Magnetic resonance imaging markers reflect cognitive outcome after rehabilitation in children with acquired brain injury

PURPOSE To test markers from conventional and diffusion Magnetic Resonance Imaging (MRI) as possible predictors of cognitive outcome following rehabilitation therapy in children with acquired brain injury (ABI). METHODS Twenty-one children (10 boys, mean age 11.6 years, range 7.1-19.4) with stroke or traumatic brain injury underwent MRI including Diffusion Tensor Imaging (DTI) before admission to the rehabilitation centre. The conventional images were scored according to a standardised injury scoring system, and mean Fractional Anisotropy (FA) was determined within the Corpus Callosum (CC), as this structure is hypothesised to play an important role in cognition. Both conventional MRI injury scores and mean FA of the CC and its sub-regions were compared with standard functional cognitive outcome scores. Relationships between MRI indices and cognitive outcome scores were assessed using multiple regression and receiver operating characteristic (ROC) analyses. RESULTS A backwards regression analysis revealed that the mean FA of the CC body and genu and the supratentorial injury score appear to represent the best predictors of outcome, together with the age at rehabilitation and time in rehabilitation. In the ROC analysis, the mean FA values of the CC body and genu and the infratentorial injury score provided the highest sensitivity, while the mean FA of the CC splenium showed the highest specificity for outcome. CONCLUSIONS The conventional MRI injury scores and DTI metrics from the CC reflect cognitive outcomes following rehabilitation. Neuroimaging methods such as MRI with DTI may therefore provide important markers for cognitive recovery after brain injury

Diffusion tensor imaging predicts motor outcome in children with acquired brain injury

BACKGROUND: Rehabilitation in children with acquired brain injury is a challenging endeavour. There is a large variability in motor recovery between patients, and a need to optimize therapies by exploiting cerebral plasticity and recovery mechanisms. This retrospective study aims to identify tract-based markers that could serve as predictors of functional outcome following rehabilitation. METHODS: Twenty-nine children with traumatic brain injury (n = 14) or stroke (n = 15) underwent a 3 T Magnetic Resonance Imaging (MRI) measurement, including Diffusion Tensor Imaging (DTI) between admission to the Hospital and onset of rehabilitation therapy at the Rehabilitation Centre. The Functional Independence Measure for Children (WeeFIM) was routinely applied at admission and discharge from the Rehabilitation Centre. Distinguishing between children with good versus poor functional independence was performed using ROC-analysis. A non-parametric partial correlation analysis between the DTI and WeeFIM motor scores was performed with age, time in rehabilitation, and time of MRI scan after injury as covariates. RESULTS: Mean fractional anisotropy (FA) from the DTI in the ipsilesional corticospinal-tract provided the highest predictive accuracy (sensitivity = 95 %, specificity = 78 %, Youden Index = 0.73, Area under the curve = 0.9), in comparison to the lesion volume or other clinical variables. Mean FA of the ipsilesional corticospinal-tract correlated positively with the WeeFIM discharge motor scores (ρ = 0.547, p = 0.004). Prediction was poorer for the lesion volume or Glasgow Coma Scale. CONCLUSION: The results suggest that DTI data could improve the prediction of functional outcome after rehabilitation in children and adolescents with stroke or traumatic brain injury. Specifically, mean FA shows the highest predictive accuracy in comparison to lesion volume or clinical scales

Comparison of DTI analysis methods for clinical research: influence of pre-processing and tract selection methods

