 The vast majority of generalized seizures are idiopathic.Some generalized seizures start as a smaller seizure that occurs solely on one side of the brain, however, and is referred to as a focal (or partial) seizure.These unilateral seizure types (formerly known as simple partial seizure or a complex partial seizure and now referred to as focal aware seizure and focal impaired awareness seizure, respectively) can then spread to both hemispheres of the brain and cause a generalized tonic clonic seizure.