Anatomical Course and Location
The superior cerebellar artery is a key branch of the vertebrobasilar system. Its topography is characterized by the following features:
- Origin: Branches from the upper third of the basilar artery (a. basilaris) immediately proximal to its bifurcation into the two posterior cerebral arteries.
- Course: Runs parallel and inferior to the posterior cerebral artery, winding around the cerebral peduncles.
- Anatomical Variations: Angiographic studies have described duplicated right superior cerebellar arteries.
Vascular Territory
The artery supplies the following structures:
- Cerebellum: Supplies the superior surface of the cerebellar hemispheres, the rostral portion of the cerebellar hemisphere, the superior vermis, and partially extends to the lateral borders of the hemispheres.
- Midbrain: Vascularizes the lateral and dorsolateral regions of the midbrain tegmentum and sends branches to the midbrain tegmentum.
- Pons: Supplies the superior part of the pons.
- Ventricular System: Gives off branches to the choroid plexus of the third ventricle.
Clinical Significance: Trigeminal Neuralgia
The superior cerebellar artery plays a major role in the pathophysiology of trigeminal neuralgia.
A vascular loop of this artery is a frequent cause of neurovascular conflict. The artery compresses the vulnerable unmyelinated root entry zone of the trigeminal nerve (n. trigeminus) as it exits the pons. The sensitive/unmyelinated root segment of cranial nerve V is approximately 2.0–6.0 mm long.
This irritation can trigger reflex facial muscle spasms in response to sharp pain. Facial sensory deficits are generally absent.
Treatment:
- Medical: Carbamazepine is the drug of choice.
- Surgical: For medically refractory cases, microvascular decompression is performed. The neurosurgeon mobilizes the nerve root away from the compressing vascular loop and places an insulating pad between them; synthetic sponges are also utilized to prevent contact between the nerve and the pulsating artery.
Angiographic Appearance and Thrombosis
Hemodynamics of the vessel can be evaluated via digital subtraction angiography (DSA) or MR angiography:
- Basilar Artery Occlusion: When occlusion is localized to the distal basilar artery, blood flow to the superior cerebellum is not visualized. Because the superior cerebellar artery anatomically originates distal to the site of obstruction, contrast medium fails to enter it.
- Retrograde Filling of the Upper Basilar Artery: Under specific hemodynamic conditions, the upper segment of the basilar artery fills with contrast retrogradely. Contrast flows from the proximal segment of the posterior cerebral artery, subsequently filling the superior cerebellar arteries via the basilar trunk.