Neoplastic and infectious aneurysms

Stroke & Vascular Disorders

Updated 05.03.2026
Released 02.08.2015
Expires For CME 05.03.2029

Neoplastic and infectious aneurysms

Authors: Victor J Del Brutto MD MS FAHA, Giana Dawod MD

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Editor: Steven R Levine MD

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Neoplastic and infectious aneurysms

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Introduction

Overview

This article reviews current knowledge about intracranial aneurysms due to infectious and neoplastic causes. Direct mural injury or invasion of intracranial arteries by infectious organisms or neoplastic cells can cause vessel wall weakening, which produces aneurysmal dilatation, often of an irregular, fusiform, or dolichoectatic shape. Infectious aneurysms, also called mycotic aneurysms, are most commonly due to bacterial pathogens, frequently occurring in the setting of bacteremia or infective endocarditis. Neoplastic aneurysms arise from tumor embolization and are classically associated with cardiac myxomas, choriocarcinoma, and, less commonly, to other malignancies. These rare, non-saccular aneurysms are highly prone to rupture and are associated with high morbidity and mortality. Although treatment remains challenging, advancements in individualized and multidisciplinary approaches utilizing surgical and endovascular techniques, in addition to antibiotic and cancer therapies, may yield treatment success.

Key points

	• Infectious or neoplastic processes can lead to intracranial aneurysm formation through direct brain arterial wall injury or invasion, typically resulting in irregular, fusiform, or dolichoectatic aneurysms, often in atypical locations compared to the more common saccular aneurysms.
	• Infectious aneurysms, also referred to as mycotic aneurysms, are more commonly caused by bacterial rather than fungal pathogens.
	• Neoplastic aneurysms most commonly arise in association with cardiac myxoma or choriocarcinoma.
	• Infectious and neoplastic aneurysms often present with intracranial hemorrhage but can also be detected incidentally.
	• Management of these aneurysms is challenging, but individualized surgical and endovascular approaches combined with systemic therapies can be effective in preventing growth or rupture.

Historical note and terminology

An aneurysm is a pathologic, localized blood vessel dilatation. Aneurysms are called “saccular” when the inflow and outflow points are in common. Conversely, non-saccular aneurysms are defined as arterial dilatations exceeding 1.5 times the normal vessel diameter and lacking a clearly defined neck, with longitudinally separate inflow and outflow segments (18). Non-saccular aneurysms may be classified as fusiform when they are spindle-shaped with focal circumferential dilatation, or as dolichoectatic when the arterial segment is elongated and tortuous with a uniformly enlarged circumference. Rarely, distinctive non-saccular aneurysms result from hematogenous seeding of microbes or neoplastic cells within the cerebral vasculature causing arterial wall weakening (46; 01). This article focuses specifically on infectious and neoplastic intracranial aneurysms.

Infectious aneurysms account for less than 5% of all intracranial aneurysms (22) and were first recognized in 1869 in association with infective endocarditis (13). The term “mycotic” is widely used today to describe aneurysms of infectious origin. It is commonly attributed to Sir William Osler; however, Osler did not use the term to describe a cerebral aneurysm. Rather, in his 1885 report, he used it in reference to endarteritis associated with an aortic aneurysm (34). It is unclear whether Osler meant to convey a fungal or bacterial etiology to the cardiac vegetations, or to simply describe "fungating" excrescences on the cardiac valves, as others had done before him. The term “mycotic,” meaning fungal, is a misnomer, as these infectious aneurysms are usually due to septic emboli and bacteremia and are rarely due to fungi (01). Moreover, "mycotic aneurysm" has been used to describe noninfective aneurysms, such as those associated with nonbacterial thrombotic endocarditis because of "fungating" excrescences on the cardiac valves.

