Aneurysm growth and hemodynamic stress

Two cases of intracranial saccular aneurysm related to an arteriovenous malformation (AVM) are illustrated, in which a remarkable growth of the sac over the years was demonstrated angiographically. According to the relevant literature, aneurysm enlargement is correlated to the flow toward the AVM, increasing the intrasaccular turbulence and stress on the wall to which “solitary” aneurysms are usually subjected. The presence of bilateral infundibular widening at the origin of the posterior communicating artery is noted in one of the cases. This finding possibly confirms further the effects of hemodynamic stress.     

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.     

Association of arteriovenous malformation and intracranial aneurysm in the posterior fossa

Two cases of a saccular aneurysm of the posterior inferior cerebellar artery associated with an anatomically related arteriovenous malformation are presented. The aneurysms were clipped and the arteriovenous malformations were totally extirpated in one-stage operations in both cases. The association of arteriovenous malformation and arterial aneurysm in the posterior fossa was reviewed in the literature.     

Spontaneous disappearance of aneurysm after total removal of accompanying intracranial arteriovenous malformation. Case report]

A 55-year-old male was hospitalized with severe headache. On admission, neurological examination revealed no abnormal findings. Plain computed tomography (CT) showed a slightly high-density area in the medial surface of the right parietal lobe. A marked enhancement in the same region was noted in enhanced CT. Cerebral angiography showed an arteriovenous malformation (AVM) in the medial surface of the right parietal lobe and two aneurysms on the right pericallosal artery which fed the AVM. In addition, a saccular aneurysm was noted at the anterior communicating artery. It was not possible to treat the AVM, two aneurysms nearby the AVM, and the unruptured anterior communicating artery aneurysm simultaneously with a single craniotomy. It was therefore decided to perform surgery for the AVM and two aneurysms nearby the AVM prior to clipping of the anterior communicating artery aneurysm. Total excision of the AVM and two aneurysms nearby the AVM was performed. Cerebral angiography performed 18 days after surgery revealed no AVM and also reduction in size was noted of the anterior communicating artery aneurysm. Three months later, repeated cerebral angiography showed disappearance of the aneurysm. This was further confirmed 15 months after surgery by angiography. From the literature, 117 cases of coexistence of AVM and aneurysms of the brain were collected and classified into three types according to their anatomical and hemodynamic correlation. It is suggested that hemodynamic stress, due to increased blood flow caused by the AVM, played a major role in the development of the aneurysm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of arterial geometry on aneurysm growth: three-dimensional computational fluid dynamics study

OBJECT: Few researchers have quantified the role of arterial geometry in the pathogenesis of saccular cerebral aneurysms. The authors investigated the effects of parent artery geometry on aneurysm hemodynamics and assessed the implications relative to aneurysm growth and treatment effectiveness. METHODS: The hemodynamics of three-dimensional saccular aneurysms arising from the lateral wall of arteries with varying arterial curves (starting with a straight vessel model) and neck sizes were studied using a computational fluid dynamics analysis. The effects of these geometric parameters on hemodynamic parameters, including flow velocity, aneurysm wall shear stress (WSS), and area of elevated WSS during the cardiac cycle (time-dependent impact zone), were quantified. Unlike simulations involving aneurysms located on straight arteries, blood flow inertia (centrifugal effects) rather than viscous diffusion was the predominant force driving blood into aneurysm sacs on curved arteries. As the degree of arterial curvature increased, flow impingement on the distal side of the neck intensified, leading to elevations in the WSS and enlargement of the impact zone at the distal side of the aneurysm neck. CONCLUSIONS: Based on these simulations the authors postulate that lateral saccular aneurysms located on more curved arteries are subjected to higher hemodynamic stresses. Saccular aneurysms with wider necks have larger impact zones. The large impact zone at the distal side of the aneurysm neck correlates well with other findings, implicating this zone as the most likely site of aneurysm growth or regrowth of treated lesions. To protect against high hemodynamic stresses, protection of the distal side of the aneurysm neck from flow impingement is critical.     

Distal aneurysms of the superior cerebellar artery and posterior inferior cerebellar artery feeding an associated arteriovenous malformation: case report.

The authors report a case of two distal aneurysms of the cerebellar arteries, one arising from the vermian branch of the posterior inferior cerebellar artery, the other arising from the hemispheric branch of the superior cerebellar artery, and both feeding an associated arteriovenous malformation (AVM). The aneurysm of the distal posterior inferior cerebellar artery was considered the source of a cerebellar hemorrhage because of the location of a hematoma in the cerebellar vermis. The life-threatening hematoma was evacuated in an emergency operation 6 hours after the acute onset of symptoms. The cerebellar aneurysms and the AVM were clipped or extirpated successfully after the patient's condition improved. The association of two rare types of aneurysms with an AVM strongly supports the theory that increased hemodynamic stress derived from the AVM plays an important role in aneurysm formation. The authors think that one should operate on the symptomatic lesion first or both the aneurysm and the AVM in the same operative procedure.     

