI findings were divided into 4 categories: normal, with extrahippocampal lesions, and hippocampal signal alterations with or without contrast enhancement. The prevalence and frequency of these MRI findings in the age groups were examined using chi-quadrat test and nominal regression model.

RESULTS

In approximately one half of the cats (49 %), MRI displayed normal findings. Extrahippocampal changes occurred in 18 % of the animals. Hippocampal alterations were present in 33 % of the cats. Hippocampal sclerosis was found histopathologically in all four MRI categories.

CONCLUSION AND CLINICAL RELEVANCE

Brain MRI was normal in approximately 50 % of the epileptic cats. Extrahippocampal changes are expected mostly in cats older than 6 years. The etiology of the hippocampal alterations is unclear in most cases. Further investigations are needed for a better understanding of the hippocampal signal alterations.

Epilepsy in British Shorthair cats in Sweden

OBJECTIVES

The primary objective of this study was to investigate the prevalence of epileptic seizures and of presumed idiopathic epilepsy (PIE, describing epilepsy of unknown origin) in a cohort of British Shorthair (BSH) cats in Sweden. The secondary objective was to describe epileptic seizure characteristics and outcome for cats with PIE.

METHODS

Owners of BSH cats born between 2006 and 2016 and registered with SVERAK (the Swedish Cat Clubs' National Association) were invited to reply to a questionnaire about their cat's general health. Owners who indicated that their cat had experienced epileptic seizures were invited to participate in an in-depth telephone interview about the epileptic seizures. The clinical characteristics of epileptic seizures in BSH cats were determined from the results of the interview.

RESULTS

In this population comprising 1645 BSH cats (representing 28% of registered BSHs), the prevalence of epileptic seizures was 0.9% and for PIE it was 0.7%. BSH cats with PIE presented with infrequent but consistent epileptic seizures. Twenty-seven percent of BSH cats with epileptic seizures had cluster seizures but none presented with status epilepticus. None of the BSH cats was treated with antiepileptic drugs, and none of the owners reported epileptic seizure remission in their cat.

CONCLUSIONS AND RELEVANCE

The prevalence of PIE in this population of BSH cats was 0.7%. The prevalence of epileptic seizures was 0.9%. In general, PIE in the BSH cat displayed a relatively benign phenotype where progression of epileptic seizures was uncommon.

Understanding the impacts of feline epilepsy on cats and their owners

BACKGROUND

Epilepsy is the most common neurological condition reported in cats. Characterised by recurrent seizures, treatment involves the administration of anti-epileptic drugs up to multiple times a day. Epilepsy and its associated treatments may impact both cats and their owners. The present study aimed to assess factors associated with quality of life (QOL) in cats with epilepsy and the burden of care in their owners.

METHODS

An online survey was developed using demographic information and the following validated measures: cat QOL, Zarit burden interview (ZBI) and the cat owner relationship scale (CORS). Regression analysis was conducted using SPSS 26.

RESULTS

Responses were completed by 141 owners from 22 countries. QOL was significantly higher in cats with controlled seizures, no adverse effects from medication and epilepsy onset before 5 years of age. ZBI was significantly lower in owners who felt supported by their veterinarian, who were over 55 and had cats with controlled seizures. Higher CORS was significantly correlated with both higher cat QOL and lower owner ZBI.

CONCLUSIONS

Adequate seizure control and close cat-owner relationships may play an important role in mitigating the impact of epilepsy on cats and their owners. Further research into understanding cat-owner relationships and successfully controlling epilepsy in cats is needed.

Evaluation of the effect of phenobarbital administration on the biochemistry profile, with a focus on serum liver values, in epileptic cats

OBJECTIVES

Phenobarbital (PB) is the most common antiseizure drug (ASD) used for the management of feline epilepsy. In dogs, PB is known to cause serum liver enzyme induction and hepatotoxicity, especially after administration long term or in high concentrations. In cats, insufficient evidence is available to draw similar conclusions. The aim of this study was to evaluate the effect of PB administration on the serum biochemistry profile of epileptic cats. As an additional objective, other adverse effects arising, related to PB treatment, were recorded.

METHODS

Medical records of four veterinary centres were retrospectively reviewed for epileptic cats receiving PB treatment. Cats were included if they had a diagnosis of idiopathic epilepsy or structural epilepsy; a normal baseline serum biochemistry profile; at least one follow-up serum biochemistry profile; no concurrent disease or had not received medication that could possibly influence liver function or lead to serum liver enzyme induction. Alkaline phosphatase, alanine aminotransferase (ALT), aspartate transaminase and gamma-glutamyl transferase activities, and total bilirubin, bile acids, glucose, albumin, total protein, urea and creatinine concentrations before and during PB administration were recorded. PB serum concentration was also recorded, when available.

RESULTS

Thirty-three cats (24 males, nine females) with a median age of 3 years (range 2 months to 12 years) met the inclusion criteria. Idiopathic or structural epilepsy was diagnosed in 25 (76%) and eight (24%) cats, respectively. The follow-up period ranged from 9 to 62 months. This study found an increase in ALT in three cats, possibly related to a PB serum concentration >30 µg/ml. No statistically significant increase in serum liver enzymes or other evaluated biochemistry parameters was found by comparing pre- and post-treatment parameters.

