Abstract Body: Background
The Medical Research Council (MRC) scale is used to assess the impact of stroke on muscle strength. Shoulder abduction and finger extension, collectively (SAFE), have been suggested to have prognostic value for stroke outcomes (e.g. PREP-2), and been recommended for use in screening for clinical trials. Few studies have assessed the neuroanatomy associated with SAFE, and other upper extremity MRC scores after stroke. In this study, we used voxel-based lesion symptom mapping (VLSM) to assess lesion locations associated with worse SAFE scores, as well as other movements assessed by the MRC scale.
Methods
A trained therapist assessed 12 individual MRC scores at the: shoulder (flexion, extension, abduction, internal and external rotation), elbow (flexion and extension), wrist (flexion and extension) and fingers (flexion, extension and abduction). Clinical neuroimaging (MRI and/or CT) was collected for all participants, and lesioned voxels traced by trained assessors and normalized to a standard template space. VLSM analysis was conducted for all 12 MRC scale scores, and SAFE score, using NiiStat. Only voxels lesioned in >10% of participants were tested.
Results
We recruited 226 stroke participants at 2 weeks post-stroke (mean age=62.6; Males=147; Right Hemisphere=131; Ischemic=199, Hemorrhagic=27). VLSM analysis showed that worse SAFE scores were significantly associated with lesions in voxels in the left and right corona radiata, adjacent and dorsal to the lateral ventricles, and consistent with the upper portions of the corticospinal tract in each hemisphere. Additionally, voxels in the putamen were also significantly associated with worse SAFE scores. Interestingly, all other MRC scores were also associated with similar lesion topography to SAFE.
Conclusion
This work demonstrates a consistent association between SAFE scores and corticospinal tract damage. The integrity of the corticospinal tract has frequently been suggested as a biomarker of stroke recovery. These findings shed light on why SAFE might be a valuable prognostic tool for stroke recovery, and a quick and efficient screening tool for clinical trials. Despite increasing use of SAFE, other muscle weakness, assessed by the MRC scale, is also represented by the same neuroanatomic regions and may share similar prognostic abilities. Continued investigation into effective prognostic tools for upper-limb recovery is warranted.