Monitoring and controlling hydrocephalus
View Patent ↗Systems and methods for monitoring cerebral spinal fluid (CSF) based on electrical impedance measurements are disclosed. The systems can include an excitation source of alternating current ( 202 ), at least two sensor electrodes ( 212,214 ) adapted for disposition within CSF in a ventricle of a subject's brain, and an impedance measuring device ( 204 ) electrically connected to the sensor electrodes ( 212,214 ) to measure impedance of CSF. Methods for controlling hydrocephalus are also disclosed and such methods can include the steps of disposing an impedance sensor ( 902 ) within CSF in a ventricle of a subject's brain, measuring impedance of the CSF with the sensor ( 902 ), and withdrawing CSF when the impedance measurement is less than a threshold value.
1. A system for monitoring cerebral spinal fluid (CSF) volume in a ventricle of a subject's brain comprising:
an excitation source of alternating current,
at least two sensor electrodes adapted for disposition within CSF in the ventricle of the subject's brain, and
an impedance measuring device electrically connected to the sensor electrodes to measure impedance of CSF to measure CSF volume in the ventricle of the subject's brain.
2. The system of claim 1 wherein the system further comprises a controller adapted to signal for withdrawal of CSF when the impedance measurement is less than a threshold value.
3. The system of claim 2 wherein the threshold value reflects an impedance difference between CSF and tissue of the subject's brain.
4. The system of claim 1 wherein the system further comprises at least four sensor electrodes adapted for disposition within CSF in the ventricle of the subject's brain.
5. The system of claim 1 wherein the impedance measuring device is adapted to measure a voltage drop between the sensor electrodes and to infer impedance from the voltage drop.
6. The system of claim 1 wherein the sensor electrodes are separated by a distance in a range of about 10 mm to about 40 mm.
7. The system of claim 1 wherein the excitation source is adapted to provide a frequency in the range of about 0.01 Hertz to about 135 kHertz.
8. The system of claim 1 wherein the alternating current is about 100 μA.
9. The system of claim 1 wherein the system further comprises at least two excitatory electrodes adapted for disposition with CSF in a ventricle of a subject's brain, for receiving alternating current from the excitation source, and for creating an electrical field extending around the sensor electrodes.
10. A method for controlling hydrocephalus in a subject's brain comprising:
disposing an impedance sensor within cerebral spinal fluid (CSF) in a ventricle of the subject's brain,
measuring impedance in the ventricle with the impedance sensor to measure volume of the CSF in the ventricle, and
withdrawing CSF when the impedance measurement is less than a threshold value.
11. The method of claim 10 wherein the step of measuring impedance further comprises applying a time-varying electrical signal and measuring a voltage with the sensor.
12. The method of claim 10 wherein the step of measuring impedance further comprises determining a voltage drop between at least two electrodes of the sensor.
13. The method of claim 10 further comprising applying an electrical field extending around the sensor.
14. The method of claim 10 wherein the threshold value reflects an impedance difference between CSF and tissue of the subject's brain.
15. A system for monitoring cerebral spinal fluid (CSF) volume in a ventricle of a subject's brain comprising:
an excitation source of alternating current,
at least two sensor electrodes adapted for disposition within the CSF in the ventricle of the subject's brain,
a measuring device electrically connected to the sensor electrodes and adapted to measure impedance between the sensor electrodes to measure CSF volume,
a CSF withdrawal mechanism, and
a controller adapted to signal the CSF withdrawal mechanism to withdraw CSF from the ventricle when the impedance is less than a threshold value.
16. The system of claim 15 wherein the system further comprises at least two excitatory electrodes adapted for receiving the alternating current and for disposition with CSF in a ventricle of a subject's brain.
17. The system of claim 15 wherein the CSF withdrawal mechanism includes a micro-pump.
18. The system of claim 15 wherein the threshold value reflects an impedance difference between CSF and tissue of the subject's brain.
19. The system of claim 15 wherein the sensor electrodes are separated by a distance in a range of about 10 mm to about 40 mm.
20. The system of claim 15 wherein the excitation source is adapted to provide a frequency in the range of about 0.01 Hz to about 135 kHz.
21. The system of claim 15 wherein the alternating current is about 100 μA.
22. The system of claim 15 wherein the measuring device is adapted to measure a voltage drop between the sensor electrodes and to infer impedance from the voltage drop.