Spontaneous saccular cerebral aneurysm in a rat

Summary A saccular cerebral aneurysm was incidentally found at the bifurcation of a fenestrated anterior cerebral artery of 35-week-old Sprague-Dawley rat. The animal had been fed a normal laboratory diet. The internal lamina extended for a short distance into the neck of the aneurysm and then suddenly disappeared. The medial layer ended abruptly at the neck of the aneurysm. The aneurysmal wall consisted mainly of connective tissue, and of some poorly stained fragments of elastic lamina. No evidence of polyarteritis nodosa or any other inflammatory reaction was obtained. These findings were the same as those observed in man. Therefore, this aneurysm proved to be of truly spontaneous origin.In contrast to experimental aneurysms in rats and in monkeys, in which aneurysms are observed very often, degenerative changes of the elastic lamina in spontaneous aneurysm in the rat were confined to the neck of the aneurysm. This fact may explain partly the difference in frequency between spontaneous and experimental aneurysms in animals. The present study indicates that degenerative changes of the elastic lamina play a very important role in the development of saccular cerebral aneurysms.     

Vascular corrosion casts mirroring early morphological changes that lead to the formation of saccular cerebral aneurysm: an experimental study in rats

OBJECT: The formation of cerebral aneurysms involves complex processes and little is known about the mechanisms by which they originate, grow, and rupture. The purpose of this study was to identify early ultrastructural morphological changes that lead to the formation of experimental cerebral aneurysms. METHODS: Twenty male Sprague-Dawley rats were subjected to cerebral aneurysm induction (renal hypertension and right common carotid artery ligation); 10 intact rats served as the control group. The animals were killed after 2 months, and a vascular corrosion cast of their cerebral arteries was prepared and screened for aneurysm development by using a scanning electron microscope. Sequential morphological changes observed at the cerebral artery bifurcation in response to hemodynamic shear stress included endothelial changes, intimal pad elevation, and saccular dilation. Endothelial cell changes were the first observed morphological changes; they were followed by various degrees of artery wall dilation. No aneurysmal changes developed in any of the control rats. Of the 20 surgically treated rats, 11 displayed aneurysmal changes. In five of these animals only changes in the endothelial cell imprints could be identified. In the other six rats morphological changes in endothelial cells were associated with different stages of aneurysmal dilation. CONCLUSIONS: This is the first study to demonstrate in vivo early morphological changes that lead to the formation of cerebral aneurysms. The morphological findings indicate the principal role of endothelial cells in the pathogenesis of cerebral aneurysms and suggest that hemodynamic shear stress and blood flow patterns may precipitate these early changes.     

Internal carotid artery dorsal wall aneurysm with configurational change: Are they all false aneurysms?

BACKGROUND: Aneurysms arising from nonbranching sites of the ICA, so-called dorsal wall aneurysm, are rare entity, and present as blister type or saccular type. Occasionally configurational changes have been observed on serial cerebral angiography: a small blister-like bulge on ICA wall on initial angiography progressing to a saccular appearance within a few weeks. Such aneurysm showing configurational change has been regarded as a false aneurysm with fragile wall just like blister-type aneurysm, and direct surgical approach has been considered highly risky. CASE DESCRIPTION: A 42-year-old woman with a subarachnoid hemorrhage revealed small "blister-like" aneurysm at the medial wall of the ICA on initial angiography. After 12 days, the following angiograms demonstrated increased aneurysmal size and change of shape into a saccular configuration. Direct surgical approach was performed. The aneurysm had a relatively firm neck, and was successfully clipped without intraoperative rupture. The dome of aneurysm was resected after clipping and the histologic examination revealed it as a true aneurysm. CONCLUSIONS: This case suggests that all dorsal wall aneurysms with configurational change are not false aneurysms, and that angiographic findings do not always correlate with the nature of the aneurysmal wall; therefore, we should give more credence to direct surgical observation rather than preoperative angiographic findings when considering the most suitable surgical option.     

