Seizures in Dogs

The Spontaneous Incidence of Neurological Clinical Signs in Preclinical Species Using Cage-side Observations or High-definition Video Monitoring: A Retrospective Analysis

When conducting toxicology studies, the interpretation of drug-related neurological clinical signs such as convulsions, myoclonus/myoclonic jerks, tremors, ataxia, and salivation requires an understanding of the spontaneous incidence of those observations in commonly used laboratory animal species. The spontaneous incidence of central nervous system clinical signs in control animals from a single facility using cage-side observations or high definition video monitoring was retrospectively analyzed. Spontaneous convulsions were observed at low incidence in Beagle dogs and Sprague-Dawley rats but were not identified in cynomolgus monkeys and Göttingen minipigs. Spontaneous myoclonic jerks and muscle twitches were observed at low incidence in Beagle dogs, cynomolgus monkeys, and Sprague-Dawley rats but were not seen in Göttingen minipigs. Spontaneous ataxia/incoordination was identified in all species and generally with a higher incidence when using video monitoring. Salivation and tremors were the two most frequent spontaneous clinical signs and both were observed in all species. Data from the current study unveil potential limitations when using control data obtained from a single study for toxicology interpretation related to low incidence neurological clinical signs while providing historical control data from Beagle dogs, cynomolgus monkeys, Sprague-Dawley rats, and Göttingen minipigs.

Continuous rate infusion of midazolam as emergent treatment for seizures in dogs

Background

Midazolam delivered by continuous rate infusion (CRI) might be effective in dogs with cluster seizures (CS) or status epilepticus (SE).

Objective

To describe the use and safety of midazolam CRI in dogs with CS or SE.

Animals

One‐hundred six client‐owned dogs presenting to a veterinary teaching hospital with CS or SE.

Methods

Retrospective review of medical records for dogs with CS or SE treated with a midazolam CRI.

Results

Seventy‐nine dogs presented with CS and 27 dogs had SE. Seizure control was achieved in 82/106 dogs (77.4%) receiving a midazolam CRI. The median dose associated with seizure control was 0.3 mg/kg/h (range, 0.1‐2.5 mg/kg/h). The median duration of CRI was 25 hours (range, 2‐96 hours). Seizures were controlled in 34/40 dogs (85%) with idiopathic epilepsy, 32/43 dogs (74%) with structural epilepsy, 12/16 dogs (75%) with unknown epilepsy, and 4/7 dogs (57%) with reactive seizures (P = .20). Seizure control was achieved in 81% of dogs with CS and 67% in dogs with SE (P = .18). Dogs with idiopathic/unknown epilepsy were more likely to survive than those with structural epilepsy (87% vs 63%, P = .009). Adverse effects were reported in 24 dogs (22.6%) and were mild in all cases.

Conclusions and Clinical Importance

Midazolam CRI is apparently safe and might be an effective treatment in dogs with CS or SE.

Investigating the efficacy of medical management for canine structural epilepsy

BACKGROUND

Structural epilepsy in dogs is often treated medically with a combination of antiseizure drugs (ASDs) and other concurrent therapies for the primary condition. Unlike idiopathic epilepsy, there have been few studies on the efficacy of medical management in structural epilepsy. This study investigated factors affecting treatment outcomes in dogs medically managed for structural epilepsy.

METHODS

Cases of 71 dogs diagnosed with structural epilepsy were identified from a referral hospital database and data were analysed retrospectively. Efficacy of treatment was assessed by survival time, seizure-free period after diagnosis and overall seizure control.

RESULTS

Results showed that the most significant prognostic indicator was the occurrence of status epilepticus (SE) before diagnosis, with these dogs having reduced survival times, shorter seizure-free periods after diagnosis and overall worse seizure control. Cluster seizure history showed similar, although not statistically significant, trends in treatment efficacy. Treatment outcomes were not significantly impacted by ASD therapy used or by specific diagnosis, with the exception of meningoencephalitis of unknown aetiology cases surviving longer.

CONCLUSION

Overall, medical management of canine structural epilepsy achieves the best treatment outcomes when the patient has no history of SE. This study may provide a basis for future investigations into the treatment of canine structural epilepsies.

A Review: Emergency Management of Dogs With Suspected Epileptic Seizures

Dogs with seizure disorders are commonly presented to the general practitioner for initial evaluation. The most common diagnosis provided is idiopathic epilepsy. As witnessing seizures is often traumatic for owners, it is important for the practitioner to understand seizure classification, know when to initiate antiepileptic drug therapy and be comfortable with client education regarding seizures. This review briefly discusses the most up-to-date classification of seizures, the necessity to obtain accurate histories and complete examinations, base-line diagnostics to perform, the importance of owner education, and when to start medications. This is not intended to discuss detailed differential lists, in-depth information on antiepileptic drug therapy, long-term management of epileptics or those refractory to their current treatment.

Clinical Risk Factors for Early Seizure Recurrence in Dogs Hospitalized for Seizure Evaluation

BACKGROUND

Epileptic seizures are a common cause for neurological evaluations in dogs.

HYPOTHESIS/OBJECTIVES

To determine the timing, frequency, and risk factors for early seizure recurrence (ESR) among dogs admitted to the hospital for seizure evaluation and to facilitate rapid decision making about whether dogs should be placed in the intensive care unit (ICU) or day ward.

ANIMALS

Nine-hundred twenty-two dogs referred for seizure investigation; 214 patients were included.

