Bilateral aneurysm formation developing from junctional dilatation (infundibulum) of the posterior communicating arteries. Case report

Stability of infundibular dilatations: a single center follow-up study and systematic review of the literature

PURPOSE

Although infundibular dilatations (IDs) have been thought to be benign anatomical variants, case reports suggest that they can grow and rupture. The aim of this study was to determine whether IDs have a tendency to grow or rupture.

METHODS

The study population was collected from the Tampere University Hospital (TAUH) Aneurysm Database. The presence of IDs was screened from the medical records and imaging studies of 356 intracranial aneurysm patients left to follow-up from 2005 to 2020. The imaging studies were reviewed to confirm the IDs, and their clinical course. Finally, we performed a systematic review of published cases of ID leading to aneurysmatic rupture from PubMed.

RESULTS

We found 97 typical IDs in 83 patients and 9 preaneurysmal lesions resembling ID in 9 patients. Out of the typical cone-shaped IDs, none grew or ruptured in a total follow-up of 409 patient-years. One preaneurysmal lesion ruptured during a follow-up: this lesion had components of both infundibular dilatation and aneurysm at the beginning of follow-up. In the systematic literature search, we found 20 cases of aneurysmatic SAHs originating from an ID. Of those, only 7 had imaging available prerupture. All 7 IDs were typically cone-shaped, but a branching vessel originating from the apex of ID was only seen in 4/7.

CONCLUSION

Typical infundibular dilatations seem to be benign anatomical variants that are stable and, thus, do not need prophylactic treatment or imaging follow-up. Likely, the SAHs reported from IDs were actually caused by misdiagnosed preaneurysmal lesions.

Ruptured Infundibular dilatation of the posterior communicating artery

OBJECTIVE

An infundibulum of the posterior communicating artery (PcomA) or infundibular dilatation (ID) is considered to be a benign anatomical variant. However, some evidence suggests that ID is a pre-aneurysmal state. This case series presents cases of ruptured IDs and aneurysms originating from the IDs.

METHODS

Between April 2002 and June 2020, 1337 patients were treated for aneurysmal subarachnoid hemorrhage (SAH). Among them, 7 patients with ruptured PcomA IDs were identified. Rupture IDs of the PcomA were categorized into 1) direct rupture of IDs, and 2) rupture of aneurysms originating from IDs. The clinical and radiographic factors were retrospectively reviewed.

RESULTS

Two patients experienced direct rupture of IDs, while the other 5 patients presented with ruptured aneurysms originating from IDs. The 2 patients with direct rupture of IDs at presentation were relatively younger (< 50 years), while the other 5 patients with ruptured aneurysms originating from IDs were over 70 and had a history of aneurysmal SAH due to other intracranial aneurysms. Ruptured IDs were treated with microsurgery or endovascular treatment. There were no complications related to the procedure for securing ruptured IDs. Five (71.4%) patients showed favorable outcomes. One patient with initial Hunt and Hess grade 4 died due to initial brain damage with cerebral vasospasm and medical complications.

CONCLUSIONS

ID of the PcomA rarely causes SAH with or without aneurysm formation. Thus, patients with IDs of the PcomA should be carefully followed up for a long period, especially those with a history of aneurysmal SAH.

An Unruptured Aneurysm Coexisting with an Infundibular Dilatation: A Case Report

BACKGROUND

Infundibular dilatation (ID) is a funnel-shaped enlargement of the origin of cerebral arteries. The coexistence of an aneurysm and ID is relatively rare. Patients with IDs are rarely followed up. However, some IDs have been reported to develop into aneurysms with subsequent rupture. Here we report on a case of an aneurysm that coexisted with ID of the posterior communicating artery.

CASE PRESENTATION

A 51-year-old woman underwent magnetic resonance imaging (MRI) to check for aneurysms and other problems. MRI revealed an unruptured aneurysm of the right internal carotid artery, for which the patient was admitted to our hospital. Three-dimensional computed tomographic angiography revealed an aneurysm, which protruded outward, and ID of the posterior communicating artery, which protruded inward. A right pterional craniotomy was performed with aneurysm clipping. The postoperative course was uneventful. In this report, we demonstrate operative views of the aneurysm and ID with the use of neuroendoscopy.

