Background and purpose: Although it has been suggested that bilateral symmetry of atherosclerosis can be found in paired arteries, including external carotid arteries and femoral arteries, it has remained unknown in intracranial arteries. We determined whether bilateral symmetry (a mirror pattern) of atherosclerosis presents in the entire cerebral arterial system.
Methods: Angiographic findings of 795 consecutive patients with ischaemic stroke, after excluding those with cardiac sources of embolism or other causes of stroke, were reviewed retrospectively. The presence (location) and severity (the degree of stenosis) of atherosclerosis were compared between left and right sides at 26 predetermined arteries/segments.
Results: We found 2230 lesions in predetermined segments/arteries from 669 patients. Amongst 509 patients with atherosclerotic lesions at two or more arteries/segments, mirror patterns were observed in 312 patients (61.3%). The mirror pattern increased steeply as the number of atherosclerotic arteries increased and was most frequently found in the carotid bulb (C1, 26.7%), followed by the middle cerebral artery (M1, 14.1%). The severity of stenosis was also correlated between left and right sides, and the correlation was highest in the C1 (r = 0.40, P < 0.001). Multiple logistic regression analyses revealed that the mirror patterns of atherosclerosis were more obvious in C1 and associated with a past history of ischaemic stroke and the number of stenotic lesions.
Conclusion: Atherosclerosis in cerebral arteries may develop and progress in a mirror pattern. In patients with cerebral artery atherosclerosis, the occurrence and progression of atherosclerosis in the contralateral cerebral artery should be considered during follow-up examination.