Seizure

Seizure is sudden uncontrolled waves of electrical activity in the brain, causing involuntary movement or loss of consciousness

Spike-waves

Seizures are abrupt disturbances in the brain's electrical activity that can lead to various physical manifestations or alterations in consciousness. Seizures occur when there's an excess of electrical activity in the brain, causing a temporary disruption in normal brain function. This surge of activity may lead to involuntary movements, changes in behavior, sensation, or awareness, including loss of consciousness.

Types of Seizures

Nude woman lying down and having artificially induced convulsions

Focal Onset Seizures

Focal onset seizures, formerly known as partial seizures, originate within networks limited to one cerebral hemisphere. They are further divided into:

• Focal Onset Aware Seizures (simple partial seizures): During these seizures, consciousness is not impaired.
• Focal Onset Impaired Awareness Seizures (complex partial seizures): These seizures involve an alteration in consciousness.

Generalized Onset Seizures

Generalized onset seizures involve both sides of the brain from the onset. They include several types such as:

• Absence Seizures (petit mal seizures): These typically involve brief periods of unconsciousness and staring.
• Tonic-Clonic Seizures (grand mal seizures): These can cause a sudden loss of consciousness, body stiffening and shaking, and sometimes loss of bladder control or biting the tongue.
• Atonic Seizures: These seizures cause a loss of muscle control and can lead to sudden falls, known as "drop attacks."
• Myoclonic Seizures: These involve sudden, brief jerky movements of muscles or muscle groups.

Symptoms

The symptoms of a seizure can vary significantly depending on the type of seizure and the part of the brain that's affected. They may include temporary confusion, a staring spell, uncontrollable jerking movements of the arms and legs, loss of consciousness, psychic symptoms such as fear, anxiety or déjà vu, and more.

Diagnosis and Treatment

The diagnosis of seizures typically involves a detailed medical history, neurological examination, and diagnostic tests such as an electroencephalogram (EEG) to measure electrical activity in the brain. Additional tests like a CT scan or MRI can help identify potential causes of seizures.

Treatment for seizures is typically aimed at controlling, stopping, or reducing the frequency of the seizures. This can often be achieved with anti-epileptic drugs (AEDs). Other treatment options may include surgery, nerve stimulation therapies, dietary therapies like the ketogenic diet, or even certain clinical trials.

Glossarry of seizures

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#-9

• absence epilepsy epilepsy in which the person has repeated absence seizures.

• absence seizuresseizures seen in absence epilepsy, in which the person experiences a momentary loss in consciousness. The person may stare into space for several seconds and may have some twitching or mild jerking of muscles. An older term for absence seizures is petit mal seizures.

• atonic seizures seizures which cause a sudden loss of muscle tone, also called drop attacks.

• auras unusual sensations or movements that warn of an impending, more severe seizure. These auras are actually simple focal seizures in which the person maintains consciousness.

• automatisms automatic involuntary or mechanical actions.

C

• clonic seizures seizures that cause repeated jerking movements of muscles on both sides of the body.

• convulsionssudden severe contractions of the muscles that may be caused by seizures.

• corpus callosotomy surgery that severs the corpus callosum, or network of neural connections between the right and left hemispheres

• déjà vu a sense that something has happened before.

D

• de novo- new, for the first time.

• Dravet syndrome-a type of intractable epilepsy that begins in infancy.

• drop attacks-seizures that cause sudden falls; another term for atonic seizures.

E

• epilepsy syndromes disorders with a specific set of symptoms that include epilepsy.

F

• febrile seizures seizures in infants and children that are associated with a high fever.

• focal seizures seizures that occur in just one part of the brain.

• frontal lobe epilepsy a type of epilepsy that originates in the frontal lobe of the brain. It usually involves a cluster of short seizures with a sudden onset and termination.

G

• generalized seizures seizures that result from abnormal neuronal activity in many parts of the brain. These seizures may cause loss of consciousness, falls, or abnormal movements such as convulsions.

• grand mal seizures an older term for tonic-clonic seizures.

H

• hemispheres the right and left halves of the brain.

• hemispherectomy – surgery involving the removal or disabling of one hemisphere of the brain.

• hemispherotomy removing half of the brain’s outer layer (cortex).

