Causes and Treatment of Epilepsy in Dogs » Womiraz
Epilepsy is one of the most common neurological disorders in dogs. It is estimated to affect about 0.75% of the dog population. The term epilepsy refers to a disease characterized by the presence of recurrent seizures caused by an abnormality in the brain. Epilepsy in dogs can be inherited (genetic or idiopathic epilepsy), caused by structural problems in the brain (structural epilepsy), or caused by an unknown cause (idiopathic epilepsy). Determining an appropriate treatment regimen for canine epilepsy depends on an accurate diagnosis of the seizure type and cause, only after that appropriate treatment options can be determined.
Classification of Seizures in Dogs
Although classification systems exist for human seizures, there is not yet a widely accepted classification system for seizures in dogs. Although human systems are sometimes used to describe canine seizures, this can be problematic. Human classifications are not always clearly applicable to dogs. Recently, however, a classification similar to the system in humans has been described. Using this system, a seizure is primarily classified according to where it started in the brain, with specific features of the seizure used to further characterize the event.
The seizure definition is the most critical information needed for the diagnosis of canine epilepsy. There are two basic types of seizures, generalized and focal.
It initially involves both sides of the brain and is characterized by distinct clinical manifestations on both sides of the body. Most generalized seizures present as bilateral involuntary muscle movements or sudden losses and increased muscle tone. During a generalized seizure, the dog’s awareness of the environment is lost and drooling, urination and defecation may occur.
It originates in a separate area of the brain and is characterized by symptoms that affect only one side or a specific part of the body. Focal seizures may include abnormal movements (facial twitches, chewing movements, rowing on a limb), behavioral symptoms (fear, attention seeking) or pupil dilation, salivation, vomiting. Awareness may not always be lost during focal seizures. A focal seizure can spread and generalize to both sides of the brain.
Identifying Seizures for Epilepsy in Dogs
When observing seizures, it is important for dog owners to keep a diary with detailed information including:
- Affected body parts
- Movements when the seizure occurs
- how often the seizures occur
- how long the seizures last
- If possible, a video recording of the entire seizure
Veterinarians and owners should also pay close attention to how dogs behave immediately after a seizure. While some animals will quickly return to normal in the post-seizure period, others may have trouble standing or moving. Blindness; sedation, anxiety, or other changes in behavior may occur. These symptoms can last for varying durations and may affect the choice of treatment.
In some cases, seizures can be caused by exposure to a particular stimulus, such as illness, toxin exposure, or metabolic problems. As such seizures are not usually treated with standard anti-epileptic drugs, any potentially precipitating event should be brought to the attention of the attending veterinarian. Reflex seizures, which are seizures that occur repeatedly after a particular exposure, such as a loud sound, flashing light, or a more complex movement or behavior, can also occur in dogs.
Breeds Prone to Epilepsy in Dogs
Clinical Signs of Epilepsy in Dogs
Seizures can vary in appearance, sometimes affecting only one part of the body, or generalized, affecting all parts of the body. Generalized seizures are more common and are usually characterized by stiff neck and legs, stumbling and falling, uncontrollable chewing, drooling, rowing of the limbs, loss of bladder control, defecation, vocalization, and severe shaking and shaking. Seizures can last from a few seconds to a few minutes, averaging 30-90 seconds, and the pet is typically unaware of the environment during this time. Later, the pet may appear confused, disoriented, dazed or sleepy; this is called the post-ictal period.
Before the seizure, many pets will also experience the aura phase; this is characterized by the pet appearing anxious, frightened or dazed, as if it can sense an impending seizure.
Causes of Epilepsy in Dogs
It is not always possible to determine the cause of seizures in dogs; however, canine epilepsies can generally be classified into one of three categories based on etiology.
idiopathic epilepsy It is defined as epilepsy with no identifiable structural cause and a putative genetic origin. In dogs aged 1-5 years with normal neurological examination, recurrent seizures in the absence of known structural abnormalities in the brain, metabolic diseases or toxin exposure are generally assumed to be a form of idiopathic epilepsy. The definition of idiopathic epilepsy suggests that the exact cause of the seizures is unknown, although the condition is assumed to be inherited. However, the cause of such epilepsies can sometimes be determined, for example, when seizures are the result of a particular genetic defect known to occur in certain breeds.
structural epilepsy, It is epilepsy detected as a result of seizures that occur due to observable damage or malformations in the brain. For example, structural epilepsy may occur after an inflammatory disease of the brain, growth of intracranial tumor, or head trauma. It can also be the result of congenital malformations or a vascular event such as a stroke. Brain abnormalities seen in structural epilepsies can sometimes be detected using an MRI or by analysis of cerebrospinal fluid. Structural epilepsy testing may be done if a dog exhibits neurological abnormalities between seizures or if the dog is outside the typical starting age range for idiopathic epilepsy.