CONCLUSIONS AND RELEVANCE

PB administration did not result in hepatic enzyme induction or other biochemical abnormalities in cats. This strengthens the safety profile of PB as an ASD in cats.

Feline temporal lobe epilepsy: seven cases of hippocampal and piriform lobe necrosis in England and literature review

CASE SERIES SUMMARY

Seven cases of feline hippocampal and piriform lobe necrosis (FHN) are described, with particular emphasis on clinical, radiographic and histopathological correlations. FHN is an uncommon acute epileptic condition resembling human autoimmune limbic encephalitis and temporal lobe epilepsy. Seizures are typically focal and feature uni- or bilateral orofacial or head twitching, hypersalivation, lip smacking, mydriasis, vocalisation and motionless staring, with inter-ictal behavioural changes such as unprovoked aggression and rapid running. Emerging evidence supports an autoimmune aetiology, although disruption of hippocampal architecture secondary to brain neoplasia has also been recognised. Most commonly, however, the underlying cause remains unknown. Diagnosis is achieved clinically and with brain MRI; electroencephalography and voltage-gated potassium channel-complex autoantibodies are currently the subject of research. Affected cats are frequently refractory to conventional antiepileptic treatment.

RELEVANCE AND NOVEL INFORMATION

Following a review of the literature, including potential complicating factors and comparisons with human medicine, the hippocampus and piriform lobe are proposed as the neuroanatomical localisation for focal seizures with orofacial involvement in cats, regardless of aetiology.

[Diagnostics in epilepsy - potential of magnetic resonance imaging]

Epilepsy is a common neurologic disease frequently encountered by small animal practitioners. The disease comprises a multiplicity of clinical presentations and etiologies and often necessitates a comprehensive as well as cost-intensive diagnostic workup. This is mandatory in order to be able to diagnose or exclude a metabolic cause of the seizures and to distinguish between idiopathic and structural epilepsy. The examination by means of magnetic resonance imaging (MRI) represents a central component of the diagnostic workup, which in turn has essential effects on treatment and prognosis. In order to achieve standardized examination and comparable results, it is of utmost importance to use defined MRI protocols. Accordingly, communication and interaction between clinical institutions may be facilitated and as of yet undetected structural changes might be recorded in future MRI techniques. This review article sets particularly emphasis on the definition and classification of epilepsy as well as its diagnostic imaging procedures and refers to statistics and specialists' recommendations for the diagnostic workup in dogs.

Transient hyperammonaemia following epileptic seizures in cats

OBJECTIVES

The aim of this study was to determine whether transient postictal hyperammonaemia exists in cats.

METHODS

The medical records of all feline patients that presented at a Swedish veterinary hospital between 2008 and 2018 were retrospectively reviewed to find those that had a recent or ongoing epileptic seizure. To qualify for inclusion, the medical record had to include information on at least one ammonia value taken in close proximity to, or during, an active seizure, the cat must have exceeded the normal upper limit of blood ammonia concentration on initial testing (reference interval 0-95 μmol/l), and there needed to be a follow-up ammonia value available within a maximum of 3 days.

RESULTS

Five cats were included in the study, and they had blood ammonia concentrations on initial testing ranging from 146 to 195 µmol/l. They were all retested within a period of 2 h to 3 days of the original reading. All five cats had a spontaneous decrease in ammonia levels without any specific treatment for hyperammonaemia.

CONCLUSIONS AND RELEVANCE

Pursuant to the findings of this retrospective study, transient hyperammonaemia may be noted after epileptic seizure in cats. Consequently, a differential diagnostic list in feline patients with hyperammonaemia could, depending on the context, include non-hepatic-related pathologies, such as epileptic seizures.

Epidemiology of recurrent seizure disorders and epilepsy in cats under primary veterinary care in the United Kingdom

Background

Little epidemiological evaluation of recurrent seizure disorders in cats currently exists in veterinary literature.

Objectives

To report the prevalence and risk factors for recurrent seizure disorders (RSD) and epilepsy in cats presented to primary care veterinary practices in the United Kingdom (UK).

Animals

A total of 285 547 cats under veterinary care during 2013 presenting to 282 primary care clinics in the UK.

Methods

Cohort study using multivariable logistic regression modeling for risk factor analysis.

Results

There were 458 confirmed RSD cases, giving a 1‐year period prevalence of 0.16% (95% confidence interval [CI], 0.15‐0.18). A subset of 114 (24.89%) cases was recorded as having epilepsy, giving a 1‐year period prevalence of 0.04% (95% CI, 0.03‐0.5). Increasing age was significantly associated with increasing odds of RSD. Breed, sex, neuter status, and body weight were not associated with RSD. Epilepsy was most frequently diagnosed in adult to middle‐aged cats. Cats aged 3.0 to <6.0 years had 3.32 times higher odds of epilepsy diagnosis compared to cats <3.0 years of age. Insured cats were more likely to be diagnosed with epilepsy compared to noninsured cats.

