An Overview of Photosensitive Epilepsy

Flashing lights can cause some people to have convulsions

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Bright flashing lights of a night club

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Photosensitive epilepsy is a type of epilepsy in which seizures can be triggered by visual images such as rapidly flickering lights or fast-paced graphics. A seizure that is brought on by a visual trigger is described as a visual reflex seizure, a photo convulsive seizure, or a photosensitive seizure. Photo convulsive seizures are uncommon, affecting an estimated 1% to 3% of people who have epilepsy, and only rarely affecting people who do not have epilepsy. 

The best approach to managing these types of seizures is identifying the visual images that can cause you to have them and taking all reasonable steps to avoid these visual irritants. Sometimes, prescription medication with anticonvulsants (anti-seizure medications) is necessary.

Symptoms

Photo convulsive seizures generally start during childhood, but they can begin at a later age. A photo convulsive seizure can involve a variety of symptoms, including involuntary (not on purpose) shaking and jerking of the body and/or impaired consciousness.

Viewing bright lights, flashing lights, strong color contrasts, rapidly moving visuals, or repetitive geometric patterns for at least several seconds precedes photosensitive seizures.

Symptoms of photo convulsive seizures can include:

Tonic-clonic seizures: The seizures triggered by visual stimuli may involve rhythmic jerking or shaking of the arm, leg, and/or face on one side of the body. These seizures can include repetitive movements of the whole body as well. 

You might be aware of what is happening during the episode or your consciousness can be impaired. These seizures generally last for a few seconds but can go on for several minutes or longer. They are described as tonic-clonic seizures or grand mal seizures.

Myoclonic seizures: Myoclonic seizures are characterized by involuntary rhythmic spasms alternating with relaxation. They generally affect only one part of the body, such as the arm.

Staring spells: A non-convulsive seizure, often described as an absence seizure or a petit mal seizure, can also be provoked by visual stimulation. These seizures are more common among children than adults and are characterized by diminished awareness without any accompanying shaking or jerking of the body. 

During one of these episodes, you would not lose muscle tone or fall down. The seizures usually last for a few seconds. Most people regain consciousness without medical treatment and are immediately able to function normally, often without any recollection of the event.

Postictal state: After your seizure is over, you may feel exhausted or disoriented. You might have a sense of tingling or weakness of part of your body. These postictal symptoms generally resolve within 12 to 24 hours.

Keep in mind that if this is the first time you have experienced weakness of your body after a seizure (or anything else that seems like a postictal state)—or if this is your first seizure, you need to seek medical attention immediately.

If you or your child has photosensitive epilepsy, you can also have seizures that are not triggered by visual stimuli in addition to your visually-provoked seizures.

What Is Not a Photo Convulsive Seizure

It is not uncommon to experience visual discomfort or headaches after looking at bright lights or contrasting colors. It is also common to continue to “see” flashing lights after the lights and flickering are gone. 

Many people become concerned that these experiences could be photo convulsive seizures. 

However, these common symptoms are not part of a photo convulsive seizure. In fact, you might not experience any discomfort or aversion to the visual images before or after having a photo convulsive seizure. 

Causes

There are a number of triggers that can provoke a photo convulsive seizure. These seizures have been reported as a result of flashing dance club lights, video games, and moving images (like in a carousel ride). Animated images seen on a computer screen, television, or movie screen have been reported to provoke photo convulsive seizures as well. Unusual causes include bar code scanners, emergency vehicles, and flashing telephone lights.

Seizure Triggers

Your brain functions as a result of electrical activity between nerve cells. Seizures can occur when there are alterations in the brain’s normal electrical activity. 

A number of health and lifestyle factors can provoke a seizure, including alcohol, drugs, fevers, sleep deprivation and others.

Visual seizures triggers are among the most unusual causes of seizures.

How Visual Stimuli Cause Seizures

Alternating changes of different colored lights such as deep red and deep blue or lights flickering at a rapid rate of around 12Hz can precipitate photo convulsive seizures among some individuals. 

For some people, the visual stimuli may produce erratic electrical activity in the occipital lobe, which is the part of the brain that integrates vision. The left and right occipital lobes are located in the farthest posterior (back) region of the brain, right next to each other.

This irregular and hyperactive electrical activity can rapidly spread from the occipital lobe to other regions of the brain, triggering a convulsive seizure and/or loss of consciousness.

