Clinico-radiologic factors in paraclinoid aneurysms associated with aneurysm rupture: A CTA study

Background and purposeParaclinoid aneurysms are commonly noted as incidental findings by computed tomography angiography (CTA), and there exists disagreement in the literature as to which patient and aneurysm characteristics predict subsequent rupture. This question is of particular significance given the complex anatomy of the paraclinoid region and the associated risks of aneurysm treatment. The purpose of this study was to determine significant associated risk factors for paraclinoid aneurysm rupture.Materials and methodsMedical records and CTA imaging from 179 patients with 205 paraclinoid aneurysms. Patient and aneurysm characteristics including aneurysm size, morphology, and multiplicity were gathered for analysis of rupture risk. Factors influencing the decision to treat or observe unruptured aneurysms were also evaluated. A Cox regression analysis was used, and results were corrected for multiple comparisons using the Bonferroni method.ResultsAneurysm size, diameter:neck ratio, and multilobularity were significantly associated with increased rupture risk; however, only multilobularity remained significant after Bonferroni correction for multiple comparisons. Intervention for unruptured aneurysms was significantly more likely to occur among younger patients and multilobulated aneurysms, or those having a larger diameter, height, height:neck ratio, or diameter:neck ratio.ConclusionsMultilobularity constitutes a significant associated risk factor for rupture among paraclinoid aneurysms. Younger age, larger size and multilobulated aneurysms are characteristics that favored treatment over observation in this cohort.     

Intracranial aneurysms: detection with three-dimensional CT angiography with volume rendering--comparison with conventional angiographic and surgical findings

PURPOSE: To assess the diagnostic accuracy of three-dimensional (3D) computed tomographic (CT) angiography for intracranial aneurysms. MATERIALS AND METHODS: The 3D CT angiograms obtained in 49 patients with or without intracranial aneurysms were evaluated by four blinded observers. Results were compared with findings at conventional angiography or surgery. A volume-rendering method was used, and 13 images obtained in different directions were reviewed in each study. The diameter of aneurysms was divided into four sizes: large, greater than 13 mm; medium, 5-12 mm; small, 3-4 mm; and very small, less than 3 mm. Results were also evaluated by means of receiver operating characteristic analysis. RESULTS: At conventional angiography, 47 aneurysms, including 14 less than 3 mm, were depicted in 35 patients. The mean sensitivity of CT angiography for very small aneurysms was 64%; small, 83%; medium, 95%; and large, 100%. Some very small aneurysms that were not depicted at conventional angiography were depicted at CT angiography, and one was proved at surgery. CONCLUSION: CT angiography has good sensitivity for depiction of intracranial aneurysms 3 mm or larger and relatively good sensitivity for aneurysms less than 3 mm. CT angiography may be a noninvasive technique for detection of asymptomatic unruptured or ruptured aneurysms.     

CT血管造影对脑动脉瘤的临床应用价值

目的 评价ＣＴ血管造影（ＣＡＴ）对脑动脉瘤的诊断价值。方法 脑动脉瘤,１９例行ＤＳＡ检查,１８例手术。用最大强度投影（ＭＩＰ）法进行血管重建。结果 ２０例患者中ＤＳＡ及手术发现２１个动脉瘤,ＣＴＡ发现０个。１９例为单发,１９例为单发,１例为多发（２个）,ＤＳＡ示位于基底动脉和左后交通动脉,ＣＴＡ未能显示后者动脉径为３～３３ｍｍ。１例有血管。靶重建、ＣＴＡ像与原始图像后交通动脉,ＣＴＡ像与原有显始图     

CT during selective arteriography: anatomical assessment of unruptured intracranial aneurysms before endovascular treatment