Role of estrogen deficiency in the formation and progression of cerebral aneurysms. Part II: experimental study of the effects of hormone replacement therapy in rats

OBJECT: The increased incidence of cerebral aneurysms in postmenopausal women appears to be related to low levels of circulating estrogen. Using a rat model of aneurysm induction, the authors found that oophorectomy increased the incidence of experimental cerebral aneurysms (Part I in this issue). In the current study they examined the effects of hormone replacement therapy (HRT) on the formation of cerebral aneurysms in rats. METHODS: Forty-five female Sprague-Dawley rats were divided into three equal groups. The animals in Groups A and B were subjected to a cerebral aneurysm induction procedure (renal hypertension and right common carotid artery ligation) followed 1 month later by bilateral oophorectomy. After an additional week the rats in Group A received 17beta estradiol continuous-release pellets. The rats in Group C served as controls. Three months after the aneurysm induction procedure, all the rats were killed and vascular corrosion casts of their cerebral arteries were prepared and checked for aneurysmal changes. Using a scanning electron microscope, the authors recorded aneurysmal changes as endothelial changes alone (Stage I), endothelial changes with intimal pad elevation (Stage II), and saccular aneurysm formation (Stage III). Aneurysmal changes (Stages I, II, and III) occurred in one third of rats that had undergone oophorectomy and were receiving HRT (Group A), compared with 87% of the rats that had undergone oophorectomy but did not receive HRT (Group B). Although most of the aneurysmal changes identified in Group A rats were limited to Stage I or II, most changes in Group B animals were identified as saccular dilation (Stage III). CONCLUSIONS: The findings demonstrated the significant protective role of estrogen against the formation and progression of cerebral aneurysms. It appears to be related to the beneficial effects of estrogen on the function and growth of endothelial cells, which play a major role in preserving the integrity of the vascular wall.     

Spontaneous cure of ruptured intracranial arterial aneurysms

The case of a patient who had spontaneous cure of an intracranial saccular aneurysm, documented by angiography, is reported. This occurred in a 41-year-old patient, admitted four months after recurrent subarachnoid hemorrhage due to an angiographically verified supraclinoid internal carotid artery aneurysm. The relevant literature is reviewed, and the possible mechanism of spontaneous aneurysmal thrombosis is briefly discussed. It is concluded that repeating angiography is not without merit in patients with already documented cerebral aneurysms who are referred for surgical treatment some time after a subarachnoid hemorrhage.     

Histology and angiography in a bifurcation aneurysm model

Laser-sealed arteriotomy has recently been shown to produce a reliable saccular aneurysm model. By applying this method to the rat abdominal aorta and performing serial angiography, the behavior of this aneurysm model at an arterial bifurcation has been studied for the first time. Three days after laser-sealed arteriotomy, no aneurysms were found, but in animals studied 7, 14, 21, and 28 days after laser-sealed arteriotomy, a 100% (17/17) aneurysm formation rate was achieved. Serial angiography did not demonstrate significant changes in size when performed at 2-week intervals, but angiography significantly underestimated true aneurysm size (p < 0.001) as a function of increasing aneurysm diameter (p < 0.001). By light-microscopic analysis, these aneurysms were similar to human cerebral saccular aneurysms. This saccular aneurysm model could be used to study various surgical and interventional radiology techniques in experimental animals.     

Follow-up of intracranial aneurysms in autosomal-dominant polycystic kidney disease

