Clinical practice of language fMRI in epilepsy centers: a European survey and conclusions by the ESNR Epilepsy Working Group

Abstract

Purpose: To assess current clinical practices throughout Europe with respect to acquisition, implementation, evaluation, and interpretation of language functional MRI (fMRI) in epilepsy patients.

Methods: An online survey was emailed to all European Society of Neuroradiology members (n = 1662), known associates (n = 6400), and 64 members of European Epilepsy network. The questionnaire featured 40 individual items on demographic data, clinical practice and indications, fMRI paradigms, radiological workflow, data post-processing protocol, and reporting.

Results: A total of 49 non-duplicate entries from European centers were received from 20 countries. Of these, 73.5% were board-certified neuroradiologists and 69.4% had an in-house epilepsy surgery program. Seventy-one percent of centers performed fewer than five scans per month for epilepsy. The most frequently used paradigms were phonemic verbal fluency (47.7%) and auditory comprehension (55.6%), but variants of 13 paradigms were described. Most centers assessed the fMRI task performance (75.5%), ensured cognitive-task adjustment (77.6%), trained the patient before scanning (85.7%), and assessed handedness (77.6%), but only 28.6% had special paradigms for patients with cognitive impairments. fMRI was post-processed mainly by neuroradiologists (42.1%), using open-source software (55.0%). Reporting was done primarily by neuroradiologists (74.2%). Interpretation was done mainly by visual inspection (65.3%). Most specialists (81.6%) were able to determine the hemisphere dominance for language in more than 75% of exams, attributing failure to the patient not performing the task correctly.

Conclusion: This survey shows that language fMRI is firmly embedded in the preoperative management of epilepsy patients. The wide variety of paradigms and the use of non-CE-marked software underline the need for establishing reference standards.

Keywords: Epilepsy; Europe; Language; Survey; fMRI.

Fig. 1

Institutional responses (number) per country. Countries with no responses are shaded gray. An asterisk indicates responding center located in Réunion (an overseas department and region of France, member of the European Union, and an island in the Indian Ocean, east of Madagascar and southwest of Mauritius)

Fig. 2

Clinical practice and indications for language fMRI. a Specialists who perform fMRI. b Physicist support. c Techniques used for assessing language lateralization. d Main indication for language fMRI. e Frequency of total language fMRI exams per month. f Frequency of language fMRI exams per month with epilepsy patients. EEG electroencephalogram, nTMS navigated transcranial magnetic stimulation, *total responses = 68, **total responses = 67

Fig. 3

Radiological workflow. a Centers assessing the fMRI task performance. b Centers ensuring that the fMRI tasks are adjusted to the patient’s cognitive status. c Centers training the patient before the scan. d Centers having special paradigms for patients with cognitive impairments. e Centers assessing handedness

Fig. 4

Language fMRI data post-processing. a Specialists who post-process fMRI. b Software used for post-processing. c Centers using a statistical threshold. d Centers using a lateralization index. e Centers using a ROI analysis to determine activation. ROI region-of-interest, *total responses = 57, **total responses = 60

Fig. 5

fMRI data presentation, storage and transfer. a Presentation format. b Storage system. c Data transfer to a neuronavigation system

Fig. 6

Language fMRI reporting and interpretation. a Specialists who report fMRI. b Proportion of exams in which specialists are able to determine language dominance. c Most common reason for the fMRI examination not being conclusive. *Total responses = 62, **total responses = 74