Improved signal-to-noise ratio and submillimeter resolution offered by 7T MRI can help in identifying subtle lesions that have escaped detection on 3T MRI. Prior studies provide early evidence to support the use of 7T in optimal diagnosis and management of epilepsy as 7T scans may increase preoperative detection of epileptogenic lesions.

This is a single institution retrospective study of patients who underwent a 7T MRI with seizure protocol between March 2018 and April 2020 in whom an initial 3T MRI was non-diagnostic for a focal structural cause of epilepsy. Electronic medical records were abstracted for epilepsy history and imaging findings.

We identified 50 patients (male 46%; median seizure onset 14 years IQR 8.8-25; median epilepsy duration prior to 7T MRI 8.5 years IQR 3.4 - 15). Of those patients with available ictal scalp EEG (36/50) seizures recorded, temporal lobe epilepsy was present in 13 patients. The median age of 7T scan was 24 years (IQR 18-40) with median interval between the two MRIs 9.8 months (IQR 3.8-23.7). Potentially epileptogenic lesions were found in 18/50 patients (36%): vascular 10%, malformation of cortical development 10%, hippocampal abnormalities 8%, and encephalocele 8%. Among patients with epileptogenic 7T abnormality identified, the lesions were lateralized to the right hemisphere in 12%, left hemisphere 18%, and bilateral 6%. Localization showed frequent involvement of temporal 18% followed by frontal 6%, periventricular 4% and parietal 2%. The epileptogenic 7T abnormality showed complete or partial concordance with ictal scalp EEG onset in 67% of patients.