Intracranial pressure (
ICP) is the pressure inside the
skull and thus in the
brain tissue and
cerebrospinal fluid (CSF). ICP is measured in millimeters of mercury (
mmHg) and, at rest, is normally 7–15 mmHg for a
supine adult. The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF. Changes in ICP are attributed to volume changes in one or more of the constituents contained in the cranium. CSF pressure has been shown to be influenced by abrupt changes in intrathoracic pressure during coughing (intraabdominal pressure),
valsalva maneuver, and communication with the
vasculature (
venous and
arterial systems).