Aneurysm symptoms and risks

Neurosurgeon Dr. Ralf Kockro explains the dangers of brain aneurysm and how to use an online risk calculator for this condition.

What are the symptoms and dangers of an aneurysm?

Patient harbouring an aneurysm can be free of symptoms for years as long as important structures of the brain and its nerves are not compressed by the aneurysm - and as long as the aneurysm does not rupture. Unruptured aneurysms may cause symptoms due to their pressure on surrounding neural tissue such as visual disturbance or epileptic seizures. The symptoms of a ruptured aneurysm range from severe headache to paralysis and unconsciousness.

How high is the risk of rupture of an unruptured intracranial aneurysm?

Several studies indicate that the probability of rupture ranges from less than 0.5% to more than 50% annually. However, it must be kept in mind that for every individual aneurysm, the risk of rupture may be higher than predicted since it is subject to factors such as aneurysm shape, concurrent medical conditions and other aspects.

What factors can increase the risk of bleeding of a brain aneurysm?

Untreated hypertension and regular tobacco smoking increase the risk of aneurysm growth and hence the likelihood of rupture. Large studies have also revealed that the risk of rupture increases with aneurysm size and that aneurysms in the posterior arterial circulation have a greater risk of rupture than anterior circulation aneurysms.

Is there a risk calculator for aneurysms that patients can use on the internet?

Patients can use the interactive aneurysm risk calculator at

Here you can input the size and location of an aneurysm in order to calculate its probability of rupture over a specified period of time. The computed probabilities of this calculator strictly reflect the aneurysm rupture rates as they were observed in the ISUIA and UCAS studies and do not take into account specific factors like the individual aneurysm shape or other medical conditions. While the aneurysm calculator provides a good categorisation and evidence based risk estimation, it is therefore important that the every aneurysm is assessed individually by a team of specialists.

From your experience which is the most dangerous aneurysm?

The most dangerous aneurysm is the one that is most likely to rupture. In this group we find large aneurysms and aneurysms with a daughter sac protruding out from their dome indicating a specifically weak and thin aneurysm wall and therefore a high risk of imminent rupture. The location of an aneurysm in the posterior circulation is likely to further increase the risk of rupture.

Find out more

Dr Ralf A. Kockro is a Consultant Neurosurgeon at Klinik Hirslanden, Zürich and a Senior Lecturer of Neurosurgery at the Universities of Zürich and Mainz, Germany. Prior to that he held positions as a Consultant Neurosurgeon at the University Hospital Zürich, the University Hospital Mainz and the Royal London Hospital.

Visit his website here

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