BACKGROUND The primary aim was to compare fractional anisotropy (FA) values derived with different diffusion tensor imaging (DTI) analysis approaches (atlas-based, streamline tractography, and combined). A secondary aim was to compare FA values and number of tracts (NT) with the clinical motor outcome quantified by the functional independence measure for children (WeeFIM). METHODS Thirty-nine DTI datasets of children with acquired brain injury were analysed. Regions of interest for the ipsilesional corticospinal tract were defined and mean FA and NT were calculated. We evaluated FA values with Spearman correlation, the Friedman and Wilcoxon tests, and Bland-Altman analysis. DTI values were compared to WeeFIM values by non-parametric partial correlation and accuracy was assessed by receiver operating characteristics analysis. RESULTS The FA values from all approaches correlated significantly with each other (p < 0.001). However, the FA values from streamline tractography were significantly higher (mean ± standard deviation (SD), 0.52 ± 0.08) than those from the atlas-based (0.42 ± 0.11) or the combined approach (0.41 ± 0.11) (p < 0.001 for both). FA and NT values correlated significantly with WeeFIM values (atlas-based FA, partial correlation coefficient (ρ) = 0.545, p = 0.001; streamline FA, ρ = 0.505, p = 0.002; NT, ρ = 0.434, p = 0.008; combined FA, ρ = 0.611, p < 0.001). FA of the atlas-based approach (sensitivity 90%, specificity 67%, area under the curve 0.82) and the combined approach (87%, 67%, 0.82), provided the highest predictive accuracy for outcome compared to FA (70%, 67%, 0.67) and NT (50%, 100%, 0.79, respectively) of the streamline approach. CONCLUSION FA values from streamline tractography were higher than those from the atlas-based and combined approach. The atlas-based and combined approach offer the best predictive accuracy for motor outcome, although both atlas-based and streamline tractography approaches provide significant predictors of clinical outcome

An Effect of bilingualism on the auditory cortex

Two studies (Golestani et al., 2007; Wong et al., 2008) have reported a positive correlation between the ability to perceive foreign speech sounds and the volume of Heschl's gyrus (HG), the structure that houses the auditory cortex. More precisely, participants with larger left Heschl's gyri learned consonantal or tonal contrasts faster than those with smaller HG. These studies leave open the question of the impact of experience on HG volumes. In the current research, we investigated the effect of early language exposure on Heschl's gyrus by comparing Spanish–Catalan bilinguals who have been exposed to two languages since childhood, to a group of Spanish monolinguals matched in education, socio-economic status, and musical experience. Manual volumetric measurements of HG revealed that bilinguals have, on average, larger Heschl's gyri than monolinguals. This was corroborated, for the left Heschl's gyrus, by a voxel-based morphometry analysis showing larger gray matter volumes in bilinguals than in monolinguals. Since the bilinguals in this study were not a self-selected group, this observation provides a clear demonstration that learning a second language is a causal factor in the increased size of the auditory cortex.This work was supported by grants from the Spanish Ministerio de Ciencia e Innovación (JCI-2009-04492, PSI2010-20168; SEJ2009-09072, Consolider-Ingenio2010-CDS-2007-00012), the Catalan Government (SGR 2009-1521), and the French National Agency for Research (ANR 2010 BLAN 1403 01). N.S.-G. received the prize ICREA Acadèmia for excellence in research, funded by the Generalitat de Catalunya. We thank Kimberly Brink for the English correction of the manuscript

An Effect of bilingualism on the auditory cortex

Two studies (Golestani et al., 2007; Wong et al., 2008) have reported a positive correlation between the ability to perceive foreign speech sounds and the volume of Heschl's gyrus (HG), the structure that houses the auditory cortex. More precisely, participants with larger left Heschl's gyri learned consonantal or tonal contrasts faster than those with smaller HG. These studies leave open the question of the impact of experience on HG volumes. In the current research, we investigated the effect of early language exposure on Heschl's gyrus by comparing Spanish–Catalan bilinguals who have been exposed to two languages since childhood, to a group of Spanish monolinguals matched in education, socio-economic status, and musical experience. Manual volumetric measurements of HG revealed that bilinguals have, on average, larger Heschl's gyri than monolinguals. This was corroborated, for the left Heschl's gyrus, by a voxel-based morphometry analysis showing larger gray matter volumes in bilinguals than in monolinguals. Since the bilinguals in this study were not a self-selected group, this observation provides a clear demonstration that learning a second language is a causal factor in the increased size of the auditory cortex.This work was supported by grants from the Spanish Ministerio de Ciencia e Innovación (JCI-2009-04492, PSI2010-20168; SEJ2009-09072, Consolider-Ingenio2010-CDS-2007-00012), the Catalan Government (SGR 2009-1521), and the French National Agency for Research (ANR 2010 BLAN 1403 01). N.S.-G. received the prize ICREA Acadèmia for excellence in research, funded by the Generalitat de Catalunya. We thank Kimberly Brink for the English correction of the manuscript