Photosensitivity and visually induced seizures.
OBJECTIVE
Interest in visually induced seizures has increased in recent years as a result of the increasing number of precipitants in our modern environment. This review addresses new developments in this field with special attention given to the emergence of new diagnostic, therapeutic and preventive approaches; it also emphasizes the importance of this condition as a public health issue.


RESULTS
Current evidence indicates the presence of two different mechanisms of photosensitivity, one dependent on luminance changes and the other on wavelength. Both mechanisms may be active in the same patient, although one may be dominant. Magnetoencephalography studies revealed an enhancement in gamma frequency preceding the development of a paroxysmal response as well as underlying uncomfortable visual illusions, suggesting that a loss of control over high-frequency oscillatory processes may be involved in the genesis of both types of phenomenon. The genetics underlying this trait remain to be determined. More precise definition of different phenotypes should help in this search. Recognition of the risks posed by the audiovisual environment for induction of seizures in photosensitive individuals, who may not even be aware of their condition, will prompt further development of guidelines and devices designed to prevent the occurrence of seizures triggered by dangerous video sequences.


CONCLUSIONS
Photosensitive epilepsy constitutes a unique benchmark model in which to address important issues in human epileptogenesis. The scope of the health risks posed by the modern audiovisual environment is increasingly being recognized, and further development of guidelines and regulations to control exposure to provocative materials are warranted.
Parra
Jaime
J
Dutch Epilepsy Clinics Foundation, SEIN, Meer en Bosch, Heemstede, The Netherlands. jparra@sein.nl
Kalitzin
Stiliyan N
SN
Lopes da Silva
Fernando H
FH
D020195:Epilepsy, Reflex / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control*; D006801:Humans; D010775:Photic Stimulation / Q000009:adverse effects*; D013690:Television