Size and Location of Ruptured Intracranial Aneurysms: A 5-Year Clinical Survey

doi:10.1016/j.wneu.2016.04.044

World Neurosurgery

Volume 91, July 2016, Pages 260-265

https://doi.org/10.1016/j.wneu.2016.04.044 Get rights and content

Background

Prospective international cohort trials have suggested that incidental cerebral aneurysms with diameters less than 10 mm are unlikely to rupture. Consequently, small ruptured cerebral aneurysms should rarely be seen in clinical practice. To verify this theory, dimensions and locations of ruptured cerebral aneurysms were analyzed across the state of Tasmania, Australia.

Methods

We retrospectively reviewed medical records and diagnostic tests of all patients admitted with ruptured cerebral aneurysms during a 5-year interval. Aneurysm location, maximum size, dome-to-neck ratio, volume, and presence of daughter sacs were determined by preoperative digital subtraction angiography or computed tomography angiography.

Results

A total of 131 ruptured cerebral aneurysms were encountered and treated by microsurgical clipping (n = 59) or endovascular techniques (n = 72). The mean maximum aneurysm diameter was 6.4 ± 3.7 mm, dome-to-neck ratio 2 ± 0.8, aneurysm volume 156 ± 372 mm³, and daughter sacs were present in 70 aneurysms (53.4%). The anterior communicating artery was the most common location (37.4%). Cumulative maximum diameters of ruptured aneurysms were ≤5 mm in 49%, ≤7 mm in 73%, and ≤10 mm in 90%.

Conclusions

Despite findings from prospective international cohort trials, small ruptured intracranial aneurysms are common in clinical practice. In consequence, it seems important to identify those patients with small but vulnerable unruptured aneurysms before conservative management is considered.

Introduction

The management of patients with small unruptured intracranial aneurysms (UIAs) is controversial. The prevalence of these lesions is approximately 3% within the general population¹; however, the annual incidence of aneurysm-related subarachnoid hemorrhage (SAH) is much lower, at 6–10 cases per 100,000.1, 2, 3, 4 SAH from rupture of an intracranial aneurysm remains a devastating condition, associated with a 30-day mortality of approximately 45% and survival morbidity of 50%.3, 4

Size and location of intracranial aneurysms frequently are thought to be the best predictors for future aneurysm rupture.5, 6, 7, 8 The retrospective International Study of Unruptured Intracranial Aneurysms (ISUIA) has demonstrated a 0.05% annual risk for aneurysm rupture in asymptomatic patients when the maximum aneurysm size was less than 10 mm². The prospective ISUIA trial has shown a rupture risk of 0.52% for aneurysm diameters between 7 and 12 mm in the anterior circulation and 2.9% for aneurysms within the posterior circulation at corresponding diameters. The ISUIA study concluded that asymptomatic aneurysms with diameters smaller than 7 mm were benign.⁹ Similar findings were encountered in the Unruptured Cerebral Aneurysm Study (UCAS). Additionally, UCAS stated that larger aneurysm size was associated with a greater hazard ratio for rupture¹⁰; however, these large multicenter trials were criticized for severe selection bias. Several other investigators have contradicted the ISUIA and UCAS trial results according to individual case series.1, 4, 5, 11, 12, 13, 14

According to ISUIA and UCAS suggestions, small ruptured intracranial aneurysms (RIAs) should be encountered rarely in clinical practice. In reality, however, small RIAs appear quite commonly. To better understand the impact of aneurysm size and location, we have reviewed clinical data and medical imaging of all patients who presented with aneurysm-related SAH for emergency microsurgical or endovascular repair within the state of Tasmania, Australia.

Section snippets

Materials and Methods

Medical records and diagnostic imaging studies were reviewed retrospectively in all patients admitted with RIAs between July 2010 and August 2015. Other causes of SAH, including mycotic or traumatic aneurysms, were excluded. Patient age, sex, and Hunt & Hess and Fisher grades were recorded. Informed written consent was obtained before emergency treatment and included data collection for research purposes. The study was approved by the institution's review board (H0015446). Maximum and minimum

Demographics, Diagnostics, and Surgical Management

Within the 5-year survey interval, 120 patients were admitted and treated with the diagnosis of RIAs. A total of 89 patients (74%) were female, median age 55 ± 13.5 (SD) years (range 18–86 years), and 31 patients (26%) were male, with a median age of 50 ± 11.1 (SD) years (range, 19–70 years). No significant age difference was found between the 2 sexes (P > 0.05, t test).