Widespread Episode of Photo Convulsive Seizures 

Many people have heard of photo convulsive seizures. There was a widely reported occurrence of these seizures on December 16, 1997, when over 700 children and adults in Japan were seen in the hospital for seizures that occurred while watching a cartoon.

About 20% to 25% of the people who experienced seizures provoked by the cartoon had experienced at least one seizure prior to the episode. Most of those who had seizures triggered by the cartoon’s rapidly animated lights did not experience any more seizures over a five-year follow-up period.

Predisposition to Photo Convulsive Seizures 

It isn’t clear why some people with epilepsy have a predisposition to visually-induced seizures. One study found that there may be a relationship between photosensitive epilepsy and the brain’s adaptation to contrasting colors. But it isn’t clear why this occurs.

Seizures and photosensitive epilepsy tend to run in families. Some genes have been found in association with epilepsy, but currently no specific gene has been identified in association with photosensitive epilepsy.

It is important to know that exposure to flashing lights or rapidly moving graphics has never been found to cause photo convulsive epilepsy or any type of epilepsy to develop.

Diagnosis

Photo convulsive epilepsy is characterized by seizures that are provoked by visual triggers. While uncommon, some people can experience a photo convulsive seizure only once and may never experience it again.

Your diagnosis is based on your seizure history; your doctors may also order some diagnostic testing to help identify your problem. If you or others who were with you recall that you were exposed to or looking at flashing lights or another visual trigger prior to having a seizure, this could suggest that you had a photo convulsive episode.

An electroencephalogram (EEG) is often used in the diagnosis of epilepsy. Some experts suggest that people who are prone to photo convulsive seizures may have an EEG pattern characterized by spikes in the occipital lobe. However, this finding is not consistent, and you can have photosensitive epilepsy even if your EEG does not show spikes in the occipital lobe. 

In some instances, your medical team may expose you to a visual trigger during your EEG examination. The trigger may provoke a seizure, supporting a diagnosis of photosensitive epilepsy.

Visual evoked potential testing may also show some characteristic abnormalities, although this is not consistent and not reliably diagnostic of photosensitive epilepsy.

Similar Conditions

Occipital seizures are rare. They are different than photo convulsive seizures. They start in the occipital lobe of the brain, but are not necessary triggered by visual stimuli. Occipital seizures may cause visual hallucinations. They can be caused by tumors or brain malformations of the occipital lobe. 

For many people, flashing lights, bright lights, or bright colors can cause headaches, discomfort, dizziness, or eye pain. This is often referred to as photosensitivity or photophobia. Photophobia is fairly common and it has not been found to be related to photo convulsive seizures. 

Treatment

If you have photosensitive epilepsy, your seizure management will focus on avoiding the visual stimuli that provoke seizures and/or medical treatment with anticonvulsants.

If you have a known seizure trigger, including a visual trigger, it is important to avoid it. Seizures are not always dangerous, but they can be.

You can experience a physical injury as a result of a seizure. And experts suggest that having seizures can make further seizures more likely due to the alterations in the brain’s electrical activity.

Some recommendations regarding photo convulsive seizure prevention include:

  • Placing a light filter on your television or computer screen to prevent excessive light contrast
  • Avoiding situations with flashing lights
  • Looking away from graphic patterns and flashing lights

If you have recurrent seizures, your doctor may prescribe one or more anticonvulsant medications to prevent them. Your anticonvulsant selection will be based on several factors, including the type of seizure (tonic-clonic, myoclonic, or absence), how often they occur, and whether you take any other medications that could interact with anticonvulsants. 

A Word From Verywell

If you or a loved one experience a seizure, it is important to have a prompt medical evaluation. A seizure can be a sign of epilepsy or another medical condition. Additionally, these episodes require expert medical care.

If you discover that any environmental factor tends to precipitate your seizures, be sure to take reasonable steps to avoid that trigger. However, precipitating factors cannot always be avoided, so it is important to be prepared in case you experience a seizure or if it is impossible to completely avoid the trigger. 

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Article Sources

  1. Brazzo D, Di Lorenzo G, Bill P, et al. Abnormal visual habituation in pediatric photosensitive epilepsy. Clin Neurophysiol. 2011 Jan;122(1):16-20. doi:10.1016/j.clinph.2010.06.002

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