Anterior Corpus Callosotomy in the Treatment of Medically Intractable Epilepsy: Multicenter Study in Japan
Authors: Baha H. , Mayanagi Y. , Mihara T. , Sakaki T. , Tanaka T. 
Published: August 2005

Purpose: Corpus callosotomy has been extensively used in the past 25 ycars Tor the treatment of patients with medically intractable epilepsy who do not qualify for resective surgery. However, several issues remain controversial; i.e., the criteria for patient selection, the timing of the operation, the extent of the callosal division, and the significance of postoperativc EEG changes. We report on the results of anterior corpus callosotomy (ACC) in 53 intractable seizure patients undertaken in a multiccnter analysis in Japan to define predictive outcome factors.

Methods: 53 patients with more than I year postoperative follow‐up (mean 43.2 months) were included. Age at the time of operation ranged from 5 to 44 years (mean 19.9), and age at the onset of epilepsy ranged from 0.3 to 23 years (mean 6.3). Preoperative diagnoses were cryptogenic or symptomatic generalized epilepsy (SGE) (34 patients), frontal lobe epilepsy (FLE) (17 patients), and severe myoclonic epilepsy in infancy (2 patients). Seizure outcome at the time of the most recent follow‐up was classified into 5 classes: Free, with complete elimination of seizure; Excellent, with >SO% reduction in seizure frequency; Good, with >50% reduction in seizure frequency;: Poor, with no significant change; Worse, with worsening of seizures and / or unacceptable neurological deficit. The relationships between outcome and clinical factors such as epileptic syndrome, seizure type, age at surgery, age of onset, duration of epilepsy, preoperative IQ, extent of callosol division, and postoperative EEG changes were analyzed.

Results: 36 of 53 patients (67.9%) showed significant improvement after the surgery. The outcome was seizure free in 4 (7.576), excellent in 18 (34.0%), good in 14 (26.4%), and poor in 17 patienfs (32.1%). There was no worse case, Four seizure‐free patients were included in pediatric group (under 15 years). 70.6% of the patients with SGE and 64.7% of those with FLE showed a significant improvement. In addition, 1 each of the 2 patients with SME showed a good and poor outcome, respectively. Significant improvement occurred in 70%‐80% of all the seizure types except for simple partial seizure (40.0%) andcomplex partial seizure (46.7%). Complete elimination of seizure was obtained in 38.1 % of drop attack, 33.3% of generalized tonic‐clonic seizure, 33.3% of myoclonic seizure. 30.0% of partial seizure with secondary generalization, and 27.8% of atypical absence. None of the clinical factors correlated significantly with the outcome cxcept for a shorter duration of epilepsy in the seizure free patients. A tzndency of a better outcome was observed in the pediatric group (p =0.093), when seizure onset was after age 1 (p=0.339), in those with a higher IQ (p = 0. I38), and when there was a disappearance or lateralizetion of thc slow spike and wave to the unilateral hemisphere on postoperative EEG (p = 0.159). There was no clear relationships between the extent of the callosal division and the outcome.

Conclusion: The results suggest that ACC is most profitably performed during the early stage of illness, except in those patients with seizure onset before age 1 associated with severe brain dysfunction. Availability of a chronological developmental IQ during infancy and computer analysis of generalized epileptiform activity prior to surgery will likely improve the quality of case selection and therefore, the surgical outcome.