Strongly lateralized activation in language fMRI of atypical dominant patients-implications for presurgical work-up.
OBJECTIVE
Functional magnetic resonance imaging (fMRI) is being used increasingly for language dominance assessment in the presurgical work-up of patients with pharmacoresistant epilepsy. However, the interpretation of bilateral fMRI-activation patterns is difficult. Various studies propose fMRI-lateralization index (LI) thresholds between +/-0.1 and +/-0.5 for discrimination of atypical from typical dominant patients. This study examines if these thresholds allow identifying atypical dominant patients with sufficient safety for presurgical settings.


METHODS
65 patients had a tight comparison, fully controlled semantic decision fMRI-task and a Wada-test for language lateralization. According to Wada-test, 22 were atypical language dominant. In the remaining, Wada-test results were compatible with unilateral left dominance. We determined fMRI-LI for two frontal and one temporo-parietal functionally defined, protocol-specific volume of interest (VOI), and for the least lateralized of these VOIs ("low-VOI") in each patient.


RESULTS
We find large intra-individual LI differences between functionally defined VOIs irrespective of underlying type of language dominance (mean LI difference 0.33+/-0.35, range 0-1.6; 15% of patients have inter-VOI-LI differences >1.0). Across atypical dominant patients fMRI-LI in the Broca's and temporo-parietal VOI range from -1 to +1, in the "remaining frontal" VOI from -0.93 to 1. The highest low-VOI-LI detected in atypical dominant patients is 0.84.


CONCLUSIONS
Large intra-individual inter-VOI-LI differences and strongly lateralized fMRI-activation in patients with Wada-test proven atypical dominance question the value of the proposed fMRI-thresholds for presurgical language lateralization. Future studies have to develop strategies allowing the reliable identification of atypical dominance with fMRI. The low-VOI approach may be useful.
Wellmer
Jörg
J
Department of Epileptology, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany. joerg.wellmer@ukb.uni-bonn.de
Weber
Bernd
B
Weis
Susanne
S
Klaver
Peter
P
Urbach
Horst
H
Reul
Jürgen
J
Fernandez
Guillen
G
Elger
Christian E
CE
D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D004292:Dominance, Cerebral; D004827:Epilepsy / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D005625:Frontal Lobe / Q000098:blood supply*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007802:Language; D007807:Language Tests; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood
D010100:Oxygen