Aneurysmal subarachnoid hemorrhage (SAH) is a fatal disease with high morbidity and mortality. While the primary injury results from the initial bleeding and cannot be influenced, secondary injury through vasospasms and delayed cerebral ischemia (DCI) during the course of the disease might be a target for intervention in order to improve outcome. To date, beside the aneurysm treatment to prevent re-bleeding and the administration of oral nimodipine, there is no causal therapy available, so that novel treatment concepts are desperately needed. There are strong indications that inflammation contributes to DCI and therefore poor outcome and plays a major role in SAH. Some studies suggest a beneficial effect of anti-inflammatory drugs like glucocorticoids (GC) in SAH patient, but there are no data from randomized controlled trials proving or disproving the beneficial effect of GC, so that current guidelines do not recommend the use of GC in SAH so far.

This multi-center trial aims to generate the first confirmatory data in a controlled randomized fashion that dexamethasone (DEX) improves the outcome in a clinically relevant endpoint in SAH patients. Moreover, this trial will generate first data in a secondary analysis, whether the initial inflammatory state of SAH patients defines a subgroup that particularly responds to a treatment with DEX.

Inclusion Criteria:

1. Male or female subjects, equal or older than 18 years old
2. Written consent to participate in the study by the patient or his legal representative (emergency inclusion by next of kin or consultant physician under the responsibility of the principal investigator is possible)
3. Confirmed diagnosis of aneurysmal SAH and onset within 48 hours before inclusion.

Exclusion Criteria:

1. SAH due to any other cause than aneurysm rupture (e.g. traumatic, arteriovenous malformation (AVM), fistula, dissection)
2. Any condition that, in the judgement of the Investigator, could impose hazards to the patient if study therapy is initiated or affects the participation of the patient in the study
3. Patients with obvious evidence of irreparable brainstem or thalamic injury
4. Patients with foreseeable difficulties to attend follow-ups adequately
5. Subjects with a physical or psychiatric condition which at the investigator's discretion may put the subject at risk, may confound the trial results, or may interfere with the subject's participation in this clinical trial
6. Current positive pregnancy test (e.g. β-HCG test in serum)
7. Known history of hypersensitivity to the investigational drug or to drugs with a similar chemical structure
8. Severe infectious diseases
9. Known angle-closure or open angle glaucoma
10. Known ulceration in the gastro-intestinal tract
11. History of gastro-intestinal bleeding
12. Long-term treatment with corticosteroids prior SAH