Analysis of Initial Angiographic False Negative Aneurysmal Patients and False Positive Non-Aneurysmal Patients

ABSTRACT

OBJECTIVE: This study was undertaken to investigate the clinical and computerized tomographic(CT) features between the false negative aneurysms, in which the cerebral aneurysms missed by the initial angiography and false positive aneurysms, in which aneurysms were not existed at surgery in spite of the aneurysm suggested by the cerebral angiography, and to verify the causes of false negative and positive aneurysms. METHODS: The differences of the clinical and CT characteristics between false negative and positive aneurysmal patients, and the sites of aneurysm in false negative aneurysmal patients and suspicious sites of aneurysms in false positive aneurysmal patients, and the main causes of cerebral aneurysms missed by initial angiography and false aneurysmal findings in cerebral angiography were investigated. RESULTS: There were 36 false negative aneurysmal patients and 14 false positive aneurysmal patients in our series. The clinical grades and amount of subarachnoid hemorrhage(SAH) in false negative aneurysmal patients were more severe than those of false positive non-aneurysmal patients. The most frequent false negative and positive aneurysmal sites were anterior communicating(Acom) arteries. All missing aneurysmal site due to incomplete study was posterior inferior cerebellar artery. The main causes for missing aneurysm in angiography were aneurysmal thrombosis with or without small size of aneurysmal neck, overlapping vessels and small size of aneurysm itself. The main causes of false aneurysmal findings in cerebral angiography were junctional dilatation of posterior communicating artery(Pcom), dilatation of perforators origin and focal atherosclerotic dilatation of cerebral main vessels. All cases who had SAH in the perimesencephalic cistern were false positive non-aneurysmal patients. In some cases of A2 aneurysm showed more severe SAH in the basal cistern than that in the anterior interhemispheric fissure. CONCLUSION: The repeat-angiography should be performed for all cases of unexplained SAH, especially for poor clinical grade patients with thick SAH and cases with incomplete visualization of all vascular trees. Surgery should be decided more carefully for patients with perimesencephalic basal cistern SAH who show Pcom artery aneurysm by cerebral angiography. We also stress that some of A2 aneurysms may show inconsistent sites of SAH from the origin of aneurysm.