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Left‐sided Interictal Epileptic Activity Induces Shift of Language Lateralization in Temporal Lobe Epilepsy: An f MRI Study
Author(s) -
Janszky Jozsef,
Mertens Markus,
Janszky Imre,
Ebner Alois,
Woermann Friedrich G.
Publication year - 2006
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1111/j.1528-1167.2006.00514.x
Subject(s) - ictal , hippocampal sclerosis , lateralization of brain function , audiology , voxel , epilepsy , temporal lobe , psychology , boston naming test , population , white matter , medicine , cardiology , magnetic resonance imaging , neuroscience , radiology , cognition , environmental health , neuropsychology
Summary: Purpose: By using speech‐activated functional MRI ( f MRI), we investigated whether the frequency of left‐sided interictal epileptic activity (IED: spikes or sharp waves on the EEG) is associated with atypical speech lateralization. Methods: We investigated 28 patients (13 men, aged 17–59 years) with left‐sided mesial temporal lobe epilepsy (MTLE) and 11 patients with right‐sided MTLE as a control population. Only patients with unilateral hippocampal sclerosis with unilateral IED were included. For f MRI of individual patients, we contrasted images sampled during covert word generation with a low‐level rest condition. With SPM99, an individual comparison for the contrast “word generation versus resting inactivity” was conducted. To characterize speech lateralization in individual patients, we calculated asymmetry indexes (AIs): the difference between activated left‐sided and right‐sided voxels was divided by all activated voxels. Analyzing long‐term EEG, the first 2 min of each hour were evaluated for the frequency of IED. Univariate associations with AIs were assessed by Pearson's correlation and by t test. When testing the independent associations, multivariate linear regression was performed. Results: The AIs in patients with left‐sided MTLE were 0.40 ± 0.53 on average (range, −0.83 to +1.0), whereas in right‐sided MTLE, they were 0.78 ± 0.15 (p = 0.029). For the further investigations, we included left‐sided MTLE patients only. The median frequency of IED was six per hour (range, 0–240). Higher IED frequency was correlated with left‐right shift of lateralization of speech f MRI activity (p = 0.002). Conclusions: Higher left‐sided spike frequency in MTLE was associated with a left–right shift of speech representation, suggesting that chronic frequent interictal activity may induce a reorganization of speech lateralization.