BACKGROUND: Approximately 8% of autosomal-dominant polycystic kidney disease (ADPKD) patients have intracranial aneurysms. The risk of growth and rupture of those discovered by presymptomatic screening is key to the feasibility and success of a screening program. This study was initiated to ascertain this risk. METHODS: ADPKD patients were offered screening with magnetic resonance (MR) imaging that included three-dimensional time-of-flight MR angiographic and three-dimensional phase-contrast sequences. Patients with aneurysms were recommended periodic surveillance, initially at 6 months and yearly, and less frequently after demonstration of their stability. RESULTS: Twenty-two saccular and one fusiform aneurysms were detected at the initial screening in 21 patients from 19 families (seven men and 14 women, 47.9 +/- 10.6 years old). All the saccular aneurysms were small (mean diameter 3.5 mm, range 2.0 to 6.5 mm) and the majority (77%) in the anterior circulation. Two patients died from unrelated causes without further follow-up. One patient was lost to follow-up. A new 2 mm middle cerebral artery aneurysm developed in one patient. One aneurysm increased from a size of 4 mm to 5 mm after a follow-up of 105 months. No aneurysmal development or growth occurred in the remaining 16 patients. No aneurysmal rupture occurred during a mean imaging follow-up of 81 months and a mean clinical follow-up of 92 months. During the period of the study, two additional ADPKD patients, with three intracranial aneurysms detected elsewhere by presymptomatic MR angiographic screening, were referred for surgical treatment. The larger size of these aneurysms (10, 8, and 8 mm) probably reflects referral bias. CONCLUSION: Most intracranial aneurysms detected by presymptomatic screening in ADPKD patients are small and in the anterior circulation. The follow-up results do not suggest an increased risk for growth and rupture, compared to those of intracranial aneurysms in the general population. These data do not support widespread screening for intracranial aneurysms in the ADPKD population.     

Therapeutic decision and management of aneurysmal subarachnoid haemorrhage based on computed tomographic angiography

The purpose of this study was to evaluate the potential of high quality computed tomographic angiography (CTA) to replace digital subtraction angiography (DSA) in cases of ruptured saccular aneurysms and perform early surgical clipping or coiling on the basis of CTA alone. In a prospective study, 100 patients with aneurysmal subarachnoid haemorrhage (SAH) diagnosed by computed tomography underwent CTA. CTA revealed a total of 118 aneurysms including all ruptured aneurysms. A decision of direct surgical clipping, endovascular coiling or therapeutic abstention was made in 89 cases (89%) on the basis of CTA alone. Sixty-one direct surgical procedures were performed after CTA. Twenty-six cases underwent DSA for immediate endovascular treatment of the ruptured aneurysm. In 11 cases (11%), a DSA was performed prior to the therapeutic decision because of unclear aneurysm. Four cases were not treated because of initial poor clinical grade. The surgical findings were compared with CTA data and were considered accurate in all but one case. All patients underwent postoperative DSA within 10 days after SAH. The sensitivity and the specificity of CTA for the detection of all aneurysms, as compared with postoperative DSA, were 95.1 and 100%, respectively. A total of six unruptured aneurysms were missed initially, but were visible retrospectively on CTA in all but one case and were found in patients with multiple aneurysms in whom the ruptured aneurysm was detected by CTA. Current quality CTA allows reliable pretreatment planning for the majority of cases of aneurysmal subarachnoid haemorrhage and diminishes the pretreatment evaluation time critically. Complementary pretreatment DSA is required in situations where CTA characteristics of the ruptured aneurysm is unsatisfactory.     

Digital subtraction angiography and dynamic computed tomography for evaluating the hemodynamics in cases of giant intracranial aneurysm

Dynamic computed tomography (CT) and digital subtraction angiography were used for postoperative evaluation of the hemodynamic changes in five patients with giant or large intracranial aneurysms. The lesions in four of these cases were giant or large aneurysms of the internal carotid artery, and were treated by occlusion of the cervical internal carotid artery and superficial temporal-middle cerebral artery anastomosis. The lesion in the fifth case was a giant aneurysm of the right vertebral artery, which was treated by proximal clipping of the vertebral artery. Preoperative digital subtraction angiography revealed aneurysmal staining, and dynamic CT scanning indicated the rapid transit of contrast medium in the dome of the aneurysm. Dynamic CT scanning immediately after operation indicated a low flow state in all of the aneurysms, suggesting that they were thrombosed. Although within a few months the peripheral edges of the aneurysms became enhanced, dynamic CT scanning revealed a slower transit of contrast medium through the centers of the aneurysms than in the basilar artery, and digital subtraction angiography failed to demonstrate aneurysmal staining, suggesting that the aneurysms remained thrombosed. The present data indicate that dynamic CT scanning and digital subtraction angiography may be useful for relatively noninvasive evaluation of the hemodynamic changes in patients with giant intracranial aneurysms.     

