Abstract W MP56: Corticospinal Tract Injury And Motor Impairment After Stroke

Abstract

INTRODUCTION: Restorative therapies improve outcomes by promoting plasticity in specific neural systems. Imaging biomarkers may provide a useful measure of injury to these systems and so might help determine if a patient has sufficient substrate remaining to derive therapeutic benefit. The pyramidal system is affected in most patients with stroke and has features useful for biomarker testing, especially the anatomy of the corticospinal tract (CST) in the cerebral peduncle (CP). The current study compared clinical performance of 3 published metrics of CST injury. METHODS: Patients with stable motor deficits 3-24 months after stroke were enrolled in 1 of 2 trials that provided 3-4 weeks of arm motor therapy. From baseline MRI, ipsilesional CST [1] white matter integrity (DTI FA in CP), [2] atrophy (CP area), and [3] extent of injury (% lesion overlap with stroke) were measured and compared to Fugl-Meyer (FM) score at baseline, as well as change in FM score across treatment. RESULTS: The 47 patients had substantial baseline motor deficits (FM= 36±14), medium-sized infarcts (30±45cc), and were 5±2.5 mo post-stroke. Baseline motor deficits were related to CST white matter integrity (r=0.49, p=0.0005) more than to % CST injured (r=-0.40, p=0.006). On the other hand, treatment-related motor gains were related only to % CST injured (r=-0.45, p=0.002). A global injury measure (total infarct volume) was weaker than CST injury in correlating with FM scores. None of the 3 CST injury measures were correlated. CONCLUSIONS: The CST injury characteristics related to motor outcome are different from the CST injury characteristics that predict capacity for improvement with therapy. In both cases, these measures did not explain the majority of variance in motor status/improvement, emphasizing that many factors in addition to CST injury are important to motor outcome after stroke. The finding that motor gains are related to % CST injured but not CST integrity provides insights into the neurobiology of brain repair in humans.