Noninvasive monitoring of changes in intracranial fluid and tissue composition

• Method for noninvasive monitoring of slow changes to cranial volume composition • Physiologic tests on humans show that minute changes are detectable • Proof-of-concept for noninvasive monitoring of space-occupying brain disorders Continuous assessment of changes in the fluid and tissue composition of the brain, as they occur with certain space-occupying disorders, is currently not possible. Recently, the noninvasive acquisition of the head’s dielectric properties has been proposed as the basis for monitoring such changes. The analysis of the corresponding electric signal, referred to as W, focused so far on intracranial fluid volume changes induced by cardiorespiratory action. Here, we report on a novel approach to acquire changes of W also in the 0 to 0.1 Hz frequency range, which would allow capturing slower processes such as edema formation. Six healthy male volunteers were tilted head-up, head-down, and subjected to bilateral jugular vein compression. W decreased during head-up tilting, while it increased during head-down tilting and jugular vein compression. These findings are consistent with anticipated changes in intracranial volume due to these maneuvers, notably the reduction of intracranial blood volume during head-up tilt and its augmentation during head-down tilt and jugular vein compression. This study provides a proof of principle for the detection of changes in W within the 0-0.1 Hz frequency range, broadening the potential clinical utility of noninvasive monitoring of cranial dielectric properties in diagnosing and managing space-occupying disorders.