Preoperative DSA was performed in 107 patients (89%). In 13 patients (11%), computed tomography angiograms was used

Discussion

Within the general population, intracranial aneurysms are reported with a frequency ranging from 0.2% to 9% and UIAs affecting 2%–5%.¹¹ Considering a Tasmanian population of 500,000, we have found an annual incidence of 24 patients or 0.005% for RIAs during the 5-year observation period. For those readers not having had the opportunity to visit beautiful Tasmania, the population is dispersed on an island with a land mass of 68,000 km² with >50% living near the capital city, Hobart. By

Conclusions

The release of the ISUIA and UCAS trial results2, 9, 10 may have influenced not only neurovascular units but medical professionals in general. The low reported rupture risks, particularly for small anterior circulation aneurysms, may have induced a paradigm shift to manage UIAs conservatively. Subsequent closer analysis of these trials, however, has demonstrated that the study designs may not accurately represent clinical reality, as a result of methodologic and selection bias shortcomings. The

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Cited by (36)

Quantitative Evaluation of Hemodynamic Changes After Multiple Intracranial Aneurysms Occlusion Using Computational Fluid Dynamics
2024, World Neurosurgery
Multiple intracranial aneurysms (MIA) are prevalent. This study conducted hemodynamic calculations on MIA to analyze the effects of occlusion of the internal carotid artery (ICA) and middle cerebral artery (MCA) aneurysms on the hemodynamics of other arteries, as well as the issue of the treatment order for these aneurysms.
The models of 9 patients with MIA were selected for the study. A computational fluid dynamics model combining 1-dimension and 3-dimension was used to obtain the vascular flow pattern and wall pressure.
There was increased pressure at the MCA and anterior cerebral artery (ACA) after occlusion of the aneurysm at the ICA. However, the pressure at the ICA has hardly changed after the aneurysm occlusion at the MCA. Occlusion of the aneurysm of different sizes at the MCA had almost no impact on the pressure at the ICA and ACA. For small aneurysm, the pressure of the ACA and MCA increases with decreasing size of the aneurysm at the ICA. After occlusion of a large aneurysm at the ICA, the impact on the pressure of the ACA and MCA is almost the same as after occlusion of a medium-sized aneurysm.
If the treatment order of ICA and MCA aneurysms cannot be determined based on patient factors and aneurysm characteristics, the MCA aneurysm should be treated as a priority.
Safety of coil embolisation in small (smaller than 5 mm) unruptured intracranial aneurysms: A retrospective multicentre analysis
2023, Interdisciplinary Neurosurgery: Advanced Techniques and Case Management
Citation Excerpt :
For example, in the Small Unruptured Aneurysm Verification Study, the annual risk of rupture for aneurysms smaller than 5 mm was 0.54%(5). However, this remains controversial because > 50% of ruptured aneurysms are small (smaller than 5 mm) [8], which indicates a discrepancy between past reports and the size of ruptured aneurysms seen in the actual clinical setting. In a nationwide registry in Japan, approximately 2,000 cases of endovascular treatment (EVT) of 3–5 mm unruptured aneurysms were performed over a 5-year period (2010–2014) [9].
Risk-benefit analysis results for the treatment of unruptured aneurysms smaller than 5 mm are controversial. This study aimed to identify the outcomes and complication associated with treating such unruptured aneurysms.
This was a retrospective study of 165 consecutive patients who underwent endovascular procedures for unruptured cerebral aneurysms of a maximum diameter 5 mm between January 2018 and March 2021. Patient background, aneurysm characteristics, adjuvant technique, volume embolization rate (VER), symptomatic complications, and modified Rankin Scale (mRS) scores were examined.
Sixty patients with sufficient data were included in the study. The mean age was 62.1 ± 14.6 years, and the median follow-up period was 12 months. The mean maximum diameter was 4.16 ± 0.63 mm, the neck diameter was 2.73 ± 0.82 mm, and 90% of patients had anterior circulation. Complete occlusion was achieved in 34 cases (57.6%). Although there were no intraoperative ruptures, complications were observed in four patients (6.7%), and one patient (1.7%) had worsened mRS score. Only one patient (1.7%) required retreatment. The first coil VER was independently associated with complete occlusion after endovascular treatment. Univariate analysis of complications showed an association between hypertension, hyperlipidaemia, and the estimated glomerular filtration rate.
No patient experienced mRS score deterioration, and only one patient developed permanent disability due to ischemic complications; hence, we could safely treat small unruptured aneurysms. Complications are not related to procedural factors such as coiling adjuvant technique. However, lifestyle-related diseases are related to complications, and we suggest that physicians should remain vigilant of the indication for coiling when treating patients with underlying diseases.
Current Management of Small Unruptured Intracranial Aneurysms in the United States: Results of a National Survey
2021, World Neurosurgery
To understand how physicians in the United States manage patients with small unruptured intracranial aneurysms and factors that influence the management.
An online survey questionnaire was designed through SurveyMonkey and distributed electronically to The Society of Interventional Surgery, American Association of Neurological Surgeons/Congress of Neurological Surgeons Joint Section of Cerebrovascular Surgery, American Academy of Neurology, and Massachusetts Neurologic Association. All participations were voluntary and anonymous.