Our aim was to investigate the usefulness of helical CT during selective angiography (CT arteriography) in pretreatment assessment of unruptured intracranial aneurysms. We studied 47 unruptured aneurysms in 34 prospectively recruited patients for whom endovascular embolisation was initially considered. As pretreatment assessment, we performed rotational digital subtraction angiography (DSA) followed by CT arteriography. The findings on axial source images (axial images) and reconstructed three-dimensional CT angiography (3D-CTA) of CT arteriography were compared to those of rotational DSA, with particular attention to the neck of the aneurysm and arterial branches adjacent to it. Information provided by CT arteriography was more useful than that of rotational DSA as regards the neck in 25 (53 %) of 47 cases and as regards branches in 18 (49 %) of 37 aneurysms. On axial images, small arteries such as the anterior choroidal artery were seen in some cases. CT arteriography can provide valuable additional information about unruptured aneurysms, which cannot be obtained by rotational DSA alone. This technique is useful for obtaining anatomical information about aneurysm anatomy and for deciding the therapeutic strategy. Received: 22 May 2000/Accepted: 25 September 2000     

Renal angiomyolipoma: relationships between tumor size,aneurysm formation,and rupture

PURPOSE: To evaluate the relationships between tumor size, aneurysm formation, and spontaneous rupture in renal angiomyolipomas. MATERIALS AND METHODS: Twenty-three patients with renal angiomyolipoma were examined with angiography and computed tomography (CT). The single largest lesion in each kidney was evaluated. Tumor size was measured at CT, and aneurysm size was measured at renal angiography. Tumor and aneurysm sizes were compared between the group with ruptured angiomyolipoma and the group with unruptured angiomyolipoma. Multiple regression analysis was performed to identify factors affecting rupture. RESULTS: Twenty-nine kidneys with angiomyolipoma were identified. Eight angiomyolipomas were hemorrhagic; the remaining 21 were not hemorrhagic. Tumor size was larger than 4 cm and aneurysm size was 5 mm or larger in all hemorrhagic lesions. There were significant differences in mean tumor size (11.4 cm +/- 5.5 [SD] vs 5.0 cm +/- 3.1, P <.02) and mean aneurysm size (13.3 mm +/- 6.2 vs 2.4 mm +/- 2.9, P <.02) between the ruptured and unruptured tumor groups. When tumor size of 4 cm or larger and aneurysm size of 5 mm or larger were used as predictors of rupture, sensitivity and specificity, respectively, were 100% and 38% with the former criterion and 100% and 86% with the latter criterion. Multiple regression analysis indicated that aneurysm size was the most important factor linked to rupture. CONCLUSION: Aneurysm formation appears to be related to tumor size, and large aneurysms confer a higher probability of rupture.     

Giant aneurysms in CT and angiography

Summary Giant intracranial aneurysms are frequently observed as incidental findings on CT and angiograms obtained for purposes other than subarachnoid hemorrhage, such as slowly evolving nerve palsy or hemiparesis. Since giant aneurysms often thrombose, the CT scan may demonstrate a large aneurysmal volume than the angiogram. This paper presents CT and angiogram findings in cerebral aneurysms with a diameter of 25 mm–60 mm. The discussion covers: sort of aneurysm (congenital, arteriosclerotic); type and degree of thrombosis; long-term results after spontaneous thrombosis; and CT examination after using epsilon-aminocaproic acid.     

Flat panel detector angiographic CT for stent-assisted coil embolization of broad-based cerebral aneurysms

