The brain stem and cranial nerves

Abstract

The brain stem is best viewed when separated from the overlying cerebral hemispheres and cerebellum (Fig. 1, Fig. 2, and Fig. 3). The brain stem is continuous with the spinal cord at the foramen magnum of the occipital bone and with the diencephalon at the incisura of the tentorium. It consists of the midbrain, pons, and medulla, which lie in close relationship to the anterior surface of the base of the occipital bone. The vertebral and basilar arteries lie between the anterior surface of the brain stem and the occipital bone. Paired cranial nerves originate or terminate in the brain stem; the exceptions are the olfactory, optic, and accessory nerves (Fig. 1). The cerebellum lies posterior to the brain stem and is attached by three pairs of fiber bundles: the inferior, middle, and superior cerebellar peduncles (Fig. 2). The brain stem, cerebellum, roots of the cranial nerves (CNs), and vertebro-basilar arterial system are located in the posterior cranial cavity or infratentorial space (see Chapter 2 for additional illustrations.).