What is a seizure?

A seizure is a burst of uncontrolled electrical activity between brain cells (also called neurons or nerve cells) that causes temporary abnormalities in muscle tone or movements (stiffness, twitching or limpness), behaviors, sensations or states of awareness.

There are different types, and each can cause different symptoms. A seizure may result from a medical condition or other issue, such as drug use.

The human brain has billions of nerve cells. They control the way we think, move, and feel by sending each other electrical signals. An abnormal electrical discharge can interfere with these signals, resulting in a seizure.

A medical condition, such as epilepsy, can cause these discharges that lead to seizures, as can a brain injury or chronic drug or alcohol misuse.

Doctors classify seizures into groups based on the part of the brain affected and how the seizure presents.

Generalized seizures

A generalized seizure results from abnormal electrical activity in both sides, or hemispheres, of the brain.

This type of seizure may be “absent” or tonic-clonic.

Absence seizures

Experts sometimes call these “petit mal” seizures. They might cause the person to spend a few seconds blinking quickly or staring into space. The person might describe it as “zoning out.”

Tonic-clonic seizures

Another name for this type is a “grand mal” seizure. Someone having a tonic-clonic seizure might cry out or lose consciousness.

They may fall to the floor and shake, jerk, or have muscle spasms. Afterward, they may feel very tired.

Focal seizures

A focal seizure happens when there is abnormal electrical activity in just one part of the brain. Doctors may also call them partial seizures.

The symptoms of a focal seizure depend on the area of the brain affected. This type of seizure might change a person’s movements, sensations, or feelings.

Someone having a focal seizure might:

make repetitive jerking movements

become floppy or stiff

cry out or scream

have a feeling of déjà vu

taste or smell something strange

experience numbness or tingling

see colored or flashing lights

hallucinate

become confused

Secondary generalized seizures

An electrical discharge that causes a seizure may start in one side of the brain and spread to both. The name for this is a secondary generalized seizure or a focal-to-bilateral tonic-clonic seizure.

When this happens, the person usually loses consciousness and starts jerking or shaking.

Health conditions that cause seizures

Seizures are often associated with a medical condition, such as:

epilepsy

diabetes

meningitis, an infection of the membranes that surround the brain

encephalitis, inflammation of the brain

dementia, including Alzheimer’s disease

a stroke

in rare cases, a brain tumor

Other causes

Some people are prone to seizure-producing electrical discharges, and the reasons are not always clear.

One or more of the following factors may be involved:

stress

not eating enough

not sleeping enough

medication side effects

drug or alcohol misuse

a head injury

Prevention

Depending on the cause, seizures may be preventable. Someone with epilepsy, for example, may be able to prevent seizures if their treatment plan is effective and they use their medication as advised.

Seizures can stem from high or low blood sugar, so for someone with diabetes, for example, the best method of prevention is to keep blood sugar levels stable. A doctor may also recommend antiepileptic drugs (AEDs).

Avoiding the misuse of drugs and alcohol and reading medication labeling carefully before starting a new treatment can also help prevent seizures.

Treatment

If a person has a single seizure, they may not need treatment. But if a doctor believes that more seizures are likely, they may recommend AEDs. These completely stop seizures in about 70% of people who take them.

If medication does not work and the seizures are focal, the doctor may suggest surgery. This may be a resection, which involves removing any abnormal tissue in the brain that is causing the seizures.

Another surgical option is called disconnection, and it involves separating the abnormal tissue responsible for the seizures from the rest of the brain.

A different option is neuromodulation, which involves wearing an implanted device that alters nerve activity — either through deep brain stimulation, responsive neurostimulation, or vagal nerve stimulation.