Conclusions and Clinical Importance

Although less common than in dogs, RSD and epilepsy still comprise an important disorder group in the UK cat population. Aging is a significant risk factor for these disorders in cats.

Prevalence and clinical characteristics of phenobarbitone-associated adverse effects in epileptic cats

OBJECTIVES

The study objective was to investigate the prevalence and clinical characteristics of phenobarbitone-associated adverse effects in epileptic cats.

METHODS

The medical records of two veterinary referral clinics from 2007 to 2017 were searched for cats fulfilling the inclusion criteria of a diagnosis of epilepsy, treatment with phenobarbitone and available follow-up information on the occurrence of adverse effects. Follow-up information was obtained from the medical records of the primary veterinarian and referral institutions and a questionnaire completed by the cats' owners.

RESULTS

Seventy-seven cats met the inclusion criteria. Fifty-eight were affected by idiopathic epilepsy and 19 by structural epilepsy. One or more of the following adverse effects were reported in 47% of the cats: sedation (89%); ataxia (53%); polyphagia (22%); polydipsia (6%); polyuria (6%); and anorexia (6%). Logistic regression analyses revealed significant associations between adverse effect occurrence and both phenobarbitone starting dosage and administration of a second antiepileptic drug (AED). For each 1 mg/kg q12h increment of phenobarbitone, the likelihood of adverse effects increased 3.1 times. When a second AED was used, the likelihood of adverse effects increased 3.2 times. No association was identified between epilepsy aetiology and adverse effect occurrence. An idiosyncratic adverse effect, characterised by severe neutropenia and granulocytic hypoplasia, was diagnosed in one cat. This resolved following phenobarbitone discontinuation.

CONCLUSIONS AND RELEVANCE

The prevalence of phenobarbitone-associated adverse effects was 47%. Sedation and ataxia were most common. These are type A adverse effects and are predictable from phenobarbitone's known pharmacological properties. In the majority of cases, adverse effects occurred within the first month of treatment and were transient. Idiosyncratic (type B) adverse effects, which were not anticipated given the known properties of the drug, occurred in one cat. Increased phenobarbitone starting dosage and the addition of a second AED were significantly associated with the occurrence of adverse effects.

Recurrent seizures in cats: Diagnostic approach - when is it idiopathic epilepsy?

Practical relevance: Seizures are one of the most common neurologic problems recognized in cats, affecting approximately 1-3% of the general population. Treatment options and prognosis are closely related to the underlying cause, so it is important that veterinarians are familiar with the diagnostic approach to cats with seizures and options for medical management. Series outline: This is the first of a two-part article series that reviews the diagnosis and treatment of seizures in cats. Part 1 outlines the classification and terminology used to describe epilepsy and epileptic seizures in cats, and discusses some of the most common and unique causes of recurrent seizures in cats. The diagnostic approach to cats with recurrent seizures is addressed, as are criteria for the diagnosis of idiopathic epilepsy.

AUDIENCE

This review of recurrent seizures in cats is intended for all veterinarians who are facing the challenges of seizure diagnosis and management in the feline patient. Evidence base: Recommendations for diagnosis and management of feline seizure disorders have historically been extrapolated from the canine and human literature. The information and guidance provided in this two-part series is based on a review of the recent published literature addressing seizure disorders and antiepileptic treatment in cats, as well as the authors' clinical experience.

Recurrent seizures in cats: Treatment - which antiepileptic drugs are recommended?

Practical relevance: Seizures are one of the most common neurological problems recognized in cats, affecting approximately 1-3% of the general population. Treatment options and prognosis are closely related to the underlying cause, so it is important that veterinarians are familiar with the diagnostic approach to cats with seizures and options for medical management. Series outline: This is the second of a two-part article series that reviews the diagnosis and treatment of seizures in cats. Part 2 describes chronic medical treatment options and prognosis for cats with recurrent seizures, and acute treatment of status epilepticus.

AUDIENCE

This review of recurrent seizures in cats is intended for all veterinarians who are facing the challenges of seizure diagnosis and management in the feline patient. Evidence base: Recommendations for diagnosis and management of feline seizure disorders have historically been extrapolated from the canine and human literature. The information and guidance provided in this two-part series is based on a review of the recent published literature addressing seizure disorders and antiepileptic treatment in cats, as well as the authors' clinical experience.

Seizure etiologic classification and long-term outcome for cats with juvenile-onset seizures

OBJECTIVE To identify seizure etiologic classification for cats that developed seizures at < 12 months of age and describe the long-term outcome of affected cats. DESIGN Retrospective cohort study. ANIMALS 15 client-owned cats with seizures that began at < 12 months of age. PROCEDURES Information on each cat was obtained from the medical records, veterinarians, and owners. Inclusion required an onset of seizures before 12 months of age and a complete medical record, including a final diagnosis. RESULTS 7 of the 15 cats had structural epilepsy, 4 had idiopathic epilepsy, and 4 had reactive seizures. Median age at seizure onset was 27 weeks (range, 0.4 to 41 weeks). Cluster seizures were reported in 6 cats, and status epilepticus was reported in 2. Age at the onset of seizures, presence of cluster seizures, and seizure semiology (ie, generalized vs focal seizures) were not significantly associated with seizure etiologic classification. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that cats that developed seizures at < 12 months of age were more likely to have structural epilepsy than idiopathic epilepsy or reactive seizures. Therefore, advanced diagnostic imaging is recommended in cats with juvenile-onset seizures if metabolic and toxic causes are excluded.

