Size Doesn't Matter: Cortical Stroke Lesion Volume Is Not Associated With Upper Extremity Motor Impairment and Function in Mild, Chronic Hemiparesis

Abstract Objectives To determine (1) the relationship between lesion volume and upper extremity (UE) motor impairment using the UE section of the Fugl-Meyer (FM) assessment; and (2) the relationship between lesion volume and UE functional outcomes using the Arm Motor Ability Test (AMAT) Functional Ability (FA) and Time scales. Design Secondary retrospective analysis of randomized controlled trial data. Setting Outpatient rehabilitation clinic. Participants Subjects with chronic stroke (N=139, 83 men; mean age ± SD of all subjects, 56.7±11.2y; mean time ± SD since stroke onset, 59.6±65.6mo; 90 subjects with right hemiparesis) and stable, active, distal UE movement. Intervention Data were collected related to subjects' lesion volume and UE movement before their participation in a multicenter, randomized controlled trial. Main Outcome Measures FM and AMAT. Results Neither age nor lesion volume was related to FM performance. The P value for the regression coefficient of lesion volume was .045 in the AMAT FA model and .016 in the AMAT Time model. Lesion volume accounted for only an additional 1.7% (AMAT FA) to 3.1% (AMAT Time) of the variability in motor function and was not clinically meaningful. Conclusions Data suggest no relationship between lesion volume and UE impairment, and a small, clinically insignificant relationship between lesion volume and UE motor function. Stroke causes metabolic changes in intact regions and diffuse structural loss in anatomically remote regions from the infarction. These other factors may account for variance in motor outcomes after stroke.