METHODS

Retrospective study. Medical records between 2000 and 2017 were reviewed to determine risk factors for ESR. Findings were compared among dogs diagnosed with idiopathic epilepsy (IE), structural epilepsy (StE) and reactive seizures (RS), as well as in all selected cases together.

RESULTS

Fifty percent of dogs had a seizure while hospitalized. In the group 53.1 and 52.2% in the StE group, whereas in the RS 40.44% had ESR. The average time to ESR was 7 hours. In IE group, abnormal postictal neurological examination with prosencephalon signs predicted ESR. In StE group, a single generalized or focal seizure 72 hours before hospital admission and abnormal neurologic examination predicted ESR. In the RS group, ERS was predicted by long-term antiepileptic monotheraphy. When all dogs were analyzed together, abnormal neurological examination, the occurrence of cluster seizures, status epilepticus, or combination of them 72 hours before presentation predicted ESR.

CONCLUSIONS AND CLINICAL IMPORTANCE

Epileptic seizures recurred in 50% of patients within a mean time of 7 hours. In general, when cluster seizures, status epilepticus or both occurred 72 hours before presentation and neurological examination was abnormal upon presentation, the dog should be placed in ICU for observation.

Intranasal Midazolam versus Rectal Diazepam for the Management of Canine Status Epilepticus: A Multicenter Randomized Parallel-Group Clinical Trial

Background

Intranasal administration of benzodiazepines has shown superiority over rectal administration for terminating emergency epileptic seizures in human trials. No such clinical trials have been performed in dogs.

Objective

To evaluate the clinical efficacy of intranasal midazolam (IN‐MDZ), via a mucosal atomization device, as a first‐line management option for canine status epilepticus and compare it to rectal administration of diazepam (R‐DZP) for controlling status epilepticus before intravenous access is available.

Animals

Client‐owned dogs with idiopathic or structural epilepsy manifesting status epilepticus within a hospital environment were used. Dogs were randomly allocated to treatment with IN‐MDZ (n = 20) or R‐DZP (n = 15).

Methods

Randomized parallel‐group clinical trial. Seizure cessation time and adverse effects were recorded. For each dog, treatment was considered successful if the seizure ceased within 5 minutes and did not recur within 10 minutes after administration. The 95% confidence interval was used to detect the true population of dogs that were successfully treated. The Fisher's 2‐tailed exact test was used to compare the 2 groups, and the results were considered statistically significant if P < .05.

Results

IN‐MDZ and R‐DZP terminated status epilepticus in 70% (14/20) and 20% (3/15) of cases, respectively (P = .0059). All dogs showed sedation and ataxia.

Conclusions and Clinical Importance

IN‐MDZ is a quick, safe and effective first‐line medication for controlling status epilepticus in dogs and appears superior to R‐DZP. IN‐MDZ might be a valuable treatment option when intravenous access is not available and for treatment of status epilepticus in dogs at home.

Retrospective epidemiological study of canine epilepsy in Japan using the International Veterinary Epilepsy Task Force classification 2015 (2003-2013): etiological distribution, risk factors, survival time, and lifespan

Background

Epilepsy is the most common neurological disease in veterinary practice. However, contrary to human medicine, epilepsy classification in veterinary medicine had not been clearly defined until recently. A number of reports on canine epilepsy have been published, reflecting in part updated proposals from the human epilepsy organization, the International League Against Epilepsy. In 2015, the International Veterinary Epilepsy Task Force (IVETF) published a consensus report on the classification and definition of canine epilepsy. The purpose of this retrospective study was to investigate the etiological distribution, survival time of dogs with idiopathic epilepsy (IdE) and structural epilepsy (StE), and risk factors for survival time, according to the recently published IVETF classification. We investigated canine cases with epilepsy that were referred to our teaching hospital in Japan during the past 10 years, and which encompassed a different breed population from Western countries.

Results

A total of 358 dogs with epilepsy satisfied our etiological study criteria. Of these, 172 dogs (48 %) were classified as IdE and 76 dogs (21 %) as StE. Of these dogs, 100 dogs (consisting of 65 with IdE and 35 with StE) were included in our survival study. Median survival time from the initial epileptic seizure in dogs with IdE and StE was 10.4 and 4.5 years, respectively. Median lifespan of dogs with IdE and StE was 13.5 and 10.9 years, respectively. Multivariable analysis demonstrated that risk factors for survival time in IdE were high seizure frequency (≥0.3 seizures/month) and focal epileptic seizures.

Conclusions

Focal epileptic seizures were identified as a risk factor for survival time in IdE. Clinicians should carefully differentiate seizure type as it is difficult to identify focal epileptic seizures. With good seizure control, dogs with IdE can survive for nearly the same lifespan as the general dog population. Our results using the IVETF classification are similar to previous studies, although some features were noted in our Japanese canine population (which was composed of mainly small-breed dogs), including a longer lifespan in dogs with epilepsy and a larger percentage of meningoencephalomyelitis of unknown origin in dogs with StE.