Arteriovenous malformation of the scalp: case report and review of the literature

BACKGROUND: Arteriovenous malformations (AVMs) of the scalp are relatively rare, and their precise natural course remains to be elucidated. We encountered a patient with a scalp AVM that progressively enlarged over the course of 3 years by capturing feeders from intracranial arteries. To our knowledge, ours is the first serial angiographic depiction of the growth of a scalp AVM and the development of a de novo aneurysm in the superior temporal artery (STA) that performed as a feeder. CASE DESCRIPTION: This 21-year-old female consulted us in 1998 complaining of right tinnitus and a pulsating mass in the retroauricular region. The initial angiogram revealed an AVM in the right temporo-parietal subcutaneous space with feeders from the STA, an occipital artery, a posterior auricular artery, and a middle meningeal artery (MMA). Three years later, she complained of enlargement of the lesion, increased tinnitus, and alopecia. Repeat angiographic study revealed the presence of a nidus and the appearance of new feeders from a contralateral MMA and an ipsilateral middle cerebral artery; there was a de novo saccular aneurysm in the right STA. On the day preceding surgery, the left MMA was embolized to control intraoperative bleeding. The AVM was removed totally without any dermal complications. CONCLUSION: This case suggests that scalp AVMs can become enlarged by capturing subcutaneous or intracranial feeders, and that the consequent hemodynamic stress may induce de novo aneurysms in scalp AVMs. Capillary endothelial cells were strongly immunostained for vascular endothelial growth factor.     

A case of cerebellar arteriovenous malformation with hemifacial spasm at onset

A case of cerebellar AVM onset with hemifacial spasm was reported. The patient, a 47 year old woman, had been suffering from lt. hemifacial spasm for 10 years, and she visited our hospital for operation. Preoperative angiography revealed that there was an AVM in the lt. cerebellar hemisphere fed by the lt. SCA and the lt. PICA. In addition, a non-ruptured saccular aneurysm was observed on the feeding SCA. The microvascular decompression was performed and the AVM was removed, since the lt. facial nerve had been compressed by this elongated and redundant PICA. After the operation, lt. hemifacial spasm disappeared. Two months after the operation, the aneurysm disappeared angiographically. These findings indicated that the hemodynamic stress due to the presence of AVM seemed to have resulted in ectasia or redundancy of the PICA and in the development of the aneurysm. Such a case was quite rare and it may be the first time to be reported in literatures.     

Angiographic study of induced cerebral aneurysms in primates

Five cynomolgus monkeys treated with unilateral carotid ligation, renal hypertension, and beta-aminopropionitrile feeding were studied repeatedly by cerebral angiography to clarify the growth process of saccular cerebral aneurysms. Repeated angiography demonstrated saccular cerebral aneurysms in three of five monkeys; two aneurysms were found 15 months and a third 12 months after the operation. At autopsy, one saccular aneurysm was found to be bilocular in shape, and the others were unilocular. Fusiform aneurysms were also observed in four monkeys. Microscopic studies revealed the walls of the saccular aneurysms were very thin and consisted of fibrous tissue. In one aneurysm, the aneurysmal sac was almost obstructed by a well-organized thrombus. No evidence of intramural hemorrhage was found in any of the saccular cerebral aneurysms. The conversion of early aneurysmal changes into saccular aneurysms was found to occur abruptly, and no consistent growth rate was noted. The multiloculation of saccular aneurysms was closely related to the size of an aneurysm. The present study indicates that a saccular cerebral aneurysm may grow abruptly from one of several different kinds of early aneurysmal changes.     

Aneurysms of the distal posterior inferior cerebellar artery; the report of 10 cases

