Table 1 Inclusion and exclusion criteria

1. Requiring surgery for an unruptured cerebral aneurysm

2. Age 18 to 80 year

1. Previous head trauma or intracranial hemorrhage

2. Current or previous examination or treatment for hydrocephalus

3. Current or previous examination or treatment for idiopathic intracranial hypertension

4. Previous operation with insertion of cerebrospinal fluid shunt

5. Global cerebral edema

6. Increased infection risks

7. Surgical complications during the primary operation

8. Unable to understand patient information