Comment Authors: Renato Oliveira, Diana Aguiar de Sousa, Department of Neurology, Hospital de Santa Maria, University of Lisbon, Portugal

Original Article: CCM Zuurbier, JP Greving, GJE Rinkel, YM Ruigrok. 2019; Higher risk of intracranial aneurysms and subarachnoid haemorrhage in siblings of families with intracranial aneurysms; European Stroke Journal; DOI: 10.1177/2396987319868048

A brain aneurysm in the family, and now what? – The genealogy of aneurysms

Intracranial aneurysms are present in approximately 3% of the adult population and their rupture results in the potentially catastrophic event of aneurysmal subarachnoid hemorrhage (aSAH). Screening for intracranial aneurysms may be considered in first-degree relatives of patients with cerebral aneurysm when two or more family members have been affected. However, few studies assessed the type of kinship and the risk of aSAH and unruptured intracranial aneurysms.

In this paper published today in the European Stroke Journal, Zuurbier and colleagues aimed to assess the risk for aSAH and/or unruptured intracranial aneurysms in first-degree relatives of aSAH patients, according to the type of kinship (parents vs. siblings vs. children).

The authors used a 22-year clinical database from a tertiary centre that performs screening for intracranial aneurysms in individuals with positive family history, defined as two or more first-degree relatives (parents, siblings, children) with aSAH or unruptured intracranial aneurysms

From 154 proband patients, family pedigrees were constructed, which included a total of 1105 proband´s first-degree relatives. Clinical data of all relatives was collected retrospectively and the relative risk of aSAH and unruptured intracranial aneurysms according to types of kinship was calculated using children as the reference.

Siblings had higher risks of both aSAH and unruptured intracranial aneurysms

Of the 1105 relatives, 146 had aSAH (13%). Screening for unruptured intracranial aneurysms was performed in 326 relatives and was positive in 63 (19%). Siblings had higher risks of both aSAH (RR 1.62, 95% CI: 1.12–2.38) and unruptured intracranial aneurysms (RR adjusted for age 2.04, 95% CI: 1.07–3.92), followed by children. Parents had the lowest risk of aSAH (RR 0,44, 95% CI: 0,24-0,81).  The mean duration of follow-up of screened relatives was 87months in siblings and 69 months in children.

Since the risk of unruptured intracranial aneurysms and aSAH was more common in siblings as opposed to children and parents, the authors hypothesize that common environmental risk factors more widely shared between siblings may be key in explaining these differences. Non-additive genetic effects may be also involved.

The main strengths of this study are the large sample size and the standardized screening protocol. However, probands or relatives not well informed about their own family history or refusing consent could have been a source of selection bias.

So, the next time a patient asks for advice on the family risk of SAH, we will know better what type of kinship is more relevant when considering risk prediction and screening advice.

The original article “higher risk of intracranial aneurysms and subarachnoid hemorrhage in siblings of families with intracranial aneurysms” is available in the Online First section of the European Stroke Journal.