Abstracts

Functional MR imaging (fMRI) is considered as a valid and non invasive method in assessing language localization in epileptic patients before neurosurgery. This test could be repeated and adapted to the cognitive level of the patient. It also gives more precise information than the Wada test and the results can be combined with those of other investigations such as imaging modalities and EEG.
From our series of 35 epileptic patients who underwent a complete presurgical evaluation (EEG-video monitoring, with subdural grids in 5 of them, structural MRI, interictal FDG-PET, cognitive tests, IQ, and fMRI language study), we selected 6 patients in whom the fMRI study was crucial for the surgical decision. This group (4M and 2F, 24 to 49 years old) included 4 patients with a cryptogenic epilepsy, 3 with a frontal focus (2 left and 1 right) and one with a right parieto-temporal focus, one patient with a left temporal (T1) tumor and one patient with a dual pathology (a post-traumatic lesion on the right parieto-temporal region and a right mesiotemporal sclerosis). All patients with an invasive monitoring underwent a 3D GRE T1-weighted MR sequence with the subdural grids in place. The fMRI protocol included at least a structural T2-weighted sequence and whole brain axial gradient echo echo planar sequences for the functional tasks (TR/TE 3000/50 ms, voxel size 3.6 mm isometric). The language paradigms were all covert and consisted in a verbal fluency task , a reading task , and an auditory task. Each paradigms alternated 6 epochs of rest with 6 epochs of task condition for a total duration of 4 min 48. Statistical t-maps of brain activation were generated with the SPM software and superimposed on the T2-weighted images (slices) and on the 3D T1-weighted images with the grids (surface rendering), after coregistration and with the knowledge of the results of the EEG monitoring.
The patient with the left T1 tumor has his Wernicke area on left T2 and T3. He has been operated without any sequelae. One patient with left frontal focus has his epileptogenic zone near and on Broca area and was considered as a candidate for VNS instead of ressection;
One patient had a bilateral localisation of the Wernicke area but more anterior than the parieto-temporal focus. One patient with a right parieto-temporal focus has his language exclusively lateralized to the left. One patient with a left frontal lobe epilepsy has been improved since his invasive monitoring and prefer to wait before surgery. The last patient with a right frontal focus will be operated in July 2003.
fMRI is reliable and useful for language areas assessment. It can be superimposed to other presurgical technics and gives more precise information than Wada test for language. fMRI should be part of the presurgical evaluation for refractory epilepsy patients or patients with brain tumor to assess the risk and/or the possibility to operate these candidates.