Radiologic Surveillance of Untreated Unruptured Intracranial Aneurysms: A Single Surgeon's Experience

doi:10.1016/j.wneu.2016.02.008

World Neurosurgery

Volume 90, June 2016, Pages 20-28

https://doi.org/10.1016/j.wneu.2016.02.008 Get rights and content

Background

The management of untreated unruptured intracranial aneurysms remains controversial. The natural history is still not well understood and many patients are not routinely followed up. We present a single surgeon's data on radiologic surveillance of these lesions.

Methods

A total of 94 patients with 152 unruptured intracranial aneurysms, with a mean follow-up time of 3.4 years from the time of diagnosis, underwent surveillance using computer tomogram angiography, magnetic resonance angiography, or digital subtraction angiography. Aneurysm growth was defined as an increase in ≥1 dimensions above the measurement error. Statistical analysis was performed.

Results

Of 152 aneurysms, 126 (83%) were <7 mm, 25 (16%) were 7–12 mm, and 1 aneurysm was 13–24 mm. Eighteen of 152 (12%) cerebral aneurysms in 17 patients grew larger; 7% (9/126) of the aneurysms were <7 mm and 36% (9/25) of the aneurysms were 7–12 mm enlarged. Spontaneous aneurysmal rupture occurred in 4 of 152 aneurysms (2.6%) (i.e., 4/94 patients [4%]), with an average initial aneurysm size of 5.7 mm. The risk of aneurysm rupture per patient-year was 5% with growth, 0.2% without growth, and there was a 24-fold increase in aneurysmal rupture risk for growing aneurysm (P = 0.005). Of aneurysms in group 1 patients (no previous subarachnoid hemorrhage [SAH]) 15% (16/109) compared with 5% (2/43) of group 2 (previous SAH) aneurysms showed evidence of growth during the study period (P = 0.0424).

Conclusions

These results support imaging follow-up of patients with untreated unruptured intracranial aneurysms, including those with aneurysms smaller than the current treatment threshold of 7 mm. Apart from the initial size, aneurysm growth is associated with an increased risk of SAH and therefore growing aneurysms warrant treatment. The data also demonstrated that incidental aneurysms, in patients without previous SAH, do not behave less aggressively, contrary to current opinion.

Introduction

The prevalence of intracranial cerebral aneurysms is approximately 2%¹ and incidence of aneurysmal rupture leading to subarachnoid hemorrhage (SAH) is approximately 8 per 100,000.² Based on these statistics, in the United Kingdom with a population of 60 million, it is predicted that there are 1.2 million individuals with cerebral aneurysms (many undiagnosed) and 4800 aneurysmal subarachnoid hemorrhages per year.

Unruptured intracranial aneurysms (UIAs) are a growing concern, given the frequency of detection on noninvasive brain imaging. Available natural history data suggest that key risk factors for hemorrhage among patients with UIAs include aneurysm size, location, presence of daughter sac, Japanese or Finnish ethnicity.³

The results of the International Study of Unruptured Intracranial Aneurysms (ISUIA) revealed a very low rupture rate of 0.05% per year for incidental asymptomatic UIA <10 mm in diameter⁴ and 0 for UIAs without a history of SAH and <7 mm in diameter.⁵ Therefore, many patients with incidental asymptomatic UIAs <7 mm in diameter are managed conservatively. As there is no consensus regarding follow-up, many patients do not undergo serial imaging.

The management of untreated unruptured cerebral aneurysms remains controversial, as the natural history is still not well understood and very few longitudinal studies have been published. We present a single surgeon's data with radiologic surveillance of UIAs.

Section snippets

Methods

Ninety-four patients with 152 untreated unruptured cerebral aneurysms underwent surveillance using computer tomogram angiography (CTA), magnetic resonance angiography (MRA), and/or digital subtraction angiography at the Institute of Neurological Science, Glasgow, United Kingdom on a yearly or 2-year basis. The lesions were studied for a mean of 3.4 years (range, 0.5–11 years) from the time of diagnosis. Case notes, neuroradiology reports, and cerebral angiograms were reviewed. These

Results

In 94 patients (74 women, 20 men) with a mean age at presentation of 53 years (range, 30–78 years), 152 unruptured incidental cerebral aneurysms were identified and subjected to longitudinal surveillance. Thirty patients (32%) had a previous history of SAH from an aneurysm separate from the aneurysm under surveillance and were designated as group 2 (as per ISUIA). The distribution of the aneurysms in this study is shown in Table 1, with most of the aneurysms located in the middle cerebral

Discussion

Overall, in this study, 12% of UIAs showed evidence of growth and aneurysmal rupture occurred in nearly 3% of our patients. This is a rate similar to a recent study⁷ from California that included 165 patients with 258 cerebral aneurysms and mean follow-up of 2.24 years. Villablanca et al⁷ reported that 18% of UIAs increased in size, with 2% of aneurysms in the cohort eventually rupturing.

With a mean follow-up of 3 years in the present study, the incidence of growth was 4% per year, with an

Conclusions

These results support imaging follow-up of all patients with untreated asymptomatic unruptured aneurysms, including those with aneurysms smaller than the current 7-mm treatment threshold. Apart from the initial size, aneurysm growth is associated with increased risk of SAH and growing lesions should be afforded early treatment. The data presented also showed that incidental aneurysms in patients without previous SAH do not behave less aggressively, contrary to current wisdom.

