Assessing Arterial Patterns in the Motor Cortex With 7 Tesla Magnetic Resonance Imaging and Vessel Distance Mapping

Leveraging high-resolution 7 T magnetic resonance imaging (MRI) and vessel distance mapping (VDM), the arterial supply patterns and dominances of the motor cortex, which could previously only be studied postmortem, were assessed in vivo and fully noninvasively. Beyond vessel patterns and dominances, the potential relation between the vascularization and the motor cortex thickness was studied. Twenty-one healthy participants underwent 7 T MRI scans to map arterial supply and motor cortex at 0.45 mm isotropic resolution. The motor cortex vasculature was segmented manually with vessel-specific labels. VDM was utilized to estimate the vessel-specific supply regions and, subsequently, assess vessel patterns and dominances. Statistical tests were applied to test if the vasculature impacts mean motor cortical thickness estimates. Vessel patterns, that is the presence of supplying vessels, were classified as three-, four-, and five-vessel patterns with a prevalence of 26.3%, 50.0%, and 23.7%, respectively. Vessel dominance, that is the ratio of supply volumes, of the ACA branches showed dominance of the pericallosal artery, callosomarginal artery, and equal contribution, in 34.2%, 34.2%, and 31.6% of the cases, respectively. For the MCA groups, the prevalence of precentral group dominance, central group dominances, and equal contribution was 13.2%, 34.2%, and 52.6%, respectively. Although the central and precentral groups were found in all hemispheres, the postcentral group was found in 28.9% of hemispheres with highly variable supply contribution. Statistical tests returned no significance for the effect of vessel patterns and dominances on the mean motor cortex thickness. With 7 T MRI and VDM, the motor cortex vascularization can be assessed fully noninvasively and longitudinally while providing overall good concordance with previous post mortem studies. Our comprehensive analysis of arterial motor cortex vascularization showed considerable variability between hemispheres, rendering the usage of pattern-specific atlases and analysis more suitable than single normative representations. The successful translation from post mortem to in vivo enables the study of vascular reserve in disorders affecting the motor cortex, such as ALS, and can be translated to other brain regions and neurodegenerative diseases in the future.