BACKGROUND AND PURPOSE: The purpose of this work was to evaluate angiographic CT (ACT) in the combined application of a self-expanding neurovascular stent and detachable platinum coils in the management of broad-based and fusiform intracranial aneurysms. MATERIALS AND METHODS: Eleven patients harboring wide-necked intracranial aneurysms were treated with a flexible self-expanding neurovascular stent and subsequent aneurysm embolization with platinum microcoils. ACT was performed after the interventional procedure to analyze stent position and the relationship of coils to the stent. Postprocessing included multiplanar reconstructions (MPRs) and maximum intensity projections (MIPs). ACT volume datasets were postprocessed for soft tissue visualization. RESULTS: Accurate stent placement with subsequent coil occlusion of the aneurysms was feasible in all of the patients. Similar to nonsubtracted digital subtraction angiography (DSA) images, radiopaque platinum stent markers showed excellent visibility in ACT as well. The stent struts themselves, hardly visible in nonsubtracted DSA, were visible in MPRs and MIPs of ACT in all of the patients. In aneurysms larger than 10 mm in diameter, accurate stent assessment at the level of the coils was limited due to beam hardening artifacts. Postprocedural ACT in all of the patients did not reveal any evidence of procedure-related intracranial hemorrhage. CONCLUSION: ACT provides cross-sectional, 3D visualization of endovascular stents otherwise hardly visible with plain fluoroscopy. ACT enables us to accurately determine stent position, which may be helpful in complex stent-assisted aneurysm coiling procedures. However, in aneurysms larger than 10 mm in diameter, beam hardening artifacts caused by the endoaneurysmal coil package impair visibility of the stent. Further data are necessary to evaluate the usefulness of ACT in stent-assisted aneurysm coiling.     

Natural history of true pancreaticoduodenal artery aneurysms

Advances in non-invasive diagnostic techniques, such as CT and ultrasonography, have improved our ability to detect unruptured pancreaticoduodenal artery aneurysms. No definitive study evaluating the natural history of these lesions or their preferred method of treatment has been published. In this report, we describe five patients with eight unruptured true pancreaticoduodenal artery aneurysms followed without treatment. Of these patients, four had coeliac axis stenosis (n = 1) or occlusion (n = 3) and one had occlusion of the superior mesenteric artery. The mean diameter of the aneurysms was 12.0 mm (range 7–17 mm). The mean duration of follow-up was 29.4 months (range 6–57 months). There was no aneurysm rupture during a total of 147 patient-months (243 aneurysm-months) of follow-up. Of the eight aneurysms, three increased in size over the follow-up period. We conclude that the risk of rupture of true pancreaticoduodenal artery aneurysms might be lower than expected from the data on ruptured aneurysms; however, careful follow-up of untreated aneurysms is necessary.True pancreaticoduodenal artery aneurysms are rare, accounting for 2% of all visceral aneurysms. More than half of true pancreaticoduodenal artery aneurysms are associated with coeliac axis stenosis or occlusion [1]. The development of pancreaticoduodenal artery aneurysms might be related to increased retrograde blood flow through the pancreaticoduodenal arcades when there is stenosis or occlusion in the coeliac axis [2]. Aneurysm formation is generally preceded by enlargement of the arcades to accommodate the increased blood flow.Although 60% of reported cases of true pancreaticoduodenal artery aneurysms presented with rupture [1], advances in non-invasive diagnostic techniques, such as CT and ultrasonography, have improved our ability to detect unruptured pancreaticoduodenal artery aneurysms. These are now found as incidental findings, usually by CT or ultrasonography. No definitive study evaluating the natural history of these lesions or their preferred method of treatment has been published. In this report, we retrospectively reviewed unruptured true pancreaticoduodenal artery aneurysms followed without treatment to assess the natural history of these lesions.     

Cost-effectiveness of treatment of unruptured intracranial aneurysms in patients with a history of subarachnoid hemorrhage

RATIONALE AND OBJECTIVES: The study goal was to evaluate the cost-effectiveness of surgery and endovascular treatment of unruptured intracranial aneurysms in patients with a history of subarachnoid hemorrhage from a previous aneurysm, incorporating the results of the prospective International Study of Unruptured Intracranial Aneurysms. MATERIALS AND METHODS: Using a Markov model, we performed a decision and cost-effectiveness analysis comparing surgery or endovascular treatment with no treatment. Twelve clinical scenarios were defined based on aneurysm size and location. Probabilistic sensitivity analyses were performed for 50- and 40-year-old cohorts. Treatment was considered to be cost-effective at an incremental cost-effectiveness ratio less than $100,000 per quality-adjusted life-year. RESULTS: In 50-year-old patients, no treatment was the most cost-effective strategy for aneurysms located in the cavernous carotid artery. For aneurysms less than 7 mm located in the anterior circulation, no treatment was the most cost-effective strategy. Endovascular treatment was the most cost-effective option for 7- to 24-mm aneurysms, whereas surgery was the most cost-effective option for aneurysms of 25 mm or larger. For aneurysms less than 7 mm and located in the posterior circulation, endovascular treatment was the most cost-effective option, whereas surgery was the most cost-effective option for 7- to 12-mm aneurysms. No treatment was the most cost-effective strategy for aneurysms of 13 mm or larger. CONCLUSION: For 50-year-old patients with a history of aneurysmal subarachnoid hemorrhage, treatment of unruptured aneurysms that are located in the cavernous carotid artery, or small (<7 mm) and located in the anterior circulation, or large (>or=13 mm) and located in the posterior circulation is ineffective or not cost-effective.     