CONCLUSION

ID can develop into a true arterial aneurysm and potentially rupture. Therefore, we need to observe the patients with IDs carefully, particularly in young women.

A tiny bleb at Junctional Dilatation of the Posterior Communicating Artery as a Predisposing Factor for Development of a De Novo Aneurysm

Formation of de novo aneurysm from a junctional dilatation at the origin site of the posterior communicating artery (PcomA) has been rarely reported. In this case report, three females in sixth decades of age developed a de novo aneurysm from the junctional dilatation of the PComA with a tiny bleb-like lesion over 5 years after initial presentation.

Infundibular dilations of the posterior communicating arteries: pathogenesis, anatomical variants, aneurysm formation, and subarachnoid hemorrhage

Background

Cerebrovascular infundibular dilations (IDs) are triangular-shaped widenings less than 3 mm in diameter, which are most commonly found at the posterior communicating artery (PCoA). The aims of this systematic review are to elucidate the natural histories of IDs, determine their risk of progression to significant pathology, and discuss potential management options.

Methods

A comprehensive literature search of PubMed was used to find all case reports and series relating to cerebral IDs. IDs were classified into three types: type I IDs do not exhibit morphological change over a long follow-up period, type II IDs evolve into saccular aneurysms, while type III IDs are those that result in subarachnoid hemorrhage without prior aneurysmal progression. Data were extracted from studies that demonstrated type II or III IDs.

Results

We reviewed 16 cases of type II and seven cases of type III IDs. For type II IDs, 81.3% of patients were female with a median age at diagnosis of 38. All type II IDs were located at the PCoA without a clear predilection for sidedness. Median time to aneurysm progression was 7.5 years. For type III IDs there was no clear gender preponderance and the median age at diagnosis was 51. The PCoA was involved in 85.7% of cases, with 57.1% of IDs occurring on the left. Most patients were treated with clipping. Risk factors for aneurysm formation appear to be female gender, young age, left-sided localization, coexisting aneurysms, and hypertension.

Conclusions

IDs can rarely progress to aneurysms or rupture. Young patients with type II or III IDs with coexisting aneurysms or hypertension may benefit from long-term imaging surveillance.

Are infundibular dilatations at risk of further transformation? Ten-year progression of a prior documented infundibulum into a saccular aneurysm and rupture: Case report and a review of the literature

Infundibular dilatations (IFDs) are conical, triangular, or funnel-shaped enlargements at the origin of cerebral arteries, and they are primarily located (7-25%) on the posterior communicating artery (PComA). Progression over time into a saccular aneurysm with a risk of rupture of a previously demonstrated IFD has rarely been reported. We report the case of a 60-year-old female who presented 10 years earlier with a subarachnoid hemorrhage caused by a left internal carotid artery aneurysm rupture. At that time, the carotid angiography showed the left internal carotid artery aneurysm and a right posterior communicating artery infundibular dilatation. Neck clipping for the left internal carotid artery aneurysm was performed and the patient was discharged with no neurological deficit. Ten years later, the patient suffered a second fatal subarachnoid hemorrhage; carotid angiography revealed a right posterior communicating artery aneurysm developed from the previously documented infundibular dilatation with a de novo right anterior choroidal artery aneurysm. This case is another proof of the small but growing number of examples of infundibular transformation over time, as well as their risk of progression into saccular aneurysms and subsequent rupture.

First demonstration of resolution of an infundibulum by direct treatment of the arterial wall with Pipeline flow-diverting stent

INTRODUCTION

Infundibula are symmetrical funnel-shaped widening, measuring more than 3 mm at its base with the branch artery arising from its apex. The pathological significance of this entity remains controversial. Although a relatively common appearance in otherwise normal angiograms, they have occasionally been described to progress into saccular aneurysms or directly rupture.

METHODS/RESULTS

We describe the first case of a disappearing infundibulum after a flow diverting stent was deployed across the infundibulum during the treatment of an adjacent aneurysm.

CONCLUSIONS

We concur in the view that infundibula are at least pre-pathological lesions that may in certain circumstances require consideration for treatment. Our case for the first time offers a potential treatment option for such situations.

