Purpose: To investigate the rate of false negative initial cerebral angiography in spontaneous SAH and to ascertain why aneurysms remain undetected. Furthermore to validate CCT in predicting the presence and site of an angiographically missed aneurysm.
Methods: Forty-two patients with spontaneous SAH were investigated, in whom initial cerebral angiography did not reveal any bleeding cause. Repeat-angiography was performed in all patients 5 to 55 days (mean 15 days) after the bleeding event. All patients underwent CCT scans within 48h after the ictus.
Results: In 8 of 42 patients (19%) repeat-angiography revealed an aneurysm missed on initial angiography. The aneurysms were located on the AcomA (n = 2), the MCA (n = 2), the ACA (n = 1), the PICA (n = 2) and the junction of ICA and PcomA (n = 1). Presumable reasons for missing an aneurysm were spasms detected in four of eight cases on initial angiography and thrombosis of the aneurysm found in two cases at surgery. In two cases, multiple additional views just revealed the aneurysm appearing different in size and shape on repeat-angiography. CCT blood distribution pattern in four cases indicated presence and site of an aneurysm, while blood distribution was non-specific in the other four cases.
Conclusion: Repeat-angiography plays an important role in defining the site of an initially occult aneurysm and should be performed in all cases of unexplained SAH. It is of particular importance if vasospasm has compromised the initial angiogram or if one part of the vascular tree is not optimally seen.