Fig. 5.

A 67-year-old woman who presented with sudden onset of severe headache. A, NCCT demonstrates a diffuse pattern of SAH with extension to the Sylvian fissures and ventricular system. B, Axial CTA source image did not demonstrate a causative vascular abnormality. C, Frontal left internal carotid angiogram obtained on the same day as the CTA did not demonstrate a causative vascular abnormality. D, Frontal left internal carotid artery angiogram obtained 8 days after the initial CTA demonstrates a 2-mm anterior communicating artery aneurysm (arrowhead). The patient underwent aneurysm coiling.