FIREWORKS and EPILEPSY

With July fourth rapidly approaching and very little information regarding how fireworks may trigger seizures in those living with epilepsy, Epilepsy.com sought out one of the top experts on photosensitivity, Dr. Guiseppe Erba, Professor of Neurology and Pediatrics at the University of Rochester, Rochester, New York.

Dr. Erba, can you explain how fireworks can trigger a seizure?

Any strong light that flashes repeatedly straight into the eyes of an individual with photosensitive predisposition to seizures has the potential for causing a seizure. In addition to the intensity of the light (luminosity) and the flicker (frequency), there are other determining factors such as the color (red being more provocative than green and blue), the contrast between light stimulus and background, and the extent to which the light stimulus fills up the field of vision. Fireworks are no exception in terms of potential risks. However, visual effects vary greatly in the course of fireworks and the risk will change accordingly.

Typically, the first part of the fireworks program consists of single shots in two or three successive stages, generating trajectories of small multicolored lights that move at slow pace, leaving an evanescent trace that quickly vanishes. The overall effect is that of a slow moving, irregular linear pattern that does not flicker. It is unlikely that single fireworks of this type may have adverse effects even on photosensitive individuals.

The conditions change dramatically during the final display of the fireworks that typically consist of a sustained barrage of multiple explosions producing bright flashes in rapid successions all over a large area of the visual field. During the final seconds of fireworks spectators are exposed simultaneously to a multitude of intensely bright white lights that flicker rapidly like a powerful strobe against the dark sky. This is therefore potentially a dangerous type of stimulation because it could possibly trigger a seizure in whoever is photosensitive. Children, who are often part of the fireworks crowd, are at greater risk than grown ups. This is because the genetic predisposition toward photosensitivity has maximal expression in the young age group.

Does the distance from the actual fireworks display affect the likelihood of triggering a seizure?

Distance always matters because it determines the area of the visual stimulus in relation to the field of vision. Whether it is an image on a TV screen or fireworks displayed in the sky, the closer the eyes are to the source, the larger is the portion of the retina that gets activated and consequently the part of the brain that gets stimulated. In the case of watching TV, the critical distance that makes a difference is a matter of a few feet. In the case of fireworks it is a matter of miles. If fireworks are watched from enough distance that the display barely gets above the horizon, there will be no danger because the stimulus occupies a small fraction of the whole field of vision. However, in order to fully enjoy the spectacle, most spectators choose to sit close enough so that the fireworks display will extend to at least half of the sky in front of their eyes. In this situation, there is potential risk. Whether predisposed individuals will have a seizure or not will depend on the presence or not of the other triggering factors such as age, the quantity of light displayed, the contrast between fireworks and background (not only the sky backdrop but also the spectator’s immediate surroundings), the color of the fireworks, and the flicker effect as previously mentioned.

What types of seizures are most commonly associated with photosensitivity?

Photosensitivity is a genetic trait and is most often associated with Primary Generalized Epilepsy (PGE), which is also a genetically inherited condition. Certain forms of PGE are more likely to carry the trait of photosensitivity than others. The most frequent association is with a particular syndrome of PGE called Juvenile Myoclonic Epilepsy (JME). As a result, the seizures triggered by photic stimulation consist most frequently of generalized manifestations such as body jerks (myoclonic seizures) or generalized tonic clonic convulsions (grand mal seizures). Both these types of seizures are commonly seen in Generalized Epilepsy. The myoclonic jerks often precede the grand mals and are a useful signal to alert the subject that a major seizure may be imminent. Individuals who are aware of their vulnerability will instinctively try to shield themselves from light stimulation as soon as they perceive involuntary muscle jerks and this maneuver may succeed in aborting the full attack.

What are the potential safety issues for people with epilepsy and photosensitivity at a fireworks gathering?

Photosensitive people who also have epilepsy are usually on medications. If the medication is appropriate and is taken properly, it provides a valid protection, although it does not completely eliminate the risk. In circumstances that combine many of the provocative factors mentioned above, a seizure may occur especially if the patient has not been fully compliant with their medication. The most vulnerable among the spectators are young individuals who are photosensitive but never had a seizure before because they were never previously exposed to sufficiently provocative visual stimulation. These subjects are unaware of the risk and are totally unprepared to face the consequences. They are not protected by medication and will not recognize the signals of an impending attack.

When a major seizure occurs in the midst of a large crowd absorbed in the contemplation of fireworks in action, the situation must be handled skillfully and without delay. Trying to get the attention of bystanders or calling an ambulance is most likely to be totally unproductive. Instead, full attention should be given to the person who is having the seizure. First aid can be provided effectively at the site by a competent adult, such as a family member, who is familiar with seizure management and can assist the patient until the attack is over. The appropriate action is not to panic and to apply the following simple rules: let the patient lie on the ground, turn the patient on one side, keep airways clear, and support the head to prevent injuries.

Are there certain precautions people with epilepsy can take before attending a July 4th firework display?

People with epilepsy should make sure they have taken their medication fully in the preceding 12 hours. If their doctor has prescribed additional medication “when needed” such as lorazepam (Ativan), it may be reasonable to take a preventive dose half hour before the beginning of the fireworks. This would be particularly indicated if the patient had previous experience with seizures that may have been triggered by some type of photic stimulation.

It is not advisable to go to fireworks display alone. People with epilepsy should be accompanied by a competent adult with experience in seizure management.

Individuals who know they are photosensitive and still wish to watch the fireworks should be particularly careful. The same word of caution applies to all individuals who never had seizures but have close relatives with history of epilepsy, particularly PGE, irrespective of whether the relative has had seizures triggered by visual stimuli or not. They are at risk of carrying the photosensitive genes without knowing it. All individuals at risk are well advised not to get too close. Watching from a distance that reduces the view of the full fireworks display to approximately one quarter of the total field of vision is a recommended precaution. They should not stand in dark surroundings but rather choose to watch the display from a well lit place. Most importantly, they should cover one eye with the palm of one hand during the grand finale of strong multiple flashing lights. Cutting down half of the visual input by covering one eye is usually sufficient to prevent abnormal brain responses to most types of photic stimulation. Finally, they should be ready to also cover the other eye immediately in case they perceive involuntary jerking in their muscles, even if slight.

Covering both eyes will exclude any further stimulation and will prevent progression into a full seizure. It is important to know that simply ‘closing’ the eyes or looking away in another direction is not sufficient. In order to prevent the seizure it is essential to completely obliterate the visual input by tightly sealing the orbit with the palm of one hand.

To learn more about photosensitivity please go to: Shedding Light on Photosensitivity, One of Epilepsy's Most Complex Conditions

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