Other factors predictive of poor prognosis include older age, preexisting severe medical illness, global cerebral edema on computed tomography (CT) scan, intraventricular and intra- cerebral hemorrhage, symptomatic vasospasm, delayed cere- bral infarction (especially if multiple), hyperglycemia, fever, anemia, and other systemic complications such as pneumonia and sepsis.71 77 Certain aneurysm factors, such as size, location, and complex configuration, may increase the risk of periprocedural complications and affect overall prognosis.78 Treatment in high-volume centers with availability of neuro- surgical and endovascular services may be associated with Natural History and Outcome of aSAH: Recommendations 1. The initial clinical severity of aSAH should be deter- mined rapidly by use of simple validated scales (eg, Hunt and Hess, World Federation of Neurological Surgeons), because it is the most useful indicator of outcome after aSAH (Class I; Level of Evidence B). 2. The risk of early aneurysm rebleeding is high, and rebleeding is associated with very poor outcomes. Therefore, urgent evaluation and treatment of pa- tients with suspected aSAH is recommended (Class I; Level of Evidence B). 3. After discharge, it is reasonable to refer patients with aSAH for a comprehensive evaluation, in- cluding cognitive, behavioral, and psychosocial assessments (Class IIa; Level of Evidence B). (New recommendation) Clinical Manifestations and Diagnosis of aSAH The clinical presentation of aSAH is one of the most distinctive in medicine. The hallmark of aSAH in a patient who is awake is the complaint the worst headache of my life, which is described by 80% of patients who can give a history.82 This headache is characterized as being extremely sudden and immediately reaching maximal intensity (thun- derclap headache). 