The objectives of this project were to assess the frequency of discordance between handedness and evoked MEG language dominance and to compare different testing modalities for language dominance in epilepsy patients.

Retrospective analysis was performed on a dataset of 337 patients who were evaluated by the UPMC Epilepsy Monitoring Unit between June 2010 and February 2021. Data included handedness, evoked MEG (N=173), fMRI (N=23), and Wada testing (N=17). Language dominance was assumed to be the opposite laterality to handedness, and MEG results were coded as consistent or discordant with this prediction. Activation in both hemispheres was coded as bilateral. When available, Wada and fMRI results were coded as either consistent or discordant with MEG. A chi-square test of independence was conducted to determine whether there was an association between handedness and discrepancy with MEG.

Eighty-four percent (N=145) of patients were right-handed, 14.5% (N=25) were left-handed, and 1.2% (N=2) were ambidextrous. Left-handed subjects were significantly more likely to have discordant MEG results (p<0.00001). 3.45% (N=5) of right-handed subjects and 60.0% (N=15) of left-handed subjects were discordant. Additionally, 29.7% (N=43) of right-handed and 36.0% (N=9) of left-handed subjects had bilateral language representation on MEG tests. This difference was not significant (p=0.53). The overall frequency of agreement between MEG and Wada was 58.8% (N=10). 69.6% (N=16) of fMRI scans were consistent with MEG.

Left-handed patients had a higher likelihood of discordance on MEG language dominance testing compared with right-handed subjects. fMRI and Wada testing are likely helpful to clarify the discordant MEG results for presurgical testing in epilepsy patients.