Abstracts

Rationale: Hemimegalencephaly (HME) is a rare cortical malformation characterized by unihemispheric hypertrophy, early-onset intractable epilepsy, and developmental delay. Staged transarterial embolization (TAE) to reduce seizure burden in neonates/infants awaiting anatomic/functional hemispherectomy may be an alternative to anatomic or functional hemispherectomy. This study characterizes the seizure burden before and after embolization in infants with hemimegalencephaly and refractory epilepsy.


Methods: Retrospective study of infants less than 3 months admitted to Children’s National Hospital from 2018-2023. Clinical variables collected include age, sex, EEG background, seizure onset, seizure types and seizure duration before, during and after the TAE procedure. Seizure burden was classified in accordance with the International League Against Epilepsy Society (ILAE) terminology. Descriptive statistics were used to describe the clinical variables.


Results: Eight infants met the criteria for TAE. The mean age of seizure onset was 10 days old (0-28 days) with the average age of first embolization at 49 days old (13-71 days). Seven infants had diffuse hemispheric cortical involvement and one patient had multilobar involvement. Fifty percent of the patients (4/8) underwent 3 stages of embolization (ACA, MCA, and then PCA territories), 3 patients had 4 stages and 1 patient had 5 stages. The most common medications on admission included phenobarbital, levetiracetam, and vigabatrin.



In the first 7 days following seizure onset, 62% (5/8) of the patients had an average of = >1 electroclinical seizures/hour, 50 % had = >1 electrographic seizures/hour. All the patients with electroclinical seizures had motor-clonic seizures (5/8), and of these patients two patients also had motor tonic, one had non-motor autonomic, and one patient had non-motor behavioral arrest seizures.



In the 24 hours prior to embolization #1, 62.5% (5/8) of the patients had an average of = >1 electrographic seizures/hour, of whom only one had >= 1 electroclinical seizures/hour. In the 24hours after embolization #1 and #2, there was a transient reduction in seizure frequency in 37.5% (3/8) patients with a return to baseline electrographic seizure frequency in the 24-72h prior to the next embolization. Following embolization #3, there was a progressive and sustained improvement in seizure frequency with only 12.5% (1/8) of the patients with an average of = >1 electrographic seizures/hour. After the final embolization (#3 in 4/8 patients, #4 in 3/8 patients, #5 in 1/8 patients), electrographic seizure freedom was ultimately achieved in 6/8 patients and with rare electrographic-only seizures in 2 patients (Table 1).




Conclusions: TAE is an effective alternative approach to reduce seizure burden in neonates or infants who are too young to undergo anatomic/functional hemispherectomy. Following the final TAE procedure, there was a complete resolution of electroclinical seizures in all patients, with resolution of the electrographic seizures in 75% of the cohort, and rare seizures in 25% of the patients.




Funding: None.