What is a focal onset seizure?

The human brain works by sending electrical signals through neurons, which are nerve cells. A seizure occurs when there’s a surge in this electrical activity. This causes a host of physical symptoms, such as muscle contractions, visual disturbances, and blackouts. Seizures can affect the entire brain. A focal onset seizure, also known as a partial seizure, is when a seizure occurs in just one area.

A focal onset seizure may occur for many reasons, including epilepsy, brain tumors or infections, heat stroke, or low blood sugar. A seizure can be treated. Diagnosing and treating the underlying cause can help reduce the number of focal seizures. Most people who experience seizures are able to live normal lives with appropriate treatment.

A seizure is the result of experiencing a surge of electrical activity in the brain. The electrical disturbance can produce a variety of physical symptoms. This is especially true with a focal onset seizure, which is a seizure that is focused in just one part of the brain. This is also called a focal seizure, but it can change into a generalized seizure, which affects the entire brain.

There are two types of focal onset seizures.

Focal aware

You won’t lose consciousness during a focal onset aware seizure, or simple partial seizure, and it will last for a minute or less. You’ll remember what happened after the seizure passes. These seizures can sometimes cause you to feel fearful or anxious.

Focal impaired awareness

You may lose consciousness during a focal onset impaired awareness, or complex partial seizure, and you won’t remember what happened. A complex seizure can last for a minute or two, and you may feel a warning sign such as a feeling of uneasiness or nausea before the seizure. You may feel sleepy and confused after the seizure.

There are many different conditions and situations that can cause seizures of any type. Sometimes, the cause is never discovered. A seizure without a known cause is called an idiopathic seizure.

Some of the possible causes of focal seizures are:

Read more: Common triggers for partial onset seizures »

Because a focal seizure affects just one part of the brain, the symptoms vary depending on the particular event. For instance, if the disturbance is in the part of your brain that affects vision, you may have hallucinations or see bright lights.

Other possible symptoms of focal seizures include:

  • muscle contractions, followed by relaxation
  • contractions on just one side of your body
  • unusual head or eye movements
  • numbness, tingling, or a feeling that something is crawling on your skin
  • abdominal pain
  • rapid heart rate or pulse
  • automatisms (repetitive movements), such as picking at clothes or skin, staring, lip smacking, and chewing or swallowing
  • sweating
  • nausea
  • flushed face
  • dilated pupils, vision changes, or hallucinations
  • mood changes
  • blackouts

A seizure itself isn’t difficult to diagnose. Your doctor can diagnose a seizure after listening to your description of your experience or the symptoms other people observed. Of more concern and greater difficulty is determining the underlying cause. Depending on your symptoms and your medical history, your doctor may run any number of tests, such as brain imaging scans, blood tests, or a spinal tap to find out the cause of your seizures.

Learn more: Seizures vs. seizure disorders »

A focal seizure can be treated as it’s happening, if the person is in a hospital environment and the seizure is severe. Your doctor may, however, be able to treat the underlying cause. If seizures are recurring, you may be given a medication to prevent them.

If someone is having a seizure of any type, it’s helpful to keep other people and objects out of the way until the seizure is over. The muscle contractions can cause the person having the seizure to lash out and hurt themselves. Clearing the area of objects and people reduces the risk of injury.

You can’t always prevent seizures, but you can control them with medications. If you’re on a medication for this purpose, take it as instructed by your doctor and don’t miss doses. Maintain a healthy lifestyle by getting plenty of sleep, eating healthy foods, exercising, and minimizing stress.

The outlook for someone who has had a focal seizure varies depending on the underlying cause. In general, however, you can control seizures effectively with medications and lifestyle changes. Surgery is only a consideration for very severe, intractable cases in which medical treatment doesn’t work.