Magnetic resonance imaging of subarachnoid hemorrhage

Summary Magnetic resonance (MR) imaging of subarachnoid hemorrhage (SAH) due to a ruptured aneurysm has been evaluated in relation to CT findings on 30 patients. In the acute stage, particularly less than 24 hours after the bleeding episode (25 patients), SAH appeared of high intensity relative to the surrounding brain on a T-2 weighted SE image but isointense where the corresponding CT scan showed blood clot of attenuation value over 60H. A T-2 weighted SE image was able to reveal subtle evidence of SAH not visible on the CT scan. The T-1 weighted IR image was not as sensitive. Blood clot (HU>60) appeared isointense, but mild and moderate SAH (HU<60) was indistinguishable from normal CSF. MR imaging was also sensitive to subacute and chronic SAH (5 patients). Three out of four SAH appearing normal on CT showed high intensity on T-2 weighted images. Thirteen out of 24 aneurysms (54%) larger than 5 mm in diameter on angiography were detected on T-2 weighted images. Smaller aneurysms less than 4 mm were not visualized. MR imaging was able to indicate the ruptured one in cases of multiple aneurysms by showing hemorrhagic lesions more clearly than CT. We conclude that MR imaging is very helpful for diagnosing SAH, particularly when CT is normal, and in indicating aneurysm location as well as rupture site.     

Anatomical and morphological factors correlating with rupture of intracranial aneurysms in patients referred for endovascular treatment

The size of intracranial aneurysms is the only characteristic shown to correlate with their rupture. However, the critical size for rupture has varied considerably among previous accounts and remains a point of controversy. Our goal was to identify statistically significant clinical and morphological factors predictive of the occurrence of rupture and aneurysm size in patients referred for endovascular treatment. We retrospectively recorded the following factors from 74 patients who presented with ruptured (40) or unruptured (34) aneurysms: aneurysm morphology (uni/multilobulated), location (anterior/posterior), maximum diameter, diameter of the neck, and the patient's age and sex. We performed stepwise discriminant, and stepwise and logistic regression analysis to identify factors predicting rupture and the size of the aneurysm at rupture. The mean diameter of the ruptured aneurysms was 11.9 ± 6.3 mm, range 3.0–33.0 mm, and that of the unruptured aneurysm 13.5 ± 5.8 mm, range 5.0–30 mm. Stepwise discriminant analysis identified aneurysm morphology (P < 0.001) and location in the intracranial circulation (P < 0.001) as statistically significant factors in predicting rupture. Stepwise regression analysis revealed that aneurysm morphology and the size of the neck were predictors of aneurysm size at rupture. Received: 30 December 1997 Accepted: 28 April 1998     

Pulmonary lymphangiomyomatosis and tuberous sclerosis: comparison of radiographic and thin-section CT findings

Chest radiographs, thin-section computed tomographic (CT) scans, and results of pulmonary function tests in nine women with pulmonary lymphangiomyomatosis and two women with pulmonary tuberous sclerosis were retrospectively evaluated. In all patients, CT demonstrated thin-walled cysts less than 20 mm in diameter scattered at random in all parts of the lungs. In eight patients, cysts larger than 20 mm in diameter were also present. Lung tissue between cysts appeared normal in all 11 patients, except one with septal lines and dependent alveolar areas of attenuation. CT showed cysts in three patients whose radiographs were normal, and it demonstrated that many lesions that appeared reticular on plain radiographs were actually cysts. CT findings correlated better with the diffusion capacity of the lungs for carbon monoxide than did the plain radiographic findings. CT was more sensitive and more precise than radiography at showing the presence and morphology of lung abnormalities.     

