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Photosensitive
epilepsy
Introduction
We would like to thank Professor G F A Harding, formerly of Aston University, England and Professor Stefano Seri, of Aston University and the Birmingham Children’s Hospital NHS Foundation for their help and support in producing this information.
Photosensitive epilepsy is the name given to epilepsy in which all, or almost all, seizures are provoked by flashing or flickering light, or some shapes or patterns. Both natural and artificial light may trigger seizures. Various types of seizure may be triggered by flickering light.
Many people think that everybody with epilepsy is photosensitive, but in fact only five in every hundred people with epilepsy are. Photosensitive epilepsy usually begins before the age of 20 years, although it is most common between the ages of seven and 19. Photosensitivity tends to affect girls more than boys. There is also evidence that photosensitive epilepsy can be passed on through the genes.
Diagnosing photosensitive epilepsy
One investigation that is carried out to diagnose epilepsy is an [electroencephalogram], or EEG. The EEG records brainwave patterns from the continuous tiny electrical signals coming from the brain. During one part of the EEG, you are asked to look at flashing lights, to see if this triggers epileptic activity in the brain. If it does, then this may indicate that you have photosensitive epilepsy.
Hertz
The word hertz (Hz) refers to how often something happens in a given time. In photosensitive epilepsy, hertz (Hz) refers to the number of flashes or flickers a second. When talking about televisions or computer screens, hertz refers to the rate the scanning lines ‘refresh’ themselves.
Most people with photosensitive epilepsy are sensitive to 16-25 Hz, although some people may be sensitive to rates as low as 3 Hz and as high as 60 Hz.
Information updated June 2007
See also...
Photosensitive |