References (14)

B.S. Baxter et al.
Factors affecting the measurement of size and CT number in computed tomography
Invest Radiol
(1981)
L.H. Pobereskin
Incidence and outcome of subarachnoid haemorrhage: a retrospective population based study
J Neurol Neurosurg Psychiatr
(2001)
R.D. Brown
Unruptured intracranial aneurysms
Semin Neurol
(2010)
Unruptured intracranial aneurysms—risk of ruptured and risks of surgical intervention
N Engl J Med
(1998)
Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment
Lancet
(2003)
R.U. Kothari et al.
The ABCs of measuring intracerebral hemorrhage volumes
Stroke
(1996)
J.P. Villablanca et al.
Natural history of asymptomatic unruptured cerebral aneurysms evaluated at CT angiography: growth and rupture incidence and correlation with epidemiologic risk factors
Radiology
(2013)

There are more references available in the full text version of this article.

Cited by (18)

Asymptomatic Intracranial Aneurysms in the Elderly: Long-Term Clinical and Radiologic Follow-Up of 193 Consecutive Patients
2020, World Neurosurgery
Citation Excerpt :
Of the 8 patients with documented aneurysm growth, none required definitive treatment, and no patient had experienced an SAH. Our findings are consistent with the literature, which reports heterogenous aneurysm growth rates (not specific to the elderly) between 1.8% and 46.0%, over mean follow-up periods between 0.8 and 21.7 years.3,11-33 Figure 3 summarizes the current literature on growth of AIAs in the general population.
Evidence is lacking regarding the role of radiologic surveillance for asymptomatic intracranial aneurysms (AIAs) in the elderly (≥65 years). We sought to establish if long-term clinical and radiologic observation is warranted for older patients with AIAs.
A retrospective cohort of 193 consecutive patients with 255 AIAs were clinically and radiologically observed between January 2011 and January 2019. The primary end points were documented aneurysm growth, subarachnoid hemorrhage, or definitive treatment with microsurgical clipping or endovascular coiling. Baseline patient and aneurysm characteristics were obtained. Univariate and multivariate comparisons were performed.
Aneurysm growth was observed in 8 patients (4.2%) at a median follow-up of 58.2 months (interquartile range, 38.4–78.5 months). The median aneurysm size at initial diagnosis was 3.5 mm (interquartile range, 2.2–5 mm). Aneurysms larger than 7 mm selected for surveillance were noted in 37 patients (19.2%). The growth rate was estimated at 0.2 mm per person-year. At the end of the study period, 175 patients (90.7%) were alive, 6 (3.1%) were lost to follow-up, and 12 (6.2%) died of unrelated causes. During the 1025.2 person-years follow-up, no patient had experienced subarachnoid hemorrhage, and none required definitive treatment. The presence of aneurysmal bleb (odds ratio, 6.02; 95% confidence interval, 1.15–31.43; P = 0.033) and multiple intracranial aneurysms (odds ratio, 10.98; 95% confidence interval, 1.27–94.91; P = 0.029) were associated with growth.
AIAs in older patients deemed suitable for conservative management do not require robust follow-up. The current study suggests a potential role for closer surveillance for patients with multiple intracranial aneurysms or aneurysms with bleb morphology.
Surveillance and screening for intracranial aneurysms
2018, Intracranial Aneurysms
The benefit of screening for unruptured intracranial aneurysm (UIA) is based on the potential morbidity and mortality benefit of prophylactic treatment. Therefore, the clinician must determine when a patient is at increased risk of harboring an aneurysm and when that risks warrants screening. Once diagnosed, the clinician must determine if the aneurysm warrants the risk of treatment. There is a cohort of UIA patients where either the aneurysm is of such low risk or the patient is at such high risk that intervention is not appropriate at the time of diagnosis. These UIA patients may be candidates for routine radiographic surveillance rather than treatment if they would be candidates for prophylactic where the UIA evolve to a higher risk for rupture. When faced with such a patient, the clinician must determine how to image the aneurysm in serial fashion and in what time frame. In this chapter, we will review the indications for and methods of screening for UIAs; discuss patient selection and protocols for UIA surveillance; and compare different screening and surveillance modalities.
Risk factors for the rupture of intracranial aneurysms: a systematic review and meta-analysis
2023, Frontiers in Neurology
Unruptured untreated intracranial aneurysms: a retrospective analysis of outcomes of 445 aneurysms managed conservatively
2023, British Journal of Neurosurgery
A survey of the radiological follow-up of unruptured intracranial aneurysms in the United Kingdom
2023, British Journal of Neurosurgery
European Stroke Organisation (ESO) guidelines on management of unruptured intracranial aneurysms
2022, European Stroke Journal

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: Conflict of interest statement: The authors declare that the article content 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 ArticleRadiologic Surveillance of Untreated Unruptured Intracranial Aneurysms: A Single Surgeon's Experience

Background

Methods

Results

Conclusions

Introduction

Section snippets

Methods

Results

Discussion

Conclusions

Factors affecting the measurement of size and CT number in computed tomography

Invest Radiol

Incidence and outcome of subarachnoid haemorrhage: a retrospective population based study

J Neurol Neurosurg Psychiatr

Unruptured intracranial aneurysms

Semin Neurol

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

N Engl J Med

Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment

Lancet

The ABCs of measuring intracerebral hemorrhage volumes

Stroke

Natural history of asymptomatic unruptured cerebral aneurysms evaluated at CT angiography: growth and rupture incidence and correlation with epidemiologic risk factors

Radiology

Original Article
Radiologic Surveillance of Untreated Unruptured Intracranial Aneurysms: A Single Surgeon's Experience