Cocco, GA; (2009) Probabilistic tractography of the whole telencephalic corticospinal tract as a predictive marker of motor recovery in chronic stroke patients. Doctoral thesis , UCL (University College London).

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Abstract

Background: Probabilistic tractography provides a voxel-based connectivity index that reflects fibre organisation and integrity. We aim to quantify the integrity of the whole telencephalic portion of the corticospinal bundle as assessed by probabilistic tractography in patients who suffered from stroke and to investigate whether the integrity of the corticospinal bundle, as assessed by probabilistic tractography, correlates with: (i) the cortical-spinal system integrity as assessed by TMS, (ii) the degree of motor impairment and/or (iii) the degree of functional improvement achieved by the patients during a two week period of intensive upper limb training. Methods: Ten patients chronic stroke patients, in whom weakness of at least wrist and finger extensors and hand interossei was present for at least 48 hours after the onset of the symptomatology of their first-ever stroke, were assessed at least one year later through traditional MRI and diffusion tensor imaging. 9 age-matched controls were also scanned. Patients underwent a two weeks intensive physiotherapy treatment of the upper limb as part of a separate clinical trial. Imaging data were acquired prior to the treatment period. Neurophysiological data and motor impairment scores were also acquired immediately before and after the treatment period. Results: Fractional anisotropy values of the whole telencephalic portion of the corticospinal bundle were able to distinguish between affected and not affected tracts. Moreover, in spite of the small number of patients investigated till now, FA values calculated on the whole telencephalic corticospinal tract seems able to predict the recovery after the rehabilitation treatment. Conclusions: Probabilistic tractography is a useful measure for detecting differences in the affected and unaffected corticospinal bundle, reflecting the fibres disruption consequent to a stroke lesion. A largely automated protocol for the tracking of corticospinal bundle is presented, with the aim to reduce the bias dependent from the manual drawing of the region of interest. Preliminary observations and considerations about the reliability of the various values of fractional anisotropy (calculated through probabilistic tractography in the whole telencephalic corticospinal tract) in predicting the degree of motor impairment and post rehabilitation recovery are discussed.

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