**2. Diagnosis**

Several grading systems, including Glasgow coma score (GCS), WFNS grade (World Federation of Neurological Societies), Hunt & Hess scale, or modified Hunt & Hess scale, have been used for initial clinical assessment of aSAH. Patients with poor-grade aSAH often present with stupor or coma because of the primary brain injury. WFNS grade has better inter- and intraobserver reliability than Hunt & Hess scale and makes it more appropriate [13]. Poor-grade aSAH is defined as WFNS grade IV or V (a GCS score of 7–12 for grade IV and 3–6 for grade V) [14]. It is important to detect ruptured aneurysms in the setting of poor-grade aSAH. These patients are often unstable and require sedation or anesthesia during examination.

Traditionally, digital subtraction angiography (DSA) is the gold standard technique for detecting ruptured aneurysms [15–19]. CT angiography (CTA) is less invasive and less time-consuming in providing information on ruptured intracranial aneurysms as a primary examination tool for aSAH. Current studies have reported the sensitivity and specificity of CTA for detecting intracranial aneurysms [20]. Matsumoto et al. [21] reported that 27 patients underwent successful surgical clipping based on CTA alone. Our previous study reported that more than a third of patients underwent successful surgical treatment on the basis of CTA alone [22]. All ruptured aneurysms were detected and clipped. Complications and clinical outcomes did not significantly differ between CTA alone and DSA group. Therefore, CTA can provide fast and accurate diagnostic and anatomic information on ruptured aneurysms and it can be safely and effectively used in most patients with poor-grade aSAH requiring surgical treatment. Patients with smaller ruptured aneurysms or multiple aneurysms may be considered for additional DSA examination.
