Abstracts

Rationale: Corpus callosotomy (CC) is a well-established palliative procedure for management of medically intractable seizures. Evidence for this procedure’s efficacy in seizure reduction is most notable in generalized epilepsies, especially those presenting as tonic or atonic seizures. CC may also be effective in patients who have focal onset of seizures, particularly with rapid secondary generalization. However, it is not clear whether outcomes can be predicted based on neuroimaging or electroencephalographic (EEG) findings. Therefore, we reviewed our experience at Minnesota Epilepsy Group with regard to seizure outcomes in patients who have undergone CC, paying particular attention to the pre-surgical imaging and EEG characteristics of these patients. Methods: Since 1990, 26 anterior and 64 complete CC procedures have been performed in children and adults under the age of 22. The records of these patients were reviewed, with particular attention to imaging characteristics, EEG findings, seizure semiology and frequency prior to CC, and seizure semiology and frequency at one year following CC. Results: Of 90 patients reviewed, 67 had clear documentation of all required information. Seizure frequency had decreased in 76.1% (n=51) of patients at one year after CC. By comparison, 13.4% (n=9) of patients experienced an increase in seizures, and 10.5% (n=7) of patients experienced no change in seizure frequency. Among the patients reviewed, 66.7% (44) had normal pre-operative brain magnetic resonance imaging (MRI), 26.7% (n=17) had bilateral or diffuse abnormalities, and 6.6% (n=6) had abnormalities localizing to one side. Imaging characteristics were not found to have a significant relationship with seizure frequency at one year after surgery. Next, EEG findings were examined. Patients who demonstrated a focal, multifocal (n=7), or combination of generalized and multifocal patterns of epileptiform activity on EEG (n=55) did not have significantly different outcomes in seizure frequency, as compared to the overall group. Patients who had only a generalized or bisynchronous pattern of epileptiform activity on EEG, in the absence of any focal epileptiform activity (n=3), did trend towards an increase in seizure activity one year following CC, although the results were again not statistically significant. Conclusions: Corpus callosotomy is a palliative procedure for seizure control, and certain seizure semiologies have been shown to have better outcomes following CC than others. Neuroimaging characteristics of the patients reviewed here did not have a significant association with seizure outcome. Additionally, it appears that pre-surgical EEG patterns are not significant in terms of seizure outcomes. However, there is the suggestion that patients who exclusively have a generalized pattern of epileptiform activity may have poorer outcomes. This is an unexpected finding, which may be further investigated in the future with a larger sample group.