Saccular aneurysm in the left main coronary artery

The patient was a 70-year-old male with a chief complaint of chest pain. Coronary angiography revealed a saccular aneurysm of 11 mm in diameter at the furcation of the left main coronary artery. Triple vessel disease was also seen. At surgery, it was judged that the risk to rupture of the aneurysm was high because the aneurysmal wall was very thin. Therefore, the blood flow into the aneurysm was blocked, and coronary artery bypass grafting was performed. In a pathological study on the aneurysmal wall, no atherosclerotic and no inflammatory changes were found, but acidic mucopolysaccharides were detected in the tunica media. Coronary aneurysms with coronary stenosis in the elderly have been reported to be arteriosclerotic without exception. Here we present this rare case of a left main coronary artery aneurysm with coronary stenosis in an old-aged patient, considered to be due to metabolic abnormalities in the smooth muscle cells.     

Saccular aneurysm in the left main coronary artery.

The patient was a 70-year-old male with a chief complaint of chest pain. Coronary angiography revealed a saccular aneurysm of 11 mm in diameter at the furcation of the left main coronary artery. Triple vessel disease was also seen. At surgery, it was judged that the risk to rupture of the aneurysm was high because the aneurysmal wall was very thin. Therefore, the blood flow into the aneurysm was blocked, and coronary artery bypass grafting was performed. In a pathological study on the aneurysmal wall, no atherosclerotic and no inflammatory changes were found, but acidic mucopolysaccharides were detected in the tunica media. Coronary aneurysms with coronary stenosis in the elderly have been reported to be arteriosclerotic without exception. Here we present this rare case of a left main coronary artery aneurysm with coronary stenosis in an old-aged patient, considered to be due to metabolic abnormalities in the smooth muscle cells.     

Subarachnoid hemorrhage in the presence of both intracranial dissecting and saccular aneurysms--two case reports

Two patients presented with subarachnoid hemorrhage (SAH) associated with both intracranial dissecting and saccular aneurysms. Case 1, a 48-year-old woman, had a saccular aneurysm of the right internal carotid artery and dissecting aneurysms of the bilateral vertebral arteries. Case 2, a 52-year-old man, had three saccular aneurysms in the anterior circulation and a dissecting aneurysm of the unilateral vertebral artery. A saccular aneurysm was responsible for the SAH in both patients. Ruptured saccular aneurysms were treated with surgical clipping and unruptured dissecting aneurysms remained untreated. SAH recurred due to bleeding from an untreated dissecting aneurysm 4 days after the initial SAH in Case 1. Triple-H therapy, which causes increased hemodynamic stress, was not administered for symptomatic cerebral vasospasm after SAH in Case 2, because of the risk of bleeding from the untreated dissecting aneurysm, and the patient suffered cerebral infarction. The risk factors for this rare association are unclear, but both patients were smokers and had hypocholesterolemia including low apolipoprotein E levels. The clinical management of patients with SAH and both dissection and saccular aneurysms is complicated. Asymptomatic dissecting aneurysm has a benign clinical course in general, but hemodynamic stress related to stroke may induce abrupt development of dissecting aneurysms. Prophylactic obliteration during the acute stage of SAH may provide better outcomes if the unruptured dissecting lesion appears as obvious aneurysmal dilatation or pearl-and-string sign and is safely treatable with endovascular trapping.     

Ruptured cerebral aneurysms associated with arterial occlusion

Seven cases of ruptured cerebral aneurysm associated with an occlusion of a large cerebral artery are reported. All seven patients had never suffered from ischemic cerebrovascular disease before the aneurysmal rupture. All nine aneurysms, including the two unruptured ones, arose on the artery serving as an important collateral pathway, and eight of the nine were found in locations where saccular aneurysms are known to occur infrequently. The role of hemodynamic factors in the pathogenesis of these aneurysms is stressed.     

