ICP is the common abbreviation for Intracranial Pressure, a measure of the pressure of the cerebro-spinal fluid surrounding the brain and spinal cord. The body produces cerebro-spinal fluid continuously and has several mechanisms for keeping it within a narrow range of pressures, generally 7-15 millimeters of mercury (mmHg). However, normal ranges run up to about 20 mmHg. After 25 mmHg, usually medical intervention is required to reduce the pressure.