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Current usage of three-dimensional computed tomography angiography for the diagnosis and treatment of ruptured cerebral aneurysmsKenichi Amagasaki MD, Nobuyasu Takeuchi MD, Takashi Sato MD, Toshiyuki Kakizawa MD, Tsuneo Shimizu MD Kanto Neurosurgical Hospital, Kumagaya, Saitama, Japan Summary Our previous study suggested that 3D-CT angiography could replace digital subtraction (DS) angiography in most cases of ruptured cerebral aneurysms, especially in the anterior circulation. This study reviewed our further experience. One hundred and fifty patients with ruptured cerebral aneurysms were treated between November 1998 and March 2002. Only 3D-CT angiography was used for the preoperative work-up study in patients with anterior circulation aneurysms, unless the attending neurosurgeons agreed that DS angiography was required.Both 3D-CT angiography and DS angiography were performed in patients with posterior circulation aneurysms, except for recent cases that were possibly treated with 3D-CT angiography alone. One hundred sixteen (84%) of 138 patients with ruptured anterior circulation aneurysms underwent surgical treatment, but additional DS angiography was required in 22 cases (16%). Only two recent patients were treated surgically with 3D-CT angiography alone in 12 patients with posterior circulation aneurysms. Most patients with ruptured anterior circulation aneurysms could be treated successfully after 3D-CT angiography alone. However, additional DS angiography is still necessary in atypical cases. 3D-CT angiography may be limited to complementary use in patients with ruptured posterior circulation aneurysms.a 2003 Elsevier Ltd. All rights reserved.Keywords: 3D-CT angiography, cerebral aneurysm, subarachnoid haemorrhage, surgery INTRODUCTIONRecently, three-dimensional computed tomography (3D-CT) angiography has become one of the major tools for the identification of cerebral aneurysms because it is faster, less invasive, and more convenient than cerebral angiography.1–7 Patients with ruptured aneurysms could be treated under diagnoses based on only 3D-CT angiography.5;6 3D-CT angiography has some limitations for the preoperative work-up for ruptured cerebral aneurysms, so additional digital subtraction (DS) angiography is still necessary, especially for aneurysms in the posterior circulation.8 Our previous study suggested that 3D-CT angiography could replace DS angiography in most patients with ruptured cerebral aneurysms in the anterior circulation.1 This study reviewed our experience of treating ruptured cerebral aneurysms in the anterior and posterior circulations based on 3D-CT angiography in 150 consecutive patients to assess the current usage of 3D-CT angiography.METHODS AND MATERIALPatient populationWe treated 150 patients, 60 men and 90 women aged from 23 to 80 years (mean 57.5 years), with ruptured cerebral aneurysm identified by 3D-CT angiography between November 1998 and March 2002.Managementof casesThe presence of nontraumatic subarachnoid haemorrhage (SAH) was confirmed by CT or lumbar puncture findings of xanthochromic cerebrospinal fluid. 3D-CT angiography was performed routinely in all patients. DS angiography was performed in patients with anterior circulation aneurysms only if additional information was considered necessary following a consensus interpretation of the initial CT and 3D-CT angiography by four neurosurgeons. Patients with ruptured aneurysms in the posterior circulation underwent both 3D-CT angiography and DS angiography except for two recent patients with typical vertebral arteryposterior inferior cerebellar artery (VA-PICA) aneurysm.Typical saccular aneurysms were treated by clipping surgery.Fusiform and dissecting aneurysms were treated by proximal occlusion by either surgery or endovascular treatment with or without bypass surgery. Regrowth of bleeding aneurysms was treated by either surgery or endovascular treatment. Postoperatively, all patients were managed with aggressive prevention and treatment of vasospasm including intra-arterial infusion of papaverine or transluminal angioplasty.3D-CT angiography acquisition and postprocessing CT angiography was performed with a spiral CT scanner (CT-W 3000 AD; Hitachi, Ibaraki, Japan). Acquisition used a standard technique starting at the foramen magnum, with injection of 130 ml of nonionic contrast material (Omnipaque; Daiichi Pharmaceutical,Tokyo, Japan). The source images of each scan were transferred to an off-line computer workstation (VIP station; Teijin System Technology, Japan). Both volume-rendered images and maximum intensity projection images of the cerebral arteries were constructed. The anterior circulation and posterior circulation were evaluated separately on thevolume-rendered images, after a general superior view was obtained. The anterior circulation was evaluated by first observing the anterior communicating artery (ACoA) by rotating the view, and then each side of the carotid system by rotating the image with editing out of the contralateral carotid artery. The posterior circulation was also evaluated by rotating the image but without editing out of any vessel. Once a possible rupture site was found, the view was zoomed and closely rotated with the other vessels edited