Abstracts

Rationale: Drug resistant epilepsy (DRE) secondary to focal cortical dysplasia (FCD) over the sensorimotor cortex presents an extremely challenging clinical scenario. Achieving seizure freedom without compromising motor function is the holy grail. We describe 2 such paediatric cases.

Methods: We reviewed our epilepsy surgery records from 2012 to 2021. We found 2 cases that fit above criteria. Both cases had similar clinical course:
Case 1) 8- & 7-year-old boys with seizure onsets at 6 and 3 years of age respectively.
Case 2) Motor function preserved over dysplastic motor cortex: seen on functional MRI & tractography.

Clinically, no focal motor deficits initially. Later both presented with reduced motor function of concordant side & worsened cognition, possibly an unusual expression of high focal interictal burden. Presurgical evaluation showed concordant data. Both patients’ seizure semiology suggested non motor onset: slightly more obvious in case 1 than case 2 (had 3 seizure semiologies). Hence a hypothesis evolved of being able to limit the resection behind central sulcus while not compromising on seizure freedom.

Unique features:
Case 1: Forced right handedness. He underwent 1 stage surgery with intraoperative electrocorticography (EcoG), neuronavigation, motor evoked potentials (MEP) with cortical mapping of eloquent areas. EcoG showed very frequent spikes over entire FCD with highest amplitude in FCD overlying postcentral gyrus.

Case 2: Stereo EEG implantation done given the complex seizure semiology. 21 spontaneous seizures showed onset in mesial end of post central gyrus. Primary motor hand function was elicited over lateral precentral gyrus. Stimulation elicited a seizure in only 1 contact in precentral gyrus. Intraoperatively, EcoG, central sulcus mapping, eloquent motor area mapping with cortical stimulation and neuronavigation was used. EcoG using 48 contact grid fortuitously captured a spontaneous seizure- onset and spread stayed postcentral.

In both cases we limited the resection of the FCD to behind the central sulcus. Postop EcoG showed no spikes. MEPs were intact.

Results: 1) Neither developed any permanent motor deficit postoperatively; in fact motor function and the EEG improved. 2) Case 1 has stayed seizure free at 5 years with 1 seizure on tapering last AED (Engel 1D). 3) Case 2 is seizure free at 2 months postop. 4) Histopathology of case 1 showed FCD 1C; awaited in case 2. 5) Both have residual FCD (seen on MRI) over the motor cortex.

Conclusions: Multimodality evaluation—presurgical and intraoperative—is needed to confirm the surgical hypothesis if eloquence is to be preserved while aiming for seizure freedom—particularly EcoG—contributed significantly especially in single stage surgery. Importantly, FCDs may not be uniformly epileptic—these 2 cases exemplify this^1,2 and resections may not always need to be extensive.

Funding: Please list any funding that was received in support of this abstract.: Nil.