The goal in this research is to develop better ways to detect and treat the damage caused by bleeding in the brain.

Patients who suffer from a bleeding in the brain (stroke or hemorrhage) often experience secondary complications that can occur up to 2 weeks after the initial bleeding. Complications can include decrease of consciousness, weakness or paralysis, difficulty with speech and language, and worsening of brain damage. These decrease a patient's chances for a good recovery. A brain scan will be used to determine the damage caused by the bleeding, and the brain's electrical activity will be monitored to detect abnormal activity. These measures will be analyzed together with routine medical information to better understand and diagnose complications.

Inclusion Criteria:

1. Age 18 to 70 years
2. World Federation of Neurosurgery (WFNS) grade III-IV, and grade V patients who improve within 24h after ventriculostomy
3. Diffuse thick or localized thick subarachnoid clot >1 mm on baseline CT (Fisher grade 3-4)
4. Ruptured saccular aneurysm demonstrated by CT-angiography or DSA
5. Onset of aSAH clinical symptoms within the preceding 72h
6. Treatment of aneurysm within 24 h after admission
7. Treatment of aneurysm by clip ligation

Exclusion Criteria:

1. SAH due to other causes (e.g. trauma, fusiform or mycotic aneurysm)
2. Only a thin diffuse layer or no visible subarachnoid blood in the initial CT
3. Admission in a clinical state with unfavourable prognosis (e.g., bilateral dilated, non-reactive pupils for more than 1h)
4. Coagulopathy (thrombocytes <60,000/ml or INR>1.5)
5. Pregnancy
6. Presence of incompatibilities for MRI, such as non-removable metals, artificial joints, electronic devices (pace maker, pumps), etc.

Patients with subarachnoid hemmorhage clinical symptoms