Inflammatory noninfectious aneurysms due to vascular inflammation are also sometimes referred to as "mycotic." They occur in systemic inflammatory diseases, presumably on an immunologic basis. For intracranial aneurysms arising due to infectious cause, some have suggested that the term “mycotic” should be reserved for those (rare) aneurysms due to fungi. Others argue that the aneurysm should be classified only after the infecting organism is discovered, which is impractical because in many cases no organism is ever identified, particularly if antibiotics have been administered. Additionally, the microbiologic profile of infectious intracranial aneurysms has also evolved over time, reflecting changes in antibiotic use, healthcare exposure, and host immunosuppression. Although the term “infectious aneurysm” is most used today, alternative terms, such as “infective aneurysm” and “microbial aneurysm,” are also encountered in the literature (23).

Neoplastic aneurysms have historically been recognized in patients presenting with recurrent embolic strokes or intracranial hemorrhages, often occurring years after the diagnosis of the underlying malignancy. These lesions are exceedingly rare, with only a limited number of cases reported in the literature (46). The proximal cause of these rare aneurysms is often metastatic cardiac myxoma or choriocarcinoma, but they can also result from other tumors, such as bronchogenic carcinoma (33).

Infectious and neoplastic intracranial aneurysms are sometimes spherical (similar to common saccular aneurysms), but they are often fusiform, ectatic, or irregular in shape. They tend to be multifocal given they are derived from a central, systemic process and involve more distal branches of intracranial arteries rather than the proximal branching points where saccular aneurysms are usually found. When detected, recognition of an infectious or neoplastic cause usually depends on inference from the clinical features or the setting.

Clinical manifestations

Presentation and course

Infectious and neoplastic intracranial aneurysms may be identified on vascular imaging in patients presenting with nonspecific systemic or neurologic symptoms, such as fever, weight loss, headache, or meningismus. In other cases, they become apparent due to clinical manifestations of local mass effect, including parenchymal or cranial nerve compression, ischemic stroke, or rupture leading to subarachnoid or intraparenchymal hemorrhage. Symptoms include sudden severe headache, focal neurologic signs, seizures, and decreased level of consciousness (22). In some cases, patients may experience sentinel headaches or subacute neurologic decline prior to rupture, reflecting progressive arterial wall destruction. Like other non-saccular aneurysms, these lesions may also produce headache or focal symptoms related to mass effect or compression of adjacent neural structures (18).

Infectious aneurysms. Early recognition of infectious intracranial aneurysms relies on integration of the clinical context and imaging features, rather than on any single diagnostic sign. Key clues include fever, bacteremia, or suspected/confirmed infective endocarditis, recent cardiac procedures, or unexplained intracranial hemorrhage, together with distal or atypical aneurysm morphology and dynamic changes on short-interval imaging (10). Rapid aneurysm growth, interval appearance of new lesions, or regression following antimicrobial therapy strongly support an infectious etiology. In patients with underlying infective endocarditis, concomitant systemic or cerebral embolic phenomena, immune-mediated vasculitic changes, and septic infarction may further complicate the clinical presentation (10).

Diagnostic criteria for infectious aneurysms have been proposed, classifying the diagnosis as clinically definite, probable, or possible (23). Diagnostic criteria are based on the presence of three, two, or one supportive feature, respectively, including multiplicity, distal location, fusiform shape, change on serial imaging, younger age, history of lumbar puncture, fever at presentation, or intraparenchymal hemorrhage. Blood cultures should be performed to confirm bacteremia and endocarditis. Transthoracic echocardiography serves as an initial screening tool for cardiac sources of embolism; however, transesophageal echocardiography is frequently required to detect small vegetations, prosthetic valve involvement, or intracardiac devices and should be pursued when clinical suspicion remains high.

Neoplastic aneurysms. Neoplastic intracranial aneurysms usually present with subarachnoid or intraparenchymal hemorrhage, headache, nausea and vomiting, and focal neurologic signs. Transient ischemic attacks or infarction due to embolism may precede the hemorrhage. The aneurysm may rarely present as a mass lesion (33; 12).

