what is the clinical significance of the first one?
It is the cause of trigeminal neuralgia.
Superior cerebellar artery
The SCA is frequently the cause of trigeminal neuralgia, where it compresses the trigeminal nerve causing lancinating pain in the distribution of this nerve on the patient's face. 
what is the largest part of the mature brain UNANSWERABLE where exactly is the cerebellum located? In the posterior cranial fossa. what is this part of the brain made up of? It consists of a tightly folded layer of cortex, with white matter underneath and a fluid-filled ventricle at the base. from where does it get its blood supply? The superior cerebellar artery, the anterior inferior cerebellar artery, and the posterior inferior cerebellar artery.
wiki:10772039
Superior cerebellar artery [SEP] Clinical significance
The SCA is frequently the cause of trigeminal neuralgia, where it compresses the trigeminal nerve causing lancinating pain in the distribution of this nerve on the patient's face. However, at autopsy, 50% of people without trigeminal neuralgia will also be noted to have vascular compression of the nerve.