Risk of Stroke due to Intracranial Atherosclerosis

Bos et al report in JAMA Neurology on the relationship between intracranial carotid artery calcifications and the risk of stroke in white populations.  As 80% to 90% of all strokes are due to acute ischemic strokes (AIS), it is important to recognize that atherosclerosis varies across the vascular beds and as such, different locations of vascular disease may have important role in AIS pathogenesis.  Atrial fibrillation and large-artery atherosclerosis such as in aortic arch and extra-cranial carotids are recognized as a major risk factors for AIS.  How common strokes occur after occlusion of the small intra-cerebral arteries, in so-called cerebral small-vessel disease is not well understood.

Between the years 2003 and 2006, a random sample of 2323 stroke-free persons (mean age, 69.5 years) underwent computed tomography scanning to quantify intracranial carotid artery calcification burden.  The population-based cohort was from the general community and part of the Rotterdam Study. All participants were continuously monitored for the occurrence of stroke until January 1, 2012.

During 14 055 person-years of follow-up, 91 participants had a stroke, of which 74 were acute ischemic strokes.  Large intracranial carotid artery calcification burden was related to a higher risk of stroke, independent of cardiovascular risk factors, ultrasound carotid plaque score, and calcification in other vessels.  Intracranial carotid artery calcification contributed to 75% of all strokes; for aortic arch and extra-cranial carotid artery calcification this incidence was only 45% and 25%, respectively.  As the sum of risk factors for strokes exceeds 100%, it suggests interaction between them as well as that unknown causes may contribute to AIS.

The findings of their study establish intracranial atherosclerosis as a major risk factor for stroke in the general white population and suggest that its contribution to the number of all acute ischemic strokes may be greater than atherosclerosis in common and internal carotid arteries as well as that from the arch of the aorta.