破裂与未破裂大脑中动脉瘤容积CT数字减影血管成像对照研究

目的探讨破裂与未破裂大脑中动脉动脉瘤(middle cerebral artery aneurysm,MCAA)在容积CT数字减影血管成像(volume CTdigital subtraction angiograhy,VCTDSA)上的形态学差异。资料与方法回顾性分析2007年9月至2010年1月54例55个MCAA VCTDSA表现,根据颅内有无出血分为破裂组和未破裂组,由两名神经放射学医师采用双盲法评价二者形状、大小、瘤颈、载瘤动脉分叉角度、瘤体纵横比(aspect ratio,AP值),比较二者在形态学上的差异。结果破裂组动脉瘤36个(65.45%),其中椎状或半球状15个(41.6%),囊状12个(33.33%),梭状3个(8.33%),球状1个(2.77%),不规则5个(13.88%);未破裂动脉瘤19个(34.55%),其中锥状或半球状11个(57.89%),囊状4个(21.05%),球状4个(21.05%),二者形状分类上有统计学差异(P<0.05)。破裂组动脉瘤瘤壁伴尖角征12个(33.33%):顶壁8个,侧壁4个;瘤样突起6个(16.67%):顶壁4个,侧壁2个;瘤体上小动脉2个(5.56...     

CT angiography for the diagnosis of aneurysm in the bifurcation of the middle cerebral artery

This study reports 10 aneurysms found in the bifurcation of the middle cerebral arteries (MCA) of seven patients, diagnosed by computed tomography angiography (CTA) and confirmed by digital subtraction angiography and surgery. Six of the 10 aneurysms bled and caused subarachnoid hemorrhage (SAH): the SAH was predominant in the Sylvian fissure where the aneurysms located. Eight aneurysms had a saccular pattern, while two had a fusiform pattern. Nine aneurysms were larger than 8 mm and were easily detected by CTA, while one aneurysm was 6 mm in diameter and was missed initially. It was found, however, after the direction of the CTA was readjusted. In conclusion, the hemorrhages of aneurysm in the bifurcation of the MCA predominated in the Sylvian fissure, and the size of the aneurysm is often big, and thus easily detected by CTA.     

Procedural morbidity and mortality of elective coil treatment of unruptured intracranial aneurysms

BACKGROUND AND PURPOSE: To report morbidity, mortality, and angiographic results of elective coiling of unruptured intracranial aneurysms. METHODS: In a 10-year period, 176 unruptured aneurysms in 149 patients were electively treated with detachable coils. Seventy-nine aneurysms were additional to another ruptured aneurysm but were coiled more than 3 months after subarachnoid hemorrhage, 59 aneurysms were incidentally discovered, and 38 aneurysms presented with symptoms of mass effect. Mean size of the 176 unruptured aneurysms was 10.6 mm (median, 8 mm; range, 2-55 mm). One hundred thirteen aneurysms (64%) were small (<10 mm), 44 aneurysms (25%) were large (10-25 mm), and 19 aneurysms (11%) were giant (25-55 mm). Thirty wide-necked aneurysms (17%) were coiled with the aid of a supporting device. RESULTS: Procedural mortality of coiling was 1.3% (2 of 149; 95% confidence interval [CI], 0.7-5.1%), and morbidity was 2.6% (4 of 149, 95% CI, 0.8-7.0%). The 4 patients with permanent morbidity were independent (GOS 4). Initial aneurysm occlusion was complete (100%) in 132 aneurysms, nearly complete (90%-98%) in 36 aneurysms, and incomplete (60%-85%) in 8 aneurysms. Six-month follow-up angiography was available in 132 patients with 154 coiled aneurysms (87.5%); partial reopening occurred in 25, mainly large and giant aneurysms (16.2%). Additional coiling was performed in 22 aneurysms and additional parent vessel occlusion in 1 aneurysm. There were no complications of additional treatments. CONCLUSION: Elective coiling of unruptured intracranial aneurysms has low procedural mortality and morbidity. For the management of unruptured aneurysms, endovascular treatment should be considered.     

