Remote Corticospinal Tract Degeneration After Cortical Stroke in Rats May Not Preclude Spontaneous Sensorimotor Recovery

• Published in: Neurorehabilitation and neural repair Vol. 35; no. 11; pp. 1010 - 1019
• Main Authors: Sinke, Michel R. T., van Tilborg, Geralda A. F., Meerwaldt, Anu E., van Heijningen, Caroline L., van der Toorn, Annette, Straathof, Milou, Rakib, Fazle, Ali, Mohamed H. M., Al-Saad, Khalid, Otte, Willem M., Dijkhuizen, Rick M.
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA SAGE Publications 01.11.2021
• Subjects: Animals; Behavior, Animal - physiology; Corpus Callosum - diagnostic imaging; Corpus Callosum - pathology; Corpus Callosum - physiopathology; Diffusion Tensor Imaging; Disease Models, Animal; Male; Motor Activity - physiology; Neural Pathways - diagnostic imaging; Neural Pathways - pathology; Neural Pathways - physiopathology; Pyramidal Tracts - diagnostic imaging; Pyramidal Tracts - pathology; Pyramidal Tracts - physiopathology; Rats; Rats, Sprague-Dawley; Recovery of Function - physiology; Sensorimotor Cortex - diagnostic imaging; Sensorimotor Cortex - pathology; Sensorimotor Cortex - physiopathology; Stroke - pathology; White Matter - pathology; diffusion magnetic resonance imaging; brain; behavior; stroke; diffusion tractography; corticospinal tract
• ISSN: 1545-9683; 1552-6844
• DOI: 10.1177/15459683211041318

Background. Recovery of motor function after stroke appears to be related to the integrity of axonal connections in the corticospinal tract (CST) and corpus callosum, which may both be affected after cortical stroke. Objective. In the present study, we aimed to elucidate the relationship of changes in measures of the CST and transcallosal tract integrity, with the interhemispheric functional connectivity and sensorimotor performance after experimental cortical stroke. Methods. We conducted in vivo diffusion magnetic resonance imaging (MRI), resting-state functional MRI, and behavior testing in twenty-five male Sprague Dawley rats recovering from unilateral photothrombotic stroke in the sensorimotor cortex. Twenty-three healthy rats served as controls. Results. A reduction in the number of reconstructed fibers, a lower fractional anisotropy, and higher radial diffusivity in the ipsilesional but intact CST, reflected remote white matter degeneration. In contrast, transcallosal tract integrity remained preserved. Functional connectivity between the ipsi- and contralesional forelimb regions of the primary somatosensory cortex significantly reduced at week 8 post-stroke. Comparably, usage of the stroke-affected forelimb was normal at week 28, following significant initial impairment between day 1 and week 8 post-stroke. Conclusions. Our study shows that post-stroke motor recovery is possible despite degeneration in the CST and may be supported by intact neuronal communication between hemispheres.