The human brain works by sending electrical signals through neurons, which are nerve cells. A seizure occurs when there’s a sudden burst of chaotic electrical activity. This causes a host of physical symptoms, like 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 begins in just one area.

A focal onset seizure may occur for many reasons. Epilepsy, brain tumors, or damage from head trauma or from a stroke can cause recurrent focal onset seizures. Infections, heatstroke, or low blood sugar can trigger a seizure.

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 disorganized or erratic electrical activity in the brain. The electrical disturbance can produce a variety of physical, behavioral, or cognitive symptoms.

This is especially true with a focal onset seizure, which is a seizure that’s 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. But there often is not a clear distinction between them.

Focal onset impaired awareness seizure

You won’t lose consciousness during a focal onset aware seizure, or simple partial seizure, and it’ll last for a minute or less.

You might remember what happened after the seizure passes, but many people do not remember what occurred during their own focal onset impaired awareness seizure. 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. You also won’t remember what happened. A complex seizure can last for a minute or two, and you may feel a warning sign like 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:

Learn more about 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), like 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

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. These include brain imaging scans, blood tests, or a spinal tap to find out the cause of your seizures.

Learn more about seizures vs. seizure disorders.

A focal seizure typically lasts for just a short time, so there isn’t usually time to treat it while it’s happening. A longer seizure, called status epilepticus, is rare but dangerous and requires emergency treatment. If there’s a cause besides epilepsy, like an infection, this underlying cause will need to be treated accordingly.

If seizures keep happening after the underlying condition is treated, or if they’re caused by idiopathic epilepsy, stroke, brain tumor, or other brain damage, anti-epilepsy medication is needed to prevent more seizures.

If someone’s having a seizure of any type, it’s helpful to keep other people and objects out of the way until the seizure is over. Involuntary muscle contractions can cause someone who’s having a seizure to accidentally become injured.

You can’t always prevent seizures, but you can control them with medications. If you’re taking medication for this purpose, take it as instructed by your doctor, and don’t miss doses. Also, make sure to get plenty of sleep, eat a balanced diet, exercise, and explore ways to minimize stress.

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