Generalised tonic-clonic seizure(Redirected from Tonic–clonic)
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.
|Classification and external resources|
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 or situationally 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 strobe-flashes or simple light/dark patterns, raised estrogen levels at ovulation, 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 seizure 'focus' area, episodically firing abnormally, creating a seizure if the focus is not abolished or suppressed via anti-convulsant drugs.
- Tonic phase
- The patient will quickly lose consciousness (though not all generalized tonic-clonic seizures involve a full loss of consciousness), and the skeletal muscles will suddenly tense, often causing the extremities to be pulled towards the body or rigidly pushed away from it, which will cause the patient to fall if standing or sitting. The tonic phase is usually the shortest part of the seizure, usually lasting only a few seconds. The patient may also express brief vocalizations like a loud moan upon entering the beginning seizure with the tonic stage, due to air forcefully expelled from the lungs.
- Clonic phase
- The patient's muscles will start to contract and relax rapidly, causing convulsions. These may range from exaggerated twitches of the limbs to violent shaking or vibrating of the stiffened extremities. The patient may roll and stretch as the seizure spreads. The eyes typically roll back or close and the tongue often suffers bruising or crushing injuries sustained by strong jaw contractions. The lips or extremities may turn slightly bluish (cyanosis) and incontinence is seen in some cases.
Due to physical, mental and nervous exhaustion, postictal sleep with stertorous breathing invariably follows a tonic–clonic seizure. Confusion and total amnesia upon regaining consciousness is usually experienced and slowly wears off as the patient becomes gradually aware that a seizure occurred and remembers their identity and location. Occasionally the patient may vomit or burst into tears from the experienced mental trauma. An additional smaller seizure can occur several minutes after the main seizure, particularly if the patient's seizure threshold has been brought unusually low by known factors or combinations of such - for example severe hangovers, sleep deprivation, elevated estrogen at ovulation, prolonged physical tiredness and/or drug use including some pharmaceuticals, alcohol and caffeine.
- David Y Ko (5 April 2007). "Tonic–Clonic Seizures". eMedicine. Retrieved 2008-03-19.
- "Epilepsy Action: Simple Partial Seizures". Epilepsy Action. British Epilepsy Association. 19 February 2008. Archived from the original on 6 March 2008. Retrieved 2008-03-19.
- "Seizure Mechanisms and Threshold". Epilepsy Foundation. Retrieved 2015-11-13.
- "Triggers of Seizures". Epilepsy Foundation. Retrieved 2017-09-30.
- Ruben Kuzniecky, M.D. (16 April 2004). "Looking at the Brain". epilepsy.com. Epilepsy Therapy Project. Archived from the original on 2007-10-12. Retrieved 2008-03-19.