Non mycotic and non traumatic distal posterior inferior cerebellar artery (PICA) aneurysms are rare, but eleven aneurysms in ten cases were reported. They all originated from subarachnoid hemorrhage due to rupture of these aneurysms. The patients in these cases were all admitted within 5 days after the onset. The neurological state of four cases on admission was grade 4 or 5 in Hunt and Kosnik's grading system. Two patients of grade 5 died within 24 hours after the onset. The CT scan on admission revealed heavy subarachnoid hemorrhage mainly in the posterior fossa. In severe cases, ventricle hematoma, cerebellar hematoma and/or subdural hematoma were evident in the posterior fossa. The locations of these eleven aneurysms were as follows: On the bifurcation of the Telovelotonsillar segment in six cases. In the cortical segment in three cases. In the anterior medullary and tonsillomedullary segment in one case. Six saccular aneurysms were situated on bifurcations of parent arteries but three saccular aneurysms did not arise from bifurcations. Two of them were not from turning points of the arteries. One fusiform aneurysm situated on the bifurcation of telovelotonsillar segment was excised, and histologically shown to be a dissecting aneurysm with hypoplasia of elastic lamina and tunica media in the parent artery. Three cases were associated with small AVM located on the superior surface of the cerebellar vermis and fed mainly by the superior cerebellar artery (SCA) in two cases, and by SCA and PICA in one case. In these cases the hemodynamic stress on PICA did not seem to increase so remarkably.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Proximal aneurysms in association with arteriovenous malformations: do they resolve following obliteration of the malformation with stereotactic radiosurgery?

One-hundred consecutive patients were identified who had arteriovenous malformations (AVMs) treated by stereotactic radiosurgery (STRS) which were totally obliterated as shown by follow-up angiography. Of these cases, seven had intracerebral aneurysms at initial angiography, two of which were multiple. Five patients had saccular aneurysms at commonly recognized sites on the circle of Willis or main proximal cerebral arteries, while two patients had aneurysms on distal AVM feeder arteries in atypical sites (one saccular, one fusiform). Saccular aneurysms at typical sites were found to be unchanged in size following AVM obliteration. The significance of this finding in the management of patients who present with subarachnoid haemorrhage and who have both aneurysms and AVMs is discussed.     

Computed tomographic diagnosis of ruptured giant posterior cerebral artery aneurysms

Ruptured giant posterior cerebral artery (PCA) aneurysms are encountered rarely. Although computed tomographic (CT) scan features of giant intracranial aneurysms have been described. CT scan features of acutely ruptured giant saccular PCA aneurysms have not been reported. A case of an acutely ruptured giant saccular PCA aneurysm with diagnostic CT scan features and autopsy confirmation is presented. Two additional cases of apoplexy with identical clinical courses and CT scan appearances, both attributed to giant saccular PCA aneurysms, are described. Diagnostic CT scan features included evidence of intraparenchymal temporal lobe and intraventricular hemorrhage, the presence of a filling defect in the temporal lobe hematoma that enhanced after intravenous contrast administration, and evidence of proximal PCA entrance into the contrast-enhanced filling defect in the intracerebral hematoma. The incidence of PCA aneurysms and the anatomy of the PCA as it relates to these giant aneurysms, their clinical presentation, and diagnostic features of the CT scan are discussed.     

Coexistence of cerebral aneurysm and angiographically occult AVM in the occipital lobe; a case report]

The authors report a case of an 8-year-old boy with coexistent aneurysm and arteriovenous malformation (AVM) at the periphery of the left middle cerebral artery. The patient was referred to our hospital because of intracerebral hematoma in the occipital lobe. Angiography revealed an aneurysm at the periphery of the left middle cerebral artery. A small AVM was found, adjacent to the aneurysm, by histological examination of the aneurysm and surrounding tissue resected by surgery. The patient was discharged uneventfully 17 days after surgery. The association of intracranial aneurysm with AVM is reported to be seen in 1.4% of patients with intracranial aneurysms, and 6.4% to 16.7% of patients with an intracranial AVM. Three hypotheses have been proposed in order to explain the association of an aneurysm with AVM: (1) Congenital multiple disorders of vascular development, (2) Hemodynamic stress resulting from the presence of an AVM, (3) Coincidence without any causal relationship between them. The coexistence of the two vascular lesions, adjacent to each other at the peripheral cerebral arteries is rare. Only 7 cases have been reported in the literature. Four of the 8 cases including ours were children, and 6 of the 8 cases were thought to have had a hemorrhage from the AVM. It is likely that the coexistence of the two lesions in our patient is of congenital origin, because the influence of hemodynamic stress from the AVM seemed little and coexistence of the lesions as found in our case is more frequently seen in childhood.     

