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Epilepsy: How Seizures Affect the Body




The brain is the “control center” of the body. It manages everything from movement and balance to emotions and memory. When a seizure occurs, some or all brain functions are affected.


The Brain Working Normally

The brain uses electrical signals to send messages throughout the body. Signals sent from different parts of the brain control different body functions. For instance, one part of the brain controls balance. Another part controls speech. A doctor can record brain signals using a test called an EEG (electroencephalogram).

The Brain During a Seizure

During a seizure, excessive electrical signals in the brain disrupt its normal activity. How this affects body functions depends on two main factors. First is the location of the seizure. For instance, a seizure in a part of the brain that controls movement might cause an arm or leg to jerk. Second is the type of seizure. For instance, a seizure that affects more of the brain may affect more of the body.

Types of Seizures

The two main types of seizures are partial and generalized.

Partial Seizures

Also called focal seizures, these seizures start in one part of the brain and may spread. There are two types:

  • Simple partial seizures. These may start with an aura, or warning. Auras are seizures that can involve strange tastes or smells, stomach upset, or a feeling of fear or déjà vu. Simple partial seizures may also involve jerking movements or hallucinations. The person is awake and aware that they are having a seizure.

  • Complex partial seizures. These may also start with an aura. The person may become motionless and have a vacant stare. Or he or she may perform “automatisms.” These are repeated movements, such as smacking lips or gesturing. The person may be awake but unaware of the seizure, or may lose consciousness.

Generalized Seizures

These seizures affect the entire brain at once. The most common types of generalized seizures are:

  • Absence seizures (petit mal seizures). These seizures involve a brief lapse of awareness. Signs can include staring, eye blinking, and lip smacking.

  • Tonic-clonic seizures (grand mal seizures). These may be the best known type of seizure. The person loses consciousness and may fall to the ground. The body stiffens and then convulses, with the arms and legs jerking rhythmically.

  • Myoclonic seizures. These seizures involve brief jerking movements. They usually affect both sides of the body.

  • Atonic seizures (drop attacks). During these seizures, the person loses all muscle control and may fall or slump over.


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