Abstracts

Rationale: Corpus callosotomy is a well-established surgical procedure for palliative seizure management, particularly effective in patients experiencing disabling seizures such as drop attacks. However, the optimal extent of callosal disconnection tailored to individuals with various seizure types remain to be incompletely understood. We explored whether the extent of section in corpus callosotomy could be tailored according to seizure type.

Methods: We retrospectively reviewed patients with drug-resistant epilepsy who underwent corpus callosotomy at a single center between 2004 and 2023. Included were patients aged ≥6 years with ≥2 years of postoperative follow-up. Seizures were classified according to the 2025 ILAE classification.

Results: Of the 36 patients reviewed (mean age 14.6 ± 6.9 years; mean follow-up 8.8 ± 5.2 years), worthwhile seizure reduction ( >50% reduction) was achieved in 68.4% (anterior 4/5 or total callosotomy) and 45.4% (anterior 2/3 callosotomy) among those with normal or focal structural etiologies, whereas only 33.3% of patients with diffuse structural abnormalities achieved a worthwhile response. By seizure type, all patients with generalized atonic seizures responded favorably regardless of the extent of section, whereas half of those with bilateral tonic–clonic seizures responded. In generalized tonic seizures, favorable outcomes were seen in 60.0% (anterior 4/5 or total) and 33.3% (anterior 2/3). SEEG exploration in a patient with tonic seizures who did not respond after anterior 2/3 callosotomy revealed low-voltage fast activity at seizure onset localized to the unilateral mesial frontal region.

Conclusions: Atonic seizures respond favorably to anterior corpus callosotomy, whereas the effectiveness of corpus callosotomy for tonic seizures depends on the extent of section. Invasive studies of tonic seizures may inform localization of the early epileptogenic network, particularly within the mesial frontal region adjacent to the corpus callosum.

Funding: None