Cardiac myxoma, the most common primary cardiac tumor, is the leading cause of tumor-related intracranial aneurysms, accounting for approximately 50% to 60% of reported neoplastic aneurysms (46). These tumors typically arise in the left atrium and occur most frequently between the third and sixth decades of life, with a female predominance. Myxomatous embolization commonly involves the central nervous system, and cerebral or systemic embolic events represent the initial presentation in up to half of patients, with ischemic stroke being the most frequent neurologic manifestation (12). Embolic risk correlates more strongly with tumor mobility than with size (27). Notably, intracranial aneurysms may develop years to decades after myxoma resection, highlighting the potential value of long-term vascular surveillance in selected patients (42).

Metastatic choriocarcinoma represents the second most frequently reported cause of neoplastic intracranial aneurysms after cardiac myxoma, accounting for approximately one quarter of documented cases (46). Although cerebral metastases occur in 10% to 20% of patients with choriocarcinoma and are often hemorrhagic, aneurysm formation is rare and largely limited to isolated case reports. The disease typically affects women aged 18 to 30 years, most often following a hydatidiform mole or other pregnancy-related events. Neurologic manifestations may arise weeks to 2 years after delivery and should raise suspicion in patients with a recent pregnancy history or unexplained vaginal bleeding, particularly when accompanied by elevated beta-human chorionic gonadotropin levels. Reported aneurysms show a strong predilection for distal middle cerebral artery branches, frequently present with intracranial hemorrhage, and may evolve rapidly carrying a high risk of rupture even during systemic therapy (43; 33).

Prognosis and complications

As these aneurysms may present with intracerebral or subarachnoid hemorrhage, the prognosis can be grave. For infectious aneurysms, the hemorrhage typically occurs in the setting of infectious endocarditis or other cause of septicemia, and the prognosis is also dependent on the systemic illness and cardiac status. Once ruptured, the mortality rate may be as high as 80% (45).

Infectious aneurysms remain challenging to treat and carry a high risk of mortality, particularly when rupture occurs. Improvements in the diagnosis and management of infectious intracranial aneurysms over the past 2 decades have led to a significant reduction in overall mortality, decreasing from approximately 40% before 2000 to 20% after 2000 (03). In a contemporary series of 24 patients with infectious intracranial aneurysms, 16 patients (67%) presented with aneurysm rupture and intracranial hemorrhage, and seven patients (29%) died during follow-up (04). Poor neurologic outcomes were primarily associated with aneurysm rupture and intracranial hemorrhage, as well as failure of initial antibiotic therapy, manifested by aneurysm growth, the development of new aneurysms, or subsequent hemorrhage.

The prognosis of neoplastic cerebral aneurysms varies according to the underlying tumor type. Outcomes are generally more favorable in aneurysms associated with cardiac myxoma, whereas aneurysms arising from malignant tumors, such as choriocarcinoma, are frequently associated with poor outcomes. Intracranial hemorrhage occurs in approximately 20% of cases related to metastatic cardiac myxoma, whereas nearly all reported cases associated with choriocarcinoma present with intracranial hemorrhage (46). Among reported cases of myxomatous aneurysms, 65% of patients show clinical improvement during follow-up, whereas 25% experience poor outcomes, defined as a modified Rankin Scale score of 3 or greater. Hemorrhagic presentation is associated with worse prognosis (46.7% poor outcomes) compared with ischemic presentation (15%) (12). In contrast, a systematic review of neoplastic intracranial aneurysms unrelated to cardiac myxoma reported overall poor outcomes, with 90-day survival of 46.2%, declining to 35.9% at 180 days. Aneurysm rupture occurred in 76.9% of cases associated with choriocarcinoma, 90.0% of lung cancer cases, and 91.0% of cases from other malignancies. Subarachnoid hemorrhage occurred in 37.5%, 40%, and 72.7%, and intracerebral hemorrhage in 58.3%, 90%, and 45.5% of these groups, respectively (33).

