Transverse topographical analysis of petit mal discharges: diagnostical and pathogenic implications.

The analysis, so far neglected, of the transverse distribution of the paroxysmal bilaterally synchronous activities (PBSA) of petit mal leads to differentiate two topographical varieties of discharges: a lateral variety, where the spike-and-wave patterns present two symmetrical maxima one on each side of the skull, and a medial variety, where the paroxysmal activity exhibits a maximal voltage on the midsagittal area of the scalp. In both cases the EEG patterns involve the frontal areas. In a group of 46 children, referred for petit mal, we have studied 3 main clinical parameters: the symptomatology of the absence, the evolution and the associations of the disease. This study results in the individualization of two forms of petit mal: (1) one marked by lateral discharges, simple absences, a good prognosis and non-specific associations with other epilepsies; (2) the other by medial discharges, complex absences, a poor prognosis and a high rate of associations with other forms of generalized epilepsies. The discussion is devoted to the pathogenic implications of the transverse topographical analysis of the PBSA of petit mal and more generally of bilaterally synchronous activities, paroxysmal or not, expressing physiological or pathological processes.