out. Theaneurysm size was measured on 3D-CT angiography as the larger of the length of the dome or the width of the neck. Manipulation was performed by the scanner technician, with a neurosurgeon to provide editing assistance.DS angiography acquisitionStandard selective three- or four-vessel DS angiograms with frontal, lateral, and oblique projections were obtained. The 3D-CT angiogram was always available as a guide for possible additional DS angiography projections. Aneurysm size was measured with DS angiography when the quality of 3D-CT angiography was inadequate. All patients except elderly patients or patients in severe condition underwent DS angiography postoperatively.Grading of patientsThe clinical conditions of the patients at admission were classified according to the Hunt and Kosnik grade.9 Clinical outcome was determined at 3 months according to the Glasgow OutcomeScale.10RESULTSThe aneurysm locations and sizes are shown in Table 1. One hundred sixteen (84%) of 138 cases of aneurysms in the anterior circulation were treated after only 3D-CT angiography, and 22 cases (16%) required additional DS angiography. Ten of 12 cases of aneurysms in the posterior circulation required both 3D-CT angiography and DS angiography, but two recent cases of typical VA-PICA aneurysm were clipped after only 3D-CT angiography (Fig. 1). The first 10 of the 22 cases in the anterior circulation, which required additional DS angiography were described previously, 1 so the most recent 12 patients are listed in Table 2. These recent cases included some atypical aneurysms. Cases 6 and 8 had a fusiform aneurysm of the internal carotid artery (ICA). Additional DS angiography was performed to obtain haemodynamic information. ICA trapping with superficial temporal artery-middle cerebral artery anastomosis was performed in Case 6 because the atherosclerotic arteries failed to demonstrate the balloon occlusion test (Fig. 2). ICA occlusion by endovascular treatment was performed in Case 8 because the patient could tolerate the balloon occlusion test. Cases 4, 9, and 10 suffered regrowth of bleeding aneurysms after clipping surgery. Clip artifacts prevented evaluation of the ruptured site as well as identification of de novo aneurysms in these cases (Fig. 3). Surgical clipping was performed in Cases 4 and 10 and endovascular treatment in Case 9. Case 11 had an ACoA aneurysm associated with an arteriovenous malformation (AVM) (Fig. 4). DS angiography was performed to evaluate the AVM. Case 12 had a large ICA-posterior communicating artery (PCoA) aneurysm, and additional DS angiography was performed because the PCoA could not be detected by 3D-CT angiography (Fig. 5). Cases 1, 2, 3, 5, and 7 presented with small aneurysms, and DS angiography was performed to exclude other lesions as well as to obtain information about the proximal ICA for patients with supraclinoid type aneurysms.Table 1 Distribution and size of cerebral aneurysms in 150 consecutive patients Site No. of patientsAnterior circulation 138ICA (supraclinoid) 3ICA bifurcation 1ICA-OphA 3ICA-PCoA 39 (1)ICA fusiform 2ACoA 50Distal ACA 4MCA 36 (1)Posterior circulation 12PCA 1BA tip 3BA-SCA 1BA trunk 1 (1)VA-PICA 3VA dissecting 3 (1)Size (mm)<5 42P5 to <12 99P12 9Number in parentheses indicates patients who underwent endovascular treatment. OphA, ophthalmic artery; ACA, anterior cerebral artery; MCA, middle cerebral artery; PCA, posterior cerebral artery; BA, basilar artery; SCA, superior cerebellar artery.Table 2 Twelve patients with ruptured anterior circulation aneurysms who underwent additional DS angiographyCase No. Location Size (mm)1 lt. ICA-PCoA 3.12 ACoA 2.23 lt. ICA supraclinoid 1.64 lt. ICA-PCoA 7.85 lt. ICA supraclinoid 2.46 lt. ICA (fusiform) 11.87 lt. ICA-PCoA 3.28 rt. ICA (fusiform) 18.89 lt. MCA 9.610 lt. ICA-PCoA 10.511 ACoA 10.112 lt. ICA-PCoA 18.2The surgical findings correlated well with the 3D-CT angiography or DS angiography. Table 3 shows the condition on admission and outcome at 3 months after surgery. Some patients with good grades on admission died of severe spasm, acute brain swelling, or poor general condition, but these outcomes were not related to the preoperative radiological information.DISCUSSIONThe present study of ruptured aneurysms in both anterior and posterior circulations found that the indications for additional DS angiography in the anterior circulation are similar to that found previously, but we experienced some new atypical cases. Treatment of fusiform aneurysms depends on the haemodynamic information, which could only be obtained by DS angiography. ACoA aneurysm associated with AVM, although the initial CT indicated that the aneurysm had bled, required accurate evaluation of the AVM prior to surgery. Clip artifacts affected 3D-CT angiography in cases of recurrent SAH after clipping surgery, so 3DCT angiography is not indicated for such cases.3D-CT angiography was only of complementary use in most of the 12 cases of posterior circulation aneurysms. Only two cases of typical VA-PICA aneurysms were treated based on only 3D-CT angiography. Typical basilar artery-superior cerebellar artery and VA-PICA aneurysms can be treated surgically after only 3D-CT angiography. DS angiography should always be performed for basilar tip aneurysms to evaluate