Evolution from an infundibulum of the posterior communicating artery to a saccular aneurysm

INTRODUCTION

An infrequent case of a de novo aneurysm formation originating from an infundibulum at the origin of the posterior communicating artery (PcomA) is presented. The aneurysm developed within 7 years in a patient who initially presented with subarachnoid hemorrhage (SAH) from a saccular aneurysm of the vertebral artery.

CASE SUMMARY

A 43-year-old female patient was admitted to our hospital on 16th June 2000 after an acute onset of massive occipital headache. A computed tomography (CT) scan showed a subarachnoid hemorrhage (SAH) around the brainstem and 4-vessel angiography revealed an aneurysm originating from the V4 segment of the right vertebral artery (VA) as the cause of the SAH. A small aneurysm at the basilar artery (BA)/superior cerebellar artery (SCA) bifurcation was also found. Injection of the left internal carotid artery (ICA) showed a diffuse enlargement at the origin of the left PcomA, which at this time was considered to be a so-called infundibulum. The VA aneurysm was treated by coil occlusion. Follow-up digital subtraction angiography (DSA) in 2005 showed a de novo aneurysm formation at the VA junction, again treated by coil occlusion. The PcomA infundibulum at the left ICA was not examined. Follow-up angiography performed in 2007 revealed a saccular de novo aneurysm of the left ICA arising from the origin of the left PcomA with a maximum diameter of 12 mm. Coil occlusion of the PcomA aneurysm was subsequently carried out.

CONCLUSION

Infundibular widening of cerebral arteries can develop into true aneurysms. Mid-term and long-term follow-up MRI (e.g., in yearly intervals) is advised for infundibula with a diameter of 3 mm or more. In patients with other aneurysm(s), with a documented de novo aneurysm formation or with a familial occurrence of aneurysms, the risk of evolution of an infundibulum to a saccular aneurysm may be increased and follow-up should be even more stringent.

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.

Early development and rupture of de novo aneurysm--case report

A 38-year-old non-smoker man presented with a ruptured aneurysm one month after clipping of a previous aneurysm. He was first admitted because of sudden onset of severe headache. Brain computed tomography showed subarachnoid hemorrhage. Angiography showed an aneurysm of the left anterior choroidal artery which was surgically clipped. Two weeks later, he was discharged without neurological deficits. One month after the initial hemorrhage, he was readmitted to the emergency room with stuporous mentality. Repeat angiography showed two aneurysms of the A2 portion of the left anterior cerebral artery which were not demonstrated by the initial angiography. The diagnosis was de novo aneurysms. The larger aneurysm was clipped and the other was coated. De novo aneurysm should be suspected if a patient with a previously clipped aneurysm complains of typical headache or any suggestive symptoms or signs of cranial nerve dysfunction, especially if known risk factors are present.

Progression of an arterial infundibulum to aneurysm: case report

In this case an aneurysm of the right posterior communicating artery developed 11 months after an infundibular dilation of this artery had been angiographycally and surgically demonstrated. In the best of the authors' knowledge, there are only eleven such cases reported in the literature. This report brings about diagnostic and therapeutic questions regarding arterial infundibula and the need of a better understanding of those lesions.

Successful treatment of a ruptured enlarged infundibular widening of the posterior communicating artery--case report

A 67-year-old female with a history of hypertension and cerebral infarction presented with subarachnoid hemorrhage (SAH) (Hunt and Kosnik grade 4). Brain computed tomography (CT) revealed a clot dominantly on the right (Fisher's classification Group 4). Cerebral angiography showed funnel-shaped widenings at the origins of the bilateral posterior communicating arteries. The maximum diameter of the widening was greater than 3 mm, so this widening was called an enlarged infundibular widening. Angiography showed a small bulge protruding posterolaterally from the wall of the right enlarged infundibular widening, and the right posterior communicating artery arose from the apex of the enlarged infundibular widening. Based on the findings of the brain CT and cerebral angiography, the diagnosis was SAH due to rupture of the right enlarged infundibular widening. Approximately 12 hours after the onset, the clot was evacuated through the right pterional approach. Bleeding from the small bulge of the right enlarged infundibular widening occurred intraoperatively, so a right-angled ring clip was applied parallel to the right internal carotid artery to obliterate the rupture point. Postoperatively, she was discharged without neurological deficit, and follow-up CT showed no other new infarction. We recommend clipping rather than wrapping or coating for similar cases of ruptured enlarged infundibular widening.