Aneurysm of peripheral cerebral arteries with developmental anomaly of the anterior cerebral artery

We report a 71-year-old woman who was initially admitted because of a ruptured internal carotid aneurysm, and found to have an aneurysm of the terminal portion (A5 portion) of pericallosal artery. Both of the aneurysms were surgically treated at one stage operation. A saccular aneurysm of the pericallosal artery was verified at operation. Right internal carotid angiography disclosed that medial part of the right anterior cerebral hemisphere was supplied by the right callosomarginal artery, and that unpaired pericallosal artery made a trifurcation at A5 portion, where the saccular aneurysm arose. According to Baptista's classification, anomaly of the anterior cerebral artery (ACA) in this patient was bihemispheric ACA type. Distal ACA aneurysms almost always locate at or near the genu of corpus callosum, either in pericallosal-callosomarginal or in pericallosal-frontopolar junction. In reviewing the literature, we were able to find 14 cases, including ours, of aneurysms located beyond either pericallosal-callosomarginal junction or the genu of corpus callosum. Also the possible role of hemodynamic stress caused by vascular anomaly for aneurysm formation are discussed.     

Incidence and risk factors for the growth of unruptured cerebral aneurysms: observation using serial computerized tomography angiography

OBJECT: The goal of this study was to examine the growth of unruptured intracranial aneurysms with the focus on the risk factors and incidence of these lesions. METHODS: One hundred sixty-six untreated cerebral saccular aneurysms were analyzed in 140 patients. The age of the patients ranged from 29 to 82 years (mean 62.8 years), the female/male ratio was 94:46, and the mean follow-up period was 17.7 months. Aneurysms were located at the internal carotid artery (ICA) in 68 patients, the middle cerebral artery (MCA) in 43, the anterior cerebral artery in 38, the basilar artery (BA) in 13, and the vertebral artery in four patients. The maximum diameter of the lesions ranged from 2 to 20 mm (mean 4.1 mm). All patients were examined using serial computerized tomography angiography to evaluate signs of aneurysm growth. Although growth was identified in 10 aneurysms (nine patients 16.4%]), no bleeding occurred. Growth-related changes were significantly associated with the size of the aneurysm and occurred in three (2.4%) of 125 aneurysms measuring 2 to 4 mm, three (9.1%) of 33 lesions measuring 5 to 9 mm, and four (50%) of eight lesions measuring 10 to 20 mm. These changes were more frequently found in aneurysms located at the BA bifurcation (two [40%] of five lesions) and the ICA (six [8.8%] of 68 lesions) than in those located at the MCA (zero of 43 lesions, p < 0.05). The 1-, 2-, and 3-year cumulative growth rates calculated using the Kaplan-Meier method were 2.5, 8, and 17.6%, respectively. CONCLUSIONS: A diameter of at least 10 mm and a location at the BA bifurcation or the ICA were significant risk factors for aneurysm growth. The incidence of growth was 2.5% in the 1st year and this risk increased yearly. Computerized tomography angiography is useful for follow up of patients with aneurysms because it allows the detection of even subtle morphological changes.     

Angiography postclipping and coiling of cerebral aneurysms

Postclipping cerebral angiography is generally not practised in the UK. The International Subarachnoid Trial (ISAT) data show that coiling compared favourably with clipping in the early posttreatment phase. We present a 4-year, single unit experience comparing cerebral angiography at 6 months postclipping and postcoiling, defining the proportion of aneurysms in either group, which were incompletely excluded from the cerebral circulation after treatment. There were 4 'dog-ear' remnants (4.6%) in the clipping group of 86 aneurysms, one of which required further surgery. Thirty-one out of 82 (37.8%) coiled aneurysms that underwent check angiography were inadequately excluded from the cerebral circulation at 6 months. Of these, to date, four patients have undergone re-coiling. Although the immediate complications of coiling may be less than those of clipping (ISAT), it seems that the degree and permanence of exclusion of an aneurysm from the cerebral circulation may be more secure with surgery. In summary, the rates of incomplete aneurysmal exclusion from the cerebral circulation, the requirement for reintervention and the requirement for continuing surveillance were all higher in the coiled population than in the clipped population.     

