Regional cerebral FDG-PET metabolic patterns across severity of extracranial internal carotid artery stenosis

Background Carotid stenosis is associated with stroke and cognitive impairment. Whether cerebral glucose hypometabolism, a marker for neurodegeneration, mediates the association between carotid stenosis and cognitive decline remains unclear. Objectives To investigate whether carotid stenosis is associated with reduced cerebral glucose metabolism measured by 18 FDG-PET. Methods We conducted a cross-sectional study of patients evaluated at Mayo Clinic (2010–2024) who underwent extracranial carotid imaging and brain 18 F-FDG-PET within 1 year. Stenosis was classified as mild (<50%), moderate (50-69%), or severe (≥70%). Regional metabolism was quantified using standardized uptake value ratios (SUVRs) normalized to the pons across 12 cortical regions; hypometabolism was defined as SUVR <1.41. Multivariable analyses adjusted for age, sex, and vascular risk factors. Results Among 84 patients, stenosis was mild in 86.9%, moderate in 4.8%, and severe in 8.3%; 44% underwent FDG-PET for clinical indications, mostly for suspected cognitive impairment. Increasing stenosis severity was associated with numerically lower metabolism in ipsilateral anterior circulation regions, without statistical significance. Adjusted odds of ipsilateral sensorimotor hypometabolism increased with stenosis severity (moderate: OR 2.90 [95%CI, 0.31–27.1]; severe: OR 5.56 [95% CI, 0.57–54.2]; P = 0.095), with attenuated associations in posterior circulation regions. Conclusion FDG-PET demonstrated a numerical association between carotid stenosis severity and reduced cerebral glucose metabolism, but this did not reach statistical significance. Larger studies with greater representation of high-grade stenosis are needed.