What is meant by reflex epilepsy?
Reflex epilepsies are a group of epilepsy syndromes in which a certain trigger or stimulus brings on seizures.
- The trigger can be something simple in the environment or something more complex.
- Simple environmental triggers include sensations like touch, light or movement.
- Complex triggers may include activities like reading, writing, doing arithmetic, or even thinking about specific topics.
- Other environmental triggers include sounds, such as church bells, a certain type of music or song, or a person's voice. Simple sound induced seizures in humans are very rare.
- Seizures also have been triggered in a few people by things like the patterns of a moving escalator step, tooth brushing, taking a hot bath, or being rubbed.
- For some people, certain rates of blinking or even specific colors may provoke seizures.
- Sensory triggers can bring seizures on within seconds, while more complex triggers might take minutes to bring on a seizure.
Common types of reflex epilepsy include:
- Photosensitivity, which is sensitivity to certain light frequencies, sunlight glittering on water, television, etc.
- Eye closure sensitivity, which is sensitivity to eye closing that is usually repeated eyelid fluttering
- Orofacial reflex myoclonia, which typically are muscle jerks around the mouth, tongue, or jaw brought on by reading or talking
- Praxis induction, which are muscle jerks induced by visual motor tasks like playing chess, playing cards, writing, drawing, etc.
- Musicogenic epilepsy, which is a sensitivity to certain music
Epilepsy with eyelid myoclonia (Jeavons syndrome) is a term often used to describe photosensitive epilepsy, particularly in childhood. Typical symptoms include gazing at the sun and while waving fingers in front of the face. During this time, the child may stare with or without fluttering their eyes.
What are common seizure types?
The types of seizures that may occur are varied, but 85% are generalized tonic-clonic (grand mal) seizures. Other seizure types include absence seizures (staring) and myoclonic seizures (jerking of the eyes, head, or arms).
Occasionally, focal seizures (arising from a small portion of the brain) may also present as a reflex epilepsy.
Who gets it? Can it be inherited?
- Photosensitive epilepsy usually begins in childhood and is often (but not always) outgrown before adulthood.
- It is more common in children with a parent who is also sensitive to flashing lights.
- Although no major gene has been identified for reflex epilepsies, it has been described in people with other epilepsy types like Dravet syndrome (usually caused by a sodium channel alteration). However, it may also occur with chromosomal (especially chromosomes 4 and 10) and other genetic disorders, including mutations in LGI1 and MECP2.
- Other reflex epilepsies may occur at any age. They affect only a small number of people with epilepsy.
- People who have reflex epilepsies generally are developmentally normal and have normal findings on a neurological examination. However, if due to a genetic mutation, cognitive problems are common.
How is it diagnosed?
- Diagnosis is made after a careful history and examination.
- An EEG (electroencephalogram) is ordered most frequently and is likely to show normal background with generalized or focal abnormal activity (polyspikes and spikes, often activated with intermittent light flashes).
- An MRI (magnetic resonance imaging) may be required in some cases.
- Advanced imaging like functional MRI might be performed on a research basis.
How is it Treated?
The best method where possible is to avoid the stimulus that triggers seizures.
- It can be difficult to avoid all flashing lights, since even driving past a line of trees with the sun flickering through can produce the same effect as a strobe light. If flashing lights cannot be avoided, it may help to cover one eye until the flashing is over.
- There has been great interest in the safety of video games for children or adults with epilepsy. Certain video games, television shows, and movies can provoke seizures. Sleep deprivation and stress or excitement caused by playing the games for a long time may also provoke seizures. Therefore, getting enough sleep and managing stress are important ways to avoid these triggers.
- Seizures that are triggered by the flashing lights and changing patterns of video games occur during the game.
- Seizures that occur later, after the person has finished playing, are not caused by the game.
Most people with reflex epilepsies also require medication because their seizure triggers are unavoidable in everyday life or they also experience seizures without detectable causes.
- Valproate (divalproex sodium, Depakote) is effective for reflex epilepsies.
- Other successful medications are clonazepam (Klonopin), clobazam (Onfi), lamotrigine (Lamictal), or phenobarbital.
What's the outlook?
In many cases, seizures in reflex epilepsy are well controlled with low doses of medication.
Some people do outgrow their seizures, but the decrease in the chance for seizures may not happen for many years: 75% of people with photosensitive reflex epilepsy continue to have seizures after age 25 if not treated.
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