Liver Histopathology and Liver and Serum Alanine Aminotransferase and Alkaline Phosphatase Activities in Epileptic Dogs Receiving Phenobarbital

Phenobarbital (PB) therapy is frequently associated with elevated serum alanine aminotransferase (ALT) and alkaline phosphatase (AP) activities in dogs without clinical signs of liver disease. The goal of this study was to determine if increased serum ALT and AP activities in clinically healthy PB-treated epileptic dogs are due to hepatic enzyme induction or to subclinical liver injury. Liver biopsies were obtained from 12 PB-treated dogs without clinical signs of liver disease but with elevated serum ALT and/or AP activities or both. Liver biopsies were obtained from eight healthy control dogs not receiving PB. Biopsies were evaluated histopathologically (all dogs) and liver homogenates were assayed for ALT (all dogs) and AP (six treated dogs, all controls) activities. As a positive control, liver cytochrome P4502B, an enzyme known to be induced by PB, was measured by benzyloxyresorufin- O-dealkylase activity and immunoblotting (five treated dogs, all controls). Serum AP isoenzyme analyses were performed. Results showed that ALT and AP activities in liver homogenates were not increased in treated dogs compared with controls, whereas the positive control for induction, CYP2B, was dramatically increased in treated dogs. Histopathological examination of liver biopsies revealed more severe and frequent abnormalities in treated dogs compared to controls, but similar types of abnormalities were found in both groups. Serum AP isoenzyme analyses in treated dogs demonstrated increased corticosteroid-induced and liver isoenzyme activities compared to controls. Results do not support induction of ALT or AP in the liver as the cause of elevated serum activities of these enzymes due to PB.

Canine Pancreas-Specific Lipase and C-reactive Protein in Dogs Treated With Anticonvulsants (Phenobarbital and Potassium Bromide)

Animals treated with anticonvulsant drugs may have increased canine pancreas-specific lipase (cPLI) values. Inflammatory conditions and specifically acute pancreatitis are of major concern in these animals. Elevation in C-reactive protein is being associated with inflammatory status in dogs and it has been correlated with the clinical severity of pancreatitis. In the present study, we investigated if there is a correlation between the cPLI increase, changes in C-reactive protein and hepatic enzymes, as well as the incidence of severe acute pancreatitis (AP) in dogs with anticonvulsant treatment (phenobarbital, or potassium bromide or both). Increased values of pancreas-specific lipase were found in 6.8% of the animals in treatment with anticonvulsants, and this increase is correlated with the increase in triglycerides, alkaline phosphatase, and alanine aminotransferase but not with C-reactive protein levels, which suggests a possible induction or release phenomenon rather than a clear severe AP. C-reactive protein levels did not affect cPLI values on the population studied. Only 2 animals had clinical and analytical data suggestive of AP, indicating a low prevalence (0.6%). In conclusion, cPLI may be increased in a low percentage of animals with anticonvulsants treatment and its increase may not be associated with severe AP. It may be induced by the anticonvulsants drugs; however, further studies are advised to rule out other possible causes that increased cPLI.

Seizure disorders in 43 cattle

Background

Large animals have a relatively high seizure threshold, and in most cases seizures are acquired. No published case series have described this syndrome in cattle.

Objectives

To describe clinical findings and outcomes in cattle referred to the Veterinary Teaching Hospital of the University of Turin (Italy) because of seizures.

Animals

Client‐owned cattle with documented evidence of seizures.

Methods

Medical records of cattle with episodes of seizures reported between January 2002 and February 2014 were reviewed. Evidence of seizures was identified based on the evaluation of seizure episodes by the referring veterinarian or 1 of the authors. Animals were recruited if physical and neurologic examinations were performed and if diagnostic laboratory test results were available.

Results

Forty‐three of 49 cases fulfilled the inclusion criteria. The mean age was 8 months. Thirty‐one animals were male and 12 were female. Piedmontese breed accounted for 39/43 (91%) animals. Seizures were etiologically classified as reactive in 30 patients (70%) and secondary or structural in 13 (30%). Thirty‐six animals survived, 2 died naturally, and 5 were euthanized for reasons of animal welfare. The definitive cause of reactive seizures was diagnosed as hypomagnesemia (n = 2), hypocalcemia (n = 12), and hypomagnesemia‐hypocalcemia (n = 16). The cause of structural seizures was diagnosed as cerebrocortical necrosis (n = 8), inflammatory diseases (n = 4), and lead (Pb) intoxication (n = 1).

Conclusion and Clinical Importance

The study results indicate that seizures largely are reported in beef cattle and that the cause can be identified and successfully treated in most cases.

Treatment in canine epilepsy--a systematic review

Background

Various antiepileptic drugs (AEDs) are used for the management of canine idiopathic epilepsy (IE). Information on their clinical efficacy remains limited. A systematic review was designed to evaluate existing evidence for the effectiveness of AEDs for presumptive canine IE. Electronic searches of PubMed and CAB Direct were carried out without date or language restrictions. Conference proceedings were also searched. Peer-reviewed full-length studies describing objectively the efficacy of AEDs in dogs with IE were included. Studies were allocated in two groups, i.e. blinded randomized clinical trials (bRCTs), non-blinded randomized clinical trials (nbRCTs) and non-randomized clinical trials (NRCTs) (group A) and uncontrolled clinical trials (UCTs) and case series (group B). Individual studies were evaluated based on the quality of evidence (study design, study group sizes, subject enrolment quality and overall risk of bias) and the outcome measures reported (in particular the proportion of dogs with ≥50% reduction in seizure frequency).

Results

Twenty-six studies, including two conference proceedings, reporting clinical outcomes of AEDs used for management of IE were identified. Heterogeneity of study designs and outcome measures made meta-analysis inappropriate. Only four bRCTs were identified in group A and were considered to offer higher quality of evidence among the studies. A good level of evidence supported the efficacy of oral phenobarbital and imepitoin and fair level of evidence supported the efficacy of oral potassium bromide and levetiracetam. For the remaining AEDs, favorable results were reported regarding their efficacy, but there was insufficient evidence to support their use due to lack of bRCTs.

