Extraction of corticospinal tract microstructural properties in chronic stroke

Information about the structural integrity of the corticospinal tract (CST) from diffusion-weighted imaging can improve our ability to understand motor outcomes in people with upper limb impairment after stroke, especially those with severe impairment. Yet, there is no consensus on which method of CST generation most accurately represents function and impairment in individuals with chronic stroke.

The aim of the study was to compare different methods of CST reconstruction and resulting microstructural properties, as well as the relationship between these properties and motor function and impairment. Fifteen individuals with mild-moderate impairment and 15 with severe impairment who were in the chronic phase post-stroke underwent a diffusion-weighted imaging scan and motor function and impairment assessments.

Different relationships existed between reconstruction methods, microstructural properties, and impairment and function. In severe stroke, fractional anisotropy (FA) emerged over and above apparent diffusion coefficient (ADC) and tract number to index CST integrity; FA correlated with impairment and function, whereas ADC and tract number did not correlate. No significant differences between methods or microstructural properties were found in mild-moderate stroke.

Our study demonstrates that CST reconstruction method influences the extraction of microstructural integrity in individuals with chronic severe stroke, with FA appearing to be the most representative method. A similar line of investigation is warranted earlier post-stroke.

Differences in this data set highlight the need to establish a common methodology for CST reconstruction and analysis which may eliminate discrepancies in interpreting DWI and enhance biomarker use post-stroke for motor function.