The role of the vertebral artery in supplying blood to the spinal cord and brain
The vertebral artery (a. vertebralis) is a paired major vessel that determines the blood supply to the structures of the neck and posterior cranial fossa. After piercing the dura mater, this artery gives off several branches to the cervical spinal cord.
The key vessel here is the anterior spinal artery (a. spinalis anterior). It almost always originates specifically from the intradural segment of the vertebral artery. Together with the paramedian branches of the vertebral artery, it not only descends to the spinal cord but also actively supplies the paramedian (ventral) parts of the medulla oblongata.
The anatomy of the vascular bed in this area features high variability. At the border of the medulla oblongata and the pons, the right and left vertebral arteries merge to form a single trunk, the basilar artery (a. basilaris).
Vertebrobasilar system and brainstem
The basilar artery lies in the basilar sulcus on the ventral surface of the pons. It supplies blood to the ventral parts of the pons and midbrain. The artery gives off numerous branches to the brainstem, which are subdivided into:
- Penetrating (paramedian) branches.
- Short and long circumferential branches.
The clinical significance of these branches is immense: their occlusion leads to severe syndromes of brainstem ischemia. The basilar artery terminates in a bifurcation, dividing into two posterior cerebral arteries (a. cerebri posterior). These terminal branches have a close functional and anatomical connection with the carotid system and are located parallel to and above the superior cerebellar artery.
Cerebellar arteries and their topography
The blood supply to cerebellar structures is provided by three pairs of large arteries:
- Posterior inferior cerebellar artery (PICA). The largest branch of the vertebral artery, originating before its merge into the basilar artery. It supplies the basal part of the cerebellar hemispheres, the inferior part of the vermis, part of the cerebellar nuclei, the choroid plexus of the fourth ventricle, and the dorsolateral part of the medulla oblongata.
- Anterior inferior cerebellar artery (AICA). The first major branch of the lower third of the basilar artery. It supplies the flocculus and the anterolateral parts of the cerebellum. It gives off a specific branch to the inner ear, the labyrinthine artery.
- Superior cerebellar artery (SCA). Originates from the upper third of the basilar artery before its bifurcation. It curves around the cerebral peduncles, supplying the rostral part of the cerebellar hemispheres, the superior part of the vermis, as well as the dorsal parts of the midbrain and its tegmentum.
Developmental anomalies and hemodynamic balance
The circulatory system of the posterior cranial fossa operates on the principle of hemodynamic balance and inverse dependence. The coverage area of the PICA is inversely proportional to the coverage area of the AICA.
Vascular asymmetry is a common occurrence. If the PICA on one side is very small, the basal part of the cerebellum on that side receives blood via:
- The ipsilateral (same-side) AICA.
- A larger contralateral (opposite-side) PICA.
In congenital hypoplasia of the vertebral artery, the underdeveloped vessel does not participate in the formation of the basilar artery. Instead, it continues entirely and exclusively into the PICA. The basilar artery in such cases forms as a direct continuation of the single healthy vertebral artery.
Cortical blood supply and connection of territories
For a complete picture of central nervous system circulation, it is important to remember anastomoses. Thus, the anterior cerebral artery (ACA) forms anastomoses with the middle and posterior cerebral arteries. The ACA supplies the corpus callosum, the parasagittal region, and the medial surfaces of the hemispheres, including the lower limb projection zones in the primary motor and sensory cortex and the cingulate gyrus.
Cortical branches of the ACA include: the orbital (I), frontopolar (II), frontal, pericallosal (III), callosomarginal (IV), and internal parietal arteries (V).
In turn, the posterior cerebral artery on the medial surface of the hemispheres gives off: the anterior and posterior temporal, posterior occipital, parieto-occipital arteries, and the calcarine artery.
Briefly: answers to topical questions
Which arteries supply the thoracic and lumbar segments of the spinal cord?
The thoracic and lumbar segments of the spinal cord are supplied by branches of the aorta that give off segmental arteries. The main vessels at these levels are:
- Posterior intercostal artery (a. intercostalis posterior) — supplies segments at the Th4–Th6 and Th9–L1 levels.
- Great radicular artery (a. radicularis magna) — also known as the artery of Adamkiewicz, it serves as the main blood supply source for the lower thoracic, lumbar, and sacral segments.
Blood from the thoracic and lumbar aortic branches flows directly into the anterior spinal artery.
Where do the posterior spinal arteries originate?
The posterior spinal arteries are formed by the union of segmental arteries, and their merging can be incomplete in places. In the lower cervical region, these vessels receive blood from the following sources:
- Vertebral artery (a. vertebralis) — participates in the blood supply along with branches of the subclavian artery.
- Subclavian artery (a. subclavia) — gives off cervical branches, with the costocervical or thyrocervical trunk acting as the primary sources.
What part of the cross-section of the spinal cord is supplied by the anterior spinal artery?
The anterior spinal artery supplies the central and anterior parts of the spinal cord parenchyma. Its vascularization zone includes the most significant structures of the anterior and lateral regions:
- Anterior horns — part of the central gray matter.
- Anterior spinothalamic tract — located in the anterior funiculi.
- Lateral spinothalamic tract — runs in the lateral funiculi.
- Lateral corticospinal tract — part of the pyramidal tract located deep within the lateral funiculi.
Three levels of cerebellar blood supply: PICA (from the vertebral artery) — inferior and posterior margin, AICA (from the basilar artery) — anteroinferior margin, SCA (from the basilar artery) — superior margin.
Class and exam questions
Where does the anterior spinal artery originate?
It almost always arises from the intradural part of the vertebral artery, descending toward the structures of the cervical spinal cord.
What happens in case of hypoplasia of one of the vertebral arteries?
An underdeveloped vertebral artery does not merge into the basilar artery, but directly continues into the posterior inferior cerebellar artery. The basilar trunk is formed from the opposite artery.
How do the cerebellar artery territories compensate for each other?
The sizes of the PICA and AICA vascular territories are inversely related: if one artery is hypoplastic, the adjacent artery from the same or opposite side compensates for the deficit.
What else to study on this topic
- Anatomy and branching of the anterior cerebral artery (ACA)
- Functionally significant cortical areas within the ACA territory
- Distribution of posterior cerebral artery (PCA) branches across the hemispheres
- Brainstem ischemia syndromes resulting from occlusion of penetrating branches
- Topography of the oculomotor nerve relative to cerebral vessels
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