Thematic sessionNatural history, epidemiology and screening of unruptured intracranial aneurysmsHistoire naturelle, épidémiologie et dépistage des anévrismes intracrâniens non rompus
Introduction
Unruptured intracranial aneurysms may give rise to subarachnoid haemorrhage in the near or distant future and sometimes these lesions warrant preventive intervention. However, in many situations uncertainty abounds and in many other situations intervention will probably do more harm than good. It is pivotal to carefully balance the risks and benefits of all treatment options and to take time to counsel the “patient”. If an incidental aneurysm is detected, it is important to refrain from descriptions as “a time bomb in your head” before referring the unfortunate patient to a neuro-interventional centre. For many of these patients no intervention is the best option, but having to live with an untreated aneurysm imposes a threat on quality of life, of which anxiety is an important component and may need managing in its own right [1]. Careful counselling and weighing the pros and cons is even more important when screening for aneurysms is considered. Screenees often have unrealistic risk perceptions [2] and screening for intracranial aneurysms is associated with considerable psychosocial effects, both positive and negative [5].
Section snippets
Prevalence of aneurysms
For adults without specific risk factors for aneurysms, the prevalence is 2.3% (95% CI, 1.7–3.1%); most of these aneurysms are small and located in the anterior circulation [6]. The prevalence of aneurysms is higher in women than in men and tends to increase with increasing age; other risk factors are smoking, hypertension, excessive use of alcohol, having one or more affected relatives with SAH, autosomal dominant polycystic kidney disease (ADPKD) and a previous episode of SAH.
Risk of rupture of unruptured intracranial aneurysms
In 2003, the international study of unruptured intracranial aneurysms (ISUIA) researchers reported on the largest ever prospectively studied cohort of patients with unruptured aneurysms [7]. The period of follow-up was relatively short (4.1 years), and the rupture risks were much lower than previously appreciated (Table 1).
A strong point of the study is that rupture risk is reported as five years cumulative risks (see below). However, the ISUIA report also has several weaknesses. First, 30% of
Treatment options for unruptured intracranial aneurysms
Neurosurgical clipping and endovascular coiling are not without risks. Those of neurosurgical clipping have been studied most intensively, because this treatment has been available the longest.
In a systematic review of studies on complications of neurosurgical clipping for unruptured aneurysms published between 1966 and 1996 the overall case fatality was 2.6% (95% CI, 2.0–3.3%); permanent morbidity occurred in another 10.9% (95% CI, 9.6–12.2%). Postoperative mortality and morbidity were
Management of patients with unruptured aneurysms
Every time an intracranial aneurysm is a surprise finding on an imaging study performed for another purpose, the risk of preventive clipping or coiling of the aneurysm at that time should be balanced against the risk of death or disability from rupture of the untreated aneurysm at some time later in life, if ruptures at all. Two pivotal factors in this balance of risks are the size and site of the aneurysm, but these factors are not necessarily helpful because both the risk of rupture and the
Screening for intracranial aneurysms
The eventual goal of screening is not to detect or to treat an aneurysm, but to increase the number of quality years of life. Therefore, before intracranial vessels are imaged, the risks and benefits of screening should be weighed up. This balance of risks includes the amount of anxiety before screening, the reassurance that can be given with a negative result, and the anxiety that can be caused by finding an aneurysm – for example, if a 3 mm aneurysm is found and is left untreated but followed
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