Abstract 1: Improvement of Sensory Function Following Rehabilitation in Chronic Stroke Is Associated With Increased Cortical Thickness

Abstract

Introduction: Loss of somatosensory function after stroke weakens the ability to adequately relate to our environment, thus significantly reduces quality of life. Neuroplastic processes of sensory recovery are poorly understood. The objective of this study was to identify cortical regions that undergo structural changes (measured by change in cortical thickness (CT)) during sensory recovery. The hypothesis was that for subjects who improve sensory acuity, CT change in regions of the bilateral sensory network correlates with change in sensory acuity. Methods: Chronic stroke survivors were treated with 12-weeks rehabilitation. Outcome measures were sensory acuity (monofilament), Fugl-Meyer upper limb coordination and CT (T1 Magnetic Resonance Imaging). CT change was calculated based on T1 images using Freesurfer longitudinal processing stream. General linear regression modeling identified cortical regions where change in CT was associated with change in sensory acuity after controlling for baseline sensory impairment and change in motor function. Cluster-wise correction for multiple comparisons was conducted using Monte-Carlo simulation at p<0.05. Results: Subjects, who improved in sensory acuity (n=18), were 55.8±13.7 year old; 10% female; 1.8±0.9 years after first ever stroke. Acuity improved from 43.9±14mm to 40.53±13mm (p=0.004). FM improved from 22.4±8 to 34.5±10 (p<0.0001). For the ipsilesional hemisphere, CT increase correlated with sensory improvement in lateral occipital gyrus (size=1543mm2; peak vertex coordinates in MNI space x=-10.9, y=-97, z=10.9, cluster wise p=0.0002) and in middle temporal gyrus (795mm2, x=-57.2, y=-56.5,z=0.9, p=0.002). For the contralesional hemisphere, increased CT was associated with improved monofilament acuity within supramarginal gyrus (930mm2 ; x=47.2, y=-43.0, z=43.2, p=0.0002) and middle temporal gyrus (974mm2; x=53.5, y=-59.6, z=-1.7; p= 0.0001). Conclusion: Rehabilitation produces modality-specific structural brain changes that can be measured by changes in cortical thickness. Improved sensation correlates with increased thickness in bilateral high-order association sensory cortices reflecting a complex nature of sensory rehabilitation.