In 21 patients withno cognitive impairment, 21 with mild cognitive impairment and 19 patients withmultiple sclerosis, imaging revealed that BBB leakage within the hippocampus was afeature of normal aging but was exacerbated in the MCI group.34 The severity of BBB leakage correlated with the CSF level of soluble PDGFRB,a marker of pericyte injury.35 Van de Haar et al.36,37 examined a small cohort of patients with early AD andage-matched controls and found that BBB leakage in early AD was associated withcognitive decline and reduced cerebral blood flow. The gene discussed is PDGFRB; the disease is Alzheimer disease.