MRI mapping of hemodynamics in the human spinal cord

Abstract

Impaired spinal cord vascular function contributes to numerous neurological pathologies, making it important to be able to noninvasively characterize these changes. Here, we propose a functional magnetic resonance imaging (fMRI)-based method to map spinal cord vascular reactivity (SCVR). We used a hypercapnic breath-holding task to evoke a systemic vasodilatory response during concurrent blood oxygenation level-dependent fMRI. SCVR amplitude and hemodynamic delay were mapped at the group level as proof-of-concept of the approach, and in two highly-sampled participants to probe feasibility/stability of individual SCVR mapping. Across the group and individuals, a strong ventral SCVR amplitude was initially observed without accounting for local regional variation in the timing of the vasodilatory response. Shifted breathing traces were used to account for temporal differences in the vasodilatory response across the cord, producing maps of SCVR delay. These maps demonstrate distinct gray matter regions concordant with territories of arterial supply. The SCVR fMRI methods described here enable robust mapping of spatiotemporal hemodynamic properties of the human spinal cord. This noninvasive approach has the potential to provide early insight into pathology-driven vascular changes in the cord, which may precede and predict future irreversible tissue damage and guide the treatment of several neurological pathologies involving the spine.