Serum levetiracetam concentrations after transdermal levetiracetam administration, 3 times daily, to healthy cats

Background

Repeated oral administration of antiepileptic drugs can be challenging for cat owners, resulting in reduced compliance, poor seizure control, and reduced quality of life for cats. Levetiracetam (LEV) has several properties that make it an appealing drug for transdermal application.

Objectives

The aims were to (1) determine if transdermal LEV, in a lipophilic, liposomic cream vehicle, resulted in serum concentrations above 5 μg/mL; (2) identify clinical adverse effects; and (3) evaluate the concentration of LEV in a lipophilic liposomic cream at set intervals.

Animals

Six healthy, client‐owned cats weighing ≤5 kg.

Methods

Prospective clinical trial. Transdermal LEV was applied to the inner pinna at a dosage of 60 mg/kg (400 mg/mL concentration) at home for 6 days. Day 7, cats were hospitalized for blood sample collection for LEV concentration at times 0 (before dose administration), 0.5, 1, 2, 3, and 4 hours after administration.

Results

Median (range) timed serum concentrations were 16.6 (8.6‐39.6) μg/mL, 16.1 (6.8‐34.4) μg/mL, 15.4 (10.1‐36.7) μg/mL, 17.4 (9.2‐32.7) μg/mL, 15.1 (8.3‐25.9) μg/mL, and 14.8 (11.9‐28.4) μg/mL, respectively. Adverse events were limited to sedation (1/6 cats) and pinna crusting (1/6 cats). The LEV, in the proposed vehicle, retained concentration above 95% at 400 mg/mL up to 5 weeks.

Conclusions and Clinical Importance

Thrice daily transdermal LEV resulted in median serum concentrations ≥5 μg/mL throughout the sampling period and clinical adverse events were minimal. Transdermal LEV can provide an alternative for cats resistant to administration of other forms of anticonvulsant medication.

Evaluation of Transdermal Administration of Phenobarbital in Healthy Cats

The purpose was to determine the safety and achievable serum concentrations of transdermally administered phenobarbital in healthy cats. The hypothesis was that transdermal phenobarbital would achieve therapeutic serum concentrations (15-45 µg/mL) with minimal short-term adverse effects. Enrolled cats had normal physical and neurologic exams and unremarkable bloodwork. Transdermal phenobarbital in a pluronic lecithin organogel-based vehicle was administered at a dosage of 3.0-3.1 mg/kg per ear pinna (total of 6.0-6.2 mg/kg) every 12 hr for 14 days. Serum phenobarbital concentrations were measured 3-6 hr after dosing at seven different times over 15 days. The mean and median serum concentration of phenobarbital at study completion were 5.57 and 4.08 µg/mL, respectively. Mean peak concentration and mean time to peak concentration were 5.94 µg/mL and 13.3 days, respectively. Mild adverse effects were observed. Potency was analyzed in three replicates of the transdermal phenobarbital gel administered; potencies ranged from 62.98 to 82.02%. Transdermal application of phenobarbital in healthy cats achieves a detectable, but subtherapeutic, serum concentration and appears safe in the short term. The use of therapeutic drug monitoring is recommended when this formulation of phenobarbital is used to ensure therapeutic serum concentrations are achieved.

Systematic review of antiepileptic drugs' safety and effectiveness in feline epilepsy

BACKGROUND

Understanding the efficacy and safety profile of antiepileptic drugs (AEDs) in feline epilepsy is a crucial consideration for managing this important brain disease. However, there is a lack of information about the treatment of feline epilepsy and therefore a systematic review was constructed to assess current evidence for the AEDs' efficacy and tolerability in cats. The methods and materials of our former systematic reviews in canine epilepsy were mostly mirrored for the current systematic review in cats. Databases of PubMed, CAB Direct and Google scholar were searched to detect peer-reviewed studies reporting efficacy and/or adverse effects of AEDs in cats. The studies were assessed with regards to their quality of evidence, i.e. study design, study population, diagnostic criteria and overall risk of bias and the outcome measures reported, i.e. prevalence and 95% confidence interval of the successful and affected population in each study and in total.

RESULTS

Forty studies describing clinical outcomes of AEDs' efficacy and safety were included. Only two studies were classified as "blinded randomised controlled trials". The majority of the studies offered high overall risk of bias and described low feline populations with unclear diagnostic criteria and short treatment or follow-up periods. Individual AED assessments of efficacy and safety profile showed that phenobarbital might currently be considered as the first choice AED followed by levetiracetam and imepitoin. Only imepitoin's safety profile was supported by strong level of evidence. Imepitoin's efficacy as well as remaining AEDs' efficacy and safety profile were supported by weak level of evidence.

