tricles. The largest of the ventricles are the two lateral ventricles, which occur in parallel and have a shape that is complex but that can be broadly described as the appearance of a medially angulated letter C with a tail extending from their back (Figure E.1). The tail is the occipital horn while the top part of the letter C is the frontal horn and the inferior and more lateral part is the temporal horn. Smaller singular third and fourth ventricles are midline structures in direct communication with the lateral ventricles. At the base of the fourth ventricle in the brain stem (laterally out the foramen of Luschka and medially out the foramen of Magendie), the CSF escapes the middle of the brain and freely flows into the subarachnoid space that extends around the outside of the brain and down into the spine to surround the spinal cord and nerve roots.
Cerebrospinal fluid is generated by small fronds of pink-orange tissue within the ventricles called choroid plexus (Figure E.2). Blood flows into and out of the choroid plexus via the choroidal vessels, and the CSF is continuously generated from within the choroid plexus in an energy-dependent process. The rate of production of CSF is about 0.2–0.3 cc/