Blood Supply of the Spinal Cord
Arterial Supply of the Spinal Cord

• The arterial supply of the spinal cord by the vertebral arteries.
• It is also from the branches ultimately from the thoracic and abdominal aorta, called the radicular arteries.
• Each vertebral artery (or posterior inferior cerebral artery) gives rise to a posterior spinal artery, which proceeds along the line of attachment of the dorsal roots.
• Each vertebral artery also gives rise to an anterior spinal artery.
• The 2 anterior spinal arteries fuse to form a single midline vessel.
• This courses along the anterior median fissure of the spinal cord.
• The posterior spinal arteries and the anterior spinal artery supply upper cervical levels with from the vertebral arteries.
• Below this, all 3 spinal arteries form a more or less continuous series of anastomoses with radicular arteries.
• Beginning with lower cervical segments, the spinal cord depends on the radicular arteries for its survival.
• The great radicular artery (of Adamkiewicz), present at the spinal cord level T12-L2 may provide the entire arterial supply for the caudal 2/3 of the spinal cord.
• The very long anterior spinal artery is usually a continuous vessel for the length of the spinal cord.
• It gives rise to hundreds of central and circumferential branches.
• These supply the anterior 2/3 of the spinal cord.
• This includes the base of the posterior horn and a variable portion of the lateral corticospinal tract.
• The posterior spinal arteries are really more of a plexiform network of small arteries.
• They supply the posterior columns, substantia gelatinosa, dorsal root entry zone, and a variable portion of the lateral corticospinal tract.

Vertebral-Basilar System
Vertebral Arteries

• The two vertebral arteries run rostrally alongside the medulla.
• They fuse at the pontomedullary junction to form the midline basilar artery.
• Before forming the basilar artery, each vertebral artery gives rise to 3 branches:

1. The posterior spinal artery;
2. The anterior spinal artery;
3. The posterior inferior cerebellar artery (PICA).

Posterior Spinal Artery

• This runs caudally along the dorsolateral aspect of the spinal cord and supplies the posterior 1/3 of that half of the cord.

Anterior Spinal Artery

• This joins the anterior spinal artery on the other side, forming a single anterior spinal artery that runs caudally along the ventral midline of the spinal cord.
• It supplies the anterior 2/3 of the cord.
• The spinal arteries do not carry enough blood from the vertebral arteries to supply more than cervical segments and are reinforced at various points caudal to this.

Posterior Inferior Cerebellar Artery

• "PICA" supplies much of the inferior surface of the cerebellar hemispheres.
• It also sends branches to other structures on its way to the cerebellum.
• As it curves around the brainstem, the artery supplies the choroid plexus of the 4th ventricle and much of the lateral medulla.
• This is a uniform occurrence of the large named branches of the vertebral-basilar system on their way to their major area of supply.

Basilar Artery

• This proceeds rostrally.
• At the level of the midbrain, it bifurcates into the 2 posterior cerebral arteries.
• Before this bifurcation, it gives rise to numerous unnamed branches.
• It also gives rise to 2 named branches:

1. The anterior inferior cerebellar artery;
2. And the superior cerebellar artery.

The vertebral arteries help to supply the spinal cord
The posterior spinal arteries and the two anterior spinal arteries, which fuse to form a single midline vessel, supply the upper cervical cord. For lower parts of the cord, the spinal arteries are reinforced by radicular arteries that are branches of the thoracic and abdominal aorta. There is a great deal of variability in this pattern. The artery of Adamkiewicz is one of the most important radicular arteries, and in some individuals it may provide the entire arterial supply for the lower two-thirds of the spinal cord.

The vertebral and basilar arteries supply the brainstem and cerebellum.  
Perhaps the most important thing to recognize about the brainstem's blood supply is just how variable the vessels can be in size and position, but still provide adequate perfusion. This means that clinical syndromes produced by occlusion of a particular vessel are also variable. Patients whom you will encounter may present with fragments or combinations of syndromes.

Brainstem arteries in the medulla, pons and midbrain have similar patterns of distribution:

• medial parts of the brainstem as far dorsal as the ventricle are supplied by long, slender penetrating branches called the paramedian branches
• dorsolateral parts of the brainstem are supplied by direct circumferential branches of the vertebral or basilar arteries, or by branches of one of the major 'cerebellar' vessels as they curve around the brainstem on their way to the part of the cerebellum they supply.

 
The blood supply of the medulla is derived from the two vertebral arteries. The midline anterior spinal artery, formed from the fusion of medial branches from each vertebral, supplies part of the central medulla (as well as much of the upper cervical cord). From its lateral side each vertebral gives off a variable branch, the posterior inferior cerebellar artery (PICA).  PICA has a complicated looping course as it swings out around the inferior olives, and runs along the dorsal lateral surface of the medulla before turning laterally and supplying the inferior surface of the cerebellum. The vertebral arteries fuse at the junction between the medulla and the pons to form the single midline basila artery which then proceeds rostrally along the surface of the anterior pons. The basilar artery also gives rise to additional large lateral vessels, most importantly, the anterior inferior cerebellar arteries and the superior cerebellar arteries.

The three major cerebellar vessels supply the posterior inferior, anterior inferior, and superior surfaces of the cerebellum respectively. The superior cerebellar artery also sends small branches penetrating deeply into the deep nuclei of the cerebellum.