Tonic-clonic seizures

Tonic–clonic seizure
Classification and external resources
Specialty	Neurology
ICD-10	G40.3
ICD-9-CM	345.3
MedlinePlus	000695
eMedicine	neuro/376
MeSH	D004830
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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.

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.

In the case of symptomatic epilepsy, it is often determined by MRI or other neuroimaging techniques that there is some degree of damage to a large number of neurons. The lesions (i.e., scar tissue) caused by the loss of these neurons can result in groups of neurons forming a seizire 'focus' area, episodically firing abnormally, creating a seizure if the focus is not abolished or suppressed via anti-convulsant drugs.

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