Abstracts

Corpus callosotomy (CC) is a procedure that has been shown to be effective in improving seizure control for patients who do not have a clear localized or lateralized seizure onset (i.e., not clear resective surgical candidates). A CC historically has been most helpful in tonic seizures, particularly tonic drops in children. It has been our suspicion through the years that some patients who undergo a CC (anterior 2/3 and complete CC) may ultimately be focal resective candidates in that following the CC, a lateralized and/or localized seizure onset can be identified. Therefore, we reviewed our experience at the Minnesota Epilepsy Group in patients who underwent both a CC and a resective procedure. Since 1991, 75 anterior 2/3 and 30 complete CCs have been performed in children. Of these patients, one had resective surgery as well. The records of these patients were reviewed with particular attention to seizure type/epilepsy syndrome, time of surgical procedure, and seizure outcome. Of the thirteen patients who underwent both a CC (anterior only with or without completion), four underwent a resection with a CC (Group I). The remaining nine patients had the procedures spread over 9 months to 7 years (Group II). Seizure types and EEG correlates included tonic, atypical absence, generalized tonic-clonic and complex partial without a clearly localized EEG onset. Of the Group I patients, all had mixed seizure types (combination of generalized tonic-clonic, tonic, myoclonic, and atypical absence). The outcome of these patients was: three had Engel class I or II, one had Engel class III, and one had Engel class IV outcomes. In Group II, six had Engel class I or II outcome, two had Engel class III, and one had Engel class IV outcome. All patients who underwent resection surgery had a frontal lobe (all or part) included in the resection. Eight had either multiple lobes (all or partial) resected as well. One had a functional hemispherectomy. Details regarding specific seizure types, etiology (if known) will be discussed as to how they relate to the timing of the procedures in these two groups as well as how the EEG findings changed. Corpus callosotomy is a palliative procedure for seizure control. Some patients may be suspected of having a focal seizure disorder, but only after or in association with a CC can the EEG lateralize or localize seizure onset. In some patients with multifocal pathology (such as tuberous sclerosis), a CC may ultimately reveal a dominant focus that may respond to a successful focal resection. Indicators for the resection include a lateralized EEG and/or a focal component to the seizure semiology.