The management of unruptured and asymptomatic intracranial aneurysms remains controversial. Since aneurysmal hemorrhage carries a high risk of mortality and morbidity it is essential to estimate the probability of aneurysm rupture in each individual case in order to decide whether treatment should be recommended. The likelihood that a given aneurysm will rupture has been the subject of many scientific studies. The largest studies looking at the natural history of unruptured aneurysms are ISUIA (International Study of Unruptured Intracranial Aneurysms) and UCAS (Unruptured Cerebral Aneurysm Study) – a Japanese undertaking. More recently, a meta-analysis of these and other, smaller trials has resulted in the development of the PHASES score which aims to predict rupture risk based on patient and aneurysm factors associated with rupture.

On this website, you will find aneurysm calculators designed to make the data from these trials easily accessible. Please read the guidance notes for each calculator for a detailed explanation of how the calculators work and their limitations.

PHASES calculator
ISUIA calculator
UCAS calculator

Disclaimer: These tools are free to use. Results are indicative only and may not be applicable to all patient groups. The decision of whether and how to treat a particular aneurysm is a complex one best made by the patient and their family under the guidance of an experienced neurosurgeon. While we will attempt to keep this tool updated, no guarantees can be made that the data presented here is accurate or current. All rights reserved.

Ralf A Kockro, M.D and Tim Killeen, Ph.D, MRCS

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