Superior cerebellar artery

The superior cerebellar artery (SCA) is a major paired branch of the vertebrobasilar circulation that supplies the upper half of the cerebellum, parts of the brainstem, and the cerebellar peduncles.

Course and anatomical segments

The superior cerebellar artery (SCA) typically arises as a single vessel from the distal basilar artery, immediately before the basilar artery terminates by dividing into the posterior cerebral arteries (PCAs). As it winds backward and outward around the brainstem, it passes through four distinct anatomical zones:

• It begins as the anterior pontomesencephalic segment, coursing beneath the oculomotor nerve (CN III).

• It transitions into the lateral pontomesencephalic segment, where it frequently dips downward along the side of the upper pons near the exit point of the trigeminal nerve (CN V), closely accompanied by the trochlear nerve (CN IV).

• It enters the fissure between the cerebellum and midbrain as the cerebellomesencephalic segment, intertwining with the trochlear nerve medial to the tentorial edge.

• It finally distributes as the cortical segment, spreading across the cerebellar surface.

Branches

Along its path, approximately 18.5 mm from its origin, the main superiror cerebellar artery bifurcates into two principal trunks:

• A rostral trunk that supplies the superior vermis, upper cerebellar hemisphere, and dorsal midbrain; and

• A caudal trunk that nourishes the lateral upper cerebellum and deep nuclei like the dentate nucleus.

• Several branches are given to the pineal body, the anterior medullary velum, and the tela choroidea of the third ventricle.

Clinical correlates

The primary clinical significance of the superior cerebellar artery (SCA) lies in its relationship to cranial nerve roots and vascular pathology:

• Trigeminal neuralgia: The SCA is frequently the compressing vascular culprit in classic trigeminal neuralgia cases. When an elongated, looping, or duplicated SCA pulsates against the root entry zone of the trigeminal nerve, it causes focal demyelination, triggering excruciating, lancinating facial pain. This neurovascular conflict is surgically treated with microvascular decompression to separate the artery from the nerve.

• Oculomotor and facial nerve conflicts: Because the oculomotor nerve travels directly between the PCA above and the SCA below, an aberrant or atherosclerotic SCA can compress CN III, leading to diplopia, ptosis, or pupillary dilation. Less commonly, an inferior loop can impinge upon the facial nerve root, causing hemifacial spasm.

• SCA Infarction: Ischemic stroke in the SCA territory leads to cerebellar hypoperfusion, characteristically presenting with acute ataxia, dizziness, vertigo, nausea, vomiting, and dysarthria.