Brainstem & Cerebellar Arterial Territories

brainstem and cerebellar arteries

• The brainstem vascular territories (as originally defined in the 1960s by Gillian and Lazorthes) divide into the following groups:
  • Anteromedial
  • Anterolateral
  • Lateral
  • Posterior
• Three arteries supply the cerebellum:
  • Superior cerebellar artery (SCA)
  • Anterior inferior cerebellar artery (AICA)
  • Posterior inferior cerebellar artery (PICA)

Brainstem compression

Compression of all three brainstem levels:

The thin paramedian region is the:

• Anteromedial group

The remainder of the brainstem (from anterior to posterior) are the:

• Anterolateral group
• Lateral group
• Posterior group

Brainstem: Specific Vascular supply

Midbrain

Key Anatomy

• The PCAs or distal basilar artery supply the midbrain, either directly or via smaller branches.
  • When basilar clot produces ischemia to the proximal PCAs, large midbrain strokes can occur and produce a so-called "top of the basilar" syndrome.

Clinical Correlation: Basilar Occlusion

Detailed Anatomy

• The anteromedial group is supplied by basilar tip and proximal PCA branches.
  • From inferior to superior, these branches are the inferior and superior paramedian mesencephalic arteries and the thalamoperforate arteries.
• The anterolateral group is supplied by PCA branches: the collicular and posteromedial choroidal arteries.
• The lateral and posterior groups are also supplied by the collicular and posteromedial choroidal arteries in concert with the superior cerebellar arteries.

Pons

Key Anatomy

• Most of the pontine arterial supply comes in the form of circumferential artery branches that travel progressively farther distances to their targets.
• The posterior portion of the pons receives additional supply from the anterior inferior cerebellar artery, inferiorly, and the superior cerebellar artery, superiorly.
• The common source for these arteries is the basilar artery.
• Basilar ischemia can produce pontine basis strokes, which can cause locked-in-syndrome.

Detailed Anatomy

• The anteromedial group is supplied by the pontine paramedian arteries.
• The anterolateral group is supplied by the short pontine circumferential arteries.
• The lateral group is supplied by the long pontine circumferential arteries and the anterior inferior cerebellar arteries.
• The posterior group is supplied by the superior cerebellar arteries: note that the posterior group is found only in the upper pons — it is not present in the mid or lower pons.

Medulla

Key Anatomy

• Key medullary arterial vessels are: the anterior spinal artery and the posterior inferior cerebellar arteries.
• The common source for these arteries is the vertebral arteries.
• As a clinical corollaries:
  • Ischemia to the posterior inferior cerebellar artery results in lateral medullary syndrome, called Wallenberg's syndrome.
  • Ischemia to the medial medulla results in Dejerine's syndrome.

Detailed Anatomy

• The anteromedial group is supplied by the anterior spinal artery and direct vertebral artery branches.
• The anterolateral group is supplied by the anterior spinal artery and the posterior inferior cerebellar arteries.
• The lateral group is supplied by the posterior inferior cerebellar arteries.
• The posterior group is supplied by the posterior inferior cerebellar and posterior spinal arteries.

The Cerebellum

Brain Atlas: Cerebellum

• The cerebellar vascular territories are supplied by the:
  • Superior cerebellar artery (SCA)
  • Anterior inferior cerebellar artery (AICA)
  • Posterior inferior cerebellar artery (PICA)

PICA (Inferior Cerebellum)

• Supplies the entire inferior cerebellum, which lies at the level of the medulla.
• It divides into lateral and medial branches, which supply the lateral and medial regions of the inferior cerebellum, respectively.

SCA (Superior Cerebellum)

• Supplies the superior cerebellum, which lies at the level of the midbrain.
• It divides into lateral and medial branches (similar to the PICA), which supply the lateral and medial superior cerebellum, respectively.

AICA, SCA, & PICA (Middle Cerebellum)

The middle cerebellum (at the level of the pons) is supplied by all three cerebellar arteries

• AICA supplies the anterior, middle cerebellum.
• PICA supplies the posterior, middle cerebellum, inferiorly.
• SCA supplies the posterior, middle cerebellum, superiorly.

• Note that the AICA supplies a large portion of the middle cerebellar peduncle, and also note that it commonly gives off the internal auditory artery, which supplies the inner ear, thus in the appropriate clinical context, sudden hearing loss can be an important harbinger of basilar occlusion.