Summary: People with asymmetrical brain arteries have a significantly higher risk of developing a cerebral aneurysm, a new study reports.
Source: University of South Australia
It’s called a silent killer. Warnings are rare, but of the million people who suffer a ruptured brain aneurysm each year, almost half will die and only a third will recover without disabilities.
A new study published in BMJ Open has measured for the first time a link between variations in size of the brain’s arteries and the likelihood of a cerebral aneurysm, providing scientists with a new screening tool to monitor people at risk.
Lead researcher, University of South Australia neuroanatomist, Dr Arjun Burlakoti, says imaging tests of 145 patients showed that people with asymmetric brain arteries have a significantly higher chance of developing an aneurysm, a ballooned vessel in the brain, that can rupture and cause a haemorrhagic stroke.
“A subarachnoid haemorrhage is the most dangerous type of stroke and occurs when a brain aneurysm leaks or ruptures, causing bleeding into the brain, killing more than 50 per cent of affected people,” Dr Burlakoti says.
“A lot of small, unruptured aneurysms go undetected in commonly used imaging techniques. They may not be diagnosed until they grow sufficiently to cause symptoms or rupture, often when it is too late.
“We looked at brain images of people with aneurysms and found that the four arteries entering the brain box, dividing into multiple segments and supplying blood to the brain, were not in proportion to each other, thus increasing peaks in blood pressure and predisposing them to ballooned blood vessels.”
Where the front part of the brain arterial network (the anterior cerebral artery, or A1) differs in left and right diameter ratio by up to 1.4, people have an 80 percent risk of developing aneurysms in that region, the most common location of ruptured aneurysms. Those with symmetrical ratios below 1.4 have a 7.8 per cent equivalent risk.
Cerebral aneurysms cause almost 500,000 deaths worldwide each year, half of them occurring in people under the age of 50, with women at greater risk.
The main symptom of a burst aneurysm is a sudden, severe headache, often accompanied by double vision, nausea and vomiting, a stiff neck, muscle weakness, confusion, seizures and cardiac arrest.
If detected early, aneurysms can be monitored and slowed by controlling blood pressure with medication and diet and lifestyle changes. They can also be surgically clipped or removed but this also carries risks of brain damage or stroke and is only recommended if there is a high risk of rupture.
“Based on our findings, MRI and CT angiograms will determine whether people have asymmetrical brain arteries and if so, they should be screened regularly for cerebral aneurysms,” Dr Burlakoti says.
He collaborated with Dr Jaliya Kumaratilake, Dr Jamie Taylor and Prof Maciej Henneberg at the University of Adelaide, Royal Adelaide Hospital and University of Zurich, respectively, in this study.
Relationship between cerebral aneurysms and variations in cerebral basal arterial network: a morphometric cross-sectional study in Computed Tomography Angiograms from a neurointerventional unit
Segments of cerebral basal arterial network (CBAN) dampen the peak pressure in blood flowing through these arteries, thus minimising the chances of development of cerebral aneurysms. The objective of this research was to find the relationship of occurrence of intracranial aneurysms to variations of the components of the CBAN.
Design and setting
This is an observational, quantitative and retrospective research, which used cerebral CT angiography (CCTA) images.
Cerebral CTA of 145 adult patients of both sexes were studied.
Main outcome measures
Diameters of segments of CBAN were measured in CCTA images and the relative size of each vessel was calculated to standardise for differences in overall arterial sizes among patients. Relationships among sizes of CBAN components were analysed. Presence of aneurysms in different parts of the CBAN was recorded.
Forty-six aneurysms in right internal carotid artery (ICA) and middle cerebral artery (MCA) and 32 aneurysms in left ICA and MCA segments were noted in 42 and 30 patients, respectively. Aneurysms in anterior communicating artery complex and vertebral-basilar arterial segments were seen in 27 and 8 patients, respectively, while they were not detected in parts of posterior cerebral artery (PCA). The significant (p<0.001) inverse relationships between sizes of posterior communicating artery and the first segment of PCA on both sides indicated that blood inputs to the second part of PCA were similar. Difference in means of the index of arterial size variation for people with aneurysms (mean 0.96, SD 0.23) and without aneurysms (mean 0.86, SD 0.22) was significant (p=0.015).
Variation in segments of CBAN was quantified. The peak pressure dampening mechanism in such arterial segments reduces the chances of development of aneurysms.