Wearable device and method for non-invasive assessment of glymphatic flow

1. A system for measuring glymphatic flow, the system comprising:

a head-mounted wearable device comprising:

an impedance circuit and a microcontroller that generate input alternating currents over a range of frequencies,

a plurality of left electrodes positioned to be located over the left frontal, temporal, and parietal lobes when the head-mounted wearable device is placed on a subject,

a plurality of right electrodes positioned to be located over the right frontal, temporal, and parietal lobes when the head-mounted wearable device is placed on the subject,

a pair of current electrodes that provide the input alternating currents over the range of frequencies to the subject during at least one intervention, the pair of current electrodes selected from among the plurality of left and right electrodes, wherein the pair of current electrodes that are selected is varied during the at least one intervention, and wherein the input alternating currents over the range of frequencies are provided to the subject in a sequence that is repeated in multiple iterations, and

a plurality of sense electrodes that collect voltage difference measurements in response to the input alternating currents, wherein the plurality of sense electrodes comprises the plurality of left and right electrodes remaining after the pair of current electrodes are selected;

a measurement validation module that:

applies a Kramer-Kronig test to the voltage difference measurements,

rejects as invalid the voltage difference measurements that fail the Kramer-Kronig test, and

generates a time-series of validated impedance spectra corresponding to each iteration over the range of frequencies, wherein a decrease in a change of the validated impedance spectra as a function of frequency over the multiple iterations indicates greater cranial interstitial fluid flow; and

a cranial fluid dynamics module that:

fits an electric circuit model to each validated impedance spectra of the time-series, and

outputs a glymphatic flow response to the at least one intervention by computing a difference of the time-series of the electric circuit model fitted to each validated impedance spectra.

2. The system of claim 1 , wherein the at least one intervention is one of sleep, sleep deprivation, drug infusion, electrostimulation, and physiological stimulation.

3. The system of claim 2 , further comprising an intervention module that controls one of the drug infusion, the electrostimulation, or the physiological stimulation.

4. The system of claim 1 , wherein the glymphatic flow response indicates a change in volume of cranial interstitial fluid.

5. The system of claim 1 , wherein the input alternating currents include at least one input alternating current having a frequency less than 10 kHz.

6. The system of claim 1 , wherein the cranial fluid dynamics module compares the glymphatic flow response to the at least one intervention to glymphatic flow responses gathered from the subject previously and provides an assessment of disease progression.

7. The system of claim 1 , wherein the cranial fluid dynamics module compares the glymphatic flow response to the at least one intervention to a population distribution of glymphatic flow responses gathered from other subjects and provides an assessment of disease progression for the subject.

8. The system of claim 1 , wherein the measurement validation module and the cranial fluid dynamics module reside in a computing device that communicates with the head-mounted wearable device.

9. The system of claim 1 , wherein the head-mounted wearable device further comprises a voltage sensing circuit and a current source or voltage source that generates the input alternating currents.

10. A method for measuring glymphatic flow, the method comprising:

providing a head-mounted wearable device worn by a subject during an intervention, the head-mounted wearable device comprising

an impedance circuit,

a microcontroller,

a plurality of left electrodes positioned to be located over left frontal, temporal, and parietal lobes when the head-mounted wearable device is placed on the subject, and

a plurality of right electrodes positioned to be located over right frontal, temporal, and parietal lobes when the head-mounted wearable device is placed on the subject;

generating, by the impedance circuit and the microcontroller, input alternating currents over a range of frequencies;

providing the input alternating currents via two current electrodes over the range of frequencies to a subject during at least one intervention, the two current electrodes selected from among the plurality of left and right electrodes, wherein the two current electrodes that are selected is varied during the intervention, and wherein the input alternating currents over the range of frequencies are provided to the subject in a sequence that is repeated in multiple iterations;

collecting, with a plurality of sense electrodes, voltage difference measurements in response to the input alternating currents, wherein the plurality of sense electrodes comprises the plurality of left and right electrodes remaining after the pair of current electrodes are selected;

applying, by a measurement validation module, a Kramer-Kronig test to the voltage difference measurements;

rejecting, by the measurement validation module, as invalid the voltage difference measurements that fail the Kramer-Kronig test;

generating, by the measurement validation module, a time-series of validated impedance spectra corresponding to each iteration over the range of frequencies, wherein a decrease in a change of the validated impedance spectra as a function of frequency over the multiple iterations indicates greater cranial interstitial fluid flow;

fitting, by a cranial fluid dynamics module, an electric circuit model to each validated impedance spectra of the time-series; and

outputting, by the cranial fluid dynamics module, a glymphatic flow response to the at least one intervention by computing a difference of the time-series of the electric circuit model fitted to each validated impedance spectra.

11. The method of claim 10 , wherein the at least one intervention is one of sleep, sleep deprivation, drug infusion, electrostimulation, and physiological stimulation.

12. The method of claim 11 , further comprising controlling, by an intervention module, one of the drug infusion, the electrostimulation, or the physiological stimulation.

13. The method of claim 11 , wherein the glymphatic flow response indicates a change in volume of cranial interstitial fluid.

14. The method of claim 11 , wherein the input alternating currents include at least one input alternating current having a frequency less than 10 kHz.

15. The method of claim 10 , further comprising:

comparing, by the cranial fluid dynamics module, the glymphatic flow response to the at least one intervention to glymphatic flow responses gathered from the subject previously; and

providing, by the cranial fluid dynamics module, an assessment of disease progression.

16. The method of claim 10 , further comprising:

comparing, by the cranial fluid dynamics module, the glymphatic flow response to the at least one intervention to a population distribution of glymphatic flow responses gathered from other subjects; and

providing, by the cranial fluid dynamics module, an assessment of disease progression for the subject.

17. The method of claim 10 , wherein the measurement validation module and the cranial fluid dynamics module reside in a computing device that communicates with the head-mounted wearable device.