Idiopathic Epilepsy (IE; primary epilepsy) is a seizure disorder in which there is no identifiable underlying metabolic or structural disease causing the seizures. It is considered a genetic disorder. IE is the most common form of epilepsy in dogs. A genetic basis is suspected or proven in several breeds of dogs, including the Beagle, Belgian Turveren, Bernese Mountain Dog, British Alsatian, Dachshund, English Springer Spaniel, German Shepherd, Golden Retriever, Irish Wolfhound, Keeshond, Labrador Retriever, Shetland Sheepdog, and Vizsla. An inherited basis is suspected in other breeds, but genetic studies have not been completed.
Historically, cats have been thought more likely to have a structural cause for their seizures, but IE does occur in cats as well. Recent studies have suggested that between 21-59% of cats with seizures have IE.
Hallmark findings in dogs
- Patients typically start to have seizures between 1-5 years of age, but juvenile (< 1 yr) and late-onset (> 5 yrs) IE is possible.
- Patients should be normal during the interictal period.
- Patients should be normal on neurological examination.
- There is be no known exposure to seizure-inducing toxins.
- Routine laboratory tests (e.g., CBC, biochemical profile, urinalysis) would all be normal.
It used to be common teaching that focal seizures indicated the presence of a structural abnormality in the brain (e.g., brain tumor, infarct). However, while generalized tonic-clonic seizures are most common in IE, the presence of focal seizures does not exclude the possibility of IE.