Quantitative EEG analyses and surgical outcome after corpus callosotomy

Purpose: To clarify the relation between quantitative electroencephalogram (EEG) findings and outcome following corpus callosotomy (CC), Methods: The degree of bilateral synchrony and morphologic similarity of sp ike-wave discharges was analyzed by using a cross-correlation analysis and the measurements of amplitude differences between bilateral homologous regi ons in 22 patients who underwent anterior CCs for intractable symptomatic g eneralized epilepsies (SGE; 17 patients) and frontal lobe epilepsy (five pa tients). Results: Interictal generalized synchronous spike-wave (GSSW) bursts in the SGE patients were disrupted and changed to unilateral spike-waves (USWs) i n 11 patients and to bilaterally independent spike-waves (BISWs) in six. Th e USW group had better surgical outcome than the BISW group. Preoperatively , the USW group had significantly lower interhemispheric synchrony (IS) and fewer regional changes in the side leading in time and the side dominant f or amplitude, suggesting unilaterally predominant epileptogenesis that trig gered the secondary bilateral synchrony. Postoperatively, the BISW group ha d a more marked reduction in IS because of independent discharges from bila teral epileptogenic areas, and the USW group had a greater amplitude differ ence because of unilateralized spike-waves. In addition, an excellent surgi cal outcome was related to (a) the preoperative degree of the morphologic s imilarity of the bilateral spike-waves (only a small variation during a bur st of spike-waves) and the few instances of regional changes in the side le ading in time and in the side dominant for amplitude; and (b) to large post operative amplitude differences. Conclusion: Preoperative quantitative EEG analyses enabled us to predict th e underlying conditions of epileptogenesis and the surgical outcomes in pat ients undergoing CC.