Clinical vignette

A 58-year-old man had a history of bladder resection for cancer, hypertension, and diabetes. He presented with left hemiparesis, and imaging revealed a right middle cerebral artery occlusion and right cerebral infarction. Etiological workup with transthoracic echocardiography revealed a vegetation on the aortic valve with severe aortic valve insufficiency. Blood cultures were negative. Antibiotics were started. One week after presentation he underwent diagnostic cardiac catheterization. After catheterization, he developed new right-sided weakness and confusion, and brain CT showed a massive left frontal lobar hematoma with intraventricular extension. CT angiogram was performed, demonstrating a spherical 4 mm x 5 mm aneurysm lying in the midst of the intraparenchymal hematoma. Urgent craniotomy was performed, with evacuation of the hematoma and clipping of the aneurysm, which during surgery, had the appearance of an infectious aneurysm. After this procedure, he slowly regained mental alertness but required a prolonged hospitalization for multiple medical complications and remained hemiparetic on the left side. He was eventually discharged to a long-term care facility.

Infectious aneurysm

This 58-year-old man with infective endocarditis developed new right hemiparesis after 1 week of antibiotic treatment. (A) Brain CT scan showed a massive left frontal lobar hematoma with intraventricular extension. (B) CT angiogra...

Biological basis

Etiology and pathogenesis

The histopathological hallmark of infectious intracranial aneurysms is the presence of infection associated with progressive destruction of the arterial wall. In the acute phase, histopathology demonstrates infiltration of the media and adventitia by polymorphonuclear cells, marked intimal proliferation, and disruption of the internal elastic lamina. Microbial organisms can often be identified within the vessel wall using appropriate staining techniques (23). Infectious intracranial aneurysms most commonly arise from hematogenous spread of septic emboli in the setting of bacterial sepsis, particularly infective endocarditis. In pooled analyses, bacterial infections represent the predominant cause of infectious intracranial aneurysms (72.8%), followed by fungal infections (13.2%), whereas viral and parasitic infections are rare (< 2%), and cultures remain negative in about 12.7% of patients (35; 03). Among identified pathogens, Streptococcus viridans (25.5%) and Staphylococcus aureus (17.4%) are the most common bacterial organisms, whereas Aspergillus is the most frequently reported fungal pathogen (7.5%) (03). In many cases, the causative organism remains unidentified. Organisms from the HACEK group are a recognized cause of culture-negative infective endocarditis and should be suspected in patients with embolic phenomena and negative blood cultures, particularly after recent dental disease or procedures (16). Viral causes have also been described, including aneurysm formation associated with varicella zoster virus and rare cases reported in patients with human immunodeficiency virus infection (39; 23).

Pathogenetically, infectious aneurysms in endocarditis typically develop when septic emboli lodge within the vasa vasorum or arterial lumen, producing arteritis and occasionally periarterial abscess formation. In other settings, infection may spread to the arterial wall from adjacent structures, such as in meningitis, cavernous sinus thrombophlebitis, osteomyelitis, or chronic sinusitis. The resulting inflammatory destruction weakens the vessel wall and, under the stress of pulsatile blood flow, leads to rapid aneurysm formation and enlargement (30; 23).

The pathogenesis of neoplastic intracranial aneurysms remains incompletely understood, although hematogenous tumor embolization is considered the most likely mechanism (33). Several additional pathways have been proposed, including direct extension from primary central nervous system tumors, endothelial injury caused by neoplastic emboli with subsequent hemodynamic alterations, dissemination through the valveless venous plexus, spread along neural or perivascular lymphatic pathways, leakage from choroid plexus or subependymal metastases, and cerebrospinal fluid dissemination following surgical procedures for parenchymal metastases (20). In many cases, the neoplastic embolus appears to initiate vascular injury, which may explain the increased prevalence of neoplastic aneurysms in patients with embolic tumor complications (33).

