Abstracts

Rationale: Children with medically refractory epilepsy caused by heterotopia and in some cases associated with other cerebral malformations often require surgical intervention.  Intraoperative MRI (iMRI) assistance with resection and ablation surgery may improve seizure outcomes. Methods: We retrospectively identified patient who underwent surgical intervention from October 2011 to June 2017 at the Children's National Medical Center with at least 6 month follow up post op.  The database was queried for demographics, iMRI, pathology, Engel outcome, morbidity and complications.   Results: A total of  6 patients underwent heterotopia surgery at our center. Four patients underwent surgery assisted with iMRI.  Age ranged from 6 months to 15 years old (2 female and 4 male).  The types of seizures were tonic (1), focal (4 – three of which presented as facilitated spasms) and 1 patient had focal and myoclonic seizures.  Of the six patients, two have Aicardi syndrome.  Four patients had periventricular heterotopia and two had both periventricular and transmantle heterotopia.  The heterotopias were at the white matter (1), gray matter (4) and both (1).   All six patients had multiple heterotopias (in 4, it was unilateral and in 2, it was bilateral).  Two patients also had associated focal cortical dysplasia (FCD).  Surgery done included Visualase assisted with iMRI (3) and resection of FCD and heterotopia (2).  One patient had an excision of heterotopia and temporal lobectomy but required a second surgery for excision of residual heterotopia and complete disconnection of the occipital with iMRI. Three out of six (50%) patients had Engel 1 outcome:  one had Visualase with evidence of thermal injury to the heterotopia, 1 had resection of the heterotopia and FCD and 1 had excision of the heterotopia plus a temporal lobectomy.  The last patient required a second surgery.  Two out of 3 patients had iMRI. One patient who had Visualase with iMRI and another with resection of FCD and heterotopia had Engel 2 outcome.  In the Engel 2 outcomes, it was unclear if there was thermal injury to the heterotopia post-surgery and the other patient had extensive frontal polymicrogyria and Aicardi syndrome.  One patient with Aicardi syndrome had Engel 4 outcome, there were continued seizures but decreased duration of clusters and possible improved focus in school performance.  The follow up MRI showed suspicion for FCD.There were no post resection complications. Conclusions: This limited observational study,  supports that the use of iMRI and Visualase  improves seizure outcomes if with evidence of complete resection or thermal injury.  The type of heterotopia, single or multiple heterotopias, and seizure type did not consistently seem to impact surgical outcome.  The study showed that  poor outcomes were seen in patients with a preexisting genetic diagnosis or where the associated FCD was not identified pre-surgery.  No neurologic deficits were seen. Funding: None