Note that the term nonprogressive means that the cause is nonprogressive, not the severity or frequency of the seizures themselves.
Epilepsy is of acquired or idiopathic origin.
Acquired or secondary epilepsy is that in which a previously active brain disorder has left the brain in a seizure prone state. An example might be a dog that is hit by a car and suffers head trauma, but survives. Idiopathic epilepsy is also known as inherited, congenital or primary epilepsy and involves recurrent seizures for which no cause can be identified. What happens during a seizure is complex, and not totally understood. In the field of human medicine much research has been devoted to how a seizure actually occurs but many questions remain to be answered.