Tonic-clonic seizure
Encyclopedia
Tonic–clonic 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 are induced deliberately in electroconvulsive therapy
.
. 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. 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 xenon strobe-flashes, 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 episodically firing abnormally, creating a seizure.
phase and the clonic phase, hence the name of the seizure, though a tonic–clonic seizure will often be preceded by an aura
.
Aura
Tonic phase
Clonic phase
Due to physical and nervous exhaustion, Postictal 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.
Sometimes people that experience having a tonic-clonic seizure for the first time become sick, such as experiencing lightheaded feelings, vomiting, nervousness and other non-life-threatening symptoms.
Seizure types
The numerous epileptic seizure types are most commonly defined and grouped according to the scheme proposed by the International League Against Epilepsy in 1981...
most commonly associated with epilepsy
Epilepsy
Epilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
and seizures in general, though it is a misconception that they are the only type.
Tonic–clonic seizures are induced deliberately in electroconvulsive therapy
Electroconvulsive therapy
Electroconvulsive therapy , formerly known as electroshock, is a psychiatric treatment in which seizures are electrically induced in anesthetized patients for therapeutic effect. Its mode of action is unknown...
.
Pathophysiology
The vast majority of generalized seizures are idiopathicIdiopathic
Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...
. However, some generalized seizures start as a smaller seizure such as a simple partial seizure
Simple partial seizure
Simple partial seizures are seizures which affect only a small region of the brain, often the temporal lobes and/or hippocampi. People who have simple partial seizures retain consciousness...
or a complex partial seizure
Complex partial seizure
A complex partial seizure is an epileptic seizure that is associated with bilateral cerebral hemisphere involvement and causes impairment of awareness or responsiveness, i.e. loss of consciousness.-Presentation:...
and then spread to both hemispheres
Cerebral hemisphere
A cerebral hemisphere is one of the two regions of the eutherian brain that are delineated by the median plane, . The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres has an outer layer of grey matter called the cerebral cortex that is...
of the brain. This is called a secondary generalization. However, factors could include chemical and neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
imbalances and a genetically determined seizure threshold
Seizure threshold
A seizure threshold is the balance between excitatory and inhibitory forces in the brain which affects how susceptible one is to seizures. Those diagnosed with epilepsy or certain other neurological conditions are vulnerable to sudden new seizures if the threshold is upset, and so must be...
, both of which have been implicated. The seizure threshold can be altered by fatigue, malnutrition, lack of sleep or rest, hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
, stress, diabetes, the presence of neon
Neon
Neon is the chemical element that has the symbol Ne and an atomic number of 10. Although a very common element in the universe, it is rare on Earth. A colorless, inert noble gas under standard conditions, neon gives a distinct reddish-orange glow when used in either low-voltage neon glow lamps or...
or xenon strobe-flashes, rapid motion or flight,
blood sugar
Blood sugar
The blood sugar concentration or blood glucose level is the amount of glucose present in the blood of a human or animal. Normally in mammals, the body maintains the blood glucose level at a reference range between about 3.6 and 5.8 mM , or 64.8 and 104.4 mg/dL...
imbalances, anxiety, antihistamines and other factors.
In the case of symptomatic epilepsy
Epilepsy
Epilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
, 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 episodically firing abnormally, creating a seizure.
Phases
The seizures are divided into two phases, the tonicTonic (physiology)
Tonic in physiology refers to a physiological response which is slow, and may be graded. This term is typically used in opposition to a fast response...
phase and the clonic phase, hence the name of the seizure, though a tonic–clonic seizure will often be preceded by an aura
Aura (symptom)
An aura is a perceptual disturbance experienced by some migraine sufferers before a migraine headache, and the telltale sensation experienced by some people with epilepsy before a seizure. It often manifests as the perception of a strange light, an unpleasant smell or confusing thoughts or...
.
Aura
- The person may feel a sense of strong déjà vuDéjà vuDéjà vu is the experience of feeling sure that one has already witnessed or experienced a current situation, even though the exact circumstances of the prior encounter are uncertain and were perhaps imagined...
, 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. This is actually a simple partial seizureSimple partial seizureSimple partial seizures are seizures which affect only a small region of the brain, often the temporal lobes and/or hippocampi. People who have simple partial seizures retain consciousness...
. 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 seizureComplex partial seizureA complex partial seizure is an epileptic seizure that is associated with bilateral cerebral hemisphere involvement and causes impairment of awareness or responsiveness, i.e. loss of consciousness.-Presentation:...
.
- 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 epilepsyEpilepsyEpilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
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 or scream 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. IncontinenceUrinary incontinenceUrinary incontinence is any involuntary leakage of urine. It is a common and distressing problem, which may have a profound impact on quality of life. Urinary incontinence almost always results from an underlying treatable medical condition but is under-reported to medical practitioners...
is seen in some cases.
Due to physical and nervous exhaustion, Postictal sleep
Postictal state
The postictal state is the altered state of consciousness that a person enters after experiencing a seizure. It usually lasts between 5 and 30 minutes, but sometimes longer in the case of larger or more severe seizures and is characterized by drowsiness, confusion, nausea, hypertension, headache or...
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.
Sometimes people that experience having a tonic-clonic seizure for the first time become sick, such as experiencing lightheaded feelings, vomiting, nervousness and other non-life-threatening symptoms.
See also
- EpilepsyEpilepsyEpilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
- Epileptic seizure and Non-epileptic seizure
- Generalized epilepsy
- Absence seizureAbsence seizureAbsence seizures are one of several kinds of seizures. These seizures are sometimes referred to as petit mal seizures ....