Detection of intracranial aneurysms: multi-detector row CT angiography compared with DSA

PURPOSE: To prospectively compare the effectiveness of multi-detector row computed tomographic (CT) angiography with that of conventional intraarterial digital subtraction angiography (DSA) used to detect intracranial aneurysms in patients with nontraumatic acute subarachnoid hemorrhage. MATERIALS AND METHODS: Thirty-five consecutive adult patients with acute subarachnoid hemorrhage were recruited into the institutional review board-approved study and gave informed consent. All patients underwent both multi-detector row CT angiography and DSA no more than 12 hours apart. CT angiography was performed with a multi-detector row scanner (four detector rows) by using collimation of 1.25 mm and pitch of 3. Images were interpreted at computer workstations in a blinded fashion. Two radiologists independently reviewed the CT images, and two other radiologists independently reviewed the DSA images. The presence and location of aneurysms were rated on a five-point scale for certainty. Sensitivity and specificity were calculated independently for image interpretation performed by the two CT image readers and the second DSA image reader by using the first DSA reader's interpretation as the reference standard. RESULTS: A total of 26 aneurysms were detected at DSA in 21 patients, and no aneurysms were detected in 14 patients. Sensitivity and specificity for CT angiography were, respectively, 90% and 93% for reader 1 and 81% and 93% for reader 2. The mean diameter of aneurysms detected on CT angiographic images was 4.4 mm, and the smallest aneurysm detected was 2.2 mm in diameter. Aneurysms that were missed at initial interpretation of CT angiographic images were identified at retrospective reading. CONCLUSION: Multi-detector row CT angiography has high sensitivity and specificity for detection of intracranial aneurysms, including small aneurysms, in patients with nontraumatic acute subarachnoid hemorrhage.     

MR angiography and surgery for unruptured familial intracranial aneurysms in persons with a family history of cerebral aneurysms.

OBJECTIVE: We used MR angiography to determine prevalence of unruptured familial intracranial aneurysms in a prepaid medical care program. We compared surgical outcomes and the cost of treating unruptured versus ruptured aneurysms. We compared the cost of MR angiography with the cost of screening mammography and with the cost of surgically treating a ruptured aneurysm. SUBJECTS AND METHODS: During a 30-month period, we performed MR angiography to show cerebral aneurysms in 63 surgical candidates who had one or more first-degree relatives with an aneurysm. Unruptured aneurysms seen on MR angiography were evaluated by digital subtraction angiography (DSA) and treated surgically. RESULTS: MR angiography showed nine unruptured aneurysms in six patients. Eight aneurysms were seen on MR angiography and nine were seen on DSA. Seven unruptured aneurysms were treated surgically. The mean treatment cost was 50% lower for an unruptured aneurysm than that for a ruptured aneurysm. No patient surgically treated for an unruptured aneurysm required rehabilitation, unlike 25% of patients with ruptured aneurysms. The annual total cost of MR angiography was equivalent to 2.9% of the annual cost of screening mammography. The annual cost of MR angiography equaled half the cost of treating one patient after aneurysm rupture. CONCLUSION: MR angiography showed a 9.5% prevalence of unruptured aneurysms among persons who had one or more first-degree relatives with a cerebral aneurysm. DSA confirmed 88% of aneurysms found on MR angiography. Persons with unruptured aneurysms had better treatment outcomes at lower cost than did patients treated for aneurysm rupture. The annual MR angiography cost was low compared with the cost of screening mammography and with the cost of treating one patient with aneurysm rupture.     

