Rapid spontaneous diminution of cisternal blood on computed tomography in patients with subarachnoid hemorrhage

BACKGROUND purpose of this study is to investigate whether rapid spontaneous diminution of cisternal subarachnoid hemorrhage (SAH) alleviates vasospasm in the corresponding arterial territory, METHODS The subjects were 103 patients in whom initial computed tomography scans were performed within 24 hours after SAH and repeated within 72 hours. We analyzed the effect of diminution of cisternal SAH on vasospasm in 16 sites in each patient. Of the total 1642 cisterns, SAH was found in 1362 (83%), of which 539 (40%) had a decrease in SAH. The highest diminution rate was 64% in quadrigeminal cistern, and the lowest rate was 27% in frontal interhemispheric fissure (IHF). In basal frontal IHF, both the incidence of diminution of SAH and its degree were significantly lower in patients with ruptured anterior cerebral artery aneurysms than in those with other site aneurysms, while in suprasellar cisterns, sylvian stems, and sylvian fissures, diminution of SAH was not affected by the side of ruptured aneurysms. The diminution of SAH in basal frontal IHF and sylvian stems was associated with less vasospasm in adjacent arteries. CONCLUSIONS We concluded that in patients with SAH, rapid spontaneous diminution of cisternal blood, which is affected by several factors, makes vasospasm in the corresponding arterial territory less likely.