This section is from the book "Anatomy Of The Arteries Of The Human Body", by John Hatch Power. Also available from Amazon: Anatomy of the Arteries of the Human Body, with the Descriptive Anatomy of the Heart.
The Inferior Artery Of The Cerebellum generally comes, on one side from the vertebral artery, and on the other from the basilar trunk: both, however, though rarely, may come from the vertebral, or, still more rarely, both may arise from the basilar. This artery after its origin takes a direction outwards, crossing in front of the pyramidal body when it arises from the vertebral, or either above or below the sixth nerve, when it arises from the basilar : it then passes backwards between the pneumogastric and spinal accessory nerves, and arrives at the inferior surface of the cerebellum. Its first branches, which are very small, are distributed to the superior extremity of the spinal marrow, the origins of the eighth and ninth nerves, the fourth ventricle, and to the inferior surface of the cerebellum; the terminating branches, which are more considerable, creep along the inferior surface of each hemisphere to its circumference, where they communicate with the superior artery of the cerebellum.