Abstracts

Rationale: Corpus Callosotomy (CC) is a palliative epilepsy procedure for patients with intractable epilepsy, primarily those with atonic or tonic seizures. The likelihood of Corpus Callosotomy being effective is higher than an additional antiseizure medication once a patient is refractory, with historical data showing seizure freedom in up to 50% of patients undergoing CC. However, while decreases in seizure frequency have been demonstrated, the dynamics of seizure reduction and recurrence have not been elucidated for the pediatric population.


Methods: Utilizing electronic medical record (EMR) data within the Children’s Hospital of Philadelphia, all patients who underwent complete microsurgical CC in the past 7 years were identified. Longitudinal epilepsy histories were reconstructed. Seizure severities were categorized in monthly time bins using the seizure frequency categories championed by the (Pediatric) Epilepsy Learning Health System (ELHS, PELHS). Longitudinal seizure frequencies and neurologic phenotypes were extracted from the EMR for all individuals and recorded in a standardized framework using the Human Phenotype Ontology (HPO). Seizure frequency pre- and post-surgery were analyzed using a Wilcoxon ranked sum test with continuity correction.


Results: 37 patients who underwent CC were identified from the EMR. All patients had clinical seizures, with most having tonic (97%, n=36) and/or atonic seizures (95%, n=35). The average seizure onset for this cohort was 34 months of age and an average age at surgery of 12 years. Seizure histories were reconstructed for 10 individuals, consisting of 1,172 patient months, and capturing 35 seizure types with a median seizure onset of 14.5 months (IQR 6 month-24 months). The most common seizure types were bilateral tonic-clonic (n=7), myoclonic (n=7), tonic (n=7), and atonic seizures (n=6). In addition, 60% (n=6) of patients experienced one or more episodes of status epilepticus. Developmental delay and hypotonia were present in 80% (n=8) and 70% (n=7) of patients, respectively. Although 50% of individuals became seizure free within the first month post-surgery, only a single individual remained seizure-free. However, comparing seizure frequency pre- and post-surgery demonstrated a significant reduction in seizure frequency (p < 0.001).


Conclusions: Outcomes after epilepsy surgery have been broadly studied at the population level, but granular data regarding the epilepsy trajectories following CC have not yet been established. While generally considered effective for tonic and atonic seizures, not all individuals become seizure free following CC. Temporary seizure freedom is achieved in 50% of patients after surgery. However, even in individuals with return of seizures, seizure frequencies are significantly reduced. Thus, establishing predictors of surgical outcome is critical and will inform future candidate selection for surgery and guide pre-surgical counseling for families.

Funding: Intramural funding from the Children’s Hospital of Philadelphia: Omics Maximizing Grant; NINDS