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intracranial pressure(ICP)
the pressure of the cerebrospinal fluid in the subarachnoid space between the skull and the brain. There is room for only limited expansion inside the skull, and any condition that causes
an increase in volume in any of the enclosed structures will cause an increase in pressure. A tumor or swelling in the brain
can increase the volume, as can leakage of blood from blood vessels inside the skull, clot formation, and dilatation of the
cerebral blood vessels. Other causes of increased pressure are the excessive production, impeded outflow, or inadequate absorption
of cerebrospinal fluid, as in hydrocephalus. Increased fluid volume creates pressure against the structures inside the skull, disrupting the blood and oxygen supply,
and resulting in cellular hypoxia. As the pressure increases, the brain mass shifts and causes compression of nerves and arteries.
intracranial pressure screw
a device for measuring the degree of intracranial pressure. Monitoring can be done on a continuous or intermittent basis. The screw is inserted through a burr hole in the frontal area
of the skull just behind the hairline, and a capped 3-way stopcock is attached to the pressure screw. High-pressure tubing
joined to the screw leads to a manometer on which pressure changes can be directly visualized, or to equipment that displays the information on an oscilloscope or graph.
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