Noninvasive sensing of intracranial water in cerebrospinal fluid and blood by near-infrared spectroscopy

Intracranial fluid pulsations have garnered significant interest due to the growing understanding of the glymphatic system and its connection to neurodegenerative diseases. Furthermore, abnormalities in neuro-hydrodynamics, such as those related to edema and stroke, are of considerable interest for continuous non-invasive monitoring in critically ill patients. In light of these interests, our objective is to develop and validate techniques, specifically functional near-infrared spectroscopy (fNIRS), for the real-time monitoring of brain fluids, including cerebrospinal fluid (CSF) and blood. In the present study, we experimented how modified plasma water content through the continuous infusion of physiological saline affects the spectral response across a wavelength range of 600 nm to 1150 nm when measured through mouse brain.