Cardiac myxoma and choriocarcinoma are the tumors most frequently associated with neoplastic aneurysms, although rare cases have been reported in association with other malignancies, including lung carcinomas, malignant fibrous histiocytoma, lymphomatoid granulomatosis, testicular chorionepithelioma, intimal sarcoma, and primary brain tumors or radiation-induced vasculopathy (32; 29; 38). Patients with Carney complex, a hereditary syndrome caused by mutations in PRKAR1A, are also predisposed through the development of cardiac myxomas (11). Histopathological studies support several mechanisms of aneurysm formation, including post-embolic endothelial injury with vascular scarring or direct tumor infiltration of the vasa vasorum leading to destruction of the arterial wall. In many reported cases, proliferating tumor cells have been demonstrated within the arterial wall, suggesting that tumor emboli penetrate the endothelium, proliferate in the subintimal space, and progressively weaken the vessel wall through fibroblastic proliferation and replacement of smooth muscle cells (46). In myxomatous aneurysms specifically, myxoma cells have been observed invading the subintima from the arterial lumen (19). Similarly, trophoblastic tumors such as choriocarcinoma possess a marked vascular invasive capacity, leading to disruption of the internal elastic lamina and aneurysm formation. The frequent distribution of neoplastic aneurysms in distal branches of the middle cerebral artery further supports tumor embolism as the underlying pathogenic mechanism.

Epidemiology

Infectious cerebral aneurysms are uncommon, accounting for less than 5% of all intracranial aneurysms (01). They most often arise as a complication of infective endocarditis, occurring in approximately 3% to 15% of affected patients, and nearly 70% of individuals with infectious cerebral aneurysms have underlying infective endocarditis (30; 17). Despite this association, only 4% to 5% of intracranial hemorrhages in infective endocarditis are attributable to identifiable aneurysms, whereas embolic ischemic stroke occurs several times more frequently (30; 21). Infectious cerebral aneurysms are reported more often in men and span a wide range of age groups, from 25 days to 85 years, although most patients are young to middle-aged adults, with a mean age of 35 ± 20 years (03). Common risk factors include intravenous drug use, poor dental hygiene, and recent dental procedures, which predispose to infective endocarditis and subsequent septic embolization. Additional risk is observed in immunocompromised states, including human immunodeficiency virus infection, high-dose glucocorticoid therapy, or malignancy and chemotherapy, whereas fungal aneurysms typically occur as opportunistic infections in immunosuppressed patients (17; 03).

Reports of neoplastic cerebral aneurysms are rare, and their true incidence is likely underestimated. These lesions may be missed when angiography is not performed after intracranial hemorrhage or when the aneurysm is obliterated after rupture or compressed by a hematoma (46).

Cardiac myxoma is the tumor most frequently associated with neoplastic aneurysms. Primary cardiac tumors occur in 0.01% to 0.33% of autopsies, about half are myxomas, and 75% to 86% arise in the left atrium (07). Embolic events occur in 30% to 50% of left atrial myxomas, with about half involving the brain, although ischemic stroke is far more common than aneurysm formation. In reported cases of cardiac myxoma–associated aneurysms, the age at diagnosis ranges from 11 to 70 years with a mean of 39.4 years, and the female-to-male ratio is approximately 3:1 (12). A study evaluating patients previously treated for left atrial myxoma found aneurysms in 23% of cases, although these had the appearance of typical saccular aneurysms of the proximal middle cerebral or carotid arteries and likely represented incidental findings rather than true neoplastic aneurysms (40).

Choriocarcinoma is another tumor associated with neoplastic aneurysms. In the United States, gestational choriocarcinoma occurs in approximately 1 in 20,000 to 1 in 40,000 pregnancies, with an incidence of 0.133 per 100,000 woman-years, although higher rates are reported in parts of Asia (06; 37). Up to 80% of choriocarcinomas develop distant metastases, most commonly to the lungs and then to the brain. Brain metastases occur in 10% to 20% of cases, but cerebral aneurysm formation related to choriocarcinoma remains rare.

