Systems and methods for detecting intrathecal penetration
View Patent ↗Systems and methods for detecting intrathecal penetration are disclosed. A method in accordance with one embodiment includes detecting a value corresponding to an impedance of an electrical circuit that in turn includes an electrical contact located within the patient, and patient tissue adjacent to the electrical contact. The method further includes comparing the detected value to a predetermined criterion, and, if the detected value meets the predetermined criterion, identifying penetration of the patient's dura based at least in part on the detected value.
1. A method for introducing a patient device, comprising:
detecting a value corresponding to an impedance of an electrical circuit, the electrical circuit including:
an electrical contact carried by an elongated flexible lead and located within the patient; and
patient tissue adjacent to the electrical contact;
comparing the detected value to a predetermined criterion;
if the detected value meets the predetermined criterion, identifying penetration of the patient's dura based at least in part on the detected value; and
if the detected value does not meet the predetermined criterion, applying a therapeutic signal to the patient's nervous system via the elongated flexible lead.
2. The method of claim 1 wherein identifying penetration includes identifying penetration through the dura by the electrical contact.
3. The method of claim 1 wherein comparing includes comparing the detected value to a reference value corresponding to a reference impedance.
4. The method of claim 3 wherein the reference impedance is 50 ohms.
5. The method of claim 3 wherein the reference impedance is less than 200 ohms.
6. The method of claim 3 wherein the reference impedance corresponds to an impedance of cerebral spinal fluid.
7. The method of claim 1 , further comprising:
if the detected value does not meet the predetermined criterion, detecting a subsequent value corresponding to an impedance of the electrical circuit and comparing the subsequent value to the predetermined criterion.
8. The method of claim 1 wherein the patient tissue is adjacent the dura of the patient's spinal cord.
9. The method of claim 1 , further comprising presenting an indication that the dura has been penetrated, in response to identifying penetration of the dura.
10. The method of claim 9 wherein presenting the indication includes presenting a visual indication at a display device.
11. The method of claim 9 wherein presenting the indication includes presenting an aural indication.
12. The method of claim 1 wherein detecting the value includes detecting multiple values at corresponding multiple points in time, and wherein identifying penetration includes identifying penetration based at least in part on a change in the detected value as a function of time.
13. The method of claim 1 wherein detecting the value includes detecting multiple values at corresponding multiple points in space, and wherein identifying penetration includes identifying penetration based at least in part on a change in the detected value as a function of space.
14. The method of claim 1 wherein applying the therapeutic signal includes applying the therapeutic signal via the electrical contact.
15. The method of claim 1 wherein the electrical contact is a first electrical contact and wherein the lead includes a second electrical contact, and wherein applying the therapeutic signal includes applying the therapeutic signal via the second electrical contact.
16. The method of claim 1 wherein applying the therapeutic signal includes modulating neural activity of neural tissue within the dura from an epidural location.
17. The method of claim 1 wherein the operation of comparing the detected value to a predetermined criterion is performed by instructions contained on a computer readable medium.
18. The method of claim 1 wherein applying the therapeutic signal includes treating chronic pain in the patient.
19. The method of claim 1 wherein comparing the detected value includes comparing detected impedance with an impedance of cerebral spinal fluid.
20. The method of claim 1 wherein the electrical contact is a distal-most contact of the elongated signal delivery device.
21. The method of claim 1 wherein the electrical contact is positioned proximally relative to a distal-most contact of the lead.
22. The method of claim 1 , further comprising applying a subthreshold detection current, below the patient's sensory and/or motor threshold level.
23. A method for making a patient device, comprising:
providing an electrical contact configured to be coupled to an impedance detector and a processor, the electrical contact being carried by an elongated flexible lead configured for implantation in a patient;
selecting a predetermined criterion based at least in part on an impedance of human cerebral spinal fluid;
providing the processor with instructions to perform the following operations:
receive information from the impedance detector corresponding to an impedance of a circuit that includes the electrical contact and patient tissue adjacent to the electrical contact;
compare the detected impedance to the predetermined criterion;
if the detected impedance meets the predetermined criterion, provide an indication that the patient's dura has been penetrated; and
if the detected value does not meet the predetermined criterion, apply a therapeutic signal to the patient's nervous system via the elongated flexible lead.
24. The method of claim 23 wherein selecting the predetermined criterion includes selecting a reference impedance value to correspond to an impedance of human cerebral spinal fluid.
25. The method of claim 24 wherein selecting the reference value includes selecting the reference value to be 50 ohms.
26. The method of claim 24 wherein selecting the reference value includes selecting the reference value to be 200 ohms.
27. The method of claim 23 wherein providing an indication includes providing an indication that the electrical contact has penetrated through the dura.
28. A patient device, comprising:
an elongated flexible lead configured for implantation in a patient;
an electrical contact carried by the lead;
an impedance detector electrically coupled to the electrical contact; and
a computer-readable medium operatively coupled to the impedance detector, the computer readable medium having instructions that, when executed, perform the following operations:
receive information from the impedance detector corresponding to an impedance of a circuit that includes the electrical contact and patient tissue adjacent to the electrical contact;
compare the detected impedance to a predetermined criterion;
if the detected impedance meets the predetermined criterion, provide an indication that the patient's dura has been penetrated; and
if the detected value does not meet the predetermined criterion, apply a therapeutic signal to the patient's nervous system via the elongated flexible lead.
29. The patient device of claim 28 , further comprising a signal generator coupled to the electrical contact, and wherein the signal generator is configured to generate the therapeutic signal at a frequency of from 3 kHz to 50 kHz.
30. The patient device of claim 28 wherein the predetermined criterion includes a reference impedance of 50 ohms or less.
31. The patient device of claim 28 wherein the predetermined criterion includes a reference impedance of 200 ohms or less.