Within the skull.

Intracranial Pressure is the pressure within the cranial cavity, influenced by brain mass, the circulatory system, cerebrospinal fluid dynamics, and skull rigidity.
Increased intracranial pressure, or rise in normal brain pressure, can be due to a rise in cerebrospinal fluid pressure. It can also be due to increased pressure within the brain matter caused by lesions, a tumor, or swelling. An increase in intracranial pressure is a serious medical issue. The pressure can damage the central nervous system by restricting blood flow through blood vessels that supply the brain, or by pressing on important brain structures. Increased intracranial pressure is an emergency. The person will be in the intensive care unit of the hospital. The health care team will measure and monitor the patient’s neurological and vital signs, including temperature, pulse, breathing rate, and blood pressure.
Treatment for increased intracrainial pressure may involve breathing support, draining of cerebrospinal fluid to lower pressure in the brain, and/or medications to decrease swelling. The underlying cause of the pressure, such as a tumor or hemorrhage must also be treated.