Conclusions

Oral phenobarbital and imepitoin in particular, as well as potassium bromide and levetiracetam are likely to be effective for the treatment of IE. However, variations in baseline characteristics of the dogs involved, significant differences between study designs and several potential sources of bias preclude definitive recommendations. There is a need for greater numbers of adequately sized bRCTs evaluating the efficacy of AEDs for IE.

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.

Comparison of concentrations of γ-aminobutyric acid and glutamate in cerebrospinal fluid of dogs with idiopathic epilepsy with and without seizure-related magnetic resonance imaging hyperintense areas in the limbic system

OBJECTIVE

To investigate differences in CSF concentrations of excitatory and inhibitory neurotransmitters in dogs with and without T2-weighted (T2W) MRI hyperintense areas in the limbic system.

SAMPLE

Archived CSF samples and stored brain MRI images of 5 healthy research dogs (group 1), 8 dogs with idiopathic epilepsy (IE) with no abnormal MRI findings (group 2), and 4 dogs with IE with hyperintense areas in the limbic system detected by means of T2W MRI (group 3).

PROCEDURES

Archived CSF samples and stored MRI images obtained from all dogs were evaluated. Dogs in groups 2 and 3 were matched on the basis of age and breed. High-performance liquid chromatography was used to evaluate glutamate and γ-aminobutyric acid (GABA) concentrations in CSF samples.

RESULTS

Glutamate concentrations were higher in CSF of both groups of dogs with IE than in healthy dogs. However, glutamate concentrations in CSF were not significantly higher in dogs with IE and with hyperintense areas than in dogs with IE but no abnormal MRI findings. Concentrations of GABA in CSF were higher in group 3 than in group 2 and in group 2 than in group 1.

CONCLUSIONS AND CLINICAL RELEVANCE

No significant difference was evident between glutamate concentrations in CSF of dogs with IE and with and without hyperintense areas detected by means of T2W MRI. However, glutamate concentrations typically were higher in CSF of dogs with IE and MRI hyperintense areas. Future studies with larger sample sizes should be conducted to confirm this finding and to determine the clinical importance of high glutamate concentrations in CSF of dogs with IE.

Is switching from brand name to generic formulations of phenobarbital associated with loss of antiepileptic efficacy?: a pharmacokinetic study with two oral formulations (Luminal(®) vet, Phenoleptil(®)) in dogs

Background

In human medicine, adverse outcomes associated with switching between bioequivalent brand name and generic antiepileptic drug products is a subject of concern among clinicians. In veterinary medicine, epilepsy in dogs is usually treated with phenobarbital, either with the standard brand name formulation Luminal® or the veterinary products Luminal® vet and the generic formulation Phenoleptil®. Luminal® and Luminal® vet are identical 100 mg tablet formulations, while Phenoleptil® is available in the form of 12.5 and 50 mg tablets. Following approval of Phenoleptil® for treatment of canine epilepsy, it was repeatedly reported by clinicians and dog owners that switching from Luminal® (human tablets) to Phenoleptil® in epileptic dogs, which were controlled by treatment with Luminal®, induced recurrence of seizures. In the present study, we compared bioavailability of phenobarbital after single dose administration of Luminal® vet vs. Phenoleptil® with a crossover design in 8 healthy Beagle dogs. Both drugs were administered at a dose of 100 mg/dog, resulting in 8 mg/kg phenobarbital on average.

Results

Peak plasma concentrations (C_max) following Luminal® vet vs. Phenoleptil® were about the same in most dogs (10.9 ± 0.92 vs. 10.5 ± 0.77 μg/ml), and only one dog showed noticeable lower concentrations after Phenoleptil® vs. Luminal® vet. Elimination half-life was about 50 h (50.3 ± 3.1 vs. 52.9 ± 2.8 h) without differences between the formulations. The relative bioavailability of the two products (Phenoleptil® vs. Luminal® vet.) was 0.98 ± 0.031, indicating that both formulations resulted in about the same bioavailability.

Conclusions

Overall, the two formulations did not differ significantly with respect to pharmacokinetic parameters when mean group parameters were compared. Thus, the reasons for the anecdotal reports, if true, that switching from the brand to the generic formulation of phenobarbital may lead to recurrence of seizures are obviously not related to a generally lower bioavailability of the generic formulation, although single dogs may exhibit lower plasma levels after the generic formulation that could be clinically meaningful.

Evaluation of plasma diazepam and nordiazepam concentrations following administration of diazepam intravenously or via suppository per rectum in dogs

OBJECTIVE

To evaluate the pharmacokinetics of diazepam administered per rectum via compounded (ie, not commercially available) suppositories and determine whether a dose of 2 mg/kg in this formulation would result in plasma concentrations shown to be effective for control of status epilepticus or cluster seizures (ie, 150 to 300 ng/mL) in dogs within a clinically useful interval (10 to 15 minutes).

ANIMALS

6 healthy mixed-breed dogs.

PROCEDURES

Dogs were randomly assigned to 2 groups of 3 dogs each in a crossover-design study. Diazepam (2 mg/kg) was administered IV or via suppository per rectum, and blood samples were collected at predetermined time points. Following a 6- or 7-day washout period, each group received the alternate treatment. Plasma concentrations of diazepam and nordiazepam were analyzed via reversed phase high-performance liquid chromatography.

