Utility of additional dedicated high-resolution 3T MRI in children with medically refractory focal epilepsy

In patients with medically refractory epilepsy and normal magnetic resonance imaging (MRI), high-resolution dedicated MRI may identify cryptic lesions. The aim of this study was to assess improvement in lesion detection and its impact on clinical management, using additional high-resolution dedicated 3T MRI in children with medically refractory epilepsy who had normal 3T epilepsy protocol MRI. Children who had resective epilepsy surgery and suspected focal cortical dysplasia (FCD) or normal 3T epilepsy protocol MRI were included. Those with other diagnosis on MRI including tumor and hippocampal sclerosis were excluded. Patients who had normal MRI on 3T epilepsy protocol underwent dedicated high-resolution 3T MRI through the epileptogenic zone, guided by video EEG, Magnetoencephalography and FDG-PET data. 101 patients with at least 1 year follow-up were included. Twenty-nine of 44 (66%) patients who had normal epilepsy protocol MRI had a lesion identified on dedicated high-resolution MRI. The addition of dedicated high-resolution MRI to standard epilepsy protocol increased sensitivity from 53.1% (95%CI: 40%–66%) to 85.9% (95%CI: 75%–93%). Identified lesions were concordant to surgical resection in all patients and guided depth/strip electrode insertion in 20/25 (80%) patients who underwent staged resection. Dedicated MRI detected small deep seated lesions in 10/20 (50%), and guided depth electrodes placement, without which it would not be feasible, as the lobar location of epileptogenic zone from other non-invasive tests were not sufficiently precise. Patients with non-lesional epilepsy on standard epilepsy protocol MR may benefit from high-resolution dedicated MRI to aid identification of an underlying lesion, which could impact surgical management and improve seizure control.