Unbranched-site aneurysm of intracranial internal carotid artery]

Most intracranial saccular aneurysms arise from the angle between a parent vessel and an arterial branch. Saccular aneurysms without relation to any arterial branch are rare. During the last 24 years, 210 patients with intracranial internal carotid artery (ICA) aneurysms were directly operated on at our institution. We found eight saccular aneurysms arising from intracranial ICA without relation to any arterial branch. So we call them unbranched-site aneurysms of intracranial ICA, and describe their unique characteristics. Of the eight cases with unbranched-site aneurysm of intracranial ICA, three were men and five were women. The age ranged from 31 to 61 years with an average age of 48. Seven cases suffered a subarachnoid hemorrhage due to ruptured unbranched-site aneurysm, and the other case had been admitted to our department because of accompanying ruptured left internal carotid-posterior communicating aneurysm. All cases of unbranched-site aneurysm presented intraoperative and/or angiographic findings of arteriosclerosis, and five of the patients had a past history of hypertension. Of the four unbranched-site aneurysms at the C2 portion of ICA, two arose from the lateral wall, one arose from the superior wall and the other arose from the infero-lateral wall of ICA. Of the four unbranched-site aneurysms at the C1 portion of ICA, three arose from the superior wall and the other arose from the supero-medial wall of ICA. Radical operation was performed in all cases and intraoperative rupture occurred in two cases. It was suggested that arteriosclerotic change in the arterial wall, and local hemodynamic stress played important roles in the development of unbranched-site aneurysms of intracranial ICA.     

Collagen type III deficiency in patients with rupture of intracranial saccular aneurysms

Samples of the middle cerebral artery (MCA) and the brachial artery were obtained post mortem from 14 patients who died following rupture of intracranial saccular aneurysms and from a control group of 14 age- and sex-matched patients who died of causes unrelated to aneurysm rupture. The biomechanical properties of ring-shaped arterial specimens were investigated by loading the specimens at a constant deformation rate until rupture. The relative amounts of collagen type I and type III were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) studies of cyanogen bromide peptides of collagen prepared from the arterial samples. A deficiency of collagen type III was demonstrated in specimens of the MCA in six of 14 patients with a ruptured intracranial saccular aneurysm. This deficiency was not accompanied by alterations in the mechanical arterial strength but resulted in a significant increase in the extensibility at stress values corresponding to blood pressures between 100 and 200 mm Hg. No difference was found between aneurysm patients and the control group in regard to the biomechanical properties of the brachial artery, despite the presence of a significant deficiency of collagen type III. The increase in vascular extensibility of the MCA may represent alterations in the fibrous structure and functional integrity of the cerebral arteries of aneurysm patients with collagen type III deficiency. Together with aggravating hemodynamic stresses, this deficiency may be an important factor in the pathogenesis of saccular aneurysms.     

Giant thrombosed aneurysm associated with an arteriovenous malformation. Case report

The authors describe a case of giant anterior cerebral artery aneurysm associated with an anatomically related arteriovenous malformation (AVM). The aneurysm was almost completely thrombosed and was resected along with the AVM.     

Clinical presentation and treatment of distal anterior inferior cerebellar artery aneurysms

Aneurysms located at the distal portion of the anterior inferior cerebellar artery (AICA) are rare, and their clinical features are not fully understood. We report the clinical features and management of nine distal AICA aneurysms in nine patients treated during the past decade at Kagoshima University Hospital and affiliated hospitals. Our series includes seven women and two men. Of their nine aneurysms, eight were ruptured and one was unruptured; six were saccular and three were dissecting aneurysms. The most prevalent location was the meatal loop (n?=?5) followed by the postmeatal (n?=?3) and premeatal segment (n?=?1) of the AICA, suggesting hemodynamic stress as an etiology of these distal AICA aneurysms. Of the nine patients, five presented with angiographic features suggestive of increased hemodynamic stress to the AICA and the common trunk of the posterior inferior cerebellar artery, with vertebral artery stenosis, marked laterality, and a primitive hypoglossal artery. We addressed eight aneurysms (eight patients) surgically; one aneurysm in one patient disappeared in the course of 3?months without surgical treatment. Of the eight surgically treated aneurysms, seven were ruptured and one was unruptured, five were clipped via lateral suboccipital craniotomy, two were trapped via lateral suboccipital craniotomy, and one was embolized. Good outcomes were obtained in six of the eight patients who underwent operation (75?%). We consider increased hemodynamic stress attributable to anatomic variations in the AICA and related posterior circulation to be the predominant contributor to the development of distal AICA aneurysms. Direct clipping and trapping yielded favorable outcomes in our series.     

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.     

Multiple unusual aneurysms and arteriovenous malformation in a single patient: a case report

A patient with multiple unusual aneurysms and an arteriovenous malformation (AVM) is presented. Aneurysms involving the meningohypophyseal trunk and the feeding vessel of the AVM were observed. Two additional aneurysms assumed a pantaloon appearance. The largest aneurysm was responsible for the patient's subarachnoid hemorrhage. This aneurysm and two adjacent aneurysms were clipped successfully, and the patient made an uneventful recovery. Subsequent angiography revealed a stable appearance of the remaining aneurysms and AVM.