Since epilepsy is a spectrum of neurological disorders and seizures that can affect any region of the brain, symptoms vary widely depending on the type of seizure. Most people will experience the same type of seizure each time, so symptoms should be similar from one seizure to the next. However, it is possible for a person to have multiple seizure types.
There are many different kinds of seizures, but they can be classified into three main types:
These seizure types describe where in the brain the seizure starts, the level of awareness during the seizure, and whether or not the seizure involves movement. The wording in this article is based on a new classification system developed in 2017 by the International League Against Epilepsy. You may also encounter older classification systems.
Generalized onset seizures affect both sides of the brain – or the same groups of cells on both sides of the brain – at the same time, leading to a loss of consciousness and postictal (after the seizure) fatigue.
Generalized tonic-clonic (GTC) seizures were previously known as grand mal seizures. There are five distinct phases to this type of seizure, though not everyone will experience all five. During the tonic phase, the body, arms, and legs will flex, then straighten, then shake. In the clonic period, contraction and relaxation of the muscles follow. The seizure ends with the postictal period, during which fatigue, vision and speech problems, and head and body aches are common. GTC seizures may be proceeded by an aura, which is sometimes actually a focal onset aware seizure (see below). Tonic-clonic seizures may also cause vomiting and loss of bladder control.
Absence seizures, formerly referred to as petit mal, typically last less than 30 seconds. Absence seizures cause a short period of staring and altered consciousness. Most likely, the person will remain standing or sitting upright. The eyes may blink rapidly, or the face or mouth may twitch. After the seizure, they may not remember what just happened. Absence seizures may happen multiple times a day.
Atonic or akinetic seizures, also called drop attacks, cause a sudden loss of muscle tone. A person may suddenly drop their head or fall from a standing position. During the seizure, the body will be limp and unresponsive.
Myoclonic seizures often occur in clusters. Myoclonic seizures cause quick movements or the sudden jerking of muscles. Myoclonic seizures may happen multiple times a day or for multiple days in a row.
Clonic seizures cause jerking, rhythmic motions of the arms and legs, sometimes affecting the face and neck. Clonic seizures can occur on both sides of the body.
Tonic seizures cause the muscles to stiffen suddenly. Tonic seizures can last as long as 20 seconds. If a person is standing when a tonic seizure begins, they usually fall.
Focal seizures affect only one part of the brain. In the past, focal onset seizures were referred to as partial seizures.
Focal onset aware seizures, previously called simple partial seizures, begin in one part or one group of cells of the brain. If a person is awake and aware during the seizure, it is called a focal onset aware seizure. Symptoms of a focal onset seizure vary depending on which part of the brain it affects, but may include visual disturbances, isolated muscle twitching, sweating, nausea, intense emotions, or unusual sensations. Focal onset aware seizures can sometimes precede a tonic-clonic seizure, leading some people to regard them as auras, warning signs, or premonitions of an oncoming generalized seizure.
During focal onset impaired awareness seizures, formerly referred to as complex partial seizures, a person may be confused, appear awake but be unresponsive, or become unconscious. Other behaviors during focal onset impaired awareness seizures may include chewing, gagging, laughing, crying, screaming, or running. Seizures last between 30 seconds to one minute. After the seizure, extreme fatigue is common.
Secondary generalized seizures begin in one part of the brain but then spread to both sides. A secondary generalized seizure is actually two seizures: a focal seizure followed by a generalized seizure.
In some cases, it is not known how or where the seizure begins. Seizures are considered unknown onset seizures if the seizure happens when a person is alone, when no one is present to witness the seizure. A doctor may be able to diagnose the seizure later as a focal or generalized seizure if more information is learned.
In some people with epilepsy, certain circumstances can trigger a seizure. Triggers vary from person to person, but among the most common are:
Identifying seizure triggers allows a person with epilepsy to avoid their triggers and hopefully to have fewer seizures. Keeping a seizure diary is a good way to identify triggers. When a seizure occurs, note the date and time, any special situations surrounding the seizure, and how it felt. There are many apps and websites that can help you track seizures and triggers.