Generalized seizures are a type of epilepsy that affects up to 40 percent of people with epilepsy. Generalized seizures occur when abnormal electrical activity occurs simultaneously across both hemispheres of the brain. This seizure activity is what makes generalized onset seizures different from other seizure types. Focal seizures, or partial seizures, occur only on one side of the brain.
Generalized seizures can take different forms, each with their own set of signs and symptoms. The differences in symptoms in generalized seizures are caused by the location in the brain where the abnormal electrical activity is happening.
To determine the type of seizure a person is experiencing, a doctor investigates a person’s brain waves following the seizure event, often using an electroencephalogram (EEG). Unusual waves or spikes in the brain’s activity can provide helpful clues as to the type of seizure. There are several types of generalized seizures, grouped by the International League Against Epilepsy into two categories — motor and nonmotor.
Motor seizures include symptoms that affect movement.
Generalized tonic-clonic (GTC) seizures used to be called grand mal seizures. A GTC seizure consists of several phases, which can vary between individuals.
The prodromal phase of a seizure happens before the seizure begins. In this phase, a person may experience a distinct feeling they associate with seizures, or a warning sign they’ve learned over time. A person with epilepsy may experience mood swings, headache, or confusion. Only 20 percent of people with epilepsy who experience GTC seizures go through this phase.
An aura is often the first indication of a GTC seizure for many people with epilepsy. Like the prodromal phase, not everyone experiences an aura. Those who have aura may report symptoms such as numbness, loss of vision, a bitter taste, or other sensations, depending on how the brain is affected.
Auras occur in the first part of the ictal phase, or the time from the beginning of a seizure until the end of the seizure. During the ictal phase, a person can experience muscle contractions, twitching, loss of bowel or bladder control, and memory lapses, among many other symptoms. GTC seizures are named after these characteristic muscle contractions — “tonic” means stiffening, and “clonic” means jerking movements.
The time period following a GTC seizure is called the postictal phase. Some people with epilepsy recover quickly. For others, the postictal phase can last as long as several days. A person might experience symptoms like soreness, nausea, or headaches, as well as sadness, memory loss, or confusion during the postictal phase. The length of the postictal phase and the types of symptoms experienced can differ depending on how the brain was impacted during the seizure.
During a tonic seizure, a person’s muscles suddenly stiffen or tighten. Then, the person loses consciousness. Their back arches because the muscles in their arms, legs, and chest tighten, and their eyes roll back in their head. The tightened chest muscles can make it difficult to breathe during a tonic seizure. This can cause a person’s lips or face to turn blue.
During a clonic seizure, a person’s muscles twitch or rhythmically jerk. This usually affects the arms and legs, but muscles in the neck and face may also be affected. Generally the jerking will slow before it stops completely. As the seizure subsides, it is common for the person experiencing symptoms to let out a deep sigh.
Myoclonic seizures can occur in clusters. They feature a rhythmic jerking motion as muscles rapidly tighten, then release.
Infants ages 3 to 12 months can develop a type of myoclonic epilepsy called infantile spasms. During this kind of seizure, an infant’s arms fly outward as their knees and back bend. Infantile spasms happen in a series or cluster, unlike colic cramps or reflux.
Nonmotor seizures lack symptoms that affect movement. Instead, these seizures can cause changes in cognition, emotion, or sensation.
Absence seizures, once called petit mal seizures, are usually short and last less than 10 seconds. During an absence seizure, a person stops what they are doing and goes blank. They may look like they are daydreaming or staring off into space. The person will likely remain upright. Afterward, they will have no memory of what happened.
Absence seizures can occur multiple times a day. Due to their short duration and subtle presentation, people nearby might not even notice the seizure.
Atypical absence seizures tend to be longer, come on slower, and have more symptoms. An atypical absence seizure may last 20 seconds or more. These seizures may also feature facial spasms, eyelid fluttering, or lip-smacking.
Atonic seizures, sometimes called drop attacks, cause a sudden loss of muscle tone. A person experiencing an atonic seizure will go limp, causing them to suddenly fall down if standing or drop their head. The person experiencing the atonic seizure will remain unresponsive until the seizure is over. Atonic seizures are also associated with a rare type of epilepsy, Lennox-Gastaut syndrome, that develops between the ages of 3 and 5.
Generalized seizures can occur in people with and without epilepsy. Someone who experiences two or more generalized seizures that are not the result of a fever may be diagnosed with generalized epilepsy.
Generalized epilepsy can be caused by a number of factors, such as damage to the brain or genetics. A person with epilepsy can also develop the condition over time as the result of a brain tumor, stroke, or infectious diseases like meningitis or encephalitis.
Risk factors for generalized epilepsy include:
Read more about causes of epileptic seizures.
There is no treatment that is effective for all types of generalized seizures. However, many treatments are available for generalized seizures. These include medications, specialized diets, and surgery. Treatments are matched to the type of seizure, where in the brain the seizure originates, and the seizure’s root cause.
Many people can control their symptoms with antiepileptic drugs (AEDs). These medications are thought to work by reducing the electrical activity in the brain that causes epileptic seizures. Depending on the type of seizure, a doctor may prescribe a broad- or narrow-spectrum AED. Broad-spectrum AEDs are effective against more than one seizure type, while narrow-spectrum AEDs are used to treat specific types. For example, absence seizures are frequently treated with a narrow-spectrum AED.
In addition to AEDs, other medications can be used to treat seizures. Sedatives like barbiturates or benzodiazepines are sometimes prescribed. Lennox-Gastaut syndrome is often treated with the benzodiazepine clonazepam (Klonopin).
Although the majority of those who experience generalized seizures can control their symptoms with medication, some epilepsy may be resistant to traditional treatments. If generalized seizures cannot be controlled with medication, a doctor may prescribe diet modifications.
The ketogenic diet is used to treat children with treatment-resistant epilepsy. This high-fat, low-carbohydrate diet increases ketones in the blood, which helps reduce seizures for some children. A similar, less extreme version of this diet may be prescribed to adults with treatment-resistant epilepsy.
In extreme cases where neither medication nor diet has improved seizure activity — or in cases where a person experiences severe, frequent seizures that are life-threatening — a doctor may recommend epilepsy surgery. Surgery for treatment-resistant epilepsy removes the part of the brain where seizures originate. In some cases, this may be a brain lesion or tumor. Depending on the type of seizure, a frontal or temporal lobe resection may be appropriate.
For people with drug-resistant generalized seizures, the most common surgical intervention is a corpus callosotomy. This procedure removes the part of the brain that joins the two hemispheres. This treatment works best in people with atonic, atypical absence, tonic, and tonic-clonic seizures.
Read more about treatments for epileptic seizures.
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