the perforating arteries nearby as well as assess the vessel tortuosity for the possibility of endovascular treatment. Treatment of VA dissecting aneurysms needs information about the true and false lumens of the VA which requires DS angiography. The small population of posterior circulation aneurysms in this study indicates that the variation of aneurysms as well as the treatment choices in the posterior circulation require DS angiography in most cases.In our series, most aneurysms measured 5–12 mm, and typical saccular aneurysms of that size could be treated after 3D-CT angiography. However, there were problems with some large aneurysms. DS angiography was not necessary if the neck and nearby arteries of a large aneurysm were clearly detected. DS angiography was necessary in two cases of large aneurysms. A case of large ophthalmic artery aneurysm was located close to the anterior clinoid process.1 Small PCoA aneurysms may not be detected by 3D-CT angiography, but the artery would not be difficult to observeduring the operation. In our case of a large PCoA aneurysm, DS angiography was performed because the large neck would prevent intraoperative observation of the PCoA.Although not experienced in our series, treatment including bypass surgery for some large or giant aneurysms will require the haemodynamic information provided by DS angiography. Some small aneurysms (less than 4 mm) required additional DS angiography. 3D-CT angiography may be better for detecting small aneurysm than DS angiography.11;12 However, we suggest DS angiography is still necessary in the following cases. Firstly, compatibility of the initial CT scan and aneurysm location by 3DCT angiography is important. Patients with ruptured aneurysm and asymmetrical SAH with laterality compatible with the rupture site present no problem. However, we cannot always depend on the initial CT scans if the SAH is diffuse or symmetrical, especially if ACoA aneurysm or basilar tip aneurysm is not found the responsible lesion. DS angiography is more useful to exclude other lesions because of the smooth opacification of the vessels.Secondly, cases with small aneurysm located on the supraclinoid portion require proximal ICA control during the operation. DS angiography is necessary to provide information about the haemodynamics including the cross circulation.Magnetic resonance (MR) angiography is potentially the only modality required for preoperative assessment of ruptured cerebral aneurysms.13 However, MR imaging is time-consuming and access to MR scanners may be restricted. Patients could be in an unstable condition in the very early period of SAH, so that the emergent condition of the patients could be much easier to manage in the CT facility. On the other hand, MR angiography does reduce the use of contrast medium, so is a safe diagnostic tool. MR angiography may be the best modality for diagnosis in patients with good grade presenting several days after the onset, because the risk of rerupture falls with time.3D-CT angiography has been used to analyze the anatomical structures for surgery.14;15 Information about the venous and arterial structures near the aneurysm are preferable, but do not always reflect the findings of DS angiography. Normal anatomical structures, such as perforating arteries and veins, are likely to be encountered during surgery although not detected clearly by 3D-CT angiography. This study of the overall management of ruptured cerebral aneurysms with 3D-CT angiography and additional DS angiography indicates that more patients with anterior circulation aneurysms will be treated after only 3D-CT angiography except for the following cases requiring additional DS angiography: Aneurysms close to bone structures, such as an ICA-ophthalmic artery aneurysm; fusiform aneurysms, and large or giant aneurysms requiring accurate neck information and haemodynamic informationfor bypass surgery; patients with discrepancies between the distribution of SAH on CT and the location of the aneurysm, especially small aneurysms, to exclude other lesions; small aneurysms located on the supraclinoid portion of ICA, which require information about haemodynamics and proximal ICA control; regrowth of aneurysms that leads clip artifacts; and aneurysms associated with AVM in related locations. A clear conclusion about patients with posterior circulation aneurysms cannot be reached because of the small population. Typical basilar artery-superior cerebellar artery and VA-PICA aneurysms can be treated surgically after only 3D-CT angiography, but 3D-CT angiography may be limited to complementary use for basilar tip aneurysms and other posterior circulation aneurysms because of the need for close observation of nearby perforating arteries and the possibility of endovascular treatment. Dissecting aneurysm, which is often observed in the VA, requires DS angiography to detect true and false lumens.REFERENCES1. Amagasaki K, Sato T, Kakizawa T, Shimizu T. Treatment of ruptured anterior circulation aneurysm based on computerized tomography angiography: surgical results and indications for additional digital subtraction angiography. J Clin Neurosci 2002; 9: 22–29.2. Anderson GB, Steinke DE, Petruk KC, Ashforth R, Findlay JM. 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