Tonic–clonic seizure

Tonic–clonic seizures (formerly known as grand mal seizures) are a type of generalized seizure that affects the entire brain. Tonic–clonic seizures are the seizure type most commonly associated with epilepsy and seizures in general, though it is a misconception that they are the only type.

Tonic–clonic seizures can be induced deliberately in electroconvulsive therapy.

Pathophysiology

The vast majority of generalized seizures are idiopathic. However, some generalized seizures start as a smaller seizure such as a simple partial seizure or a complex partial seizure and then spread to both hemispheres of the brain. This is called a secondary generalization. Factors could include chemical and neurotransmitter imbalances and a genetically determined seizure threshold, both of which have been implicated. The seizure threshold can be altered by fatigue, malnutrition, lack of sleep or rest, hypertension, stress, diabetes, the presence of neon or xenon strobe-flashes, fluorescent lighting, rapid motion or flight, blood sugar imbalances, anxiety, antihistamines and other factors.