Objective：Although prediction of functional recovery after lacunar infarction is challenging, quantitative evaluation of brain imaging may be promising. In this article, we investigate association of the amount of corticospinal tract (CST) injury on Computed Tomography (CT) and functional recovery of lacunar infarction in the corona radiata.Methods：In 24 patients with lacunar infarction of the corona radiata, we investigated association of the amount of virtual CST injury with upper and lower limb motor function at 90 days after the stroke onset. The optimal area of the virtual CST to predict motor function was also determined. Finally, we evaluated whether the quantitative CST injury predicted practical motor function regarding activities of daily living.Results：The amount of virtual CST injury, evaluated with Hounsfield unit value of CT, was significantly associated with upper and lower limb function at 90 days after stroke onset. Among them, 6 mm radius CST circle for upper limb had the highest regression coefficient to predict Brunnstrom stage for the upper extremity (R2＝0.69), grip strength (R2＝0.52) and Simple Test for Evaluating Hand function (R2＝0.75). Also, 7 mm radius CST circle for lower limb had the highest regression coefficient to predict Brunnstrom stage for the lower extremity (R2＝0.51), weight bearing index (R2＝0.53) and Berg Balance Scale (R2＝0.52). These virtual CSTs predicted practical function including practical upper limb and ambulation.Conclusion：Quantitative evaluation of CST on CT predicted functional recovery after lacunar infarction of the corona radiata.

Objective：Although prediction of functional recovery after lacunar infarction is challenging, quantitative evaluation of brain imaging may be promising. In this article, we investigate association of the amount of corticospinal tract (CST) injury on Computed Tomography (CT) and functional recovery of lacunar infarction in the corona radiata.Methods：In 24 patients with lacunar infarction of the corona radiata, we investigated association of the amount of virtual CST injury with upper and lower limb motor function at 90 days after the stroke onset. The optimal area of the virtual CST to predict motor function was also determined. Finally, we evaluated whether the quantitative CST injury predicted practical motor function regarding activities of daily living.Results：The amount of virtual CST injury, evaluated with Hounsfield unit value of CT, was significantly associated with upper and lower limb function at 90 days after stroke onset. Among them, 6 mm radius CST circle for upper limb had the highest regression coefficient to predict Brunnstrom stage for the upper extremity (R2＝0.69), grip strength (R2＝0.52) and Simple Test for Evaluating Hand function (R2＝0.75). Also, 7 mm radius CST circle for lower limb had the highest regression coefficient to predict Brunnstrom stage for the lower extremity (R2＝0.51), weight bearing index (R2＝0.53) and Berg Balance Scale (R2＝0.52). These virtual CSTs predicted practical function including practical upper limb and ambulation.Conclusion：Quantitative evaluation of CST on CT predicted functional recovery after lacunar infarction of the corona radiata.