Electrode Configuration for an Implantable Electroacupuncture Device

Abstract

An implantable electroacupuncture device (IEAD) treats a disease or medical condition of a patient through application of stimulation pulses applied at a specified acupoint or other target tissue location at a very low duty cycle. In a preferred implementation, the IEAD is an implantable, coin-sized, self-contained, leadless device having at least two electrodes attached to an outside surface of its housing, with at least one electrode on the top or bottom surface of the housing functioning as a cathode, and at least one electrode on the perimeter edge of the housing functioning as an anode. The electrodes may be segmented to include an array of smaller cathodic or anodic electrodes, each of which may be selectively turned ON or OFF so as to provide a convenient mechanism for adjusting the density of the stimulus current flowing through the cathodic electrode surface area.

What is claimed is: 
     
         1 . An implantable electroacupuncture (EA) device adapted to be implanted at a specified acupoint of a patient, the electroacupuncture device comprising:
 a disc-shaped housing having a top surface, a bottom surface, and a perimeter edge connecting the top surface to the bottom surface;   at least one cathodic electrode and at least one anodic electrode formed to reside on, or comprise an integral part of, the surfaces of the housing, wherein the at least one cathodic electrode is on the top or bottom surface of the housing, and the at least one anodic electrode is on the perimeter edge surface of the housing;   stimulation circuitry residing inside the housing and electrically coupled to the at least one cathodic electrode and the at least one anodic electrode, wherein the stimulation circuitry generates stimulation pulses of electrical current that are delivered to body tissue surrounding the housing through the at least one cathodic electrode and the at least one anodic electrode in accordance with a prescribed stimulation regimen;   wherein the at least one cathodic electrode is configured from a prescribed electrode material having a surface area sufficiently large to allow a desired current density to flow through it without causing electrode corrosion, and further   wherein the at least one cathodic electrode is positioned sufficiently far from the at least one anodic electrode so as to prevent current shunting to occur between the at least one cathodic electrode and the at least one anodic electrode before the stimulation pulses of electrical current have penetrated into the body tissue a specified distance.   
     
     
         2 . The EA device of  claim 1 , wherein the cathodic electrode comprises a first cathodic electrode located on the top surface of the housing and a second cathodic electrode located on the bottom surface of the housing, and wherein the stimulation circuitry residing inside of the housing includes switching circuitry that selectively activates (i) only the first cathodic electrode, or (ii) only the second cathodic electrode, or (iii) both the first and second cathodic electrodes when the stimulation pulses are delivered to the body tissue in accordance with the prescribed stimulation regimen. 
     
     
         3 . The EA device of  claim 2 , wherein the first and second cathodic electrodes each comprise multiple small cathodic electrodes distributed over the top and bottom surface areas of the housing in accordance with a prescribed pattern. 
     
     
         4 . The EA device of  claim 3  wherein the at least one anodic electrode comprises multiple small anodic electrodes distributed around the perimeter edge of the housing. 
     
     
         5 . The EA device of  claim 3  wherein the stimulation circuitry includes additional cathodic switching circuitry that selectively energizes only a desired grouping of the first and second cathodic electrodes, wherein the location of the body tissue receiving the stimulation pulses may be selected by controlling which groups of electrodes are energized and which are not energized, wherein an energized electrode comprises an electrode that is turned ON by the switching circuitry so that an electrical current may flow through the electrode, and a non-energized electrode comprises an electrode that is turned OFF by the switching circuitry so as to prevent electrical current from flowing through the electrode. 
     
     
         6 . The EA device of  claim 1  wherein the at least one cathodic electrode comprises a single cathodic electrode located in the center of a bottom surface of the housing, the bottom surface comprising that surface of the housing adapted to face towards a target tissue location below the specified acupoint on the skin surface of the patient. 
     
     
         7 . The EA device of  claim 6  wherein the stimulation circuitry generates monophasic stimulation pulses having a magnitude of between 2 to 25 ma, a pulse width of between 100 to 600 msec, and a frequency of between 1 and 5 Hz. 
     
     
         8 . The EA device of  claim 7  wherein the housing has a diameter of no greater than 25 mm, a thickness no greater than 3 mm, and is adapted to be implanted at acupoint P6 at a tissue depth of between 3-6 mm. 
     
     
         9 . The EA device of  claim 8  wherein the stimulation regimen provides a stimulation session during which stimulation pulses are continuously generated, wherein the stimulation session has a duration of between 10 and 60 minutes, and further wherein, after an initialization period of no longer than two weeks, the stimulation session is applied to the patient no more than twice a week and no less than once every other week. 
     
