[Subarachnoid Hemorrhage of Unknown Origin at Initial Imaging Investigation]

In some patients with spontaneous subarachnoid hemorrhage(SAH), initial imaging investigations may not be able to detect a bleeding source;repeat imaging may be necessary to reveal these lesions. We reviewed a consecutive series of 45 patients with SAH and negative initial digital subtraction angiograms(DSA)during a 15-year period. The aims were to document the frequency and reason for the negative initial investigations, to determine the appropriate modality and timing of repeat examinations, and to investigate the identified bleeding sources. Twenty-eight(62%)patients underwent repeat DSA, 35(78%)underwent magnetic resonance imaging(MRI), and 33(73%)underwent computed tomography angiography(CTA). Nine lesions(5 small aneurysms, 2 craniocervical junction arteriovenous fistulas, 1 arteriovenous malformation, and 1 internal carotid artery dissection)were identified on subsequent DSA after 2-3 weeks. Most aneurysms were identified on an atypical vascular tree. CTA or MRI alone were unable to disclose the culprit lesions. In retrospect, human errors including oversight were the major reasons for the negative initial investigation results. It is, however, difficult to search for a tiny vascular lesion that might be anywhere in the cranium. Repeat DSA is still the gold standard for the inspection of hidden bleeding sources in patients with SAH of unknown origin.