• hypothalamic hamartoma a rare form of childhood epilepsy that is associated with malformations of the hypothalamus at the base of the brain.

I

• infantile spasms clusters of seizures that usually begin before the age of 6 months. During these seizures the infant may bend and cry out.

• intractable hard to treat; about 30 to 40 percent of people with epilepsy will continue to experience seizures even with the best available treatment.

J

• juvenile myoclonic epilepsy a type of epilepsy characterized by sudden muscle (myoclonic) jerks that usually begins in childhood or adolescence.

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K

• ketogenic diet a strict diet rich in fats and low in carbohydrates that causes the body to break down fats instead of carbohydrates to survive.

L

• Lafora disease a severe, progressive form of epilepsy that begins in childhood and has been linked to a gene that helps to break down carbohydrates.

• Lennox-Gastaut syndrome a type of epilepsy that begins in childhood and usually causes several different kinds of seizures, including absence seizures.

• lesion damaged or dysfunctional part of the brain or other parts of the body.

• lesionectomy surgical removal of a specific brain lesion.

• lobectomy surgical removal of a lobe of the brain.

M

• monotherapy treatment with only one antiepileptic drug.

• multiple subpial transection a type of operation in which surgeons make a series of cuts in the brain that are designed to prevent seizures from spreading into other parts of the brain while leaving the person's normal abilities intact.

• myoclonic seizures seizures that cause sudden jerks or twitches, especially in the upper body, arms, or legs.

N

• neocortical epilepsy epilepsy that originates in the brain's cortex, or outer layer. Seizures can be either focal or generalized, and may cause strange sensations, hallucinations, or emotional changes.

• nonconvulsive any type of seizure that does not include violent muscle contractions.

• nonepileptic seizures any phenomena that look like seizures but do not result from abnormal brain activity. Nonepileptic events may include psychogenic seizures or symptoms of medical conditions such as sleep disorders, Tourette syndrome, or cardiac arrhythmia.  Pseudoseizure is an older term for nonepileptic seizure.

P

• post-ictal post-seizure.

• prodrome a feeling that a seizure is imminent, which may last hours or days prior to the seizure.

• progressive myoclonus epilepsy a type of epilepsy that has been linked to an abnormality in the gene that codes for a protein called cystatin B. This protein regulates enzymes that break down other proteins.

R

• Rasmussen's encephalitis a progressive type of epilepsy in which half of the brain shows continual inflammation.

• responsive stimulation a form of treatment that uses an implanted device to detect a forthcoming seizure and administer intervention such as electrical stimulation or a fast-acting drug to prevent the seizure from occurring.

S

• seizure focus an area of the brain where seizures originate.

• seizure threshold a term that refers to a person's susceptibility to seizures.

• seizure triggersphenomena that trigger seizures in some people. Seizure triggers do not cause epilepsy but can lead to first seizures or cause breakthrough seizures in people who otherwise experience good seizure control with their medication.

• status epilepticus a potentially life-threatening condition in which a seizure is abnormally prolonged. Although there is no strict definition for the time at which a seizure turns into status epilepticus, most people agree that any seizure lasting longer than 5 minutes should, for practical purposes, be treated as though it was status epilepticus.  Repeated seizures without regaining consciousness between the events is also considered a form of status epilepticus.

• sudden unexpected death in epilepsy (SUDEP) death that occurs suddenly for no discernible reason. Epilepsy increases the risk of unexplained death about two-fold.

T

• temporal lobe epilepsy the most common epilepsy syndrome with focal seizures.

• temporal lobe resection a type of surgery for temporal lobe epilepsy in which all or part of the affected temporal lobe of the brain is removed.

• tonic seizures seizures that cause stiffening of muscles of the body, generally those in the back, legs, and arms.

• tonic-clonic seizures seizures that cause a mixture of symptoms, including loss of consciousness, stiffening of the body, and repeated jerks of the arms and legs. In the past these seizures were sometimes referred to as grand mal seizures.

V

• vagus nerve stimulator  – a surgically implanted device that sends short bursts of electrical energy to the brain via the vagus nerve and helps some individuals reduce their seizure activity.

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See Also

• Epilepsy
• Neurology
• Electroencephalography

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