Among all the participants, 53.8% of them were neurosurgeons, 33.0% were neurointerventional radiologists, and 13.2% were neurologists. For management of aneurysms 2–4 mm, 87.8% of respondents favored routine surveillance with imaging follow-up, 3.8% preferred routine treatment, and 8.5% recommended routine treatment or follow-up only for high risk patients. In total, 25.5% preferred annual follow-up, and 67.9% liked follow-up once in a year and then space out at various intervals. For aneurysms between 5 and 7 mm, 73.6% supported routine treatment, 20.8% favored surveillance with imaging follow-up, and 5.7% recommended treating or follow-up only high-risk groups. In total, 58.5% preferred annual follow-up, whereas 34.9% liked follow-up once in a year and then space out at various intervals. For routine follow-up, 64.1% of the physicians chose magnetic resonance angiography without contrast, and 40.6% preferred computed tomography angiography.
For aneurysms 2–4 mm, majority of the physicians preferred regular follow-up, whereas for aneurysms 5–7 mm, the majority favor treatment. There remains heterogeneity in practice among physicians in the United States regarding follow-up strategies for small unruptured aneurysms. Further studies are needed to evaluate the optimal management strategy, follow-up frequency and duration of imaging for small unruptured intracranial aneurysms.
Rupture of intracranial aneurysms in patients with blunt head trauma: Review of the literature
2020, Clinical Neurology and Neurosurgery
With a prevalence of 1–5 %, intracranial aneurysms are common. However, only 20–50 % of these aneurysms will rupture during a person’s lifetime. This often happens spontaneously without exogenous factors. In the present study we reviewed the literature concerning the relation between trauma and rupture of a pre-existing aneurysm.
All studies that reported a causal relation between trauma and rupture of a pre-existing aneurysm were included, irrespective of study design. They were limited though to those written in English or German. Excluded were studies with traumatic aneurysms, studies where the rupture of an aneurysm lead to trauma and studies with doubts about the order of events.
Thirteen studies with twenty-two cases of ruptured aneurysm in context with trauma and two unpublished cases were included. Fourteen patients were involved in a fight, seven patients in a bike/motorbike/bus accident and three got hit on the head in a setting outside of interpersonal violence. The aneurysm was located in internal carotid artery in most cases (7/24). The clear majority of patients (19/24) did not survive.
Arteries and aneurysms can rupture in context with head trauma although this is rarely the case. Patients after head trauma with typical blood pattern for aneurysmal SAH in the native CT scan should receive conventional angiography to exclude a vascular or aneurysmal rupture, even when CT-angiography is inconspicuous.
Aging Changes of Aneurysmal Subarachnoid Hemorrhage: A 35-year, Hospital-Based Study
2020, Journal of Stroke and Cerebrovascular Diseases
The etiology and background factors which cause decreases in the size of ruptured intracranial aneurysms remain unclear.
To clarify the age- and sex-related differences in aneurysmal subarachnoid hemorrhage (SAH) based on a 35-year-old hospital database and demographic data.
A database of patients admitted to our hospital with aneurysmal SAH from 1983 to 2017 was split into 5-year intervals and analyzed. Demographic data of the general population were also analyzed for reference.
Altogether, 1,523 aneurysmal SAH events were enrolled in the analysis. Age (p<0.001), proportion of elderly patients ≥ 65 years old (p<0.001), female sex (p=0.005), very small aneurysms less than 5 mm (p<0.001), and the yearly-averaged number of fatal events showed increasing trends. The proportion of aneurysm size of 10 mm or more (p = 0.011) and the yearly-averaged population of Shimane prefecture (p < 0.001) showed declining trends. In the subgroup analyses, the proportion of very small aneurysms was found to increase significantly in the non-elderly male and elderly female subgroups. The proportion of large aneurysms (10 mm or more) decreased in the non-elderly subgroup (p<0.05). As for the elderly subgroups, the yearly-averaged number of events did not show a significant tendency, although the yearly-averaged population of Shimane prefecture showed an increasing trend.
We found an increasing trend in the prevalence of very small aneurysms in elderly females. Recent aging may contribute to this trend. The number of aneurysmal SAH events was confirmed to not increase, despite the increased aging population of Shimane prefecture.
Impact of Ruptured Aneurysm Circulation on Mortality: A Nationwide Inpatient Sample Analysis
2020, Journal of Stroke and Cerebrovascular Diseases
This study investigates the effect of aneurysm circulation on mortality and patient outcomes after aneurysmal subarachnoid hemorrhage (SAH) within the United States.
A retrospective cohort study was conducted using the Nationwide Inpatient Sample (NIS), a part of the Healthcare Cost and Utilization Project (HCUP), with ICD-10 codes for non-traumatic SAH between 2015-2016. Aneurysms were stratified as either anterior or posterior circulation. Multivariate logistic regression was used to find the impact of selected variables on the odds of mortality.
The NIS reported 1,892 cases of non-traumatic SAH within the study period that were predominantly anterior circulation (82.6%), female (68.6%), white (57.7%), with mean age of 59.07 years, and in-hospital mortality of 21.4%. Anterior circulation aneurysms were associated with lower severity of initial illness (p = 0.014) but higher likelihood of vasospasm (p = 0.0006) than those of the posterior circulation. In a multivariate logistic regression analysis, mortality was associated with posterior circulation aneurysms (OR: 1.42; CI 95% 1.005-20.10, p = 0.047), increasing age (OR: 1.035; 95% CI 1.022-1.049; p < 0.0001), and shorter hospital stays (OR: 0.7838; 95% CI 0.758-0.811; p < 0.0001). Smoking history (OR: 0.825; 95% CI 0.573-1.187, p > 0.05) and vasospasm (OR: 1.005; 95% CI 0.648-1.558; p > 0.05) were not significantly associated with higher odds of mortality.
Mortality following aneurysmal SAH is associated with posterior circulation aneurysms, and increasing age, but not smoking history or vasospasm. These findings may be useful for prognostication and counseling patients and families.