CONCLUSIONS

This systematic review reflects an evidence-based assessment of the published data on the AEDs' efficacy and safety for feline epilepsy. Currently, phenobarbital is likely to be the first-line for feline epileptic patients followed by levetiracetam and imepitoin. It is essential that clinicians evaluate both AEDs' effectiveness and tolerability before tailoring AED to the individual patient. Further studies in feline epilepsy treatment are by far crucial in order to establish definite guidelines for AEDs' efficacy and safety.

Survival in 76 cats with epilepsy of unknown cause: a retrospective study

Survival of cats with epilepsy of unknown cause (EUC) has not been reported. Seizure semiology and its relationship to treatment outcome and survival was studied in a population of 76 cats. A questionnaire for seizure semiology was developed based on experimental data. Seizure semiology was characterised by owner interviews at least one year after discharge. Seizures were classified as (1) primary generalised and (2) focal without and (3) with secondary generalisation. Median age at seizure onset was four (range 0.3-18) years. One-third of cats with EUC presented with primary generalised seizures and 78 per cent of those with initially focal seizures progressed to secondary generalised seizures. Clinical signs of generalised seizures included sudden onset of loss of consciousness and tonic-clonic seizures, while cats with focal seizures had unilateral signs. Antiepileptic drug (AED) therapy was initiated in 62 cats. Complete remission rate was 42 per cent and the median survival time was 3.2 (range 1-11) years with or without AED, and 91 per cent were still alive at the time of interview. Neither semiology nor seizure type predicted survival, response to treatment and outcome in cats with EUC. A seizure-free status of more than 12 months was observed in 79 per cent of cats without AED.

Clinical reasoning in feline epilepsy: Which combination of clinical information is useful?

We sought to identify the association between clinical risk factors and the diagnosis of idiopathic epilepsy (IE) or structural epilepsy (SE) in cats, using statistical models to identify combinations of discrete parameters from the patient signalment, history and neurological examination findings that could suggest the most likely diagnosis. Data for 138 cats with recurrent seizures were reviewed, of which 110 were valid for inclusion. Seizure aetiology was classified as IE in 57% and SE in 43% of cats. Binomial logistic regression analyses demonstrated that pedigree status, older age at seizure onset (particularly >7years old), abnormal neurological examinations, and ictal vocalisation were associated with a diagnosis of SE compared to IE, and that ictal salivation was more likely to be associated with a diagnosis of IE than SE. These findings support the importance of considering inter-ictal neurological deficits and seizure history in clinical reasoning.

The Seizuring Cat

Practical relevance Although seizures occur less commonly in cats compared with dogs, they are one of the most common forms of neurological disease in the feline patient. Cats may experience both focal (partial) and generalized seizures and causes are divided into primary disorders, in which there is no underlying cause (ie, idiopathic epilepsy), and secondary disorders. Cats with secondary seizure disorders have either an underlying structural lesion or metabolic disease.

Patient group Seizures affect cats of all ages. Cats with idiopathic epilepsy tend to be younger (approximately 3.5 years) than cats with secondary seizure disorders (approximately 8 years).

Audience This review of feline seizures is directed at all veterinarians who treat cats, both in an emergency setting as well as in general practice.

Clinical challenges Refractory seizures are often a diagnostic and therapeutic challenge. A systematic approach to the seizuring cat is described, easing the task of diagnosing the cause of the seizures. In addition, novel antiepileptics are discussed, which can be used as add-on drugs in challenging feline seizure cases.

Evidence base Compared with the canine counterpart, the literature regarding treatment of feline seizures is less established. Recent clinical trials and studies are focusing on new treatment options for feline seizures. Specifically, these studies, some of which are ongoing, have led to the use of levetiracetam, zonisamide and pregabalin as add-on antiepileptics in cases that are refractory to phenobarbital.

Magnetic resonance features of the feline hippocampus in epileptic and non-epileptic cats: a blinded, retrospective, multi-observer study

BACKGROUND

Hippocampal necrosis in cats has been reported to be associated with epileptic seizures. Magnetic resonance imaging (MRI) features of temporal lobe (TL) abnormalities in epileptic cats have been described but MR images from epileptic and non-epileptic individuals have not yet been systematically compared. TL abnormalities are highly variable in shape, size and signal, and therefore may lead to varying evaluations by different specialists. The aim of this study was to investigate whether there were differences in the appearance of the TL between epileptic and non-epileptic cats, and whether there were any relationships between TL abnormalities and seizure semiologies or other clinical findings. We also investigated interobserver agreement among three specialists.

METHODS

The MR images of 46 cats were reviewed independently by three observers, who were blinded to patient data, examination findings and the review of the other observers. Images were evaluated using a multiparametric scoring system developed for this study. Mann-Whitney U-tests and chi-square were used to analyse the differences between observers' evaluations. The kappa coefficient (k) and Fleiss' kappa coefficient were used to quantify interobserver agreement.

