Memory Performance is Related to Language Dominance as Determined by the intracarotid amobarbital procedure

Objective The goal of this study was to explore the relationship between language and memory lateralization in patients with epilepsy undergoing the intracarotid amobarbital procedure. Methods In 386 patients, language lateralization and memory lateralization as determined by laterality index (LI) were correlated with each other. Results Language lateralization and memory lateralization were positively correlated (r = 0.34, P \u3c 0.01). Correlations differed depending on the presence and type of lesion (χ2 = 7.98, P \u3c 0.05). LIs correlated significantly higher (z = 2.82, P \u3c 0.05) in patients with cortical dysplasia (n = 41, r = 0.61, P \u3c 0.01) compared with the group without lesions (n = 90, r = 0.16, P \u3e 0.05), with patients with hippocampal sclerosis falling between these two groups. Both memory (P \u3c 0.01) and language (P \u3c 0.01) LIs were higher in right- compared with left-sided lesions. Conclusion Correlation of language and memory is more pronounced in patients with structural lesions as compared with patients without lesions on MRI

Atypical Language Lateralization in Epilepsy Patients

Purpose:  To investigate whether atypical language dominance in epilepsy patients is related to localization and type of lesions. Methods:  Four hundred and forty-five epilepsy patients received bilateral Wada testing. Language was classified as left (L), right (R), bilateral-dependent (BD, speech arrest after left and right injections), or bilateral-independent (BI, no speech arrest after either injection). Groups were compared regarding handedness and magnetic resonance imaging (MRI) lesions. Lesions were classified as “early” (congenital), “late” neocortical (acquired after birth), and hippocampal sclerosis (HS). Results:  Of all patients, 78% were L, 6% R, 7% BD, and 9% BI. Right-handers with left lesions did not differ from those without lesions. Left-handers with normal MRI did not differ from right-handers. Left-handers with early left lesions were most likely R (46%). Left-handers with late neocortical left lesions were most likely BD (37%); those with left HS were most likely BD (33%) or L (33%). In both latter groups, R language was rare (13% and 11%, respectively). Discussion:  The data support the notion that R dominance may indicate development of functional language areas in the right hemisphere following an early insult. BD language may signal defective maintenance of right hemispheric language caused by a late left hemispheric insult at a time when left dominance has already started to develop. In contrast, BI language may represent a variant with functional language representation in both hemispheres

Temporal lobe white matter asymmetry and language laterality in epilepsy patients.

Recent studies using diffusion tensor imaging (DTI) have advanced our knowledge of the organization of white matter subserving language function. It remains unclear, however, how DTI may be used to predict accurately a key feature of language organization: its asymmetric representation in one cerebral hemisphere. In this study of epilepsy patients with unambiguous lateralization on Wada testing (19 left and 4 right lateralized subjects; no bilateral subjects), the predictive value of DTI for classifying the dominant hemisphere for language was assessed relative to the existing standard-the intra-carotid Amytal (Wada) procedure. Our specific hypothesis is that language laterality in both unilateral left- and right-hemisphere language dominant subjects may be predicted by hemispheric asymmetry in the relative density of three white matter pathways terminating in the temporal lobe implicated in different aspects of language function: the arcuate (AF), uncinate (UF), and inferior longitudinal fasciculi (ILF). Laterality indices computed from asymmetry of high anisotropy AF pathways, but not the other pathways, classified the majority (19 of 23) of patients using the Wada results as the standard. A logistic regression model incorporating information from DTI of the AF, fMRI activity in Broca\u27s area, and handedness was able to classify 22 of 23 (95.6%) patients correctly according to their Wada score. We conclude that evaluation of highly anisotropic components of the AF alone has significant predictive power for determining language laterality, and that this markedly asymmetric distribution in the dominant hemisphere may reflect enhanced connectivity between frontal and temporal sites to support fluent language processes. Given the small sample reported in this preliminary study, future research should assess this method on a larger group of patients, including subjects with bi-hemispheric dominance

Language Outcome after Left Anterior Temporal Lobectomy in Patients with Discordant Functional Magnetic Resonance Imaging and Intracarotid Sodium Amobarbital Testing Results

Language Outcome after Left Temporal Anterior Lobectomy in Patients with Discordant Functional Magnetic Resonance Imaging and Intracarotid Sodium Amobarbital Testing Results Rationale: Previous research has examined concordance rates between Wada and fMRI language lateralization indices (LIs) and has yielded variable results with limited post-surgical language outcome data. Therefore, additional evidence of the concurrent and predictive validity of fMRI LIs is needed. We will calculate Wada/fMRI LI concordance rates in the largest sample to date, investigate predictors of discordance and examine the ability of each procedure to predict language outcome in discordant cases. Methods: A consecutive series of 229 presurgical epilepsy patients who underwent Wada testing and fMRI will be included in the study. Wada LIs (% correct inject right –% correct inject left condition) were calculated based on performance on comprehension, naming, repetition and reading language tasks. fMRI LIs ((L-R)/(L+R) where L = number of activated left hemisphere voxels and R = number of activated right hemisphere voxels) were calculated for four ROIs using a published semantic decision/tone decision task. Discordance will be determined using a difference score of .50. Regression analyses will be performed to investigate factors that are predictive of discordance and the predictive value of Wada and fMRI in discordant cases. Results: Available by conference date. Conclusions: We hypothesize a discordance rate of approximately 1 in 10. We hypothesize predictors of discordance may be posterior cerebral artery filling, crossflow ratings, abnormal vasculature, duration of drug effect, fMRI behavioral performance and activation threshold, motion artifacts, MTS, and IQ

