Electrode selection for sub-threshold modulation therapy

1. A neuromodulation system for use with a patient, comprising:

a plurality of electrical terminals configured to be respectively coupled to a plurality of electrode sets:

modulation output circuitry configured to independently deliver super-threshold anodic electrical energy and super-threshold cathodic electrical energy from each of the electrode sets via the electrical terminals to the patient, and to deliver sub-threshold electrical energy from an effective one of the electrode sets via the electrical terminals to the patient, the sub-threshold electrical energy being below a patient perception threshold and the super-threshold electrical energy being at or above the patient perception threshold, the patient perception threshold being a boundary below which a patient does not sense delivery of the electrical energy and at or above which the patient does sense delivery of the electrical energy;

memory configured to store an anodic perception threshold of the super-threshold anodic electrical energy respectively delivered from each of the electrode sets to the patient, and store a cathodic perception threshold of the super-threshold cathodic electrical energy respectively delivered from each of the electrode sets to the patient; and

control circuitry configured to compute a ratio between the anodic perception threshold and the cathodic perception threshold for each of the electrode sets, and select one of the electrode sets as the effective electrode set from which the modulation output circuitry delivers the sub-threshold electrical energy to the patient based on the computed ratios.

2. The neuromodulation system of claim 1 , further comprising a user interface configured to receive input from a user, wherein the control circuitry is configured to store the anodic perception thresholds and cathodic perception thresholds in response to the user input.

3. The neuromodulation system of claim 1 , further comprising monitoring circuitry configured to sense evoked compound action potentials (eCAPs) in the patient in response to the delivery of the super-threshold anodic electrical energy and the super-threshold cathodic electrical energy from each of the electrode sets to the patient, wherein the control circuitry is configured to store the anodic perception threshold and cathodic perception thresholds in response to the sensing of the eCAPs by the monitoring circuitry.

4. The neuromodulation system of claim 1 , wherein the control circuitry is configured to automatically select the one electrode set as the effective electrode set without input from the user.

5. The neuromodulation system of claim 1 , wherein the control circuitry is configured to automatically select a plurality of candidate electrode sets from the plurality of electrode sets based on the computed ratios, wherein the neuromodulation system further comprises a user interface configured to display the candidate electrode sets to the user, and receive input from the user, wherein the control circuitry is further configured to select one of the candidate electrode sets as the effective electrode set in response to the user input.

6. The neuromodulation system of claim 1 , wherein the control circuitry is configured to select the electrode set with the ratio between the anodic perception threshold and the cathodic perception threshold closest to unity as the effective electrode set.

7. The neuromodulation system of claim 1 , wherein the control circuitry is configured to create a paresthesia map comprising a body region of perceived paresthesia resulting from the delivery of the super-threshold electrical energy from each of the electrode sets, and to select the one electrode set as the effective electrode set based on the paresthesia map.

8. The neuromodulation system of claim 7 , wherein the control circuitry is configured to select the electrode set corresponding to the body region of perceived paresthesia that matches a body region of pain as the effective electrode set.

9. The neuromodulation system of claim 8 , wherein the control circuitry is configured to compute a coverage score of a relative match between each body region of perceived paresthesia and the body region of pain, and to select the one electrode set as the effective electrode set based on the coverage score.

10. The neuromodulation system of claim 9 , wherein the control circuitry is configured to compute a total score from the ratio and the coverage score for each of the electrode sets, and to select the one electrode set having a highest total score as the effective electrode set.

11. The neuromodulation system of claim 1 , wherein the delivered sub-threshold electrical energy has a frequency greater than 1500 Hz.

12. The neuromodulation system of claim 1 , wherein the delivered sub-threshold electrical energy has a pulse duration lower than 200 μs.

13. The neuromodulation system of claim 1 , wherein the delivered sub-threshold electrical energy comprises an electrical pulse train.

14. The neuromodulation system of claim 13 , wherein the electrical pulse train is a biphasic pulse train.

15. The neuromodulation system of claim 14 , wherein the biphasic pulse train has an active anodic phase.

16. The neuromodulation system of claim 14 , wherein the biphasic pulse train has a passive cathodic recharge phase.

17. The neuromodulation system of claim 1 , wherein each of the electrode sets comprises a single electrode.

18. The neuromodulation system of claim 1 , wherein the control circuitry is configured to select another one of the electrode sets as another effective electrode set based on the ratios, and wherein the modulation output circuitry is configured to deliver sub-threshold electrical energy from the other effective electrode set to the patient.

19. The neuromodulation system of claim 18 , wherein the control circuitry is configured to compute a distribution of the sub-threshold electrical energy among the effective electrode sets based on a ratio between the anodic perception thresholds and/or the cathodic perception thresholds of the effective electrode sets.

20. A spinal cord modulation system for use with a patient, comprising:

a plurality of electrical terminals configured to be respectively coupled to a plurality of electrode sets to deliver therapeutic electrical energy for alleviating pain:

modulation output circuitry configured to independently deliver super-threshold anodic electrical energy and super-threshold cathodic electrical energy from each of the electrode sets via the electrical terminals to the patient, and to deliver sub-threshold electrical energy from an effective one of the electrode sets via the electrical terminals to the patient, the sub-threshold electrical energy being below a patient perception threshold and the super-threshold electrical energy being at or above the patient-perception threshold, the patient perception threshold being a boundary below which a patient does not sense paresthesia and at or above which the patient does sense paresthesia;

memory configured to store an anodic perception threshold of the super-threshold anodic electrical energy respectively delivered from each of the electrode sets to the patient, and store a cathodic perception threshold of the super-threshold cathodic electrical energy respectively delivered from each of the electrode sets to the patient; and

control circuitry configured to compute a ratio between the anodic perception threshold and the cathodic perception threshold for each of the electrode sets, and select one of the electrode sets as the effective electrode set from which the modulation output circuitry delivers the sub-threshold electrical energy to the patient based on the computed ratios.