RESULTS

Plasma concentrations of diazepam and nordiazepam exceeded the targeted range ≤ 3 minutes after IV administration in all dogs. After suppository administration, targeted concentrations of diazepam were not detected in any dogs, and targeted concentrations of nordiazepam were detected after 90 minutes (n = 2 dogs) or 120 minutes (3) or were not achieved (1).

CONCLUSIONS AND CLINICAL RELEVANCE

On the basis of these results, administration of 2 mg of diazepam/kg via the compounded suppositories used in the present study cannot be recommended for emergency treatment of seizures in dogs.

Epilepsy after head injury in dogs: a natural model of posttraumatic epilepsy

PURPOSE

In humans, traumatic brain injury (TBI) is one of the most common causes of acquired (symptomatic) epilepsy, but as yet there is no treatment to prevent the development of epilepsy after TBI. Animal models of posttraumatic epilepsy (PTE) are important to characterize epileptogenic mechanisms of TBI and to identify clinically effective antiepileptogenic treatments. The prevalence and phenomenology of naturally occurring canine epilepsy are similar to those in human epilepsy. However, the risk of epilepsy after TBI has not been systemically studied in dogs. We therefore performed a large retrospective study in 1,000 dogs referred to our clinical department over a period of 11.5 years with the aim to determine the incidence of early and late seizures after head trauma in this species.

METHODS

Two strategies were used: in group I (n = 392), we evaluated whether dogs referred for the treatment of a head trauma (group Ia) or other trauma (group Ib) developed seizures after the trauma, whereas in group II (n = 608) we evaluated whether dogs referred for the treatment of recurrent epileptic seizures had a history of head trauma. Data for this study were obtained from our clinical database, questionnaires sent to the dogs' owners, and owner interviews.

KEY FINDINGS

In group Ia, 6.6% of the dogs developed PTE, which was significantly different from group Ib (1.9%), indicating that head trauma increased the risk of developing epilepsy by a factor of 3.4. The risk of PTE increased with severity of TBI; 14.3% of the dogs with skull fracture developed PTE. In group II, 15.5% of the dogs with epilepsy had a history of head injury, which was significantly higher than the incidence of PTE determined for group Ia.

SIGNIFICANCE

Our study indicates that head trauma in dogs is associated with a significant risk of developing epilepsy. Therefore, dogs with severe TBI are an interesting natural model of PTE that provides a novel translational platform for studies on human PTE.

Electroencephalographic recordings in dogs suffering from idiopathic and symptomatic epilepsy: diagnostic value of interictal short time EEG protocols supplemented by two activation techniques

The diagnostic value of interictal short time electroencephalographic (EEG) recordings in epileptic dogs under general anaesthesia with propofol and the muscle relaxant rocuronium bromide was investigated. Two activation techniques, namely photic stimulation and hyperventilation, were evaluated for their potential to enhance the diagnostic validity of these recordings. Sixty-one dogs suffering from idiopathic epilepsy and 28 dogs suffering from symptomatic epilepsy were included. Electroencephalograms were recorded using five subdermal EEG electrodes (F3, F4, Cz, O1 and O2). All 89 EEGs were analysed visually and 61 were also evaluated quantitatively with fast Fourier transformation. Interictal paroxysmal epileptiform activity was found in 25% of idiopathic and in 29% of symptomatic epileptic dogs. Quantitative analysis of the EEGs (qEEGs) detected significant differences of frequency analysis in single reading points without any continuous changes of frequency bands. A comparison between healthy and affected brain hemispheres in seven dogs with focal lesions of one hemisphere did not show any significant differences in qEEG analysis. qEEG was not more sensitive than visual evaluation. Despite the use of activation techniques, the results showed that short time EEG recordings in epileptic dogs can detect interictal epileptic activity in less than one third of all seizuring dogs and is not a useful screening method.

Add-on treatment with verapamil in pharmacoresistant canine epilepsy

PURPOSE

Verapamil add-on treatment has been suggested as a novel therapeutic concept for overcoming transporter-mediated pharmacoresistance. Efficacy data have been limited so far to case reports in individual epileptic patients. Therefore, we aimed to thoroughly evaluate the efficacy and tolerability of verapamil add-on treatment.

METHODS

In a prestudy in healthy Beagle dogs the tolerability of verapamil add-on treatment was investigated. The efficacy of verapamil was then evaluated in 11 dogs with phenobarbital-resistant epilepsy.

KEY FINDINGS

Verapamil add-on treatment (6.2-7.3 mg/kg) did not affect phenobarbital concentrations in plasma or cerebrospinal fluid. Side effects observed in healthy as well as in epileptic dogs comprised bradycardia and a decrease in blood pressure. Therefore, we had to limit the dosage to 1-1.5 mg/kg in the main study. In phenobarbital nonresponders, verapamil failed to improve seizure control. Verapamil treatment was discontinued prematurely in five animals due to worsening of seizure control or lack of an effect. In the remaining animals, seizure frequency tended to increase during the verapamil add-on phase, reaching a mean of two seizures per month compared to the pre-verapamil phase with phenobarbital monotherapy (mean of 1.4 seizures per month). In view of the detrimental effects in the majority of the dogs, the study had to be discontinued and no further animals were enrolled.