Language Outcome After Left Temporal Lobectomy in Patients with Discordant fMRI and Sodium Amobarbital Testing Results

The rationale for this study was to examine 1) language lateralization discordance rates between fMRI and the IAT in pre- surgical epilepsy patients and 2) naming outcome after left ATL in a group of patients for whom IAT and fMRI language LIs were discordant. Participants were 229 consecutive pre-surgical epilepsy patients who underwent the IAT and fMRI. IAT LIs (% correct inject right -% correct inject left condition) were calculated based on performance on comprehension, naming, repetition and reading language tasks. The fMRI LIs [(L-R)/(L+R) where L = number of activated left hemisphere voxels and R = number of activated right hemisphere voxels) were calculated for lateral, angular gyrus, temporal, and frontal regions of interest (ROIs) using a published semantic decision task. Discordance was determined using cut scores and difference scores for each method. Regression analyses were performed to investigate predictors of discordance. Additionally, regression formulas developed from a separate sample for predicting language outcome using fMRI and IAT LIs were applied to the discordant cases so that observed and predicted outcome scores could be compared with each method. Discordance rates ranged from 14-17%, depending on ROI. Atypical language dominance on fMRI was most predictive of discordance. Of discordant cases who underwent left ATL, language outcome was more accurately predicted by each method in approximately half the cases. When fMRI indicates left language dominance, IAT LI concordance is high. However, when fMRI indicates atypical language dominance, concordance rates with the IAT decrease. Post-operative language outcome data suggests that the IAT and fMRI each predict outcome in certain cases, suggesting some error variance with each mapping method

Imaging memory in temporal lobe epilepsy: predicting the effects of temporal lobe resection

Functional magnetic resonance imaging can demonstrate the functional anatomy of cognitive processes. In patients with refractory temporal lobe epilepsy, evaluation of preoperative verbal and visual memory function is important as anterior temporal lobe resections may result in material specific memory impairment, typically verbal memory decline following left and visual memory decline after right anterior temporal lobe resection. This study aimed to investigate reorganization of memory functions in temporal lobe epilepsy and to determine whether preoperative memory functional magnetic resonance imaging may predict memory changes following anterior temporal lobe resection. We studied 72 patients with unilateral medial temporal lobe epilepsy (41 left) and 20 healthy controls. A functional magnetic resonance imaging memory encoding paradigm for pictures, words and faces was used testing verbal and visual memory in a single scanning session on a 3T magnetic resonance imaging scanner. Fifty-four patients subsequently underwent left (29) or right (25) anterior temporal lobe resection. Verbal and design learning were assessed before and 4 months after surgery. Event-related functional magnetic resonance imaging analysis revealed that in left temporal lobe epilepsy, greater left hippocampal activation for word encoding correlated with better verbal memory. In right temporal lobe epilepsy, greater right hippocampal activation for face encoding correlated with better visual memory. In left temporal lobe epilepsy, greater left than right anterior hippocampal activation on word encoding correlated with greater verbal memory decline after left anterior temporal lobe resection, while greater left than right posterior hippocampal activation correlated with better postoperative verbal memory outcome. In right temporal lobe epilepsy, greater right than left anterior hippocampal functional magnetic resonance imaging activation on face encoding predicted greater visual memory decline after right anterior temporal lobe resection, while greater right than left posterior hippocampal activation correlated with better visual memory outcome. Stepwise linear regression identified asymmetry of activation for encoding words and faces in the ipsilateral anterior medial temporal lobe as strongest predictors for postoperative verbal and visual memory decline. Activation asymmetry, language lateralization and performance on preoperative neuropsychological tests predicted clinically significant verbal memory decline in all patients who underwent left anterior temporal lobe resection, but were less able to predict visual memory decline after right anterior temporal lobe resection. Preoperative memory functional magnetic resonance imaging was the strongest predictor of verbal and visual memory decline following anterior temporal lobe resection. Preoperatively, verbal and visual memory function utilized the damaged, ipsilateral hippocampus and also the contralateral hippocampus. Memory function in the ipsilateral posterior hippocampus may contribute to better preservation of memory after surgery

Atypical language organization following perinatal infarctions of the left hemisphere is associated with structural changes in right-hemispheric grey matter.

AIM To assess how atypical language organization after early left-hemispheric brain lesions affects grey matter in the contralesional hemisphere. METHOD This was a cross-sectional study with between-group comparisons of 14 patients (six female, 8-26 years) with perinatal left-hemispheric brain lesions (two arterial ischemic strokes, 11 periventricular haemorrhagic infarctions, one without classification) and 14 typically developing age-matched controls (TDC) with functional magnetic resonance imaging (fMRI) documented left-hemispheric language organization (six female, 8-28 years). MRI data were analysed with SPM12, CAT12, and custom scripts. Language lateralization indices were determined by fMRI within a prefrontal mask and right-hemispheric grey matter group differences by voxel-based morphometry (VBM). RESULTS FMRI revealed left-dominance in seven patients with typical language organization (TYP) and right-dominance in seven patients with atypical language organization (ATYP) of 14 patients. VBM analysis of all patients versus controls showed grey matter reductions in the middle temporal gyrus of patients. A comparison between the two patient subgroups revealed an increase of grey matter in the middle frontal gyrus in the ATYP group. Voxel-based regression analysis confirmed that grey matter increases in the middle frontal gyrus were correlated with atypical language organization. INTERPRETATION Compatible with a non-specific lesion effect, we found areas of grey matter reduction in patients as compared to TDC. The grey matter increase in the middle frontal gyrus seems to reflect a specific compensatory effect in patients with atypical language organization