Diagnostic workup

Patients presenting with systemic illness and neurologic symptoms are typically evaluated with brain MRI. In individuals with infective endocarditis, MRI with contrast, along with gradient-echo or susceptibility-weighted sequences, increases sensitivity for detecting cerebral abscesses and microhemorrhages. When subarachnoid or intracerebral hemorrhage is identified, evaluation for an underlying aneurysm is essential. Noninvasive vascular imaging with CT angiography or MR angiography now provides excellent sensitivity for most cerebral aneurysms, and diagnostic evaluation usually begins with one of these modalities. However, aneurysms associated with bacterial endocarditis are often small and located in distal cerebral vessels, which makes them more likely to be missed on imaging focused on the circle of Willis. CT and MR angiography demonstrate moderate-to-high sensitivity and specificity for detecting infectious aneurysms (44). Digital subtraction cerebral angiography remains the gold standard and may be required to identify smaller or more distal lesions (41). In patients with unexplained intracranial hemorrhage and suspicion for infectious or neoplastic aneurysm, catheter angiography should be performed if initial CT or MR angiography studies are negative to ensure thorough evaluation for small or distal aneurysms.

Although noninvasive imaging is less sensitive than catheter angiography for detecting small aneurysms, brain MRI can reveal indirect signs of septic embolization, such as microinfarctions or microhemorrhages (01). Susceptibility-weighted imaging is particularly sensitive for detecting microhemorrhages that may signal an underlying aneurysm. In a study of 151 patients with infective endocarditis, infectious aneurysms were identified in only 4.6%, and a normal magnetic resonance imaging scan had a negative predictive value of 97.7%, suggesting that cerebral angiography may be reserved for patients with neurologic deficits or hemorrhage on imaging (31). A meta-analysis of 21 studies including 2133 patients reported direct evidence of infectious aneurysms in 6.2% of cases and found that MRI altered therapeutic or surgical management in approximately 13% to 14% of patients, supporting a potential role for screening MRI in infective endocarditis (02).

Contemporary recommendations from the American Heart Association and the European Society of Cardiology emphasize early neuroimaging in patients with neurologic symptoms but do not clearly define the role of systematic vascular imaging in guiding procedural timing. Systemic anticoagulation during cardiac surgery carries a potential risk of intracranial hemorrhage, particularly in patients with infectious intracranial aneurysms. Although noninvasive imaging is generally sufficient for hemorrhage detection, digital subtraction angiography remains the most sensitive modality for aneurysm identification. The current literature reflects that increasing catheter angiography utilization over time is associated with improved survival. These findings highlight the need for prospective studies to refine guideline-based imaging strategies and to better define optimal timing across the disease course (14).

Management

Infectious aneurysms. There are currently no standardized guidelines for the management of intracranial infectious aneurysms. For unruptured infectious aneurysms, targeted antimicrobial therapy is the first-line treatment and should be guided by blood or cerebrospinal fluid culture results. When cultures are unavailable or negative, empiric therapy should be initiated based on the suspected source of infection. Most reports support a minimum of 4 to 6 weeks of antimicrobial treatment (17). Patients managed conservatively require close monitoring with serial vascular imaging to assess aneurysm stability.

Invasive treatment should be considered because of the poor natural history, particularly in cases of rupture, aneurysm growth despite antimicrobial therapy, high-risk morphologic features, or when anticoagulation is required for cardiac surgery. Endovascular options include coil embolization, liquid embolic agents such as N-butyl cyanoacrylate or ethylene-vinyl alcohol copolymer, and parent artery occlusion. Stent-assisted techniques and flow diversion have been reported but remain challenging due to the need for dual antiplatelet therapy and the potential risk of device infection. Surgical approaches include clipping, wrapping, bypass procedures, or aneurysm excision with vessel reconstruction and may be preferred for superficial aneurysms or when associated with hematoma or mass effect (01).

