Intracranial pressure is a cornerstone in neurosurgical care used in a variety of diseases. However currently, doubts regarding normal intracranial pressure exist. Few studies have investigated normal intracranial pressure in truly normal adults. The aim of this study is to investigate intracranial pressure in adults who have normal intracranial pressure physiology.

In this prospective, multicenter, clinical study, the intracranial pressure of 10 adults requiring surgery for an unruptured aneurysm will be investigated. These patients are thought to be normal in terms of intracranial pressure physiology. At the end of their surgery for an aneurysm, a telemetric intracranial pressure monitoring sensor will be implanted. Afterward, intracranial pressure curves will be obtained non-invasively 1., 14., 30 and 90 days after implantation. The intracranial pressure will be investigated in 5 different positions (supine, lumbar, upright sitting, standing and walking). Furthermore, a 24-hour measurement will be performed in their home environment, thus investigating intracranial pressure under daily activities.

Inclusion Criteria:

• Above the age of 18
• Requiring surgery for a "cold" (unruptured) aneurysm

Exclusion Criteria:

• Current or previous examination or treatment for hydrocephalus
• Current or previous examination or treatment for idiopathic intracranial hypertension
• Previous operation with insertion of cerebrospinal fluid shunt
• Previous trauma with intracranial hemorrhage
• Global cerebral edema
• Increased infection risks
• Surgical complications during the primary operation
• Unable to understand patient information