Abnormal visual habituation in pediatric photosensitive epilepsy

Objective: To investigate visual habituation - a measure of visual cortical excitability - in photosensitive patients in pediatric age and compare the findings with a matched sample with idiopathic generalized epilepsies without photosensitivity and with normally developing children.

Methods: We presented a full-field black-and-white checkerboard pattern, at 3 reversal/s with 100% contrast binocularly for 600 consecutive trials and measured the N75-P100 and P100-N145 pattern-reversal visual evoked potential inter-peak amplitudes and N75, P100, N145 latencies for the six blocks of 100 responses. As a measure of habituation we used the slope of the linear regression line of the N75-P100 and P100-N145 peak-to-peak amplitudes. The slope of the linear regression line of the N75-P100 and P100-N145 latencies was also analyzed.

Results: Statistical analysis revealed significant differences between the three groups in the slope index of N75-P100 PR-VEP amplitude, with increased or constant amplitude in the PS group compare to the IGE and ND across the six blocks.

Conclusions: Our results support the notion that photosensitivity is associated with altered control of excitatory and inhibitory cortical processes. The causal relationship between habituation deficit and photo-paroxysmal response needs to be further investigated with longitudinal studies.

Significance: This study supports the hypothesis that suppression of PR-VEP is a sensitive intermediate phenotype, which discriminates patients with photosensitivity from those with generalized epilepsies in pediatric age.