Although the brainstem is small, comprising only about 2.6% of total brain weight, the size of this structure belies its importance. First, all ascending and descending tracts linking the spinal cord and the forebrain traverse the brainstem. Second, there are…
The mesencephalon, or midbrain, is the most rostral portion of the brainstem. It gives rise to cranial nerves III and IV, conducts ascending and descending tracts, and contains nuclei that are essential to motor function. Caudally the midbrain is continuous…
The metencephalon consists of the pons and cerebellum. The pons is the middle segment of the brainstem, the caudal part being the medulla and the rostral portion being the midbrain. Although comprising only about 1.3% of the brain by weight,…
The medulla oblongata, or myelencephalon, is the most caudal segment of the brainstem. It extends from the level of the foramen magnum to the pons-medulla junction. The cavity of the medulla consists of a narrow, caudal part, which is the…
The term brainstem (sometimes written brain stem ) can mean either the portion of the brain that consists of the medulla oblongata, pons, and midbrain or the portion that consists of these structures plus the diencephalon. This book follows the…
Although small in diameter, the spinal cord is the most important conduit between the body and the brain. Recall that many cranial nerves contain sensory fibers that receive information from, and motor fibers that project to, diverse body areas; these…
About 50% of the problems that occur inside the cranial cavity and result in neurologic deficits are vascular in origin. Consequently, a detailed understanding of cerebrovascular patterns is absolutely essential to establish an accurate diagnosis of the neurologically compromised patient.…
The human nervous system is extremely delicate and lacks the internal connective tissue framework seen in most organs. For protection, the brain and spinal cord are each encased in a bony shell, enveloped by a fibrous coat, and delicately suspended…
The ventricular spaces of the brain are the adult elaborations of the neural canal of early developmental stages. These spaces, the choroid plexuses in them, and the cerebrospinal fluid (CSF) produced by the choroid plexus are essential elements in the…
The central nervous system (CNS) develops from primitive ectoderm, one of the three germ layers of the embryo. From a few dozen cells that together weigh perhaps a microgram, the brain becomes an organ weighing about 800 g at birth,…