A proportion of unruptured aneurysms may stabilize or regress with antibiotic therapy. However, some lesions continue to enlarge, rupture, or are accompanied by new aneurysm formation despite antimicrobial treatment (30). In a systematic review including more than 1000 cases, medical management achieved aneurysm resolution without hemorrhage or procedural complications in only 44% of patients and was associated with a mortality of 28%, compared with approximately 90% treatment success and mortality rates of 1% to 12% among patients treated with surgical or endovascular approaches (03). Predictors of treatment failure include younger age, larger aneurysm size, and rupture at presentation (05). These findings should be interpreted cautiously because of potential publication bias and selection of healthier patients for interventional management.

Analyses have shown increasing use of endovascular therapy for infectious intracranial aneurysms. Proximal aneurysms are often treated with stent-assisted coiling or flow diversion, whereas distal lesions are more commonly managed with liquid embolic agents, such as N-butyl cyanoacrylate or Onyx, frequently combined with parent artery occlusion. Although earlier concerns focused on device infection in bacteremic patients, contemporary studies report low complication rates. Liquid embolic agents offer advantages, including minimal infection risk, no requirement for antiplatelet therapy, precise delivery, and low rates of distal stroke or hemorrhage (03; 15).

In patients with infective endocarditis, completion of the antibiotic course is generally recommended before valve replacement surgery unless heart failure or high embolic risk requires earlier intervention. Treatment of the systemic infection and stabilization of the cardiovascular condition usually precede treatment of an unruptured infectious aneurysm. In selected stable cases, serial MRI has been proposed to monitor resolution of susceptibility-weighted microhemorrhages that may represent infectious aneurysms before elective cardiac surgery (25). Ruptured infectious aneurysms carry a high risk of rebleeding and a poor prognosis, with mortality approaching 50% among patients with infective endocarditis and intracranial hemorrhage (30). The sequencing of aneurysm treatment and cardiac valve surgery can therefore be challenging. A systematic review reported that when the order of procedures was specified, aneurysm treatment preceded cardiac surgery in 85% of cases, most often through endovascular management (36).

Neoplastic aneurysms. When a neoplastic aneurysm is identified, evaluation for an underlying malignancy is essential and should include imaging of the chest, abdomen, and pelvis to assess for metastatic disease. Serial vascular imaging is recommended, particularly if new neurologic symptoms develop or prior symptoms worsen, as delayed and recurrent aneurysm formation has been well described. Incidentally discovered neoplastic aneurysms may often be managed conservatively with observation. Aneurysms associated with cardiac myxoma are frequently multiple and may remain relatively stable over time, allowing treatment to focus on lesions that enlarge or become symptomatic during follow-up (20). Symptomatic myxomatous aneurysms should be treated when feasible. Surgical options include aneurysm excision or wrapping, particularly in cases of hemorrhage or progressive enlargement, whereas endovascular parent vessel occlusion has emerged as an effective alternative. Targeted radiation therapy has also been reported in isolated cases for progressive fusiform aneurysms, resulting in stabilization or obliteration of the lesions (24).

In aneurysms related to choriocarcinoma, most patients have concurrent pulmonary metastases, and management is primarily directed at the underlying malignancy. Aggressive systemic chemotherapy, often combined with intrathecal chemotherapy and whole-brain radiation therapy, has been associated with cure rates of approximately 60% to 80% in patients with brain metastases from gestational trophoblastic disease (09). Multidrug chemotherapy regimens may achieve primary cure rates of 65% to 80%, with salvage therapies increasing overall cure rates to nearly 90% (28). Surgical intervention is generally reserved for patients with mass lesions, ruptured aneurysms, or isolated aneurysms located in non-eloquent brain regions. Whole-brain radiation therapy has also been used to achieve rapid control of cerebral metastases (08).

