Method and system for neural tissue modification

Abstract

A method and apparatus for altering a function of neural tissue in a patient. An electromagnetic signal is applied to the neural tissue through an electrode. The electromagnetic signal has a frequency component above the physiological stimulation frequency range and an intensity sufficient to produce an alteration of the neural tissue, the alteration causing the patient to experience a reduction in pain, and a waveform that prevents lethal temperature elevation of the neural tissue during application of the electromagnetic signal to the neural tissue.

1. A system for altering a function of neural tissue in a patient comprising:
 a) signal applicator adapted to apply an electrical signal output to said neural tissue;  
 b) a signal generator that generates a electrical signal output having at least one frequency component above a physiologic stimulation frequency range, said at least one frequency component producing an alteration of a function of at least a portion of said neural tissue, and said electrical signal output having a waveform that produces an average power deposition in the neural tissue corresponding to non-lethal average temperature elevation of said at least a portion of said neural tissue when said electrical signal output is applied to said neural tissue through said signal applicator, wherein said waveform has a peak voltage, said peak voltage being sufficient to produce said alteration; and  
 c) a signal coupler that couples said signal generator and said signal applicator.  
 
     
     
       2. The system of  claim 1 , further comprising:
 a temperature sensor that senses temperature of said at least a portion of the neural tissue and produces an output signal representative of said temperature; and  
 a frequency component intensity control to adjust the intensity of the frequency component to maintain the temperature of the neural tissue below a lethal thermal level when said electrical signal is applied to said neural tissue.  
 
     
     
       3. The system of  claim 1 , wherein said electrical output signal is a radiofrequency signal. 
     
     
       4. A system for altering a function of neural tissue in a patient comprising:
 a) an electrode adapted to apply an amplitude modulated electrical signal to the neural tissue of the patient;  
 b) a signal generator that generates an amplitude modulated electrical signal having at least one frequency component above a physiological stimulation frequency range, said amplitude modulated electrical signal producing an alteration of a function of the neural tissue while producing the average power deposition in the neural tissue corresponding to non-lethal temperature elevation of said neural tissue when the amplitude modulated electrical signal is applied to the neural tissue through said electrode, wherein said amplitude modulated electrical signal has a peak voltage, said peak voltage being sufficient to produce said alteration; and  
 c) an electrical coupling between said signal generator and said electrode to apply said multiple modulated electrical signal to said electrode.  
 
     
     
       5. The system of  claim 4  further comprising:
 a modulation amplitude control that adjusts the amplitude of said amplitude modulated electrical signal.  
 
     
     
       6. The system of  claim 4  wherein the amplitude modulated electric signal has a peak voltage in the range of 10 to 30 volts. 
     
     
       7. A method for altering the function of neural tissue in a patient comprising the steps of:
 a) generating an electrical signal having at least one frequency component above a physiologic stimulation frequency range, said at least one frequency component producing an alteration of at least a portion of said neural tissue, and said electrical signal having a waveform that produces an average power deposition in the neural tissue corresponding to non-lethal average temperature elevation of said at least a portion of said neural tissue when said electrical signal is applied to said neural tissue, wherein said electrical signal has a peak voltage, said peak voltage being sufficient to produce said alteration; and  
 b) applying said electrical signal to said neural tissue.  
 
     
     
       8. The method of  claim 7  further comprising the steps of:
 a) sensing the temperature of said at least a portion of the neural tissue;  
 b) generating a temperature signal representative of the sensed temperature of said at least a portion of the neural tissue; and,  
 c) adjusting the intensity of the at least one frequency component in response to said temperature signal in order to maintain the average temperature of said at least a portion of the neural tissue below lethal temperature levels when the electrical signal is applied to said neural tissue.  
 
     
     
       9. A system for altering a function of at least a portion of neural function of tissue in a patient comprising:
 a) a generator that generates an electromagnetic signal having at least one high frequency component above a physiologic stimulation frequency range, said ta least one high frequency component have a modulated waveform that produces alteration of the function of said at least a portion of said neural tissue when applied to said tissue through an electromagnetic signal applicator, wherein said modulated waveform has a peak voltage, said peak voltage being sufficient to produce said alteration.  
 
