Types of Seizures

A focal seizure (sometimes also called a partial seizure) is a seizure that affects only a specific area of the brain. Focal seizures can be simple (in which patients remain conscious) or impair the patient’s awareness. A focal impaired-awareness seizure is a focal seizure in which the patient is not aware of their surroundings. They can begin as a simple seizure that spreads to other areas of the brain and causes loss of consciousness or awareness.

Generalized seizures are caused by abnormal electrical activity occurring simultaneously in all parts of the brain. This type differs from partial seizures, which usually affect only one part of the brain. There are six types of generalized seizures: absence seizures, atonic seizures, myoclonic seizures, clonic seizures, tonic seizures, and tonic-clonic seizures.

A Jacksonian seizure is typically what is called a simple partial seizure, meaning that the person does not lose consciousness or awareness, and excessive neuron firing only occurs in one part of the brain, so that abnormal movement or sensation is limited to one part or one side of the body. It usually starts with twitching or tingling in a finger, toe, or a corner of the mouth, and then “marches” to affect larger parts of the body, such as the entire hand or foot.

Partial seizures are caused by the sudden disorganized firing of electrical signals from one nerve cell to another in one part of the brain. Because the defective signaling is limited to only a part of the brain, these seizures also are called focal seizures. Depending on the affected part of the brain, partial seizures vary in their effects on the person’s movement, sensation, or behavior.

Simple partial seizures, also called focal onset aware seizures, are a type of seizure caused by defective nerve signaling in a localized part of the brain. These seizures are usually the first ones to occur in patients with Batten disease who may later develop more severe generalized seizures. Simple partial seizures may also be a kind of warning, or so-called aura, before a stronger seizure occurs.

When a seizure lasts for more than five minutes or a patient experiences numerous seizures without recovering between them, the patient is said to be experiencing status epilepticus. It usually occurs without warning, and the patient usually does not remember the event. Status epilepticus can be life-threatening and is considered a medical emergency.