RESULTS

The overall interobserver agreement was moderate to good (k =0.405 to 0.615). The MR scores between epileptic and non-epileptic cats did not differ significantly. However, there was a significant difference between the MR scores of epileptic cats with and without orofacial involvement according to all three observers. Likewise, MR scores of cats with cluster seizures were higher than those of cats without clusters.

CONCLUSION

Cats presenting with recurrent epileptic seizures with orofacial involvement are more likely to have hippocampal pathologies, which suggests that TL abnormalities are not merely unspecific epileptic findings, but are associated with a certain type of epilepsy. TL signal alterations are more likely to be detected on FLAIR sequences. In contrast to severe changes in the TL which were described similarly among specialists, mild TL abnormalities may be difficult to interpret, thus leading to different assessments among observers.

Seizures in horses: diagnosis and classification

Seizures are a diverse and very common set of chronic neurologic disorders in humans and dogs but are less common in horses. Seizures refer to a specific clinical event (described as sudden and severe) regardless of the etiology, which includes both intracranial and extracranial causes. Therefore, after briefly reviewing some definitions, this article aims to describe the use of a standardized classification, which could facilitate a logical approach for the clinician to establish a diagnosis, as well as to use a consistent mode of communication. For instance, seizures can be classified by type (ie, focal vs generalized) or etiology (ie, reactive, symptomatic, cryptogenic, idiopathic). In particular, epilepsy, a brain disorder characterized by recurrent seizures can be classified as primary (ie, genetic origin) or secondary (ie, acquired). This review further discusses the limitations associated with the clinical workup of horses with seizures. This is germane to the fact that the identification of the underlying cause remains challenging due to the technical limitations of imaging the equine adult brain. Indeed, as in man and dogs, epilepsies of unknown cause (ie, cryptogenic) account for the majority of all epilepsies. Therefore, although electroencephalography and advanced brain imaging techniques (eg, computed tomography and magnetic resonance imaging) are becoming increasingly available, information obtained from the history, physical, and neurologic examinations and progression of clinical signs and response to treatment remain essential in the workup of horses with seizures.

Magnetic resonance imaging and computed tomography findings of Dyke-Davidoff-Masson-like syndrome in a cat

CASE REPORT

A 3.5-year-old spayed female Domestic Shorthair cat was evaluated for new onset seizures and lateralising signs indicative of a lesion in the right prosencephalon. Magnetic resonance imaging and computed tomography of the head revealed hypoplasia of the right cerebral hemisphere and changes in the overlying cranium, including hyperostosis and expansion of the diploic space, resulting in an increased pneumatisation of the rostral bones of the cranium. A congenital injury to the cerebral hemisphere and secondary changes of the cranium in response to the decreased brain parenchyma was presumed. Similar changes have been previously recognised in human patients with unilateral anomalies of the cerebral hemispheres, termed Dyke-Davidoff-Masson syndrome (DDMS).

CONCLUSION

The case presented is the first clinical and imaging description of a cat with a syndrome that closely resembles DDMS in humans. The description of the syndrome allows recognition of an additional differential for seizures in a young patient and informs the clinician of the imaging characteristics of the cranium seen with early loss of brain parenchyma.

International veterinary epilepsy task force recommendations for systematic sampling and processing of brains from epileptic dogs and cats

Traditionally, histological investigations of the epileptic brain are required to identify epileptogenic brain lesions, to evaluate the impact of seizure activity, to search for mechanisms of drug-resistance and to look for comorbidities. For many instances, however, neuropathological studies fail to add substantial data on patients with complete clinical work-up. This may be due to sparse training in epilepsy pathology and or due to lack of neuropathological guidelines for companion animals.The protocols introduced herein shall facilitate systematic sampling and processing of epileptic brains and therefore increase the efficacy, reliability and reproducibility of morphological studies in animals suffering from seizures.Brain dissection protocols of two neuropathological centres with research focus in epilepsy have been optimised with regards to their diagnostic yield and accuracy, their practicability and their feasibility concerning clinical research requirements.The recommended guidelines allow for easy, standardised and ubiquitous collection of brain regions, relevant for seizure generation. Tissues harvested the prescribed way will increase the diagnostic efficacy and provide reliable material for scientific investigations.

Hippocampal sclerosis in feline epilepsy

Hippocampal sclerosis (HS) refers to loss of hippocampal neurons and astrogliosis. In temporal lobe epilepsy (TLE), HS is a key factor for pharmacoresistance, even though the mechanisms are not quite understood. While experimental TLE models are available, there is lack of models reflecting the natural HS development. Among domestic animals, cats may present with TLE-like seizures in natural and experimental settings. With this study on the prevalence, segmental pattern and clinicopathological correlates of feline HS, we evaluated the translational value for human research. Evaluation schemes for human brains were applied to epileptic cats. The loss of neurons was morphometrically assessed and the degree of gliosis was recorded. Hippocampal changes resembling human HS were seen in about one third of epileptic cats. Most of these were associated with infiltrative diseases such as limbic encephalitis. Irrespective of the etiology and semiology of seizures, total hippocampal sclerosis was the most prevalent form seen in epileptic animals. Other HS types also occur at varying frequencies. Segmental differences to human HS can be explained by species-specific synaptic connectivities and a different spectrum of etiologies. All these variables require consideration when translating results from feline studies regarding seizure-associated changes of the temporal lobe and especially HS.

