Canine epilepsy can be classified into primary (idiopathic) and secondary (symptomatic) epilepsy, which is similar to human epilepsy. Primary epilepsy in both species is inherited and characterized by the absence of recognizable causative lesions. Secondary epilepsy is linked to a variety of lesions such as brain tumors, trauma, encephalitis, lysosomal storage diseases, congenital malformations, and metabolic-toxic injury. Correspondingly, various subtypes of secondary epilepsy have been recognized. The pathogenesis of secondary epilepsy is basically associated with selective loss of inhibitory neurons that disturbs the balance between excitation and inhibition.