Epilepsy in the Dog
By Dr. Bob Marquis
A seizure is the clinical manifestation of abnormal electrical brain activity. When they are chronic and recurring, the term epilepsy is given. It is important to remember that epilepsy is not a single disease, but a group of conditions, just as pneumonia is not a specific disease, but a process shared by a range of diseases. It is important to remember then, that the term epilepsy is not synonymous with siezure. A dog may ingest a poison and have a single seizure. Clearly this is not epilepsy.
When recurrent seizures occur due to an identifiable brain lesion, such as a tumor, this is called secondary epilepsy. Idiopathic epilepsy, or primary epilepsy, is the term given when there is no identifiable structural lesion in the brain. Idiopathic epilepsy is by far the most common cause of seizures in the dog. Seizures can take many different forms depending on the location and extent of the abnormal electrical brain activity. For the sake of simplicity, we will divide these types into two descriptions:
1. Generalized-onset Seizures- those in which both cerebral hemispheres of the brain are involved. Most commonly this presents as spastic limb movements with altered consciousness (formerly called grand mal seizures). There is alternating contraction and flexion of muscles with the dog falling to his side. Salivation, vocalization, defecation and urination are common. During this phase, the dog is unable to respond to external stimulation. These can also present with only muscle rigidity (tonic) or contraction/relaxation (clonic).
2. Focal-onset Seizures- those in which the initial clinical signs indicate only one region of the brain is involved. These are often called focal seizures and may be either motor or sensory. Focal motor seizures may for instance present with abnormal movements of a body part- turning the head to one side, repetative chewing movements (chewing gum fits), or drawing one leg up to the body. Focal sensory seizures may present as tingling, obscure pain manifestations or even visual hallucinations. These obviously can be difficult to diagnose in dogs. There are numerous other types of focal seizures in addition to motor and sensory.
Most dogs with idiopathic epilepsy present with their first seizure between 1 and 5 years of age. Any breed, including mixed breeds, and either sex can be affected. A genetic basis is strongly suspected in a number of breeds including beagle, dachshund, golden retriever and Labrador retriever, among others. Epilepsy is not rare in the dog.
At Tiara Rado, we see many dogs each month with epilepsy- both previously undiagnosed patients, as well as animals in all stages of treatment. Not all dogs with epilepsy require treatment. If seizures are mild and infrequent, treatment may not be indicated. Guidelines that are used to dictate the need for treatment include frequency and severity of seizures, duration of each seizure and the tendency of seizures to occur in multiples or clusters. In addition, the post seizure recovery time (called the post-ictal phase) may be important for determining the need for treatment. Of all of these, the tendency for seizures to occur in clusters is most dangerous. As seizures become closer together, there is danger of them becoming continuous (status epilepticus). This is a life threatening emergency.
Treatment options for dogs with epilepsy have improved significantly. Most dogs with idiopathic epilepsy can expect to have a good quality of life. The ideal goal of treatment is to completely eliminate seizures and avoid side effects. This level of control without side effects remains ellusive, however. A more realistic goal is to reduce the frequency and severity of seizures to a level that does not compromise the quality of life for the pet and family while avoiding serious side effects. Achieving this, like so many problems in veterinary medicine, requires teamwork between patient, owner and veterinarian.