Comparative evaluation of cerebral aneurysms with selective arterially enhanced CT and DSA

The purpose of our study was to compare selective arterially enhanced spiral computed tomographs (ACT) with digital subtraction angiographies (DSA) in the presurgical assessment of cerebral aneurysms. A total of 24 aneurysms in 18 patients were explored in a prospective study by ACT and DSA, using an interactive combined CT-angiography suite. Dimensions of the aneurysm, its relation to the parent vessel, and the aneurysmal index were defined on DSA and on surface-shaded display of 3D reformatted images obtained from ACT. Results were correlated with surgical findings. Three aneurysms suspected on DSA were not confirmed by ACT. One fusiform aneurysm suspected on DSA corresponded to a sacciform aneurysm on ACT. Surgical findings confirmed 20 sacciform aneurysms. The aneurysmal index could be measured in all 20 cases of sacciform aneurysms on ACT and could not be determined with confidence in 55 % of the cases on DSA. DSA and ACT gave identical results in 35 % of cases. In 10 %, the index measured by ACT was superior to that determined by DSA for aneurysms which had a diameter of less than 3 mm. In conclusion, the combination of DSA and ACT improved the results of DSA alone. ACT is a reliable method to measure the aneurysmal index in aneurysms with a diameter superior to 3 mm. Received 4 September 1997; Revision received 20 November 1997; Accepted 24 December 1997     

Accuracy of high resolution computed tomography in direct diagnosis of cerebral aneurysms

Summary With high resolution computed tomography (CT) of the skull, performing rapid series of 1.5 mm slices during an intravenous bolus injection of contrast medium, an angiography-like image (angio-CT) of the basal cerebral arteries can be obtained. From 76 consecutive angiographically or autopsy-verified cerebral aneurysms of vaious size down to 3 mm in diameter, 74 (97.4%) were shown up by the angio-CT. One ruptured and one incidental aneurysm escaped CT visualization. Besides the correct localization of the aneurysms, angio-CT provides information concerning the size and main direction of the aneurysms and yields, in addition, a coronal view of the aneurysms and their surrounding structures. Pitfalls for mis-diagnosis can be the following: Aneurysms of below 5 mm in diameter, located at the supraclinoid part of the carotid artery, multiple or non-ruptured aneurysms, bony or movement artefacts, poorly contrasted vessels due to wrong injection technique of contrast medium or vasospasm, and incorrect interpretation.     

The perianeurysmal environment: influence on saccular aneurysm shape and rupture

PURPOSE: The purpose of this study was to evaluate whether interactions between intracranial cerebral saccular aneurysms and the perianeurysmal environment (PAE), in the form of contact constraints, influence aneurysm shape and risk of rupture. METHODS: A total of 190 consecutive aneurysms during a 34-month period were retrospectively analyzed. Of these, 124 were ruptured (group 1) and 66 were unruptured (group 2). Pretreatment high-resolution CT angiography was available for each aneurysm and was the determinant inclusion criterion. Aneurysm size and location, type of hemorrhage, initial Glasgow Coma Scale rating, World Federation of Neurological Societies grade, Fisher grade, and presence of concomitant aneurysms were recorded. Contact constraints between aneurysms and anatomical structures of the PAE were identified for each aneurysm and further subdivided into balanced or unbalanced depending on whether contact constraints occurred symmetrically on the aneurysm wall. Regular or irregular shape was recorded and correlated to contact constraints. RESULTS: Compared with unruptured aneurysms, ruptured aneurysms were found to be larger and more irregular, to develop more contact constraints with the PAE, and to show higher rates of unbalanced contact constraints. Ruptured aneurysms had a tendency to be found in locations of a constraining PAE. Irregular shape was positively correlated with the presence of an unbalanced contact constraint, even in the absence of obvious contour deformations from an imprint of an adjacent structure. CONCLUSION: The existence of contact constraints between intracranial saccular aneurysms and the PAE were shown to influence shape and risk of aneurysm rupture. Modifications of wall shear stress by contact constraints are discussed. Analysis of contact constraints between aneurysm and the PAE could be considered additional parameters in the assessment of risk of aneurysm rupture.