Doctors can sometimes identify the cause of a person’s seizures. There are two main types of seizure based on whether or not they can determine the cause:
- Idiopathic, or cryptogenic: There is no apparent cause, or the doctor cannot pinpoint one.
- Symptomatic: The doctor knows what the cause is.
There are also three seizure descriptors — partial, generalized, and secondary generalized — depending on which area of the brain the seizure originates in.
A person’s experience during a seizure will depend on the affected brain area and how widely and quickly the electrical activity in the brain spreads from that initial area.
The sections below discuss partial, generalized, and secondary generalized seizures in more detail.
A partial seizure occurs when the epileptic activity takes place in one part of a person’s brain. There are two subtypes of partial seizure:
- Simple partial seizure: During this type of seizure, the person is conscious. In most cases, they are also aware of their surroundings, even when the seizure is in progress.
- Complex partial seizure: During this type, the seizure impairs a person’s consciousness. They will generally not remember the seizure. If they do, their memory of it will be vague.
A generalized seizure occurs when the epileptic activity affects both halves of the brain. The person will usually lose consciousness while the seizure is in progress.
There are several subtypes of generalized seizure, including:
Tonic-clonic seizures: Perhaps the best-known type of generalized seizure, tonic-clonic seizures cause loss of consciousness, body stiffness, and shaking. Doctors previously called these grand mal seizures.
- Absence seizures: Previously known as petit mal seizures, these involve short lapses of consciousness wherein the individual appears to be staring off into space. Absence seizures often respond well to treatment.
- Tonic seizures: In tonic seizures, the muscles become stiff, and the person may fall.
- Atonic seizures: A loss of muscle tone causes the individual to drop suddenly.
- Clonic seizures: This subtype causes rhythmic, jerking movements, often in the face or one arm or leg.
- Myoclonic seizures: This subtype causes the upper body or legs to suddenly jerk or twitch.
Secondary generalized seizure
A secondary generalized seizure occurs when the epileptic activity starts as a partial seizure but spreads to both halves of the brain. As this seizure progresses, the person will lose consciousness.