Seizures/Epilepsy

Liaison: Jan Young

Epilepsy is a chronic condition characterized by recurrent seizures. Seizures are involuntary muscle activity caused by an abnormal electrical storm in the brain. Epilepsy can be either idiopathic or primary (unknown cause) or secondary (caused by something else). In idiopathic epilepsy there is no identifiable abnormality other than the seizures themselves and it is assumed to be hereditary. It typically begins between 1 and 5 years. In secondary epilepsy the seizures are the result of an identifiable cause such as a brain lesion or other medical condition. Secondary epilepsy commonly begins in the first year or in older dogs.

Seizures can manifest in many ways and can be very brief (seconds) or can last for many minutes or, in rare occasions, hours or until they are stopped by medical intervention.

Signs and Symptoms

Generalized Seizures:

Generalized, tonic-clonic (grand mal) seizures are the most common in dogs. These begin with the tonic phase, a contraction of all skeletal muscles and loss of consciousness resulting in the dog typically falling on his side with stiff legs and the head often arched back. There may be involuntary vocalization or twitching, drooling, and loss of bowel/bladder control. This phase is usually brief and is then followed by a clonic phase characterized by rhythmic movements including jaw and legs (paddling motions).
Less commonly generalized seizures can just be tonic or just clonic and rarely tonic-clonic seizures may be mild enough that consciousness is not lost.
Petit mal seizures are a brief generalized seizure often characterized by simple staring for a brief period and then the dog returns to normal.

Partial (focal) seizures are less common. In this type of seizure the abnormal electrical activity does not spread to include the entire brain. A seizure may begin as a partial seizure and then spread to become generalized (tonic-clonic). Partial seizures are much more likely to be secondary, resulting from a specific cause. Partial seizures can be either simple (only affect the area of the brain that controls movement) and characterized by focal twitching or blinking, or complex (psychomotor seizures originating in the part of the brain that controls behavior) where consciousness is altered and there may be bizarre behavior such as unprovoked aggression or repetitive behavior.
Status epilepticus is a prolonged seizure or a series of seizures that occur continuously or repeatedly in a 24 hour period and is a medical emergency. Untreated, it can lead to brain damage and even death.

Seizures are typically preceded by a period of abnormal behavior called the pre-ictal phase. The dog may show signs of anxiety and apprehension: whining, pacing, panting, seeking comfort from the owner. The seizure itself is the ictal stage. Most generalized seizures are followed by a post-ictal phase which can last from minutes to hours and is characterized by stupor, disorientation, and/or blindness.

Causes

Idiopathic or primary epilepsy is believed to be an inherited condition. It is a fairly common disorder in canines but relatively rare in Samoyeds compared with some other breeds. Secondary epilepsy or seizures are due to specific brain lesions or other medical conditions.

Risk Factors

First degree relatives with idiopathic epilepsy.

Secondary epilepsy or seizures are due to specific medical conditions such as brain trauma or tumor, ingestion of toxins, infection, and certain metabolic conditions.

Diagnostic Tests

Perhaps the most important information your vet needs is an accurate description (or even a video) of the seizure or episode. This, together with a good physical and neurological examination of your pet, will be very useful in helping diagnose the cause of your dog's seizure(s). Based on this information your vet will obtain a variety of blood tests (complete blood count (CBC), blood chemistries, thyroid function tests) and a urinalysis. Depending on the results of these tests, further studies may be indicated: MRI or CT brain scan, spinal tap, electroencephalogram (EEG), or other laboratory tests.

Idiopathic epilepsy is a diagnosis of exclusion. If all of the above studies are normal then a diagnosis of primary epilepsy is made.

Treatment Guidelines

Note: Treatment of animals should only be performed by a licensed veterinarian. Veterinarians should consult the current literature and current pharmacological formularies before initiating any treatment protocol.

Medications are the treatment of choice for epilepsy however not all dogs with epilepsy require medication. This is a choice that is made by the veterinarian and the owner of the animal. When medications are used, they are usually a life-long therapy and cannot be discontinued suddenly. Common drugs which are used for canine epilepsy include phenobarbital, primodone, potassium bromide and Valium (diazepam). In certain instances, more uncommon medications are needed. The medication regimen must be customized for each dog. Other treatments may include surgery (for specific brain lesions), vagal nerve stimulation, and special diets.

Management

Seizures lasting for more than 5-10 minutes (actual seizure, not including pre- and post-ictal stages), or three seizures within a 24 hour period, is considered a medical emergency and the dog should be taken to a veterinarian immediately.

Because idiopathic epilepsy is believed to be inherited, affected dogs or dogs with primary relatives with this type of epilepsy should not be bred.