Abstracts

Rationale: About 1/3 of adults and 1/4 of children with epilepsy develop drug‐resistant epilepsy (DRE). Focal resection is often unsuitable for diffuse or bilateral seizures, and corpus callosotomy (CC) is a common alternative. Data suggests "drop" seizures respond well to CC, yet optimal candidates, surgical approach, and outcome predictors are unclear. We analysed a retrospective DRE cohort in our institution that underwent CC to contribute to this data, detailing demographics, neurodevelopmental history, surgical technique, and epilepsy outcomes, emphasizing “drop” seizures.

Methods: Between 2005–2024, CC was performed on 80 DRE patients (86 total CCs as four underwent staged/revision procedures). Clinical and operative notes and EEG and MRI data were extracted, and organised using institutional AI tools. Seizure types followed ILAE classification. “Drop” seizures – a heterogeneous group of atonic, tonic, GTC, or focal seizures causing falls – were treated as a unique semiology.

Results: There were 51 males and 29 females. Mean age at first seizure: 1.8 (± 2.7) years; at CC 11 (± 5.4) years. At CC 71/85 (84 %) were verbal and 42/86 (49 %) ambulatory. 74/86 (86 %) had > 2 seizure types; 46/86 (54 %) had > 3. “Drop” (83/86; 97 %) and tonic (64/86; 74 %) were most common. 38/86 (44 %) ≥ 1 epilepsy syndrome: 29 (34 %) had IESS and 22 (26 %) had LGS. 35/86 (41 %) had ≥ 1 prior epilepsy surgery, most often VNS (26; 30 %) and CC (8; 9 %).

Of the CC cases, 18 (21 %) were anterior, two (2 %) posterior, and 66 (77 %) complete. Four were staged; two anterior-to-complete, one anterior-to-complete-to complete, and one complete-to-complete-to-posterior. Nine (10 %) had coincident surgeries: three frontal disconnections, three hemispheric disconnections, two frontal biopsies, and one frontal resection.

Mean perioperative stay was 8.9 (± 7.7) days. 38 (44 %) had complications; fever/infection (9; 10 %) and enteral tube placement for poor intake (8; 9 %) were most common. 21 (24 %) had ≥ 1 further surgeries: VNS (13; 15 %), repeat CC (6; 7 %), hemispherectomy (4; 5 %). Mean time to repeat surgery was 21.6 (± 12.6) months.

85/86 (99 %) had follow-up. Mean time to one-year follow-up was 10.8 (± 4.7 months); and to final follow-up (49.1 ± 45.3 months). At one year, 82/85 (96 %) noted “drop” seizure outcomes: 31 (38 %) free, 32 (39 %) improved, 19 (23 %) not improved. 83/85 (97 %) noted “non-drop” seizure outcomes, 12 (14 %) free, 46 (55 %) improved, 25 (30 %) not improved. At final follow-up, 82/85 (96 %) noted “drop” outcomes: 31 (38 %) free, 31 (38 %) improved, 20 (24 %) not improved. 83/85 (97 %) noted “non-drop” outcomes: 9 (11 %) free, 46 (55 %) improved, 28 (34 %) not improved.

Conclusions: Our study reflects prior CC series in DRE with “drop” seizures.[1] We further find that initial seizure response appears to be sustained over time in most patients. Ongoing work includes stratifying outcomes via case factors (such as age and technique at CC) to identify predictors of seizure freedom and improvement. Prospective studies remain essential to validate optimal patient selection and surgical approach for CC in DRE.

1. Chourasia et al. Epilepsia Open. 2023;8(4):1596–1601. doi:10.1002/epi4.12819.

Funding: N/A.