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Tonic–clonic seizure
Classification and external resources
ICD-10 G40.3
ICD-9 345.1
eMedicine neuro/376
MeSH D004830

Tonic–clonic seizures are a type of generalized seizure that affects the entire brain. Formerly known as grand mal seizures or gran mal seizures, these terms are now discouraged and rarely used in a clinical setting.[citation needed] 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. (See seizure types)

Tonic–clonic seizures are induced deliberately in electroconvulsive therapy.

Contents

Pathophysiology

The vast majority of generalized seizures are idiopathic.[1] 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.[2] In the case of idiopathic epilepsy, the cause of the seizures is uncertain. However, 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 laser flashes or lights, rapid motion or flight, blood sugar imbalances, anxiety,antihistamines and other factors.[3]

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.[4] The lesions (i.e., scar tissue) caused by the loss of these neurons can result in groups of neurons episodically firing abnormally, creating a seizure.

Phases

The seizures are divided into two phases, the tonic phase and the clonic phase, hence the name of the seizure, though a tonic–clonic seizure will often be preceded by an aura.

  • Aura
The person may feel a sense of strong déjà vu, lightheadedness and/or dizziness, unusual (and possibly inappropriate) emotions, intense feelings of discomfort or foreboding, altered vision and hearing (which may or may not include hallucinations), and sometimes other symptoms [5]. This is actually a simple partial seizure. Sometimes, the person will lose complete awareness and start making odd or pointless repetitive movements (such as picking at clothes or lip smacking) towards the end of the aura, at which point the seizure has progressed to become a complex partial seizure.

The aura stage occurs because tonic–clonic seizures often start in an isolated area of the brain, known as the seizure focus, and gradually spreads to the whole brain, whereupon loss of consciousness occurs and becomes a tonic–clonic seizure. An aura may last as little as a few minutes or as long as several hours, though some with epilepsy do not experience them at all. Many auras are followed by a tonic–clonic seizure.

  • Tonic phase
The person will quickly lose 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 person to fall if standing. The tonic phase is usually the shortest part of the seizure, usually lasting only a few seconds. The person may also express vocalizations like a loud moan during the tonic stage, due to air forcefully expelled from the lungs.
  • Clonic phase
The person'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 person may roll and stretch as the seizure spreads. The eyes typically roll back or close and the tongue often suffers bruising sustained by strong jaw contractions. Incontinence is seen in some cases.

Due to physical and nervous exhaustion, Post-ictal sleep invariably follows a tonic–clonic seizure. Confusion and complete amnesia upon regaining consciousness is usually experienced and slowly wears off as the person becomes gradually aware that a seizure occurred.

First aid

Many people who experience tonic–clonic seizures will be aware of an oncoming seizure for up to several minutes before the full seizure begins. This is called an aura and is typically a simple partial seizure or a complex partial seizure that has spread to the whole brain. However, many people who have epilepsy do not experience auras. If a person reports a seizure is imminent, safety should be ensured. The person should be placed into the recovery position. Remove any objects that may pose a danger to the person during the seizure. If the person does not experience an aura and goes directly into a seizure, they should be gently eased to the ground, if possible.

Once the convulsions begin, the seizure must simply run its course. No attempt to restrain the person should be made because of the risk of injury to either party. Instead, reduce the risk of injury by placing something soft under the person's head and try to prevent the person's limbs and body from bumping into walls or other objects. If the person vomits, the person's head should be placed to the side to allow the vomit to run out of the mouth without blocking the airway. Nothing should ever be placed into the person's mouth, as this can cause the person to bite their tongue, choke or injure the person placing the object into their mouth. Contrary to popular belief, it is not possible for someone having a seizure to swallow their tongue. The frenulum linguae prevents this. In this state however the tongue may obstruct the person's breathing.

Once the seizure ends, the person stops convulsing, the limbs go limp, and the person is completely unconscious for a while. Once the person starts to come to, they are usually tired, disoriented, and unaware they had a seizure. A person having a seizure should never be left unattended until they fully recover.

If the person is known to have epilepsy, it is not usually necessary to call an ambulance. However, medical attention should be sought immediately if: the person is not known to have epilepsy, the seizure lasts four to five minutes or longer, the person has a second seizure before regaining consciousness (status epilepticus), or the person suffers self-injury or stops breathing (apnea) during or after the seizure.

See also

References

  1. ^ David Y Ko (5 April 2007). "Tonic–Clonic Seizures". eMedicine. http://www.emedicine.com/neuro/topic376.htm#section~clinical. Retrieved 2008-03-19. 
  2. ^ "Epilepsy Action: Simple Partial Seizures". Epilepsy Action. British Epilepsy Association. 19 February 2008. http://www.epilepsy.org.uk/info/simple.html#Secondarygeneralisation. Retrieved 2008-03-19. 
  3. ^ "Seizure Mechanisms and Threshold". Epilepsy Foundation. http://www.epilepsyfoundation.org/answerplace/Medical/seizures/science/mechanisms.cfm. Retrieved 2008-03-19. 
  4. ^ Ruben Kuzniecky, M.D. (16 April 2004). "Looking at the Brain". epilepsy.com. Epilepsy Therapy Project. http://www.epilepsy.com/epilepsy/looking_brain.html. Retrieved 2008-03-19. 
  5. ^ http://www.epilepsy.com/101/ep101_symptom

External links

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