Quantitative EEG Analyses and Surgical Outcome After Corpus Callosotomy

Abstract

Summary: 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 spike-wave discharges was analyzed by using a cross-correlation analysis and the measurements of amplitude differences between bilateral homologous regions in 22 patients who underwent anterior CCs for intractable symptomatic generalized epilepsies (SGE; 17 patients) and frontal lobe epilepsy (five patients).Results: Interictal generalized synchronous spike-wave (GSSW) bursts in the SGE patients were disrupted and changed to unilateral spike-waves (USWs) in 11 patients and to bilaterally independent spike-waves (BISWs) in six. The 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 for amplitude, suggesting unilaterally predominant epileptogenesis that triggered the secondary bilateral synchrony. Postoperatively, the BISW group had a more marked reduction in IS because of independent discharges from bilateral epileptogenic areas, and the USW group had a greater amplitude difference because of unilateralized spike-waves. In addition, an excellent surgical outcome was related to (a) the preoperative degree of the morphologic similarity of the bilateral spike-waves (only a small variation during a burst of spike-waves) and the few instances of regional changes in the side leading in time and in the side dominant for amplitude; and (b) to large postoperative amplitude differences.Conclusion: Preoperative quantitative EEG analyses enabled us to predict the underlying conditions of epileptogenesis and the surgical outcomes in patients undergoing CC. Key Words: Corpus callosotomy-Epilepsy-Cross-correlation analysis-EEG-Surgical outcome.Because the corpus callosum is thought to be a major pathway in the bilateral generalization of seizure discharges, corpus callosotomies (CCs) have been performed to reduce the frequency and severity of intractable seizures, especially secondarily generalized seizures, and they have provided a marked improvement in seizure control for many patients (1-1 1). Electroencephalogram (EEG) changes reported after CCs consist of a disruption of bilateral synchrony associated with amplitude asymmetry, localization or lateralization of seizure discharges, and the appearance of bilaterally independent spike-waves (BISWs) (3,(12)(13)(14)(15). However, the relation Accepted February 25, 1999.Address correspondence and reprint requests to Dr. T. Matsuzaka at Department of Pediatrics, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852, Japan. E-mail: neuro@net.nagasaku.ac.jp between these EEG changes and patients' surgical outcome has not been clarified, in part because of a lack of quantitative data on the EEG changes. Therefore we analyzed the degree of bilateral synchrony and morphologic similarity o...

The role of the interictal EEG in selecting candidates for resective epilepsy surgery

“…Postoperative EEGs for these six patients demonstrated a reduction in generalized discharges as well as generalized seizures. Some series found that a "lateralized" pattern on the EEG predicted a better outcome or fewer discharges after surgery; however, this finding did not reach significance [69,[71][72][73][74][75][76]. EEG as an independent variable lacks significance in general, and suggests that the interictal EEG is not predictive of outcome [69,[77][78][79][80][81].…”

Predictive value of MEG using gradient magnetic field topography (GMFT) for seizure outcome following anterior corpus callosotomy (ACC) in patients with drop attacks

“…Secondary bilateral synchrony has been diagnosed based on both preoperative EEG and exploring for lateralized abnormalities on neuroimaging postoperatively (Spencer et al, 1985;Matsuzaka et al, 1999). In contrast, Oguni et al (1994) did not detect any significant difference in post-ACC seizure outcomes between patients characterized by generalized spike and waves (GSW) and without a predominant lateralization (Oguni et al, 1994).…”

Evaluation of Interhemispheric Time Difference by Magnetoencephalography Before and After Total Callosotomy-Two Case Reports-

“…Interictal scalp EEG may have no predictive value for the outcome of callosotomy. 16,19) Statistical study has shown a correlation between preoperative quantitative EEG and surgical outcome, 5,6,12) but the EEG selection criteria for individuals remains questionable. Magnetoencephalography (MEG) is known to have higher spatial resolution than EEG because of the negligible distortion caused by the head conductivity.…”

“…Callosotomy is known to diminish several types of seizures, especially drop attacks. 3,4,11,12,19,23,24) Electrophysiologically, callosotomy results in reduction in the frequency of epileptic discharges, lateralization of discharges into one hemisphere, and organization of background activity. 11,21) The corpus callosum must be the most important pathway for bilateral synchrony to obtain favorable seizure outcome after callosotomy.…”