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

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.

Subarachnoid Hemorrhage with Negative Initial Angiography

In 614 of 793 cases with subarachnoid hemorrhage(SAH), four vessel cerebral angiography was performed to investigate the source of the hemorrhage. The first four vessel study revealed 501 cases of ruptured cerebral aneurysms; during initial pan-angiography studies, 113 SAH patients did not show vascular lesions. Thirty two of 71 patients(45.1%) showed aneurysms on repeat angiography: fifteen of them had aneurysms in the anterior communicating artery. Among patients whose Hunt Hess grade on admission was poor(III-IV), the possibility of revealing aneurysm during repeated angiography was higher than in those whose grade was good(I-II)(p<0.05, Fisher exact test). On repeat angiography, the age, sex and CT grade of patients with aneurysm were indistinguishable from those of patients without: even in those who on initial angiography showed angiographic vasospasm, the chance of revealing an aneurysm was the same as in those without spasm. We concluded that repeated angiography, especially after 3 weeks of ictus, was valuable for the detection of an initially undefined aneurysm.

Subarachnoid Hemorrhage with Negative Angiography: Whether or not to Repeat the Angiography

In recent years there has been a tendency to abandon repeat cerebral angiography in patients with subarachnoid hemorrhage(SAH) if the initial angiogram is normal because prognosis is said to be excellent. Our experiences does not support such a conclusion. In 291 cases with subarachnoid hemorrhage(SAH), four vessel cerebral angiography was performed to investigate a source of the hemorrhage. The first four vessel study on admission revealed 234 cases(80.4%) of ruptured cerebral aneurysms. Fifty-five of 291 patients with primary subarachnoid hemorrhage(SAH) did not show vascular lesion in initial pan-angiography studies. In order to define the benefit of control angiography these patients were reviewed. Among 41 patients who underwent repeat angiography, a second angiography showed an aneurysm in 24(58.5%). Twelve of the twenty-four cases had aneurysms in the anterior communicating artery. But the age, sex, initial clinical grade and CT grade of patients with aneurysm in repeat angiography were indistinguishable from thoses of patients without aneurysm. Even in the patients who showed angiographic vasospasm in intial angiography, probability of revealing an aneurysm was not different from those without spasm. We conclude that repeat angiography is necessary in the cases of SAH with normal initial angiogram regardless of the CT findings and the presence of vasospasm.