Mapping the Vasculature of the Spinal Cord

4.3.1 Rationale

Spinal cord blood vessels are millimeter- to submillimeter-sized blood vessels that are hard to visualize in the human body. In vivo imaging of spinal cord arteries and veins was until recently only possible using invasive catheter-based angiography, which involves a radiation burden and needs to be performed by experienced specialists. Noninvasive imaging of spinal cord blood vessels had only recently become available in a robust way using computed tomography (CT) and magnetic resonance (MR) angiography. It was mainly from clinical research in aortic aneurysm surgery that the request came to develop noninvasive visualization of spinal cord arteries to avoid the risk of paraplegia induced by damaging the spinal cord blood supply. Traditional MR angiography techniques at that time (prior to 2000) were not able to depict normal intradural arteries and were restricted to the visualization of pathologically dilated arteries and veins. Today, techniques have strongly improved vessel-to-background contrast because they use relatively fast contrast-enhanced imaging techniques that are now able to depict and differentiate normal spinal cord arteries from veins.

In this chapter, the relevant vascular anatomy of the spinal cord is first briefly outlined. Then, a technique of fast contrast-enhanced MR angiography is described to image normal spinal arteries and veins. Finally, the possible confounding effect of the variable and unpredictable course of spinal cord veins in relation to the blood oxygen level–dependent (BOLD) effect of spinal cord functional MR imaging (fMRI) will be addressed.

4.3.2 Vascular Anatomy

To understand the thoracolumbar spinal cord vasculature, it is useful to divide the spinal cord vasculature into the supplying arterial part (inlet) and draining venous part (outlet) (see Figure 4.3.1 ). In this section, a general outline of the spinal cord vasculature will be given as can be imaged with human invasive or noninvasive angiography techniques. In this context, it is important to notice that interindividual anatomic variation is the rule rather than the exception (also see Chapter 4.1 regarding the intersubject variability of BOLD responses).

ANATOMY OF THE SPINAL CORD VASCULATURE

Anterior cord surface: one spinal artery and one median vein that runs in the anterior median sulcus
Posterior cord surface: one or two very small posterolateral spinal arteries and one “median” vein. The course of the posterior median vein is more tortuous and is not strictly median as compared to the anterior median vein

FIGURE 4.3.1, Coronal anatomical drawing of the largest inlet artery and outlet vein of the thoracolumbar spinal cord. The largest supplier of the thoracolumbar spinal cord, which is therefore considered the most important, is the Adamkiewicz artery. This inlet artery, or great anterior radiculomedullary artery, originates from a posterior branch of a segmental artery and connects to the anterior spinal artery with an ascending and descending branch. The descending branch is larger and has a typical hairpin turn. On the posterior cord surface, there are two laterally located spinal arteries. Venous drainage of the anterior cord surface is preformed by a large collecting anterior median vein, which in turn drains the blood to a radiculomedullary vein. The largest of the outlet veins on the anterior cord surface is the great anterior radiculomedullary vein (GARV), which connects to a segmental vein that eventually merges with the vena cava. Note the anatomical similarities in the configuration between the Adamkiewicz artery and the GARV, which both exhibit a hairpin-like configuration. However, the Adamkiewicz artery is normally thinner, has a shorter intradural span, and is located more cranially than the GARV.

4.3.2.1 You're Reading a Preview

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