Contents

  1. Epilepsy and its treatment in dogs
    1. Introduction
    2. Physiology of epilepsy
    3. Types of canine epilepsies
    4. Diagnosis and identification
      1. Gene mutations
      2. Process of elimination
    5. Factors influencing susceptibility for canine epilepsy
      1. Breed
      2. Age
    6. Diagnostics and treatment
      1. Phenobarbital
      2. Side effects Phenobarbital
      3. Potassium bromide
      4. Benefits of potassium bromide
      5. Side effects potassium bromide
    7. Conclusion
    8. References
    9. Other referenced materials

Epilepsy and its treatment in dogs

Introduction

Epilepsy is the most common medical neurological disorder in dogs, and even due to anti-epileptic drugs, many dogs still suffer from seizures. It is important to study canine epilepsy and its cause, so a treatment can be offered. In this research paper we will address different causes, treatments and risk factors related to canine epilepsy.

Physiology of epilepsy

At a cellular and molecular level, the pathogenesis and pathophysiology of epilepsy are being studied thoroughly, but still little is known about the cause of epilepsies in dogs (Cui et al, 2017). Epilepsy is defined as recurring seizures caused by an abnormality in brain function. These repetitive seizures are a result of the brain’s response to abnormal systemic metabolism, such as hypoglycemia, hypocalcemia, uremia, etc (Cui et al, 2017). The frequency and severity of seizures vary. Certain factors such as sleep deprivation, stress and hormonal factors show an increase in seizures (Forsgård et al, 2018). There are also recorded a correlation between the severity of a seizure and breed. Epilepsy is not terminal. Quality of life is the most important factor for a chronic medical disease like epilepsy. Euthanasia may be used as an option if the dog's quality of life is dramatically reduced or the financial and emotional burden exceeds the owner's limitations (Podell et al, 2016).

Types of canine epilepsies

Epilepsy can be inherited (genetic epilepsy), from structural defects in the brain (symptomatic epilepsy) or it can be caused by an unknown cause (idiopathic epilepsy) (“Epilepsy Research Initiative”, 2021). Identification of the type of epilepsy is important as it will tell what treatment is best suited.

Some gene mutations can be identified and help in the diagnosis of epilepsy. Most studies, however, have yet to identify causative gene mutations, implying that inheritance may involve several or many susceptibility genes and reflect additional environmental interactions (Ekenstedt et al, 2012). The symptomatic type of epilepsy can be caused either by abnormal brain structure, brain abnormalities such as tumors, head trauma or infectious diseases such as rabies or tetanus (Cui et al, 2017). Idiopathic is the most common type of epilepsy, and also the hardest type of epilepsy to identify as there is no direct cause for the seizures (Hülsmeyer et al, 2015).

Diagnosis and identification

For diagnosis, at least two unprovoked seizures are necessary, or one seizure paired with other symptoms, such as an acute head injury, past stroke, or an abnormality on an electroencephalogram (EEG) brain scan (Hülsmeyer et al, 2015). But this is only successful in some cases as most cases of epilepsy in dogs are from unknown causes.

Gene mutations

There are two types of canine epilepsies for which gene mutations have been identified: progressive myoclonic epilepsies and idiopathic epilepsy (Ekenstedt et al, 2013). So far, nine genes have been identified as being associated with progressive myoclonic epilepsies in a variety of dog breeds (Ekenstedt et al, 2013). Genetic idiopathic epilepsy research has been less effective, with only one relevant gene identified (Ekenstedt et al, 2013). For these ten kinds, genetic testing is available to help with diagnosis, prognosis, and breeding options (Ekenstedt et al, 2013). Process of elimination As mentioned much is still unknown about the cause of epilepsy in dogs. Therefore, it is also difficult to accurately diagnose. As with idiopathic epilepsy, it is a process of elimination (Unger et al, 2021). When all other neurological disorders resulting in seizures have been disproven the answer is usually idiopathic epilepsy.

Process of elimination

As mentioned much is still unknown about the cause of epilepsy in dogs. Therefore, it is also difficult to accurately diagnose. As with idiopathic epilepsy, it is a process of elimination (Unger et al, 2021). When all other neurological disorders resulting in seizures have been disproven the answer is usually idiopathic epilepsy.

Factors influencing susceptibility for canine epilepsy

Through studies and research veterinarians have learned that some specific breeds are more genetically predisposed to epilepsy. There is also evidence supporting that age is a major risk factor. Knowing the risk factors is necessary to be as well-prepared as possible for a possible seizure.

Breed

The idiopathic type of epilepsy, which often has a genetic base, is more common in some breeds than others. Different breeds of Shepherds, Beagles, Border Collies, Labrador Retrievers, Basset Hounds, Poodles and English Springer Spaniels are among the breeds most commonly diagnosed with epilepsy (Cherubini, 2016). In the future, further research into epilepsy in specific breeds can lead to the development of personalized or breed-specific treatment plans (Hülsmeyer et al, 2015).

Age

Most of the research done on canine epilepsy is in agreement that there is an increasing seizure risk with aging (Hulsmeyer, 2015). Seizures is a common symptom of a variety of medical conditions, and with age a dog´s health deteriorates. The severity of the seizures may also worsen over time and age.

