7-15 mmHg. The normal intracranial pressure in an adult lying on their side is 7-15 mmhg, although pain and lying in a tightly contracted position can drive this up even in healthy people.
Think blood flow. The major concept in measuring brain pressure is to think about brain blood flow. The perfusion pressure is the comparison of intracranial pressure versus the blood pressure that is pushing blood into the brain. These measurements need to be carefully monitored in an ICU setting and adjusted carefully. If icp spikes and/or BP drops the brain will suffer lack of brain blood flow and die.