SIGNIFICANCE

The failure of the maximum tolerated dosage to improve seizure control in dogs with phenobarbital-resistant epilepsy argues against the suitability of verapamil add-on treatment to overcome pharmacoresistance. Deterioration of seizure control in some individual animals suggests that verapamil might also exert unfavorable effects on seizure thresholds or its spread.

Clinical comparison of primary versus secondary epilepsy in 125 cats

In the present study 125 cats with recurrent seizures were analysed. The main goal was to investigate the aetiology and compare primary epilepsy (PE) with secondary epilepsy (SE) regarding signalment, history, ictal pattern, clinical and neurological findings. Seizure aetiology was classified as PE in 47 (38%) and SE in 78 (62%) cats. SE was caused mainly by intracranial neoplasia (16), hippocampal necrosis (14), toxicosis (eight), and encephalitis (seven). A significant difference between PE and SE was found in: age, body weight, duration of seizure, occurrence of status epilepticus and neurological deficits. Status epilepticus, altered interictal neurological status and seizure onset over the age of 7 years indicated SE more frequently than PE. If the seizures occurred during resting conditions and rapid running occurred the aetiology was more likely to be PE than SE.

Metabolic and toxic causes of canine seizure disorders: A retrospective study of 96 cases

A wide variety of intoxications and abnormal metabolic conditions can lead to reactive seizures in dogs. Patient records of dogs suffering from seizure disorders (n=877) were reviewed, and 96 cases were associated with an underlying metabolic or toxic aetiology. These included intoxications by various agents, hypoglycaemia, electrolyte disorders, hepatic encephalopathy, hypothyroidism, uraemic encephalopathy, hypoxia and hyperglycaemia. The incidence of the underlying diseases was determined. The most common causes of reactive seizures were intoxications (39%, 37 dogs) and hypoglycaemia (32%, 31 dogs). Hypocalcaemia was the most frequent electrolyte disorder causing reactive seizures (5%) and all five of these dogs had ionised calcium concentrations ≤0.69 mmol/L. Eleven per cent of dogs with seizures had metabolic or toxic disorders and this relatively high frequency emphasises the importance of a careful clinical work-up of cases presented with seizures in order to reach a correct diagnosis and select appropriate treatment options.

Retrospective clinical comparison of idiopathic versus symptomatic epilepsy in 240 dogs with seizures

In the present study, 240 cases of dogs with seizures were analysed retrospectively. The aim was to examine the underlying aetiology and to compare primary or idiopathic epilepsy (IE) with symptomatic epilepsy (SE) concerning signalment, history, ictal pattern, clinical and neurological findings. The diagnosis of symptomatic epilepsy was based on confirmed pathological changes in haematology, serum biochemistry, cerebrospinal fluid (CSF) analysis and morphological changes of the brain by CT/MRI or histopathological examination. Seizure aetiologies were classified as idiopathic epilepsy (IE, n = 115) and symptomatic epilepsy (SE, n = 125). Symptomatic epilepsy was mainly caused by intracranial neoplasia (39) and encephalitis (23). The following variables showed significant difference between the IE and SE group: age, body weight, presence of partial seizures, cluster seizures, status epilepticus, ictal vocalisation and neurological deficits. In 48% of the cases, seizures were found to be due to IE, while 16% were due to intracranial neoplasia and 10% to encephalitis. Status epilepticus, cluster seizures, partial seizures, vocalisation during seizure and impaired neurological status were more readily seen with symptomatic epilepsy. If the first seizure occurred between one and five years of age or the seizures occurred during resting condition, the diagnosis was more likely IE than SE.

Prospective study of zonisamide therapy for refractory idiopathic epilepsy in dogs

OBJECTIVES

Investigation of the efficacy of zonisamide as an add-on therapy in dogs with refractory epilepsy.

METHODS

Thirteen dogs fulfilled the inclusion criteria of poor seizure control despite adequate serum levels of phenobarbital, potassium bromide or both. One further dog was treated with zonisamide as monotherapy because of severe blood dyscrasia due to phenobarbital treatment. Various seizure parameters were evaluated retrospectively for a four month period without zonisamide and prospectively for the same time period under zonisamide add-on therapy. The study time period was extended by up to 17 months to evaluate long-term outcome.

RESULTS

Data of 11 dogs could be evaluated: nine of them were responders. The median reduction of seizure frequency of all dogs on zonisamide add-on therapy was 70 per cent (range 14 to 100 per cent). Only transient central nervous system side effects were reported. No further increase of liver enzymes occurred. In three of the responder dogs, seizure control subsided after individual time periods (between 69 days and seven months).

CLINICAL SIGNIFICANCE

In dogs with refractory epilepsy, zonisamide may have a beneficial effect on seizure control. In three responder dogs, seizure activity relapsed possibly because of an induction of tolerance. Limiting factors are the high costs.

Idiopathic epilepsy in dogs: owners' perspectives on management with phenobarbitone and/or potassium bromide

OBJECTIVES

To explore seizure management from the perspective of the owners of dogs with idiopathic epilepsy.

METHODS

Questionnaires were mailed to owners of 29 dogs under management for suspected or diagnosed idiopathic epilepsy through the clinics of the Small Animal Hospital of the University of Glasgow Veterinary School, using either phenobarbitone or potassium bromide alone or in combination.

