Symmetry and interhemispheric propagation of paediatric photoparoxysmal response.

AIM OF THE STUDY

To investigate the speculated interhemispheric symmetry and the pattern of propagation of paediatric photoparoxysmal response.

CLINICAL RATIONALE FOR THE STUDY

Quantitative analysis of the photoparoxysmal response (PPR) to intermittent photic stimulation is a promising method of assessing photosensitivity (PS). The pattern of PPR propagation underlies the model used for calculations. The generalisation of a discharge should correspond with the parameters objectively characterising the PPR in both cerebral hemispheres. However, to date no evidence of a postulated symmetry has been demonstrated.

MATERIALS AND METHODS

Our analysis was performed by comparing the EEG amplitude and interhemispheric coherence (ICoh) in both hemispheres in 100 non-epileptic individuals of both sexes, aged 5-18 years, with PS grade IV (the PPR group) and without PS (the control group). The amplitude and ICoh values were recorded and analysed statistically.

RESULTS

The distribution of amplitude values between the hemispheres was comparable in both groups, but was significantly different between the PPR group and the control group. Individual tracks of propagation revealed hemispheric symmetry. Interhemispheric coherence values were significantly higher in occipital, temporal and fronto-polar areas in children with PS.

CONCLUSIONS AND CLINICAL IMPLICATIONS

This study provides objective evidence of interhemispheric symmetry in paediatric PPR, which supports the link with generalised seizures. Interhemispheric propagation is facilitated in children with PS, and propagation is more likely in the occipital and temporal regions.