An MRI investigation of the diurnal relationship between cerebral hemo-metabolic activity and bulk cerebrospinal fluid flux

Motivation: An improved understanding of how endogenous cerebral hemo-metabolic activity regulates neurofluid circulation and its relevance to understanding mechanisms of peptide retention and the sequelae of neurodegenerative proteinopathies. Goal(s): To investigate diurnal changes in perfusion and oxygen extraction fraction (OEF), and relate to changes in CSF flux. Approach: 40 MRIs were performed on 10 adults at 7:00-9:00, 11:00-13:00, 16:00-18:00, and 19:00-21:00. OEF, cerebral perfusion, and CSF flux values were calculated. Results: Cortical and ChP perfusion increase, whereas OEF decreases, from morning to evening. This parallels an increase in CSF flux, with the largest change in flux occurring from morning to mid-day. Impact: Concurrent measures of cerebral perfusion, oxygen extraction fraction, and CSF flow performed at different times of day can be used to help inform how ongoing, endogenous hemo-metabolic tone may regulate neurofluid circulation.