Abstracts

Rationale: Callosotomies have been used mainly in children with drop-attacks in intractable epilepsy. The procedure has been used less frequently since the vagus nerve stimulator was introduced for the same indication. Callosotomy has however got some revival. We present data on callosotomy in the Swedish epilepsy surgery program 1990-2004. Methods: The Swedish National Epilepsy Register has national coverage and encompasses data on all patients operated in Sweden since 1990. For the purpose of the present study we analysed data from the period 1990-2004 regarding all callosotomy procedures. Seizure outcome is reported, even if the procedure is mainly palliative to prevent drop attacks and is also sometimes used to protect a healthier hemisphere in staging procedures such as early stages of Rasmussen encephalitis. Our definition of complications is that a minor complication is fully resolved ? 3 months, while a major complication persists and to some extent affects daily life. Results: In all 85 callosotomies were performed, 68 anterior, 5 posterior and 12 complete. In 14 cases it was performed as a reoperation. Onset age of epilepsy was (mean; median, Q1; Q3) 3.7; 2.0; 0.4; 5.0 and age at surgery was 16.6; 14.0; 5.2; 23.3. In 42% the imaging was normal or inconclusive. IQ level was ?70 in 7.1%, 50-69 in 40.0% and below 50 in 52.9 %. Preoperative monthly seizure frequency was 396; 150; 50; 360. Four patients (4.7%) had undergone invasive evaluation. Postoperative seizure frequency was 169; 50; 3; 106. Of the patients with a completed 2-year follow up four patients became seizure free (5.4 %), 9 (12.2%) had more than 75 % reduction of seizure frequency, 16 (21.6 %) had 50-75% reduction of seizure frequency and 45 (60.8%) less than 50 % reduction. The four patients who became seizure free had a preoperative seizure frequency of 78; 31; 2; 107, which is almost half of what the remaining patients had. The number of callosotomies performed was 55 in1990-94, 23 in1995-99 and 7 in 2000-04. In the complete patient material the number of surgical complications were 5 (5.8%) minor (4 wound infections and one pulmonary embolism) and 1 (1.2%) major ( a subdural hematoma resulting in a slight hemiparesis and mutism). Conclusions: In spite of decreasing use, corpus callosotomy can be of certain benefit for selected patients, and may lead to a substantial reduction of seizure frequency. Even if seizure freedom is not the primary goal some patients do become seizure free and in this material 29 patients (39.2%) had a seizure reduction of more than 50%. Callosotomy should be considered when there is no focality, MRI negativity, bilateral synchrony in the EEG and frequent drop attacks. In this material callosotomy was a safe procedure, with a low risk for complications. In Sweden there is a consensus to try vagus nerve stimulation first, and to consider callosotomy if the effect of VNS is insufficient.