Expansion of corticomedullary junction high-susceptibility region (cmj-hsr) with aging: A clue in the pathogenesis of alzheimer's Disease?

Background: Susceptibility-weighted imaging (SWI) microscopy on a 7.0T system demonstrated the corticomedullary junction (CMJ) to be a high-susceptibility region (HSR) in young normal subjects, suggesting that functional alteration of cortical microcirculation could be assessed with this imaging method. Methods: Focused microscopic studies were performed on the parietal association cortex in 74 normal volunteers (ages 20-79 years; 35 female, 39 male) using a SWI algorithm on a system constructed based on General Electric Signa LX (Waukesha, WI, USA), equipped with a 900-mm clear bore superconducting magnet operating at 7.0T. Results: There was a clear-cut reduction in the thickness of the normal-appearing cortex (cortex, R²= .5290, P < .001) and expansion of CMJ-HSR (R²= .6919, P < .001). The sum of cortex thickness and CMJ-HSR thickness was essentially constant, suggesting that the observed expansion of CMR-HSR with aging likely occurred within the cortical mantle. Conclusion: CMJ-HSR expands significantly as a function of aging. Since CMJ-HSR represents a functionally distinct area with relatively slow venous flow, the observed expansion is believed to reflect alteration in cerebral microcirculation with increased age, providing another clue for pathogenesis of Alzheimer's disease.