What is epilepsy?
Epilepsy is a brain disorder characterized by recurrent seizures without a known cause or abnormal brain lesion (brain injury or disease). In other words, the brain appears to be normal but functions abnormally. A seizure is a sudden surge in the electrical activity of the brain causing signs such as twitching, shaking, tremors, convulsions, and/or spasms.
What causes epilepsy?
The exact cause of epilepsy is unknown, but a genetic basis is suspected in many breeds. Common breeds that have a higher rate of epilepsy include Beagles, Bernese Mountain Dogs, Border Collies, Boxer Dogs, Cocker Spaniels, Collies, Dachshunds, Golden Retrievers, Irish Setters, Irish Wolfhounds, Keeshonds, Labrador Retrievers, Poodles, St. Bernards, Shepherds, Shetland Sheepdogs, Siberian Huskies, English Springer Spaniels, Pembroke Welsh Corgis, and Wire-Haired Fox Terriers. Epilepsy is somewhat common in dogs and rare in cats.
What are the clinical signs of epilepsy?
Seizures can vary in appearance and can be localized or focal (only affecting part of the body - see handout “Focal Seizures and FlyBiting in Dogs”) or generalized (affecting the whole body – see handout “Seizures in Dogs”). Generalized seizures are more common and are often characterized by a stiffening of the neck and legs, stumbling and falling over, uncontrollable chewing, drooling, paddling of the limbs, loss of bladder control, defecating, vocalizing, and violent shaking and trembling. Seizures can last a few seconds to a few minutes, on average about 30-90 seconds, and the pet is typically unaware of the surroundings during this period. In some rare cases, the seizures will not stop or be prolonged and this is referred to as status epilepticus.
Afterwards, the pet may appear confused, disoriented, dazed, or sleepy; this is called the post-ictal period.
Prior to the seizure, many pets will also experience the aura stage; this is characterized by the pet appearing anxious, frightened, or dazed, as if the pet can sense an upcoming seizure. It is estimated that up to two percent of all dogs will have a seizure in their lifetime.
How is epilepsy diagnosed?
Epilepsy is a diagnosis of exclusion; the diagnosis of epilepsy is made only after all other causes of seizures have been ruled out. A thorough medical history and physical examination are performed, followed by diagnostic testing such as blood and urine tests and radiographs (X-rays). Additional tests such as bile acids, cerebrospinal fluid (CSF) testing, computed tomography (CT) or magnetic resonance imaging (MRI) may be recommended, depending on the initial test results. In many cases a cause is not found; these are termed idiopathic. Many epilepsy cases are grouped under this classification as the more advanced testing is often not carried out due to cost or availability. A dog’s age when seizures first start is also a prevalent factor in coming to a diagnosis.
"Epilepsy is a diagnosis of exclusion"
What is the treatment of epilepsy?
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 be continued for life. Stopping these medications suddenly can cause seizures.
The risk and severity of future seizures may be worsened by stopping and re- starting anticonvulsant drugs. Therefore, anticonvulsant treatment is often only prescribed if one of the following criteria is met:
- More than one seizure a month: You will need to record the date, time, length, and severity of all episodes in order to determine medication necessity and response to treatment.
- Clusters of seizures: If your pet has groups or 'clusters' of seizures, (one seizure following another within a very short period of time), the condition may progress to status epilepticus, a life- threatening condition characterized by a constant, unending seizure that may last for hours. Status epilepticus is a medical emergency.
- Grand mal or severe seizures: Prolonged or extremely violent seizure episodes. These may worsen over time without treatment.
Irregular dosing schedules (including starting and then stopping the medication, or forgetting to give pills causing blood levels to fluctuate) may predispose your pet to more frequent or more violent seizures, so it is important to give the medication on time.
The most common medication is phenobarbital and it has been used for many years with good success. Other medications that may be considered first choice drugs include potassium bromide (Kbr), zonisamide, and levetiracetam (Keppra®). In some patients, multiple drugs may need to be used. Additional drugs that are sometimes added in include gabapentin or clonazepam.
Blood monitoring tests are done at specified intervals (weeks to months) for phenobarbital and potassium bromide. These tests are used to help determine the correct dosing levels but also to check organ function in some cases as the medications may have dangerous side effects. Your veterinarian will determine the proper treatment plan for your pet's condition.
What is the prognosis for a pet with epilepsy?
Most dogs do well on anti-seizure medication and are able to resume a normal lifestyle. Some patients continue to experience periodic break-through seizures. Many dogs require occasional medication adjustments, and some require the addition of other medications over time.