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: Conflict of interest statement: The authors declare that the content of this article was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Original ArticleSize and Location of Ruptured Intracranial Aneurysms: A 5-Year Clinical Survey

Background

Methods

Results

Conclusions

Introduction

Section snippets

Materials and Methods

Demographics, Diagnostics, and Surgical Management

Discussion

Conclusions

Lancet

Lancet

Surg Neurol

Incidence of subarachnoid hemorrhage: role of region, year, and rate of computed tomography: a meta-analysis

Stroke

Unruptured intracranial aneurysms—risk of rupture and risks of surgical intervention

N Engl J Med

The frequency of subarachnoid hemorrhage from very small cerebral aneurysms (<5 mm): a population-based study

Cureus

What is the significance of a large number of ruptured aneurysms smaller than 7 mm in diameter?

J Korean Neurosurg Soc

Natural history of unruptured intracranial aneurysms: probability of and risk factors for aneurysm rupture

J Neurosurg

Risk of rupture from incidental cerebral aneurysms

J Neurosurg

Long-term follow-up study of unruptured intracranial aneurysms

Neurosurgery

The natural course of unruptured cerebral aneurysms in a Japanese cohort

N Engl J Med

A review of size and location of ruptured intracranial aneurysms

Neurosurgery

Aneurysm size: a prognostic factor for rupture

Br J Neurosurg

Original Article
Size and Location of Ruptured Intracranial Aneurysms: A 5-Year Clinical Survey