Diagnostics and treatment

If a veterinarian decides it is necessary to start maintenance anticonvulsant or antiepileptic therapy on a patient, the decision should be based on the frequency and severity of the seizures. AED or antiepileptic drugs should be considered in animals suffering from more than 2 epileptic seizures over a 6 month period, as long as the seizure is not caused by exposure to toxins over a period of time. When a dog is set on AED it is important that the owner keeps a calendar and tracks the seizures that may still occur, after the treatment is started. By maintaining a good cooperation between the veterinarian and owner it is possible to check the drug level and, if needed, switch to another drug. When it comes to AEDs monotherapy is recommended but if needed an additional drug can also be considered.

Phenobarbital

In general, phenobarbitone (LuminalⓇ or BarbitaⓇ) or potassium bromide are considered first-choice treatment in seizuring dogs and cats (Podell et al, 2016). It can also be used as a sedative because the drug works by decreasing and stabilizing the neurons in the brain. Phenobarbital is often preferred by veterinarians due to its low cost and clinical safety. In addition to this its concentration is easily monitored in the serum. The recommended dose of phenobarbital is 2-4 mg/kg/day, given orally in every species and it takes approximately 2 week to reach a constant serum concentration (Shell, 2016). Since the medication is given orally and the half time is long, the time needed to stabilize the serum concentration will vary between the individuals. Further monitoring of the drug levels should be done 2 weeks after the treatment is started and after potential dosage change. If seizure control has been achieved, monitoring should still take place after 6-12 months. Tolerance to phenobarbital is common in dogs treated over a longer period of time, and this may result in decreased seizure control. by increasing the dosage up to 25%, the control may be restored. Tapering is extremely important with phenobarbital, because it is addictive. If the drug is stopped abruptly the animal may suffer “barbiturate withdrawal” seizures (Shell, 2016).

Side effects Phenobarbital

Along with physical dependence, there are some side effects to the drug. polyuria, polyphagia, anxiety, sedation and polydipsia are common but usually decrease during the first 2 weeks (Shell, 2016). Because of hepatotoxicity and liver failure associated with too high serum concentrations (>35 mcg/mL), frequent blood work is important (Shell, 2016). more rarely seen side effects are anorexia, vomiting, yellowing of the skin and facial itchiness. While the animal is treated with phenobarbital other medications like aspirin, tagamet, chloramphenicol (antibiotic) should be avoided. Primode and phenytoin are additional AEDs that cannot be given at the same time as phenobarbital (Shell, 2016).

Potassium bromide

Bromide appears to stabilize neuronal cell membranes through interfering with chloride transport across cell membranes and amplifying the action of GABA through hyperpolarizing membranes. Bromide (potassium or sodium salt) can be used as a first-line AED in epileptic dogs, as an adjuvant AED in dogs with refractory seizure disorders, or for dogs who have unacceptable side effects from phenobarbital or other AEDs (Shell, 2016). In places where bromide is not available as a pharmaceutical formulation (such as the United States), an analytical grade can be bought from a chemical supply firm, but handling the packaging should be done with caution. Bromide can be made as a solution with various concentrations (the most common are 100 mg/mL, 200 mg/mL, and 250 mg/mL), as well as tablets and capsules (Shell, 2016).

Benefits of potassium bromide

In dogs, the elimination half-life is exceptionally lengthy (24 days), therefore it takes around 4 months to reach steady state kinetics. Bromide is excreted through the kidneys, thus it should not be given to dogs with kidney disease unless they are closely monitored. If there is azotemia, a different AED can be used, or the first bromide dose might be cut in half and serum concentrations monitored. Bromide is beneficial in dogs with liver problems since it does not undergo hepatic metabolism (Shell, 2016). Because a daily maintenance dose can take up to 4 months to reach steady state serum concentration, there are times when a loading dose of bromide should be given (for example, severe seizures, monthly seizures, or the necessity to switch from phenobarbital to bromide due to phenobarbital toxicity). Over a one to four-day period, an oral loading dose of 400–600 mg/kg of bromide is divided into four doses and given with food. Smaller doses, such as 50 mg/kg given for 4–6 days, may decrease the negative effects (such as nausea and vomiting) produced by a rapid rise in serum bromide levels (Shell, 2016).

Side effects potassium bromide

In general, most dogs tolerate bromide treatment but there are some side effects to the drug. Bitter taste, gastric irritation, nausea (especially with the potassium form), polyuria, polydipsia, polyphagia, drowsiness, ataxia, and pancreatitis are all possible side effects of bromide. It should be taken with food, and the amount and kind of food should be consistent (Shell, 2016). This is because the dietary salt level affects bromide excretion through the kidneys. Bromide medication must be titrated to each individual animal based on therapeutic drug monitoring as well as the owner monitoring for early indicators of toxicity. Reports of hindlimb weakness should be investigated as a possible case of bromide toxicosis by monitoring blood bromide levels and stopping bromide for a few days to see if the weakness improves. Lethargy, disorientation, delirium, and coma are all symptoms of severe bromide toxicosis (Shell, 2016)).

Conclusion

The purpose of this research paper was to identify the different types of epilepsy, discuss different treatment options and recognize the possible predispositions in dogs. Based on the data collected, it can be concluded that there are multiple factors relevant in the diagnosis of epilepsy, and the treatment plan is dependent on the type of epilepsy. It is important to continue research on epilepsy and relevant treatment in dogs so that veterinary clinicians, researchers, breeders and pharmaceutical agencies can as best as they can diagnose, treat and decrease the amount of epileptic dogs.

References

Other referenced materials

dog_epilepsy (last edited 2022-05-08 18:49:05 by 4659E)