発作 l:はじめに

A seizure is a transient episode of abnormal, excessive electrical activity in the brain that disrupts normal neurologic function. Epilepsy is a chronic disorder in which a person has a long-term tendency to have repeated, unprovoked seizures due to genetic, structural, or metabolic causes. Not everyone who experiences one seizure develops epilepsy.

Focal seizures begin in a specific brain region and may preserve awareness, causing sensory symptoms like tingling or unusual smells called an aura. Generalized seizures affect both brain hemispheres simultaneously and always impair consciousness, often causing a person to collapse, stiffen, and jerk rhythmically. These classifications help guide treatment and prognosis.

An aura is a warning sensation or sensory symptom that may occur before some focal seizures when awareness is preserved. Common auras include tingling sensations, unusual smells, visual disturbances, or other perceptual changes. The aura provides patients with advance notice that a seizure may be beginning.

The postictal state is a temporary recovery period following a seizure, often marked by confusion, fatigue, or drowsiness. During this phase, the brain gradually returns to normal function. The duration and severity of postictal symptoms vary depending on seizure type and individual factors.

Status epilepticus is a life-threatening medical emergency defined as a seizure lasting more than five minutes or repeated seizures without regaining consciousness between episodes. This prolonged abnormal electrical activity can cause brain damage and requires immediate medical intervention. Increased intracranial pressure may develop during this critical state.

A convulsion is a seizure characterized by intense, involuntary muscle contractions causing violent shaking and rapid muscle movements. However, not all seizures are convulsive; some seizures, such as absence seizures, involve minimal movement or no visible muscle contractions despite abnormal brain electrical activity occurring.

A prodrome may appear hours before a seizure begins, presenting nonspecific symptoms like mood changes, headaches, or irritability. These early warning signs differ from an aura, which occurs immediately before focal seizures with preserved awareness. Recognizing prodromes can help patients prepare for potential seizures.