Gradual lesion expansion and brain shrinkage years after stroke.

Abstract

Lesioned brains of patients with stroke may change through the course of recovery; however, little is known about their evolution in the chronic phase. Here, we aimed to quantify the extent of lesion volume change and brain atrophy in the chronic poststroke brain using magnetic resonance imaging. Optimized T1-weighted scans were collected more than once (time between visits=2 months to 6 years) in 56 patients (age=36-90 years; time poststroke=3 months to 20 years). Volumetric changes attributable to lesion growth and atrophy were quantified with automated procedures. We looked at how volumetric changes related to time between visits, using nonparametric statistics, after controlling for age, time poststroke, and brain and lesion size at the earlier time. Lesions expanded more in patients who had longer time-intervals between their imaging sessions (partial rank correlation ρ=0.56; P<0.001). The median rate of lesion growth was 1.59 cm(3) per year. Across patients, the whole-brain atrophy rate was 0.95% per year, with accelerated atrophy in the ipsilesional hemisphere. We show gradual lesion expansion many years after stroke, beyond that expected by normal aging and after controlling for other variables. Future studies need to understand how structural reorganization enables long-term recovery even when the brain is shrinking.