Epilepsy of unknown causeis used to describe a condition in which a structural cause is suspected but cannot be determined in the diagnostic evaluation. Reactive seizures, seizures that occur in response to certain stimuli (such as metabolic disorder or toxins) are not considered a type of epilepsy as they are not caused by an abnormality in the brain.
Diagnosing Epilepsy in Dogs
Idiopathic epilepsy is diagnosed by excluding other acquired diseases that may also indicate seizures. A minimal database of complete blood count, biochemical analysis, and urinalysis is useful for excluding other underlying systemic diseases outside of the brain. These diagnostic testing procedures also help ensure that the animal is healthy for anesthesia. Magnetic resonance imaging is the imaging technique of choice for the possible diagnosis of epilepsy, excluding other diseases defined by structural lesions such as inflammation or brain tumor. Analysis of cerebrospinal fluid can help diagnose and rule out inflammatory disease. At the same time, the diagnosis should be confirmed by making EEG measurements. All these tests must be done to make sure your dog’s seizures are caused by epilepsy.
Epilepsy Treatment in Dogs
The decision to start antiepileptic drug therapy depends on a number of factors, including the cause of the seizures, the risk of recurrence, the type of seizure, and the side effects of the drug. Your veterinarian will make this decision based on benefit versus side effects for your dog and individualized patient assessment. Long-term seizure management is more successful in dogs, particularly in dogs with frequent seizures and dog breeds known to have severe epilepsy, if treatment is started early after seizure onset.
Anticonvulsants (anti-seizure medications) are the treatment of choice for epilepsy. There are several commonly used anticonvulsants and once treatment is started, it will likely continue for life. Stopping these drugs suddenly can cause seizures.
The risk and severity of future seizures may be worsened by stopping and restarting anticonvulsant medications. Therefore, anticonvulsant therapy is prescribed only when one of the following criteria is met:
- More than one seizure per month: You will need to record the date, time, length, and severity of all seizures to determine medication need and response to treatment.
- Clusters of seizures: If your pet has groups or ‘clusters’ of seizures (one seizure follows another in a very short time), the condition may progress to status epilepticus, a life-threatening condition characterized by a continuous, unending seizure. Status epilepticus is a medical emergency.
- Major or severe seizures: Attacks of prolonged or extremely severe seizures. These can worsen over time without treatment.
Drugs Used for Epilepsy in Dogs
Phenobarbital is a common anti-seizure medication used in dogs and is usually given twice daily. Irregular dosing schedules (including starting and then stopping medication or forgetting to give pills that cause blood levels to fluctuate) can predispose your pet to more frequent or more severe seizures, so it’s important to administer medication on time.
When starting this medication, phenobarbital levels are measured via blood samples every two to four weeks until the correct dosage is determined. Once the therapeutic dose has been determined for your pet, phenobarbital blood levels and liver function tests will need to be monitored at least every six months to ensure that phenobarbital levels remain within the therapeutic range (ie, they are not dangerously high or low). If phenobarbital blood levels become too high, liver failure may develop, resulting in death. If the levels are too low, the seizures cannot be controlled.
Additional medications such as potassium bromide or newer human anti-seizure medications such as zonisamide (brand name Zonegran®) or levetiracetam (brand name Keppra®) may be used. Your veterinarian will determine the appropriate treatment plan for your pet’s condition.
Systematic monitoring of seizure control, systemic effects of the drug, and drug concentrations in the blood is important after initiation of treatment. The focus of monitoring treatment is to optimize seizure control while minimizing adverse effects. Epilepsy management depends on the correct observation of the patient when assessing the effectiveness of treatment.
Epilepsy Prognosis in Dogs
Most dogs are successful on anti-seizure medication and can resume a normal lifestyle. Some patients continue to experience periodic intermittent seizures. Many dogs require occasional medication adjustments, and some require the addition of other medications over time.
Causes and Treatment of Epilepsy in Dogs » Womiraz