Radicular artery

The radicular arteries are the first branches of the dorsal division of the segmental arteries and their regional equivalents. The blood supply of the bony spine consists of arteries, which come directly off the segmental and radicular arteries. Anterior central arteries derive from the segmental artery and supply the anterior and anterolateral portions of the vertebral body. The radicular arteries usually provide the blood supply to the posterior portion of the vertebral body via posterior central arteries and the arch via prelaminar arteries. Thus, the vertebral body is mainly supplied by posterior and anterior... 

Those spinal radicular arteries that are radiculo-medullary arteries, supplying nerve root, pial plexus and medulla, branch in a very typical way to form the anterior spinal artery. The ascending branch continues the direction of the radicular artery in the midline of the anterior surface. The descending branch, being the larger one at thoracolumbar levels, forms a hairpin curve as soon as it reaches the midline at the entrance of the anterior fissure (Fig. 17.3). The artery runs above the vein. The maximum diameter of a spinal radiculomedullary artery or the anterior... 

Fig. 17.3. Selective spinal DSA in a 59-year-old woman, p.a. projection. Injection of the 12th left thoracic segmental artery. Filling of the radiculomedullary arteries T12 and T10 on the left side (arrows) and the anterior spinal artery system. Collateral filling of the right-sided segmental arteries via retrocorpo-ral anastomoses (arrowheads). These extradural anastomoses can compensate for focal vessel occlusions at the level of the radicular artery...

Even if spatial and contrast resolution of these imaging modalities will increase in the future, it might be difficult to differentiate the artery from the vein on the anterior surface of the cord. The anterior spinal artery and vein run very close together. The branching of a radicular artery or vein has a very similar hairpin-configuration, and the level at which a segmental in- or outflow occurs cannot be predicted in a given case. 

Selective spinal DSA has a better spatial resolution and plays a main role in the exclusion of spinal vascular malformations. In selected cases affection of the radicular artery and occlusion of the anterior spinal artery system can be demonstrated as well as collateral supply even in the later course of the ischemia (Mull et al. 2002). Thus, spinal DSA helps to identify pathologic vascular conditions in spinal cord ischemia. The main indication remains to exclude a spinal vascular malformation. Angiographic information about the acute phase of spinal cord ischemia is not yet available. 

The posterior cerebral artery supplies the occipital lobe and portions of the medial and inferior temporal lobe. The arterial supply of the spinal cord is derived from the vertebral arteries and the radicular arteries. The brain is supplied by the internal carotid arteries (the anterior circulation) and the vertebral arteries, which join at the pon tomedullary junction to form the basilar artery (collectively termed the posterior circulation). The brainstem is supplied by the posterior system. The medulla receives blood from branches of the vertebral arteries as well as from the spinal arteries and the posterior inferior cerebellar artery (PICA). The pons is supplied by paramedian and short circumferential branches of the basilar artery. Two major long circumferential branches are the anterior inferior cerebellar artery (AICA) and the superior cerebellar artery. The midbrain receives its arterial supply primarily from the posterior cerebral artery as well as from the basilar artery. The venous drainage of the spinal cord drains directly to the systemic circulation. By contrast, veins draining the cerebral hemispheres and brain stem drain into the dural sinuses. Cerebrospinal fluid also drains into the dural sinuses through unidirectional valves termed arachnoid villi. 

Fig. 4. 15a-c. Venous drainage patterns of spinal dural arteriovenous malformations. (NR, nerve root RA, radicular artery DM, dura mater M, medulla). Meningeal branch of the radicular artery feeds arteriovenous shunt located on the dura (small arrow), a Venous drainage by epidural veins (arrow), b Venous drainage via epidural veins and aperimedullary vein (arrow) into the coronal venous plexus (arrowheads), c Exclusive venous drainage by perimedullary vein (arrow) and the coronal venous plexus (arrowheads)... 

The ASA is transversely reinforced by branches of deep cervical arteries at the neck and by posterior intercostal (PIA) and upper lumbar arteries at the trunk. Both of the latter derive segmentally from the descending thoracic and abdominal aorta and range between 0.5 and 5mm in diameter (Boll et al. 2006). The PIA and lumbar arteries send rami dorsales, from which again the radicular arteries (synonymous with radicomed-ullary artery or spinal branch) as feeders of the spinal cord originate. The radicular arteries divide soon into anterior and posterior branches that support either the anterior or the posterior spinal arteries. 

The posterior spinal arteries arise from the vertebral or posterior inferior cerebellar arteries and pass as two at each side along the dorsal aspect of the spinal cord. They are sustained to the lower spinal levels by being predominantly fed by the posterior branches of the radicular arteries. The posterior spinal arteries supply the dorsal third of the spinal cord and have a caliber of less than 0.5 mm. 

Standard transverse images reconstructed from a 3D data set with overlapping thin slices may be sufficient for visualization of the posterior intercostal and lumbar arteries as well as of their proximal rami dorsales. The AKA or other anterior radicular arteries of significant dimension may be localized on transverse sections as well, if a second vessel with arterial contrast begins to accompany the usually sohtary ASA in the thoracolumbar region (Fig. 24.2). 

PIA (3), muscular branch of ramus dorsalis (4), and radicular artery of ramus dorsalis (5). c Curved MPR proving continuity between ASA (J), AKA (2), PIA (3), and aorta... 

For classification, the anatomical relationship to associated extradural, intradural, or intramedullary vasculature has to be depicted. While extradural lesions are fed by arterial branches generally arising from extradural portions of the radicular arteries, intradural and intramedullary lesions show a supply from intradural radicular pedicles or from the ASA or posterior spinal arteries (Kim and Spetzler 2006). 

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