Abstracts

Rationale: Epileptic seizures have been triggered by cartoons containing scenes with flickering colours, and especially long-wavelength red has been demonstrated to be the most provocative colour. However, studies (Sternberg& Patry,1979; Parra et al. 2008) and clinical practice have shown that individual differences in sensitivity to colour exist. In genetic studies the PPR is used as an endo-phenotype, but the role of colour might be helpful in identifying sub-endo-phenotypes. The purpose of our study is to determine whether per patient a fingerprint could be made by ranking the sensitivity to the different primary colours (red, orange, yellow, green and blue). Methods: In 11 consecutive photosensitive patients (6 female, 5 male; age range: 12-72 years) and in 11 control patients (5 female, 6 male; age range: 14-46 years) a standardised 21-channel EEG has been recorded, with extensive Photic stimulation (IPS) of separate trains of flashes (5 sec each) with a Grass photo-stimulator PS33. The lamp was placed at 30 cm distance and besides normal white diffuse light standard coloured Grass filters were used in front of the lamp. Both lower and upper thresholds of the photosensitivity ranges have been determined separately for white light and all colours. This method allowed us to determine possible differences in sensitivity to the various colours, in a safe way. The colours were tested in random order. Results: None of the control patients were sensitive to any colour nor white light. Nine patients showed a PPR at all colours, one patient at all colours except the yellow one and one other patient exclusively at red. Orange (5 patients) and yellow (4 patients) were the most provocative colour, and green and blue the least. The spectrum of color sensitivity differed among the patients although two patients showed the same pattern as well as a father and daughter. Conclusions: Although orange, yellow and red are the most provocative colours in the patients tested, indeed individual differences in sensitivity to different colours and especially in its ranking order were found. The standardised use of five coloured filters in front of a photostimulator in patients sensitive to white flickering light can probably be helpful in delineating further epilepsy phenotypes. Family studies need to be performed to confirm this.