Systems and methods for producing asynchronous neural responses to treat pain and/or other patient conditions

1. A therapy system for treating a patient's pain, comprising:

a signal delivery element positionable to deliver an electrical stimulation signal to a target neural population of the patient;

a pulse generator coupleable to the signal delivery element to transmit the electrical stimulation signal to the signal delivery element; and

a machine-readable medium containing instructions that, when executed, cause the pulse generator to transmit the electrical stimulation signal to neurons of the target neural population via the signal delivery element, wherein the electrical stimulation signal is selected to have a target stimulation frequency that is above a threshold frequency that corresponds to a refractory period for individual neurons of the target neural population, and wherein the target stimulation frequency is in a range of from about 3 kHz to about 10 kHz.

2. The therapy system of claim 1 wherein the electrical stimulation signal comprises a first set of pulses interleaved with a second set of pulses, and wherein the frequency of the first set of pulses is less than the threshold frequency, the frequency of the second set of pulses is less than the threshold frequency, and the frequency of the first set of pulses and the second set of pulses combined is greater than the threshold frequency.

3. The therapy system of claim 2 wherein individual pulses of the first set of pulses are spaced apart from individual pulses of the second set of pulses.

4. The therapy system of claim 1 wherein the electrical stimulation signal includes a continuous string of biphasic, paired pulses, wherein individual paired pulses correspond to an individual cycle, and wherein individual cycles immediately follow corresponding preceding individual cycles.

5. The therapy system of claim 1 wherein the electrical stimulation signal includes:

a first pulse pattern having a continuous string of biphasic, paired pulses; and

a second pulse pattern having a plurality of sets of interleaved pulses, wherein individual sets of pulses have a frequency that is less than the threshold frequency, and wherein the instructions, when executed, apply the first pulse pattern for a predetermined time period and subsequently apply the second pulse pattern.

6. The therapy system of claim 5 wherein the electrical stimulation signal comprises a plurality of biphasic, charge-balanced, paired pulses, wherein individual neighboring pulses correspond to a cycle, and wherein individual cycles immediately follow corresponding preceding individual cycles.

7. A therapy system for treating a patient's pain, comprising:

an implantable lead having at least one electrode, wherein the lead is positionable to deliver an electrical stimulation signal to a target neural population of the patient, wherein the target neural population includes multiple neurons, and wherein individual neurons have a refractory period;

an implantable pulse generator coupleable to the implantable lead to transmit the electrical stimulation signal to the implantable lead; and

a machine-readable medium containing instructions that, when executed, cause the pulse generator to transmit the electrical stimulation signal to the target neural population via the implantable lead, wherein the electrical stimulation signal is selected to have a target frequency that is greater than a threshold frequency corresponding to the refractory period, and wherein the target frequency is in a range of from about 3 kHz to about 10 kHz.

8. The therapy system of claim 7 wherein the electrical stimulation signal comprises a plurality of sets of interleaved pulses, wherein each individual set of pulses has a frequency that is less than the threshold frequency.

9. The therapy system of claim 8 wherein the electrical stimulation signal includes a quiescent period having no pulses, and wherein the quiescent period is less than the refractory period.

10. A method for treating a patient's pain, comprising:

selecting a frequency for a stimulation signal based at least in part on a threshold frequency corresponding to a refractory period for neurons of a target neural population, wherein the frequency is in a range of from about 3 kHz to about 10 kHz; and

programming a therapy system to direct the stimulation signal to the target neural population to produce an asynchronous sensory neuron response.

11. The method of claim 10 , further comprising:

identifying lower back pain in the patient; and

positioning a lead having a plurality of electrodes proximate to the T10 or T11 vertebra to deliver the stimulation signal.

12. The method of claim 10 wherein programming the therapy system to direct the stimulation signal to the target neural population includes programming the therapy system to direct a constant frequency stimulation signal.

13. The method of claim 10 wherein programming the therapy system to direct the stimulation signal to the target neural population includes programming the therapy system to direct a plurality of sets of pulses to the target neural population, and wherein each individual set of pulses has a frequency that is less than the threshold frequency, and wherein a frequency of the plurality of sets of pulses combined is greater than the threshold frequency.

14. The method of claim 10 wherein programming the therapy system to direct the stimulation signal to the target neural population includes programming the therapy system to direct a first pulse pattern to the target neural population for a predetermined time period and subsequently direct a second pulse pattern to the target neural population, wherein the first pulse pattern includes a continuous string of biphasic, paired pulses, wherein the second pulse pattern includes a plurality of sets of interleaved pulses, and wherein individual sets of pulses have a frequency that is less than the threshold frequency.

15. The method of claim 10 wherein selecting a frequency for a stimulation signal includes selecting a frequency that is at least twice the threshold frequency.

16. The method of claim 10 wherein programming the therapy system to direct the stimulation signal to the target neural population includes programming the therapy system to direct a pulse pattern to the target neural population, the pulse pattern having a quiescent period with no pulses, and wherein the quiescent period is less than the refractory period.

17. The method of claim 10 wherein programming the therapy system to direct the stimulation signal to the target neural population includes:

programming the therapy system to direct a first pulse pattern to the target neural population to initiate the asynchronous sensory neuron response; and

programming the therapy system to direct a second pulse pattern, different from the first pulse pattern, to the target neural population to extend the duration of the asynchronous sensory neuron response.

18. The method of claim 10 wherein programming the therapy system to direct the stimulation signal to the target neural population includes programming the therapy system to direct a pulse pattern to the target neural population, the pulse pattern having a plurality of sets of interleaved pulses, and wherein the period between any neighboring pulses is less than the refractory period.

19. The method of claim 10 , further comprising programming the therapy system to vary the frequency of the stimulation signal to decrease power usage while extending the asynchronous sensory response.

20. The method of claim 10 , further comprising selecting a pulse pattern for the stimulation signal to reduce power consumption, wherein the pulse pattern includes a quiescent period.