Cerebrospinal fluid dynamics and discordant amyloid biomarkers

OBJECTIVE: Do MRI-based metrics of a CSF-dynamics disorder, disproportionately enlarged subarachnoid-space hydrocephalus (DESH), correlate with discordant amyloid biomarkers (low CSF β-amyloid 1–42, normal Aβ-PET scan)? METHODS: Individuals ≥50 years from the Mayo Clinic Study of Aging, with MRI, (11)C-Pittsburgh compound B (Aβ) PET scans, and CSF phosphorylated-tau protein and Aβ42, were categorized into four groups: normal/ abnormal by CSF β-amyloid 1–42 and Aβ amyloid PET. Within groups, we noted MRI patterns of CSF-dynamics disorders; categorization into low-CSF β-amyloid 1–42/normal Aβ-PET scan versus normal-CSF and PET groups; and Aβ-PET accumulation-change rate. RESULTS: 100 participants (21%) in the abnormal-CSF/normal-PET group had highest DESH-pattern scores and lowest CSF-phosphorylated-tau levels. Among normal amyloid-PET individuals, a one-unit DESH-pattern score increase correlated with 30%-greater odds of abnormal amyloid CSF after age and sex adjustment. Mean rate over time of amyloid-PET accumulation in abnormal-CSF/normal-PET individuals approximated individuals with normal amyloid values. Adjusting for phosphorylated-tau, abnormal CSF-amyloid/normal amyloid-PET individuals had higher mean amyloid-PET accumulation rates than normal individuals. CONCLUSIONS: CSF dynamics disorders confound β-amyloid and phosphorylated-tau CSF-biomarker interpretation.