There are many potential causes of seizures: toxins, tumors, genetic disease such as epilepsy, infections, even scarring in the brain from past trauma. Seizures resulting from metabolic problems or toxicity (i.e. when the brain itself is normal) are called reactive seizures. Seizures resulting from identifiable brain abnormalities are called structural seizures. Seizures for which no clear cause can be found are called primary seizures and the patient is said to have epilepsy.
It turns out that dogs of certain age groups tend to have common causes for their seizures. This means that certain diagnostic tests are especially important in dogs of one age group while other tests are going to be more important for dogs in another age group. Here are some basic concepts concerning how age is an important consideration:
Reactive Seizures: Seizures resulting from metabolic problems or toxicity (i.e., when the brain itself is normal).
Secondary Seizures: Seizures resulting from an identifiable brain abnormality.
Primary Seizures: Seizures for which neither of the above problems apply (i.e., when no cause can be found).