Predicting functional motor potential in chronic stroke patients using diffusion tensor imaging

Abstract

Electrophysiological and neuroimaging studies suggest that the integrity of ipsilesional and inter-hemispheric motor circuits is important for motor recovery after stroke. However, the extent to which each of these tracts contributes to the variance in outcome remains unclear. We examined whether diffusion tensor imaging (DTI)-derived measures of corticospinal and transcallosal tracts predict motor improvement in an experimental neurorehabilitation trial. 15 chronic stroke patients received bihemispheric transcranial direct current stimulation and simultaneous physical/occupational therapy for five consecutive days. Motor impairment was assessed prior to and after the intervention. At baseline, the patients underwent DTI; probabilistic fiber tracking was used to reconstruct the pyramidal tract (PT), alternate descending motor fibers (aMF) and transcallosal fibers connecting primary motor cortices (M1-M1). Ipsilesional corticospinal tracts (PT, aMF) and M1-M1 showed significantly decreased fractional anisotropy (FA) and increased directional diffusivities when compared to age-matched healthy controls. Partial correlations revealed that greater gains in motor functions were related to higher FA values and lower directional diffusivities of transcallosal and ipsilesional corticospinal tracts. M1-M1 diffusivity had the greatest predictive value. An additional slice-by-slice analysis of FA values along the corticospinal tracts demonstrated that the more the ipsilesional FA profiles of patients resembled those of healthy controls, the greater their functional improvement. In conclusion, our study shows that DTI-derived measures can be used to predict functional potential for subsequent motor recovery in chronic stroke patients. Diffusivity parameters of individual tracts and tract combinations may help in assessing a patient’s individual recovery potential and in determining optimal neurorehabilitative interventions.

Structural and Resting-State Brain Connectivity of Motor Networks After Stroke

“…27 Although these tractography studies may be informative, they do require tracing of individual tracts between seed regions and may thus not yet be applicable for routine clinical use. Approaches that try to automatically map all possible fiber tract connections (the connectome) using voxelwise connectivity matrices 28 or try to estimate remote stroke effects from normal connectivity maps 29 may be promising alternatives to tractography, but require further exploration.…”

Impact of White Matter Damage After Stroke

“…To complement these findings, a study in healthy subjects revealed an association of function and microstructure of transcallosal motor connections (Wahl et al, 2007). In chronic stroke patients, DTI-derived measures of transcallosal motor fibres as well as ipsilesional corticospinal tracts (PT and aMF) could be used to explain the therapeutic response to rehabilitation: the more the diffusivity profiles resembled those observed in healthy subjects, the greater a patient's potential for functional recovery (Lindenberg et al, 2011 …”

Extent of Bilateral Neuronal Network Reorganization and Functional Recovery in Relation to Stroke Severity

“…However, final sensorimotor performance outcome correlated positively with FA in ipsilesional corticospinal tract regions subacutely, where poor functional outcome was linked to subacutely low FA, in line with DTI studies in human patients (Thomalla et al, 2004;Puig et al, 2010;Radlinska et al, 2010). Furthermore, a recent experimental rehabilitation trial demonstrated that greater interventioninduced gains in motor function were related to higher FA in transcallosal and ipsilesional corticospinal tracts of chronic stroke patients (Lindenberg et al, 2012). Thus, preserved structural integrity of the ipsilesional corticospinal tract appears to be a critical factor for good functional outcome after unilateral stroke and could therefore be a primary target for therapeutic repair strategies.…”