Photosensitivity and Epilepsy

Alberto Verrotti MD, PhD; Daniela Trotta, MD; Carmela Salladini, MD; Giovanna di Corcia, MD

Disclosures

J Child Neurol. 2004;19(8):571-578. 

In This Article

Definition and Epidemiology

Photosensitive epilepsy is a well-known condition characterized by seizures in patients who show photoparoxysmal responses on electroencephalography (EEG) elicited by intermittent photic stimulation.[1,2]

First, it is important to define separately what a photoparoxysmal response is and what photosensitive epilepsies are Photoparoxysmal responses can be defined as epileptiform EEG responses to intermittent photic stimulation or to other visual stimuli of everyday life. If a child shows photoparoxysmal responses on his EEG, he can be considered an intermittent photic stimulation-sensitive child. These photoparoxysmal responses are frequently found in nonepileptic children.[3,4] The appearance of spikes in nonepileptic patients has been neurophysiologically interpreted as an excessive neuronal discharge that is limited within the subcortical structures and does not clinically express itself (subclinical epilepsy or masked epilepsy).[5] On the contrary, many children can suffer from a peculiar type of epilepsy, and they are considered intermittent photic stimulation-sensitive children; it is possible that their photoparoxysmal responses are an incidental finding, but, more frequently, the presence of photoparoxysmal responses is strictly related to that type of epilepsy.[2]

It has been known for more than a century that flickering sunlight can provoke epileptic seizures in susceptible patients.[6] The modern technologic environment has led to a dramatic increase in exposure to potential trigger stimuli; nowadays, television and video games are among the most common triggers in daily life.[1,7,8,9,10,11,12,13,14,15,16] Other provocative visual stimuli in the contemporary environment include discotheque lighting, rolling escalators (a moving, striped pattern), rotating helicopter blades,[17,18,19,20] and sunlight reflected from snow or the sea or interrupted by roadside structures or trees.[21] In Europe, more than 60% of epileptic photosensitive patients experience their first photosensitive seizure while watching television.[7]

Although the prevalence of photosensitivity depends on the methods of photic stimulation and definition of the photoparoxysmal response, in epileptic patients, it seems to range from 2 to 9.9%,[7,18,22] and the prevalence of photosensitive epilepsy is 1 in 4000.[23] The prevalence of photosensitivity in nonepileptic individuals ranges from 0.5 to 8.9% of the population[4,24,25,26,27,28,29,30] and is higher around the age of puberty.[31] It is important to emphasize that photoparoxysmal responses in nonepileptic persons rarely evolve into epilepsy.[3,4] Of course, photosensitivity does not constitute an epileptic syndrome on its own because it can be found in all of the main categories of epileptic disorders (generalized or localization-related, idiopathic, cryptogenic, or symptomatic epilepsies) and even within the context of situation-related seizures.[2,28,32,33]

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