Idiopathic epilepsy (that with no ascertainable cause during life or even after death) is identified by a process called “diagnosis of exclusion.” It involves ruling out all other potential intracranial (inside the skull) and extracranial (outside the skull) disorders that could cause the observed epileptic symptoms. These can include toxins, metabolic disorders, abnormal brain conformation, heat stroke, encephalitis, brain tumor, stroke, kidney failure, liver failure, genetic degenerative diseases, canine distemper, cancer, cardiovascular disease, head trauma and narcolepsy, among others.
The initial database usually includes blood sampling and analysis for a complete blood count and a serum chemistry panel, together with a urinalysis. These can be quite useful in identifying causes of the dog’s condition if the results are abnormal. Serum bile acid evaluation, both before and after a meal, can also be useful to exclude certain possible contributing causes. Of course, a complete history and thorough physical and neurological examinations are essential to the diagnostic process.
A number of more advanced techniques are available to help diagnose or rule out epilepsy as well. These include skull radiographs (x-rays), electroencephalogram (EEG), magnetic resonance imaging (MRI), computed tomography (CT/CAT scan) and a spinal tap with subsequent evaluation of cerebrospinal fluid (CSF).
Intoxication and poisoning can cause signs virtually identical to those seen in epileptic dogs. Common canine toxins include lead, antifreeze/ethylene glycol, carbamate, metaldehyde, animal baits/strychnine, insecticides/organophosphates, chocolate and other toxins. These must be ruled out before a definitive diagnosis of epilepsy can be made. Insect bites or stings and cardiac abnormalities can also cause symptoms that mimic those of epilepsy.