ASSOCIATION BETWEEN CLINICAL FEATURES AND WHITE-MATTER MICROSTRUCTURAL INTEGRITY IN CHRONIC AND SEVERE UPPER-LIMB MOTOR DEFICITS AFTER A BRAIN LESION

F. Kaneko^1,2, Y. Miyawaki^1,2,3, W. Kuwahara^1,2, M. Okawada^1,2, K. Tanamachi^1,2, M. Yoneta², M. Kawakami²

¹Tokyo Metropolitan University, Department of Physical Therapy, Faculty of Health Sciences Graduate School of Health Sciences, Tokyo, Japan, ²Keio University School of Medicine, Department of Rehabilitation Medicine, Tokyo, Japan, ³National Institute of Advanced Industrial Science and Technology, Human Augmentation Research Center, Chiba, Japan

Background: Severe upper-limb motor deficits after a brain lesion are common complications that drastically disturb patients’ ability to perform daily activities. Such motor deficits can result from corticospinal tract (CST) damage; however, their principal characteristics and the potential of CST damage to determine the extent of impairment remain unclear. Meanwhile, other indices might also affect motor deficits and determine their severity, forming various subtypes within chronic and severe upper-limb motor deficits.

Purpose: This study aimed to clarify the relationship between clinical features and neural bases of chronic and severe upper-limb motor deficits post brain lesion through exploratory analyses.

Methods: We enrolled 45 patients with brain lesions in this study. Fluid-attenuated inversion recovery magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) were performed using a 1.5-T MRI scanner with a head coil. To identify white-matter regions, we created 37 regions of interest (ROIs) using the International Consortium for Brain Mapping DTI-81 atlas. Fractional anisotropy (FA) in each ROI was calculated as an index of regional white-matter microstructural integrity. Severe and chronic upper-limb motor deficits, including spasticity, were assessed using clinical scales. Regarding their scores, we first conducted a principal component analysis that statistically summarized the clinical features in two principal components (PC). We then performed a path analysis (multiple regression model) with FA values in the affected posterior internal capsule (pIC), unaffected pIC, affected anterior internal capsule (aIC), and unaffected aIC as independent variables, and two PC scores as dependent variables. Furthermore, we confirmed the coefficients of determination to investigate whether their FA values can significantly explain the variance in each PC score.

Results: Principal component analysis showed that the clinical features of chronic and severe upper-limb motor deficits can be described as a comprehensive severity (PC1) and a tradeoff relationship between proximal motor functions and distal spasticity (PC2). Path analysis revealed significant standardized path coefficients from the affected pIC to PC1 and the FA of the affected aIC to PC2. The coefficient of determination in PC1 was significant, whereas that in PC2 was not.

Conclusions: Results of the relationship between PC1 and pIC suggest that the pIC comprising the CST contributes to the severity of upper-limb motor deficits to the greatest extent. Furthermore, this study suggests that upper-limb motor deficits can be characterized according to the degree of aIC damage by forming a trade-off relationship between proximal motor functions and distal spasticity.

Implications: We revealed a significant relationship between clinical features and regional white-matter microstructural integrity in chronic and severe upper-limb motor deficits after a brain lesion. This is a fundamental neurological finding underlying the clinical features in chronic and severe upper-limb motor deficits after a brain lesion.

Funding acknowledgements: This study was supported by AMED (Grant Number JP18he0402255) and JSPS KAKENHI (Grant Number JP19H01088).

Keywords:
Motor function
Brain lesion
Diffusion tensor imaging

Topics:
Neurology: stroke
Neurology
Disability & rehabilitation

Did this work require ethics approval? Yes

Institution: Shonan Keiiku Hospital

Committee: The Ethics Committee of the Shonan Keiiku Hospital

Ethics number: 17-0001