Presurgical EEG‐fMRI shows promise in difficult‐to‐localise focal epilepsy


By Michael Woodhead

5 Dec 2019

Experience at one Australian centre supports the use of EEG-fMRI to define the epileptic focus in patients with refractory focal epilepsy.

Clinicians at the Austin Hospital in Melbourne say their use of the imaging technique over the last 16 years has shown that it is feasible in a tertiary centre and can aid surgical planning in this very complex patient cohort.

In a retrospective review of 118 patients with drug-refractory, difficult-to-localise focal epilepsy, they found that 50% of EEG-fMRI studies were successful in detecting interictal epileptiform discharges (IEDs) and mapping the distribution of activity associated with them. The results critically influenced the decision to offer surgery for 17% of the successful studies.

Writing in Epilepsia, Professor Graeme Jackson and colleagues say their results and those of other preliminary studies suggest that surgery based on localisation from the EEG-fMRI result can lead to good seizure outcomes.

The review found that in the 118 patients who underwent EEG-fMRI pre-surgical assessment, 59 had epileptic activity present and 51 had a significant BOLD response.

Of the 21 patients who underwent surgery, the EEG-fMRI results had a critical impact on the decision in 10 patients (17%), and was supportive of surgical localisation in 11 patients. Of these patients good surgical outcomes  (ILAE class 1 or 2) were seen in 80% and 73% respectively.

The success rate of the imaging in localising epileptic activity improved from 42% prior to 2012 to 67% after new technology was adopted. And IEDs were seen more often during EEG-fMRI when performed on hospital inpatients than in outpatients.

Professor Jackson said there were many challenges to establishing routine use of EEG-fMRI technology in tertiary settings, including cost and expertise, as well as a turnaround time of weeks for analysis.

Nevertheless these barriers could be overcome to have results that would help inform decisions on surgery for patients with refractory focal epilepsy.

The next step is to evaluate  whether EEG-fMRI ultimately benefit individual patients and improve clinical outcomes, the study authors said.

“We therefore consider it is time for a systematic, well-controlled, and suitably powered clinical trial, to evaluate whether EEG-fMRI can improve outcomes for patients.”

“Only with this evidence will it be possible to accurately estimate the potential cost vs benefit of routine clinical EEG-fMRI for presurgical planning in epilepsy, and to argue for the additional resourcing of radiology (MRI) and neurophysiology (EEG) that will be needed to enable provision of this technology more widely across epilepsy centres,” they concluded.

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