Wavelength Dependence of Photoparoxysmal Responses in Photosensitive Patients with Epilepsy

Authors


Address correspondence and reprint requests to Dr. Y. Takahashi at Department of Pediatrics, Gifu University School of Medicine, 40 Tsukasa-machi, Gifu 500-8705, Japan. E-mail: yukito@cc.gifu-u.ac.jp

Summary:

Purpose: We tried to specify the relation between the photoparoxysmal response (PPR) and the wavelength spectra of flashing light in various photosensitive epileptic syndromes in the physiologic state.

Methods: Intermittent photic stimulation (IPS) by a Grass PS22 photic stimulator was performed with wavelength-specific optical filters in photosensitive patients with epilepsy (idiopathic generalized epilepsy, IGE; hereditary dentatorubral-pallidoluysian atrophy, DRPLA) and photosensitive subjects without epilepsy.

Results: Five of 19 normal trichromat patients with IGE and an IGE patient with deuteranomaly showed wavelength-dependent PPRs. The wavelength-dependent PPRs were elicited only by IPS containing wavelength spectra ∼700 nm in the normal trichromat patients. Two of four patients with DRPLA showed wavelength-dependent PPRs, and two other DRPLA patients showed quantity-of-light-dependent PPRs. Quantity-of-light-dependent PPRs are elicited by IPS containing more than a certain quantity of light, independent of the wavelength composition of the flashing light. Two of five subjects without epilepsy showed wavelength-dependent PPRs.

Conclusions: There are wavelength-dependent and quantity-of-light-dependent pathophysiologic mechanisms for eliciting PPRs by low-luminance IPS. Consideration of the quantity and wavelength composition of light from electronic screens will lead to the prevention of photosensitive seizures induced by electronic screen games.

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