Therapeutic serum phenobarbital concentrations obtained using chronic transdermal administration of phenobarbital in healthy cats

Seizures are a common cause of neurologic disease, and phenobarbital (PB) is the most commonly used antiepileptic drug. Chronic oral dosing can be challenging for cat owners, leading to poor compliance. The purpose of this study was to determine if the transdermal administration of PB could achieve serum PB concentrations of between 15 and 45 μg/ml in healthy cats. Nineteen healthy cats were enrolled in three groups. Transdermal PB in pluronic lecithin organogel (PLO) was applied to the pinnae for 14 days at a dosage of 3 mg/kg q12h in group 1 (n = 6 cats) and 9 mg/kg q12h in group 2 (n = 7 cats). Transdermal PB in Lipoderm Activemax was similarly applied at 9 mg/kg q12h for 14 days in group 3 (n = 6 cats). Steady-state serum PB concentrations were measured at trough, and at 2, 4 and 6 h after the morning dose on day 15. In group 1, median concentrations ranged from 6.0–7.5 μg/ml throughout the day (observed range 0–11 μg/ml). Group 2 median concentrations were 26.0 μg/ml (observed range 18.0–37.0 μg/ml). For group 3, median concentrations ranged from 15.0–17.0 μg/ml throughout the day (range 5–29 μg/ml). Side effects were mild. One cat was withdrawn from group 2 owing to ataxia and sedation. These results show therapeutic serum PB concentrations can be achieved in cats following chronic transdermal administration of PB in PLO at a dosage of 9 mg/kg q12h. More individual variation was noted using Lipoderm Activemax. Transdermal administration may be an alternative for cats that are difficult to medicate orally.

Seizures and epilepsy in cats

Seizures are a common presenting complaint in cats, although causes and options for the treatment of seizures in this species have been historically poorly described in the veterinary literature. Seizure manifestation in cats may be different than what is typically seen in dogs, but the underlying causes of seizure activity are the same. These include primary epilepsies, structural epilepsies, and reactive seizures. Although primary epilepsy was once believed to be rare in cats, we now commonly appreciate this syndrome, albeit at a lower frequency than in dogs. Because of this, a complete diagnostic work-up is recommended for all cats presenting for initial evaluation of seizures. Symptomatic treatment of seizures in cats is similar to dogs, with only a few limitations related to species-specific antiepileptic drug toxicities. The goal of this review is to summarize the recent veterinary literature related to feline seizures, with a focus on seizure classification, clinical manifestation, diagnostic evaluation, and treatment options.

A clinical and diagnostic approach to the patient with seizures

Seizures are one of the most common neurologic problems encountered by the small animal practitioner. Successful management of the patient with seizure is facilitated by an appropriate diagnostic workup to identify underlying causes when they exist. Veterinary patients with seizures can be divided in to 3 main categories based on underlying cause: those with primary epilepsy, those with structural epilepsy, and those with reactive seizures. Additionally, some patients may be given a label of unknown epilepsy when they do not meet the criteria for a diagnosis of primary epilepsy, but no structural or reactive cause of seizures can be identified. This article reviews the key clinical findings associated with each of the 3 main categories of seizures and suggests a standardized approach to the diagnostic workup for patients with seizure based on their signalment and neurologic examination findings.

Terminology and classification of seizures and epilepsy in veterinary patients

The classification of epileptic seizures and epilepsy is a controversial and dynamic topic that has undergone many iterations in human medicine. The International League against Epilepsy is a multinational organization that has formed a number of task forces and subcommittees to study this issue, and has ratified several reports outlining recommended terminology and classification schemes for human patients. Veterinary publications on this issue have generally adapted these schemes to fit small animal patients, but a formally endorsed system to classify seizures and epilepsy has never been developed for veterinary patients. This review outlines the classification systems that have been published for human patients and summarizes previous efforts by veterinary authors to utilize these methods. Finally, a set of definitions and terminology for use in veterinary patients is proposed, which includes a glossary of descriptive terminology for ictal semiology and a diagnostic scheme for classification of individual patients. This document is intended as a starting point of discussion, which will hopefully eventually result in a formally ratified document that will be useful for communication between health professionals, the design of clinical trials and for guiding treatment decisions and prognostication for veterinary patients with seizures.

