In a novel finding that may assist screening for cerebral aneurysms, Australian researchers have shown that  variations in the size of major cerebral arteries play a significant role in risk of intracranial aneurysms.

University of South Australia neuroanatomist Dr Arjun Burlakoti and colleagues have used cerebral CT angiography imaging to show that people with asymmetric and variant cerebral arterial segments have a significantly higher chance of developing an aneurysm.

In a paper published in BMJ Open they say their findings support the hypothesis that symmetry in the size of cerebral arteries dampens the peak pressure in blood flow, thus minimising the chances of development of cerebral aneurysms.

Their study collected CCTA images for 145 adult patients with complicated and ruptured aneurysms , who were referred to the Neuro-interventional Centre at the Royal Adelaide Hospital (RAH) for treatment.

Diameters of segments of cerebral basal arterial network (CBAN) were measured for 46 aneurysms in right internal carotid artery (ICA) and middle cerebral artery (MCA) and 32 aneurysms in left ICA and MCA segments.

The investigators noted that 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 analysis showed there were 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.

There was also a significant 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).

“Therefore, these statistically significant differences in the variation of segments of CBAN suggests that the correctly formed (minimally variant) segments of CBAN served to best equalise the blood pressure peaks preventing the development of cerebral aneurysms,” they concluded.

“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.

The study investigators noted that previous work had suggested that significant asymmetry in the anterior cerebral artery, with a difference in left and right diameter ratio by up to 1.4, was associated with an 80% risk of developing aneurysms in that region, the most common location of ruptured aneurysms. In contrast, people with symmetrical ratios below 1.4 had a 7.8% equivalent risk.

“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 said

“Patients who have asymmetric and variant cerebral arterial segments in CBAN should be monitored regularly. This finding could be considered as one of the criteria for screening the cerebral ,” he added.