RESULTS

The postal survey had an 86 per cent response rate. Analysis of the responses demonstrated that "the dog's quality of life", "adequate seizure frequency" and "acceptable side effects of antiepileptic drugs" were the three greatest concerns for owners; 52 per cent of owners strongly agreed that the seizure management for their dog was adequate, though the seizure frequency reported varied within this group; the majority of owners did not consider the administration of medication a nuisance. However, approximately 60 per cent of owners reported that caring for an epileptic dog had an effect on the organisation of their free time, though this was not dependent on perception of seizure control. Opinions as to the value of further diagnostic procedures, in particular intracranial imaging, were significantly affected by having pet health insurance.

CLINICAL SIGNIFICANCE

From the owners' perspective, adequacy of seizure control is determined by the balance between "the dog's quality of life", "adequate seizure frequency" and "acceptable side effects of antiepileptic drugs". A frequency of less than one seizure every three months is associated with the perception by owners of adequate seizure control.

Assessment and treatment of central nervous system abnormalities in the emergency patient

Disease of or injury to the central nervous system is a common rea-son for hospital admission on an emergency basis in veterinary medicine. Head injuries, seizures, and diseases that lead to intra-cranial hypertension frequently result in significant alteration of neurologic function. A thorough understanding of the pathophysiologic disturbances that occur during these conditions is para-mount for providing stabilizing emergent care. A detailed approach that focuses on meticulous physical evaluation, provision of timely and optimal stabilizing treatment, and continued monitoring can aid in improving outcomes in animals with signs and symptoms of neurologic disease or injury.

Clinical description and mode of inheritance of idiopathic epilepsy in English Springer Spaniels

OBJECTIVE

To determine clinical characteristics and mode of inheritance of idiopathic epilepsy (IE) in English Springer Spaniels.

DESIGN

Original study.

ANIMALS

45 dogs with IE and 74 siblings and their respective parents.

PROCEDURE

IE was diagnosed on the basis of age at the time of seizure onset and results of laboratory testing and neurologic examinations. Simple segregation analysis was performed with the Davie method.

RESULTS

Median age at the onset of seizures was 3 years; however, 9 (20%) dogs were between 5 and 6 years old at the time of the onset of seizures. Twenty-one dogs (47%) had generalized seizures, and 24 (53%) had focal onset seizures. Results of segregation analysis were consistent with partially penetrant autosomal recessive or polygenic inheritance. Simulated linkage indicated that there was a 58% chance of obtaining suggestive linkage with the available pedigrees.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of the present study suggest that in English Springer Spaniels, IE segregates in a manner that is consistent with partially penetrant autosomal recessive inheritance (ie, a single major locus with modifying genes) or polygenic inheritance. Given enough families with accurate phenotypic information and available DNA, it should be possible to use genetic linkage analysis to identify chromosomal segments containing the causative gene or genes.

Potassium bromide, an anticonvulsant, is effective at alleviating seizures in the Drosophila bang-sensitive mutant bang senseless

Human seizure disorders are a major health concern due to the large number of affected individuals, the potentially devastating consequences of untreated seizure occurrences, and the lack of an effective treatment for all patients. Although anticonvulsants have proven very helpful in treating seizures and remain the best option available for treatment, not all afflicted individuals respond to medication and many only do so in unique drug combinations or at the cost of adverse side-effects. Therefore, new and more effective anticonvulsants are continually sought after to combat this illness. In this study, we present results which offer the possibility of using Drosophila bang-sensitive (BS) mutants as a tool to screen anticonvulsants. By feeding the BS mutants a known anticonvulsant, potassium bromide, we have demonstrated that the drug dramatically reduces the seizures of bang senseless, the most severe of the BS mutants. This methodology suggests that the Drosophila system can potentially be a powerful instrument for assaying and testing new compounds with anticonvulsant properties.

Serum alkaline phosphatase isoenzyme profiles in phenobarbital-treated epileptic dogs

BACKGROUND

Serum total alkaline phosphatase (AP) activity commonly is high in dogs receiving phenobarbital. Specific isoenzymes responsible for this increase are not well documented.

OBJECTIVES

The purposes of this study were 1) to qualitatively and quantitatively describe serum AP isoenzymes in phenobarbital-treated dogs and 2) to monitor changes in serum AP isoenzyme activities associated with phenobarbital treatment over time.

METHODS

Serum AP isoenzyme activities were determined in a cross-sectional study of 29 dogs receiving phenobarbital (duration of treatment 2 months to 6.5 years). Additionally, in a prospective study of 23 dogs, serum AP isoenzyme activities were determined before and 3 weeks, 6 months, and 12 months after the start of phenobarbital treatment. Isoenzyme activities were quantitatively determined using wheat germ lectin precipitation and levamisole inhibition, and qualitatively (ie, present or absent) evaluated using cellulose acetate affinity electrophoresis.

RESULTS

In phenobarbital-treated dogs with high serum total AP activity in the cross-sectional study, the increase was due predominantly to increased activities of the corticosteroid-induced (C-AP) and liver (L-AP) isoenzymes. Prospectively, serum total AP and L-AP activities were significantly higher at 3 weeks, 6 months, and 12 months after the start of phenobarbital treatment compared with pretreatment values. Serum C-AP and bone isoenzyme (B-AP) activities were significantly higher after 6 and 12 months of treatment. B-AP accounted for only a small amount of the total AP activity. No unusual or previously unidentified AP isoenzymes were identified.

CONCLUSIONS

Phenobarbital treatment was associated with increased C-AP and L-AP isoenzyme activities and with a minor increase in B-AP activity. No unique "phenobarbital-induced" isoenzyme was identified. Isoenzyme analysis does not appear to be useful for differentiating between high serum total AP due to phenobarbital therapy and other causes.