Outcomes

With antibiotic therapy, infectious aneurysms decrease in size or resolve on serial angiograms in 30% to 50% of cases (30). However, overall morbidity and mortality is high, particularly in cases presenting with intracranial hemorrhage. In these cases, the prognosis will largely depend on the severity of the presenting hemorrhage. In a systematic literature review, an overall mortality of 24% has been found, with a significant trend toward decreasing mortality in more recent years (03). Open surgical treatment with isolation of the aneurysmal vessel can successfully prevent rupture and reduce mortality in many of the cases, although the friable nature of the inflamed vascular wall can add to the difficulty and morbidity of aneurysm clipping. Endovascular treatment approaches are increasingly applied, aiming for aneurysm coiling or aneurysm trapping through parent artery occlusion Despite concerns regarding placement of foreign material in an infected tissue, endovascular treatment is becoming the most frequent treatment strategy (03). A single center study encompassing both ruptured and unruptured infectious aneurysms showed good outcomes (mRS ≤ 2) measured at 6 months in 61% of patients treated with endovascular management (26).

Neoplastic aneurysms can stabilize or even completely resolve with appropriate treatment of the underlying tumor (46). Aneurysms related to cardiac myxoma have a relatively positive prognosis, with 34 of 58 cases in the literature showing stabilization or disappearance on follow-up imaging. However, the prognosis is substantially worse (with very high mortality rates) in aneurysms due to choriocarcinoma or other neoplasms (46).

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Contributors

All contributors' financial relationships have been reviewed and mitigated to ensure that this and every other article is free from commercial bias.

Authors

Victor J Del Brutto MD MS FAHA

Dr. Del Brutto of the University of Miami Miller School of Medicine and Jackson West Medical Center has no relevant financial relationships to disclose.
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Giana Dawod MD

Dr. Dawod of the University of Miami / Jackson Memorial Hospital has no relevant financial relationships to disclose.
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Editor

Steven R Levine MD

Dr. Levine of the SUNY Health Science Center at Brooklyn has no relevant financial relationships to disclose.
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Former Authors

James R Brorson MD
Matthew M Smith MD

Patient Profile

Age range of presentation: 2 to 65+ years
Sex preponderance: female>male, >1:1
Heredity: none
Population groups selectively affected: none selectively affected
Occupation groups selectively affected: none selectively affected

ICD & OMIM codes

ICD-10: Cerebral aneurysm, nonruptured: I67.1

Subarachnoid haemorrhage, unspecified: I60.9

Congenital cerebral aneurysm (nonruptured): Q28.3
ICD-11: Cerebral aneurysm, nonruptured: 8B22.5

Aneurysmal subarachnoid haemorrhage: 8B01.0

Congenital cerebral nonruptured aneurysm: LA90.42

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Neoplastic and infectious aneurysms

Differential Diagnosis

Atherosclerotic fusiform aneurysm
Dissecting aneurysm
Saccular (berry) aneurysm
Traumatic or iatrogenic pseudoaneurysm
Abscess
- Granulomatous or autoimmune vasculitis
- Septic embolic infarction with hemorrhagic transformation
- Hemorrhagic metastasis
- Primary CNS tumor with vascular invasion
- Arteriovenous malformation
- Cavernous malformation
- Dural arteriovenous fistula

Vascular lesions	Atherosclerotic fusiform aneurysm Dissecting aneurysm Saccular (berry) aneurysm Traumatic or iatrogenic pseudoaneurysm
Infectious and inflammatory conditions	Abscess Granulomatous or autoimmune vasculitis Septic embolic infarction with hemorrhagic transformation
Neoplastic and hemorrhagic mimics	Hemorrhagic metastasis Primary CNS tumor with vascular invasion
Arteriovenous and developmental lesions	Arteriovenous malformation Cavernous malformation Dural arteriovenous fistula

Neoplastic and infectious aneurysms

Cite this article

Introduction

Overview

Key points

Historical note and terminology

Clinical manifestations

Presentation and course

Prognosis and complications

Clinical vignette

Biological basis

Etiology and pathogenesis

Epidemiology

Prevention

Differential diagnosis

Confusing conditions

Diagnostic workup

Management

Outcomes

Special considerations

Pregnancy

Anesthesia

Media

References

Contributors

Authors

Editor

Former Authors

Patient Profile

ICD & OMIM codes

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