Analysis of Clinical Utility of Functional MRI in Neurosurgical Decision-Making in Focal Epilepsy

Functional MRI (fMRI) has proven valuable in presurgical planning for people with brain tumors. However, it is underutilized for patients with epilepsy, likely due to less data on its added clinical value in this population. We reviewed clinical fMRI referrals at the QEII Health Sciences Center (Halifax, Nova Scotia) to determine the impact of fMRI on surgical planning for patients with epilepsy. We focused on reasons for fMRI referrals, findings and clinical decisions based on fMRI findings, as well as postoperative cognitive outcomes.

We conducted a retrospective chart review of patients who underwent fMRI between June 2015 and March 2021.

Language lateralization represented the primary indication for fMRI (100%), with 7.7% of patients also referred for motor and sensory mapping. Language dominance on the side of resection was observed in 12.8% of patients; in 20.5%, activation was adjacent to the proposed resection site. In 18% of patients, fMRI provided an indication for further invasive testing due to the risk of significant cognitive morbidity (e.g., anterograde amnesia). Further invasive testing was avoided based on fMRI findings in 69.2% of patients. Cognitive outcomes based on combined neuropsychological findings and fMRI-determined language dominance were variable.

fMRI in epilepsy was most often required to identify hemispheric language dominance. Although fMRI-determined language dominance was not directly predictive of cognitive outcomes, it helped identify patients at low risk of catastrophic cognitive morbidity and those at high risk who required additional invasive testing.