Background: Recent data have shown that atherosclerotic calcification of the intracranial vasculature is an independent risk factor for ischemic stroke. The relationship between the most commonly used marker of high risk intracranial atherosclerosis, the percent degree of luminal stenosis, and calcium burden in the intracranial circulation has not been investigated.
Materials and Methods: We evaluated the relationship between atherosclerotic calcification and luminal stenosis in the intracranial internal carotid arteries (ICAs). Using a prospective stroke registry, we identified patients who had non-contrast computed tomography (NCHCT) and either CT angiography (CTA) or magnetic resonance angiography (MRA) examinations as part of a diagnostic evaluation for ischemic stroke. We used NCHCTs to qualitatively (Modified Woodcock Visual Score) and quantitatively (Agatston-Janowitz calcium score) evaluate ICA calcium burden and angiography to measure arterial stenosis (Figure). We calculated correlation coefficients between the degree of narrowing and calcium burden measures.
Results: In 470 unique carotid arteries (235 patients), 372 (79.1%) had atherosclerotic calcification detectable on CT while only 160 (34%) had measurable arterial stenosis (p < 0.001). We found a weak linear correlation between qualitative (R = 0.48) and quantitative (R = 0.42) measures of calcium burden and the degree of luminal stenosis (p < 0.001 for both). Of 310 ICAs with 0% luminal stenosis, 216 (69.7%) had measureable calcium scores.
Conclusion: There is only a weak correlation between intracranial atherosclerotic calcium scores and luminal narrowing, which may be explained by the greater sensitivity of NCHCT compared to angiography in detecting the presence of measurable atherosclerotic disease. Future studies are warranted to evaluate the relationship between stenosis and calcium burden in predicting stroke risk.