gms | German Medical Science

Objective: Little is known about the affection and degree of functional restoration and reorganization of the motor system in patients who show modest or no recovery of motor function in the long-term following stroke. Initial results indicate the remaining corticospinal integrity to be a key prerequisite for efficient rehabilitation and the extent of CST-damage to predict the outcome in individual patients. We examined the possibility to predict functional restoration and the motor pattern of rehabilitation in chronic stroke by DTI-based probabilistic tractography of cortico-spinal tract (CST).

Method: Twelve stroke patients underwent a twenty-day training program. Before and after the training clinical evaluation with the Fugl-Meyer Assessment (FMA) was performed. In the pre-training phase MR images (T1, diffusion-weighted images) were acquired.Oxford-Cambridge FMRIB Software Library diffusion toolbox was used for pre-processing and analysis of the DTI-data. Motor cortex (M1) and peduncles were manually identified and segmented in both hemispheres in the individual T1 images. FDT (FMRIB diffusion Toolbox) was used to generate Diffusivity images. Probabilistic tractography was carried out starting from the peduncle on each side. Probability of peduncle to ROI connectivity was estimated intra-hemispherically. For every ROI-to-ROI connection a lateralization index was calculated. Every training-day the patients performed kinematic exercises and assessments using a gravity-supporting arm-exoskeleton (Armeo Spring, HOCOMA, Zürich, Switzerland). Training algorithms were designed for highly repetitive ADL-like grasping exercises. FMA-development and kinematic measurements were compared to initial CST-integrity, assessed by probabilistic DTI.

Results: All patients improved significantly in several kinematic parameters and the covered training volume in the course of the rehabilitative program. There were significant differences in the endpoint of volume and kinematic parameters between different patients with respect to the CST integrity. Patients with CST integrity regained more likely a natural movement pattern as performed by healthy subjects. These patients gained a significantly higher FMA-score at the end of the training regime as well.

Conclusions: Probabilistic DTI-based CST connectivity predicts the clinical outcome and functional restoration of chronic stroke patients following a rehabilitative training.