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Epilepsy: How Seizures Affect the Body

The brain is your body’s control center. It manages everything from movement and balance to emotions and memory. When a seizure happens, some or all brain functions are temporarily affected.

The brain working normally

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

Normal EEG tracing.
Normal EEG.

The brain during a seizure

During a seizure, excessive and abnormal electrical signals in your brain disrupt its normal activity. The way this affects body functions depends on 2 main factors. First is the location of the seizure in your brain. For instance, a seizure in a part of your brain that controls movement (the motor cortex) might cause your arm or leg to jerk.

The second factor is the spread of the seizure to other parts of the brain. For instance, a seizure that affects more of your brain may affect more of your body.

Types of seizures

The types of seizures include:

  • Focal seizures. This is when the abnormal electrical activity starts in one part of the brain. These seizures used to be called partial seizures.

  • Generalized seizures. These are seizures that start on both sides of the brain at the same time.

  • Unknown onset. This is when it isn't known if the seizure is focal or generalized. It may be difficult to know which type until special tests such as an EEG are done.

  • Focal to bilateral seizure. This is when a seizure starts in one side or part of the brain (focal) and then spreads to both sides.

Partial seizure EEG tracing.
Partial seizure EEG
Generalized seizure EEG tracing.
Generalized seizure EEG

Focal seizures

Focal seizures that start in one spot of the brain may also be described by any change in awareness with the seizure.

  • Focal aware. The person having a seizure remains aware of their surroundings. They may be unable to talk during the seizure but have no lapses in awareness or consciousness.

  • Focal impaired awareness. People with this type of seizure will have temporary loss of awareness. This can be very brief (few seconds) to much longer. The old term for this is complex partial seizure.

  • Awareness unknown. This is when it can't be determined if the person's awareness is affected or not.

Focal seizures are further described depending on if the seizure causes movements or not.

  • Focal motor seizure. This is when abnormal movements result from a focal seizure. The movements can include twitching, jerking, or stiffening movements of a body part. Or they can be movements such as licking lips, rubbing hands, walking, or running.

  • Focal non-motor seizure. These occur when there are no movements, but the person may have vision changes, thoughts, or sensation from the seizure.

Generalized seizures

Generalized seizures are classified by whether the seizure causes abnormal movement or not.

  • Generalized motor seizure. This is when a seizure involving both sides of the brain is linked to abnormal movements such as stiffening or jerking. It's also called a tonic-clonic seizure.

  • Generalized non-motor seizure. This is a seizure that affects awareness but doesn't cause motor symptoms. Some people will have minor movements that repeat, such as blinking or staring. This is also called an absence seizure.

Other effects of seizures on your body

After a generalized motor seizure, it's not uncommon for people to feel soreness in their muscles when they wake up. Some people bite their tongues or have incontinence of their urine or bowel during these seizures. You may have changes in your skin color or sweating. People who have seizures in their sleep may only be aware they had a seizure because they feel sore or find they had incontinence when they wake up.

Seizures can also affect your heart rate, blood pressure, or other vital signs. These changes are often short term (temporary) and get better after the seizure stops. During a seizure, brain cells can be injured, especially with prolonged seizures. For these reasons, it's important to have good control of seizures.

Seizures that affect your movements or consciousness can pose a danger. When a seizure affects awareness of surroundings, you may be unable to focus on what you are doing. This is particularly dangerous because you may lose control of a vehicle or heavy machinery.

Motor seizures (generalized or focal) can result in injury. With generalized motor seizures, you can fall and be injured. The motor movements with focal or generalized seizures can also cause injury by causing you to contact dangerous objects nearby such as a hot stove or a sharp knife.

People with seizures that affect awareness or motor function should take care to prevent injuries. Your ability to drive may be affected. Your driving may be limited, based on your provider's advice and local laws. You may need to take care not to swim or shower alone because of the risk of drowning during a seizure. Heights such as being on a ladder and other similar dangers can result in serious injury if you have a seizure. Your provider can advise you on what to do to stay safe.

Online Medical Reviewer: Anne Fetterman RN BSN
Online Medical Reviewer: Joseph Campellone MD
Online Medical Reviewer: Raymond Kent Turley BSN MSN RN
Date Last Reviewed: 8/1/2021
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