Serial neuroimaging of a growing thrombosed giant aneurysm of the distal anterior cerebral artery--case report

An 81-year-old female presented with a giant aneurysm of the distal anterior cerebral artery (A3) which grew from a small saccular aneurysm to a huge aneurysm within 36 months before manifesting as a mass lesion. The thrombosed portion of the aneurysm showed growth, whereas the aneurysmal cavity did not change in size. Computed tomography and magnetic resonance imaging showed new bleeding in the thrombosed portion. Hemorrhage into the thrombus and/or aneurysmal wall might have caused the aneurysmal growth. She refused surgery and was discharged with no deficits. Distal anterior cerebral artery aneurysm which shows neuroimaging signs of growth requires regular follow up as such lesions may become giant before manifesting clinical symptoms.     

A ruptured aneurysm in the hypoplastic proximal anterior cerebral artery (A1 portion); case report

A case of ruptured aneurysm in the hypoplastic proximal anterior cerebral artery (A1 portion) is reported. This 25-years old man complained of the sudden onset of severe headache and vomiting on January 11, 1989. He was referred to our hospital on the same day, and CT scan revealed subarachnoid hemorrhage. Cerebral angiography on the next day revealed an aneurysm in the hypoplastic A1 portion of the right anterior cerebral artery, and no branch was present at the site of the aneurysmal neck. He was operated on using the right pterional approach. The A1 portion was trapped and the aneurysm was removed successfully. The histology of the aneurysm was that of the usual type of the saccular aneurysm. The post-operative course was uneventful. He was discharged with no neurological deficit two months after the operation. As far as we know, there has been no report on a ruptured aneurysm in the hypoplastic A1 portion. We also reviewed the 55 aneurysms in the A1 portion that have been reported in the literature.     

Giant pericallosal artery aneurysm: case report and review of the literature

Pericallosal artery aneurysms comprise 5% of all intracranial saccular aneurysms and are usually small. Giant cerebral aneurysms mostly occur in major arteries. To date, 12 cases of giant pericallosal artery aneurysm have been reported in the literature. An unusual giant thrombosed pericallosal artery aneurysm is reported here. A 65-year-old female presented with headache and personality changes. Computed tomography, magnetic resonance imaging, and cerebral angiography revealed a right-sided giant thrombosed pericallosal artery aneurysm. The patient was operated via an anterior interhemispheric approach and the neck of the aneurysm was successfully clipped. The postoperative period was uneventful. This rare lesion is one of few cases presented in the literature in which neuroradiologic and neuropathologic evaluation was completely performed and the neck of the aneurysm was clipped. Received: 14 November 2000 / Accepted: 4 January 2000     

Aneurysm growth and enlargement of pre-aneurysmal lesions

Three patients with cerebral aneurysms newly growing and enlarging for 2 to 10 years are reported. Case 1, a 54-year-old woman, had subarachnoid hemorrhage due to rupture of an intracranial aneurysm, growing from a small residual aneurysmal neck on the left internal carotid artery 10 years after the repair of the aneurysm. Case 2, a 63-year-old man, had a junctional dilatation on the left internal carotid-posterior communicating artery, developing into ruptured aneurysm about 10 years after the first hemorrhage. Case 3, a 52-year-old man, had multiple aneurysms on the bilateral bifurcations of middle cerebral arteries and left anterior cerebral artery-frontopolar artery junction. Angiography 2 years after the repair of the aneurysms revealed the new growth of a small aneurysm on the anterior cerebral artery at the junction of the fronto-orbital artery, developing from a localized vascular dilatation which had been recognized by the preoperative angiography. The existence of pre-aneurysmal lesions in arterial wall and the addition of hemodynamic impingement were thought to be one of the precipitating factors of aneurysmal formation. The pre-aneurysmal lesions in our study are as follows; a small part of thin wall of residual aneurysmal neck, a junctional dilatation, and a small evagination of arterial wall. It is necessary to discriminate a junctional dilatation and a small evagination of arterial wall from a small aneurysm with observation from multiple directions by the preoperative angiographic study. Our observations suggest that preaneurysmal lesions of the cerebral artery may develop into aneurysm and rupture, and hence the follow-up angiography is recommended for the cases with a preaneurysmal lesion or a small aneurysm for many years.