The progression of an infundibulum to aneurysm formation and rupture: case report and literature review

OBJECTIVE AND IMPORTANCE

Infundibula (IFs) are funnel-shaped symmetrical enlargements that occur at the origins of cerebral arteries and are apparent on 7 to 25% of otherwise normal angiograms. They are frequently considered as normal anatomic variants of no pathogenic significance.

CLINICAL PRESENTATION

We report the case of a ruptured posterior communicating artery aneurysm that had developed at the site of a previously known IF in a 49-year-old hypertensive woman. She had a poor conscious level at admission, with widespread subarachnoid hemorrhage and obstructive hydrocephalus.

INTERVENTION

The patient was immediately ventilated, and an external ventricular drain was inserted. The aneurysm was successfully clipped; however, secondary hemorrhage occurred both before and during craniotomy. She developed marked hypernatremia and subsequently died.

CONCLUSION

This is the 11th case of IF-to-aneurysm progression reported. It suggests that in certain cases, serial investigations may be indicated with IFs to detect aneurysm formation and preempt rupture.

Unexpected results in long-term medically treated ruptured intracranial aneurysm including data on 14 patients followed more than 30 years each

This is the longest reported follow-up of patients with ruptured intracranial aneurysms treated entirely medically with hypotension. Patients with ruptured brain aneurysms, untreated except for plain bedrest, are at a well-recognized risk of recurrent hemorrhage. Some surgically treated patients also remain at risk of recurrent hemorrhage in follow-up. This is a review of results in patients whose active but entirely medical (hypotensive) treatment was started in the first 10 years of a 40-year study. It suggests a way of reducing risks in both of the above 2 groups. 53 consecutive patients with proven ruptured brain aneurysm(s) were treated as early as possible with medical-hypotensive therapy alone by the author and followed, personally, until death or, if they survived, for at least 30 years each (or until lost to follow-up). The patients included many considered to have been poor operative risks with some having been designated inoperable by the referring neurosurgeons. As part of the long-term follow-up, magnetic resonance angiography (MRA) has been begun. Long-term follow-up was defined as the time beginning after 9 weeks from (admission) hemorrhage. 9 patients had died during the earlier stages of hemorrhage (and treatment) i.e., before the 9 weeks period had elapsed; their data was presented previously. This yielded 44 patients for long-term follow-up. Only 2 patients (both had multiple aneurysms) on this regimen have died of either proven hemorrhage (1 patient) or presumed hemorrhage (1 patient). Most patients survived and maintained an excellent condition. Medical-hypotensive therapy of ruptured intracranial aneurysms has produced much better long-term results than expected. This is significant for (1) patients requiring medical treatment alone and (2) surgically treated patients who may benefit from additional long-term protection.

Clinical study of enlarged infundibular dilation of the origin of the posterior communicating artery

Although some aneurysmal dilations of the origin of the posterior communicating artery (PCoA) that are revealed on carotid angiogram are true aneurysms or preaneurysmal lesions, the authors warn that diagnosis should not be based only on the size and shape of the dilation, especially when the PCoA does not fill. In the present retrospective study, the authors analyzed intraoperative and angiographic findings in 32 patients with 34 lesions of the PCoA that were preoperatively diagnosed as aneurysms. Only 10 of the lesions were true aneurysms (six cases) or enlarged infundibular dilations with reddish bulges (that is, preaneurysmal bulge; four cases) at the origin of the PCoA. All of the other 24 lesions, including one lesion with PCoA occlusion, were merely enlarged infundibular dilations without any wall abnormality. A well-developed PCoA was observed only in cases of true aneurysm and dilation with reddish bulge. No other clinical or angiographic characteristics proved useful in identifying the type of lesions. These findings may be helpful to the physician in evaluating the clinical features of such lesions and in determining the diagnosis of enlarged infundibular dilation of the PCoA.

Subarachnoid hemorrhage due to rupture of infundibular dilation of a circumflex branch of the posterior cerebral artery: case report

The authors describe a rare case in which an infundibular dilation at the origin of a circumflex branch of the P1 segment of the posterior cerebral artery caused subarachnoid hemorrhage. Wrapping was performed by a subtemporal approach in the delayed stage. At the time of surgery, the rupture point was found in the infundibular dilation.