Retrospective study of morbidity and mortality of captive Iberian lynx (Lynx pardinus) in the ex situ conservation programme (2004-June 2010)

Medical records of 120 Iberian lynx (Lynx pardinus) from the captive breeding population (CBP), 96 of which were older than 1 wk old, were studied from January 2004 to June 2010. From a total of 413 clinical signs recorded, it was possible to obtain a diagnosis in 258 (62.5%). Inappetence, skin wound, and vomiting had the highest incidence. Adult (2 to 6 yr old) and juvenile (1 wk to 1 yr old) animals accounted for most of the clinical signs. Vitamin D toxicosis and intraspecific trauma accounted for 55.4% and 15.1% of the clinical signs, respectively. Renal toxicosis due to the administration of supplements with an excess of vitamin D occurred in 2009 and affected a total of 39 individuals. Intraspecific trauma cases were predominantly observed from sibling aggression. Diet-related conditions consisted of sporadic cases of fatal salmonellosis, dermatophytosis, and gastrointestinal episodes. Suspected idiopathic epilepsy and femoral neck metaphyseal osteopathy were also observed. A total of 15 animals older than 1 wk old died including five vitamin D toxicosis cases and three juveniles due to intraspecific trauma. Mycobacterium bovis was found as a secondary infection in two animals that died from vitamin D toxicosis. Abortions, premature births, and stillbirths accounted for 12 mortalities, and 13 neonatal deaths due to maternal neglect or bacterial sepsis were observed. Data show that improvement of diet-related conditions is a key factor in preserving the health of animals in the CBP. Thus, the control of food and supplement composition, rabbit farm suppliers, and hygiene should be standardized and improved. Furthermore, data recording and diagnostic protocols should be standardized.

Epilepsy in cats: theory and practice

The veterinary literature on epilepsy in cats is less extensive than that for dogs. The present review summarizes the most important human definitions related to epilepsy and discusses the difficulties in applying them in daily veterinary practice. Epileptic seizures can have a wide range of clinical signs and are not necessarily typical in all cases. Whether a seizure event is epileptic can only be suspected based on clinical, laboratory, and neuroimaging findings as electroencephalography diagnostic techniques have not yet been developed to a sufficiently accurate level in veterinary medicine. In addition, the present review aims to describe other diagnoses and nonepileptic conditions that might be mistaken for epileptic seizures. Seizures associated with hippocampal lesions are described and discussed extensively, as they seem to be a special entity only recognized in the past few years. Furthermore, we focus on clinical work‐up and on treatment that can be recommended based on the literature and summarize the limited data available relating to the outcome. Critical commentary is provided as most studies are based on very weak evidence.

Hippocampal Necrosis in a Cat from Australia

This paper reports findings from a feline case of hippocampal necrosis. A seven-year-old neutered female cat was seen with a history of behavioural change followed by complex focal seizures. The cat was severely pyrexic on presentation and anisocoria was present. It was treated with cooling, intravenous fluid, and phenobarbitone administration which was later changed to levetiracetam. An MRI was performed and revealed findings of a hypointense T1 and hyperintense T2 signal in the hippocampus and inferior temporal gyrus with mild gadolinium uptake, findings which were consistent with previous cases of hippocampal necrosis. The cat was witnessed to vomit and aspirate 24 hours after diagnosis leading to cardiac arrest and death. Postmortem examination revealed a subacute degenerative encephalopathy involving the hippocampus.

Clinical characterization of epilepsy of unknown cause in cats

BACKGROUND

The diagnosis of feline epilepsy of unknown cause (EUC) requires a thorough diagnostic evaluation, otherwise the prevalence of EUC could be overestimated.

HYPOTHESIS

Feline EUC is a clinically defined disease entity, which differs from feline hippocampal necrosis by the absence of magnetic resonance imaging (MRI) signal alteration of the hippocampus. The objectives of this study were (1) to evaluate the prevalence of EUC in a hospital population of cats by applying well-defined inclusion criteria, and (2) to describe the clinical course of EUC.

ANIMALS

Eighty-one cats with recurrent seizures.

METHODS

Retrospective study--medical records were reviewed for cats presented for evaluation of recurrent seizures (2005-2010). Inclusion criteria were a defined diagnosis based on laboratory data, and either MRI or histopathology. Final outcome was confirmed by telephone interview with the owner. Magnetic resonance images were reviewed to evaluate hippocampal morphology and signal alterations.

RESULTS

Epilepsy of unknown cause was diagnosed in 22% of cats with epilepsy. Physical, neurologic, and laboratory examinations, and either 1.5 T MRI and cerebrospinal fluid analysis or postmortem examination failed to identify an underlying cause. Cats with EUC had a higher survival rate (P < .05) and seizure remission occurred frequently (44.4%).

CONCLUSION AND CLINICAL IMPORTANCE

A detailed clinical evaluation and diagnostic imaging with MRI is recommended in any cat with recurrent seizures. The prognosis of cats with normal MRI findings and a clinical diagnosis of EUC are good. Standardized imaging guidelines should be established to assess the hippocampus in cats.

Seizuring cat: what to ask, what to do?

A seizuring cat can be a challenging case for every veterinarian and, therefore, the correct diagnosis and the appropriate management of such a case requires understanding of the most common causes of feline seizures. The underlying cause of the seizures should be investigated by a thorough questioning of the diagnostic approach and most likely diagnoses. If the cause of the seizures can be found then the appropriate therapeutic approach may improve the prognosis. The treatment of the feline seizures is similar to the canine patients; however, the differences should be kept in mind. This article is tailored to answer the most common questions that veterinary surgeons should ask themselves when dealing with a seizuring cat.