Acta Neurochirurgica

, Volume 160, Issue 12, pp 2419–2423 | Cite as

Risk factors for growth of conservatively managed unruptured intracranial aneurysms

  • Enrico Giordan
  • Thomas J. Sorenson
  • Waleed Brinjikji
  • Roanna Vine
  • Giuseppe LanzinoEmail author
Original Article - Vascular Neurosurgery - Aneurysm
Part of the following topical collections:
  1. Vascular Neurosurgery – Aneurysm



Unruptured intracranial aneurysms (UIAs) occur in 2–3% of the adult population, but, once discovered, do not always require treatment. Untreated patients are usually followed with serial imaging to identify interval growth. In this study, we assessed the risk and risk factors for growth in a homogenous series of patients with conservatively managed UIAs.


Data from consecutive patients without history of subarachnoid hemorrhage and a conservatively managed UIA were retrospectively reviewed and only patients with at least 2 years of radiological follow-up were included in our study. We evaluated patients for the incidence of UIA growth, as well as analyzed risk factors for UIA growth.


In 349 patients and 385 conservatively managed UIAs with 2210 patient-years of radiological follow-up, the risk of growth was 2.9% per aneurysm-year. Size (diameter greater than 5 mm), location (basilar artery apex), and weight loss (decrease in BMI over follow-up period) were all significantly associated with increased risk of UIA growth. There was a greater risk of UIA growth during the first 3 years of follow-up (7.5% per aneurysm-year) compared to the remaining years (2.7% per aneurysm-year).


Conservatively managed UIAs in patients without prior history of SAH have a 2.9% risk of growth per aneurysm-year. UIAs greater than 5 mm in diameter, those located at the basilar artery apex, or patients who experience a decrease in BMI are more likely to grow and warrant closer follow-up. The risk of aneurysm growth is increased in the few years after diagnosis and decreases afterward.


Unruptured intracranial aneurysms Growth Rupture Size Location Body mass index 


Compliance with ethical standards

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. For this type of study formal consent is not required. All included patients agreed to be included in our aneurysm research database.

This article does not contain any studies with animals performed by any of the authors.

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Neurologic SurgeryMayo ClinicRochesterUSA
  2. 2.School of MedicineUniversity of MinnesotaMinneapolisUSA
  3. 3.Department of RadiologyMayo ClinicRochesterUSA

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