Figure 1

Pressure and flow compartments in the brain. Illustration of the pressure and flow "compartments" considered throughout the paper. Pressure can be measured anywhere within the cranium, and both mean pressure as well as pulse amplitude are generally considered to be position-independent. From a technical standpoint, however, pressure measurement is usually restricted to the lateral ventricles, cisternum magnum or the brain parenchyma. Flow, on the other hand, varies considerably with both magnitude (i.e., mean flow) and pulsatility strongly depending on fluid type (e.g., arterial blood vs. CSF) and on location. The figure indicates typical locations for CSF flow measurement. Blood velocity measurements (not shown) are generally restricted to the larger inlet/outlet vessels of the cranium (e.g., carotid, basilar, middle cerebral arteries, sagittal and straight sinuses).