The main cause of spontaneous SAH was aneurysmal rupture, and misdiagnosis results in severe neurologic disability and death. DSA is good modality for aneurysm detection. However, in 15% of patients with spontaneous SAH, no aneurysmal structure is found on the initial DSA.
4) This might be due to a very small microaneurysm, occult aneurysm concealed by hemorrhage or vasospasm, hemorrhage from a venous system, or inadequate technique.
2)6) Although these misdiagnose may have been unavoidable, the result is severe neurologic disability and death. Therefore, when initial DSA revealed no aneurysm, repeat DSA is required in order to reduce the incidence of morbidity and mortality due to misdiagnosis.
In the current study, all patients who had negative findings on the initial DSA underwent repeat DSA; 28 of the patients had a negative initial DSA, and cerebral aneurysms were found in two patients (false-negative rate 7.1%). The rate of misdiagnosis was reduced, compared to other studies, which might be due to developments in the capacity of diagnostic DSA. We evaluated the necessity of repeat DSA with negative initial DSA according to the SAH pattern. PN-SAH is a distinct characteristic imaging pattern of nontraumatic, nonaneurysmal SAH, which is associated with a good clinical outcomes.
13) Compared to aneurysmal SAH, it usually presents only with headaches and no mental deterioration and with a good clinical grade.
9)13) On admission, clinical grades corresponding to GCS scores and the GOS score at discharge was higher in the PN-SAH group than in the NPN-SAH group; however, these results showed no statistical significance. Most of these patients had good clinical outcomes, however, one patient in the NPN-SAH group died due to re-bleeding and consequential vasospasm.
Two patients had an aneurysm on repeat DSA and the size and shape of the aneurysms were changed between the initial and repeat DSA. These two aneurysms were located on the dorsal wall of the ICA. Two of the false-negative initial DSA patients showed an NPN-SAH pattern on the initial CT scan. When compared to the PN-SAH group, the NPN-SAH group had a high false-negative rate (16.7%) (0%,
p = 0.175). Based on the results of our study, because structural abnormalities, such as aneurysms, can be obscured in the first angiogram, repeated DSA is always indicated in patients with NPN-SAH patterns upon CT scan and negative initial DSA. In particular, configurational changes have been observed in serial cerebral angiography of supraclinoid dorsal wall aneurysms. Repeated DSA should result in reduced false-negative rates and the incidence of re-bleeding. PN-SAH patterns have a very high predictive value for normal angiogram.
10) Due to improvements in diagnostic imaging capabilities, such as three-dimensional rotational angiography (3-DRA), the recent incidence of DSA-negative SAH has shown a remarkable reduction. This technique is better for resolving complicated anatomy, allowing the investigator to detect aneurysms that are otherwise not visible when using conventional DSA. Ishihara et al.
4) reported that the incidence of DSA-negative SAH was 8.6% in the DSA group and 4.2% in the 3-DRA group. Although DSA with 3-DRA is the gold standard for detection of aneurysms, it is invasive and may be associated with neurological complications. In our series of 16 PN-SAH patients, the cause of bleeding was not detected through repeated DSA. Thus, provided that the initial DSA was technically adequate and revealed no vasospasm, a repeat DSA might not be required.
11) We advocate the need for only a single DSA with 3-DRA in the PN-SAH group. Due to the benign clinical course of this subgroup, we believe that the risks of DSA are too high in comparison with CT angiography.
12)14) CT angiography has multiple advantages over DSA, as it is a noninvasive, widely available technique, which requires shorter time, and uses less contrast media than the DSA performed in patients with negative CT angiography.
3) However, when the hemorrhage shows an NPN-SAH pattern, repeat DSA is necessary due to the possibility of aneurysmal SAH, even if the initial DSA is negative (
Fig. 4). Configurational changes have occasionally been observed in repeat DSA: blister-like aneurysms have shown changes in configuration into a saccular type and have even shown spontaneous regression.
1)7)