     
     
       10. A system for altering a function of neural tissue in a patient comprising:
   signal applicator adapted to apply an electrical signal output to said neural tissue;        a signal generator that generates an electrical signal output having at least one frequency component above a physiologic stimulation frequency range, said at least one frequency component producing an alteration of a function of at least a portion of said neural tissue, and said electrical signal output including interrupted radiofrequency waveforms having predetermined time periods of on - time bursts of radiofrequency output of a first predetermined duration, each on - time burst being followed by an off - time output period of a second predetermined duration that produces an average power deposition in the neural tissue corresponding to non - lethal average temperature elevation of said at least a portion of said neural tissue when said electrical signal output is applied to said neural tissue through said signal applicator, wherein said interrupted radiofrequency waveforms each have a peak voltage, said peak voltage being sufficient to produce said alteration; and        a signal coupler that couples said signal generator and said signal applicator.     
     
     
       11. The system of  claim 10 , wherein the generator and signal coupler are adapted to apply the interrupted radiofrequency waveforms to the tissue in a ratio of on- time bursts of radiofrequency output to off - time bursts of approximately two percent.   
     
     
       12. The system of  claim 10  wherein the magnitude of the output during said off- time output periods is zero.   
     
     
       13. The system of  claim 10  wherein the magnitude of the output during said off- time output periods in minimal.   
     
     
       14. The system of  claim 10 , further comprising:
   a temperature sensor that senses temperature of said at least a portion of the neural tissue and produces an output signal representative of said temperature; and        a frequency component intensity control to adjust the intensity of the frequency component to maintain the temperature of the neural tissue below a lethal thermal level when said electrical signal is applied to said neural tissue.     
     
     
       15. A method for altering the function of neural tissue in a patient comprising the steps of:
   a )  generating an electrical signal having at least one frequency component above a physiologic stimulation frequency range, said electrical signal output including interrupted radiofrequency waveforms having predetermined time periods of on - time bursts of radiofrequency output of a first predetermined duration, each on - time burst being followed by an off - time output period of a second predetermined duration that produces an average power deposition in the neural tissue corresponding to non - lethal average temperature elevation of said at least a portion of said neural tissue when said electrical signal is applied to said neural tissue, wherein said interrupted radiofrequency waveforms each have a peak voltage, said peak voltage being sufficient to produce said alteration; and        b )  applying said electrical signal to said neural tissue.     
     
     
       16. The method of  claim 15 , wherein the applying step includes applying the interrupted radiofrequency waveforms to the tissue in a ratio of on- time bursts of radiofrequency output to off - time bursts of approximately two percent.   
     
     
       17. The method of  claim 15  wherein the magnitude of the output during said off- time output periods is zero.   
     
     
       18. The method of  claim 15  wherein the magnitude of the output during said off- time output periods is minimal.   
     
     
       19. The method of  claim 15  further comprising the steps of:
   a )  sensing the temperature of said at least a portion of the neural tissue;        b )  generating a temperature signal representative of the sensed temperature of said at least a portion of the neural tissue; and,        c )  adjusting the intensity of the at least one frequency component in response to said temperature signal in order to maintain the average temperature of said at least a portion of the neural tissue below lethal temperature levels when the electrical signal is applied to said neural tissue.     
     
     
       20. A system for altering a function of neural tissue in a patient comprising:
   a signal applicator adapted to apply an electrical signal output to the neural tissue;        a signal generator that generates an electrical signal output having at least one frequency component above a physiologic stimulation frequency range, said at least one frequency component producing an alteration of a function of at least a portion of the neural tissue, and said electrical signal output including interrupted radiofrequency waveforms having predetermined time periods of on - time bursts of radiofrequency output of a first predetermined duration, each on - time burst being followed by an off - time output period of a second predetermined duration that produces an average power deposition in the neural tissue corresponding to non - lethal average temperature elevation of said at least a portion of said neural tissue when said electrical signal output is applied to said neural tissue through said signal applicator, wherein said on - time burst has a peak voltage, said peak voltage being in a range that includes  10  volts to  30  volts or more; and        a signal coupler that couples said signal generator and said signal applicator.     
     
     
       21. The system of  claim 20 , wherein a number of said on- time bursts of radiofrequency output to a number of said off - time bursts defines a ratio, said ratio being about two percent.