Clinical characteristics and inheritance of idiopathic epilepsy in Vizslas

Medical record, seizure survey, and telephone interview information was obtained for 29 Vizslas with idiopathic epilepsy (IE), 74 unaffected siblings, and 41 parents to determine the common clinical characteristics and most likely mode of inheritance. IE was diagnosed on the basis of the age of seizure onset, laboratory results, and neurologic examination findings. Computerized tomography (CT) or magnetic resonance imaging (MRI) scan with cerebrospinal fluid (CSF) analysis was required for the inclusion of dogs with an age of seizure onset of < 6 months or > 5 years. Simple segregation analysis was performed with an ascertainment correction and chi-square analysis. IE appeared to be familial in these pedigrees, with 79% of affected Vizslas exhibiting partial onset seizures. Partial seizure signs included a combination of limb tremors, staring, pupillary dilatation, or salivation without loss of consciousness in > 50% of the dogs with partial signs. The estimated segregation frequency of P = .22 (95% CI, P = .08 to .36) was consistent with autosomal recessive inheritance; however, polygenic inheritance could not be excluded as a possibility. Simulated linkage with FASTSLINK estimated that the average logarithm of odds (LOD) score would be 3.23 with a 10-centimorgan (cM) whole-genome scan for these families, indicating that these families would be useful for a whole-genome scan to potentially find the chromosomal segment(s) containing the epilepsy gene or genes. We conclude that IE in Vizslas appears to be primarily a partial onset seizure disorder that may be inherited as an autosomal recessive trait.

Complex partial status epilepticus induced by a microinjection of kainic acid into unilateral amygdala in dogs and its brain damage

OBJECTIVE

In order to investigate kainic acid (KA)-induced amygdaloid seizure and seizure-induced brain damage in dogs, and to compare these findings with that in other species, a KA-induced seizure model in dogs was produced.

MATERIAL AND METHODS

Normal beagle dogs were used. A Teflon cannula for KA injection was inserted into the left amygdala, and cortical or depth electrodes were positioned. One week after surgery, 1.5 microg of KA was microinjected into the left amygdala. EEGs and the behavior of the animals were monitored for 2 months after KA injection. In addition, neuron-specific enolase levels in the cerebrospinal fluid (CSF-NSE) were measured intermittently. At 2 months after the injection, histopathological studies were performed.

RESULTS

KA-treated dogs showed limbic seizures that started from the left amygdala within 30 min after injection. The seizures developed into complex partial status epilepticus (CPSE), and started independently from the bilateral amygdala during the CPSE. The CPSE lasted for 1-3 days, and the animals showed no spontaneous seizures during the 2-month observation period. A significant increase in CSF-NSE was observed immediately after CPSE. Histopathologically, extensive necrosis, which formed large cavity lesions, was observed around the bilateral amygdala.

SUMMARY

A microinjection of KA into unilateral amygdala in dogs induced CPSE. The seizures elicited independently from bilateral amygdala, and bilateral limbic structures suffered extensive injury. In addition, CSF-NSE was demonstrated as a useful marker of acute neuronal damage.

Use of vagal nerve stimulation as a treatment for refractory epilepsy in dogs

OBJECTIVE

To evaluate safety and efficacy of vagal nerve stimulation in dogs with refractory epilepsy.

DESIGN

Placebo-controlled, double-masked, crossover study.

ANIMALS

10 dogs with poorly controlled seizures.

PROCEDURE

A programmable pacemaker-like device designed to deliver intermittent stimulation to the left cervical trunk of the vagus was surgically implanted in each dog. Dogs were assigned randomly to two 13-week test periods, 1 with nerve stimulation and 1 without nerve stimulation. Owners recorded data on seizure frequency, duration, and intensity, as well as adverse effects.

RESULTS

No significant difference in seizure frequency, duration, or severity was detected between overall 13-week treatment and control periods. During the final 4 weeks of the treatment period, a significant decrease in mean seizure frequency (34.4%) was detected, compared with the control period. Complications included transient bradycardia, asystole, and apnea during intraoperative device testing, and seroma formation, subcutaneous migration of the generator, and transient Horner's syndrome during the 14-day period between surgery and suture removal. No adverse effects of stimulation were detected, and most owners were satisfied with the treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

Vagal nerve stimulation is a potentially safe approach to seizure control that appears to be efficacious in certain dogs and should be considered a possible treatment option when antiepileptic medications are ineffective.

Clinical presentations of naturally occurring canine seizures: similarities to human seizures

The clinical presentations of 119 canine seizures from 41 Standard Poodles and 11 Dalmatians were classified according to a modified version of the International League Against Epilepsy (ILAE) seizure classification system. Standardized use of the ILAE system with dogs not only should facilitate research in veterinary medicine, which has no standard criteria for seizure classification, but also should facilitate comparisons between canine and human seizures. We found that for more than 80% of both breeds, at least some of their seizures had partial onsets. However, because it was common for partial seizures to secondarily generalize, the majority of Poodles (81%) and Dalmatians (91%) experienced at least some generalized seizures. Among partial seizures, complex partial were more frequent than simple partial. For both breeds, two thirds of those with partial onset seizures had exclusively complex partial. Among dogs with primary or secondarily generalized seizures, 80% of both breeds had tonic-clonic seizures.