     
         10 . An implantable electroacupuncture (EA) device adapted to be implanted at a specified acupoint of a patient, the electroacupuncture device including:
 a leadless, disc-shaped, hermetically-sealed housing having a top surface, a bottom surface, and a perimeter edge connecting the top surface to the bottom surface;   at least one cathodic electrode and at least one anodic electrode formed to reside on, or comprise an integral part of, the surfaces of the housing;   stimulation circuitry residing inside the housing and electrically coupled to the at least one cathodic electrode and the at least one anodic electrode, wherein the stimulation circuitry generates stimulation pulses of electrical current that are delivered to body tissue surrounding the housing through the at least one cathodic electrode and the at least one anodic electrode in accordance with a prescribed stimulation regimen, wherein the stimulation regimen defines the duration and rate at which a stimulation session is applied to the body tissue, said stimulation regimen requiring that the stimulation session have a duration of T 3  minutes, wherein T 3  is at least 10 minutes, and a rate of occurrence of once every T 4  minutes, wherein the ratio of T 3 /T 4  is no greater than 0.05, and wherein during each stimulation session EA stimulation pulses having one or more specified widths and amplitudes are generated at one or more specified rates; and;   a coin-cell type primary battery residing inside the housing that provides the operating power for the stimulation circuitry, wherein the primary battery has an internal impedance that is greater than 5 ohms, and wherein the coin-cell primary battery has sufficient capacity to power the operation of the EA device in accordance with the prescribed stimulation regimen for at least two years;   wherein the at least one cathodic electrode is configured from a prescribed electrode material having a surface area sufficiently large to allow a desired current density to flow through it without causing electrode corrosion, and further   wherein the at least one cathodic electrode is positioned sufficiently far from the at least one anodic electrode so as to prevent current shunting to occur between the at least one cathodic electrode and the at least one anodic electrode before the stimulation pulses of electrical current have penetrated into the body tissue a specified distance.   
     
     
         11 . The EA device of  claim 10  wherein the at least one cathodic electrode is on the top or bottom surface of the housing, and the at least one anodic electrode is on the perimeter edge surface of the housing. 
     
     
         12 . The EA device of  claim 11  wherein the at least one cathodic electrode is located on a top or bottom surface of the housing and positioned no closer than 5 mm from the closest edge of the nearest at least one anodic electrode, wherein the total surface area of the at least one cathodic electrode is no smaller than about 0.5 mm2. 
     
     
         13 . The EA device of  claim 12  the at least one cathodic electrode comprises a first cathodic electrode located on a top surface of the housing and a second cathodic electrode located on a bottom surface of the housing, and wherein the stimulation circuitry further includes switching circuitry that selectively activates (i) only the first cathodic electrode, or (ii) only the second cathodic electrode, or (iii) both the first and second cathodic electrodes when the stimulation pulses are delivered to the body tissue in accordance with the prescribed stimulation regimen. 
     
     
         14 . The EA device of  claim 13  wherein the at least one anodic electrode is formed as a ring electrode residing substantially around a perimeter edge of the housing. 
     
     
         15 . The EA device of  claim 14  wherein the first and second cathodic electrodes each comprise multiple small cathodic electrodes distributed over the top and bottom surface areas of the housing in accordance with a prescribed pattern. 
     
     
         16 . The EA device of  claim 15  wherein the stimulation circuitry includes additional cathodic switching circuitry that selectively activates only a desired grouping of the first and second cathodic electrodes, wherein the location of the body tissue receiving the stimulation pulses may be selected by controlling which groups of electrodes are activated and which are not activated, wherein an activated electrode comprises an electrode that is turned ON by the switching circuitry so that an electrical current may flow through the electrode, and a non-activated electrode comprises an electrode that is turned OFF by the switching circuitry so as to prevent electrical current from flowing through the electrode. 
     
     
         17 . An implantable electroacupuncture (EA) device adapted to be implanted at a specified acupoint of a patient, the electroacupuncture device comprising:
 a leadless, hermetically-sealed disc-shaped housing;   at least one cathodic electrode and at least one anodic electrode formed in a symmetrical pattern on the surfaces of the housing;   stimulation circuitry residing inside the housing and electrically coupled to the at least one cathodic electrode and the at least one anodic electrode, wherein the stimulation circuitry generates stimulation pulses of electrical current that are delivered to body tissue surrounding the housing through the at least one cathodic electrode and the at least one anodic electrode in accordance with a prescribed stimulation regimen, wherein the stimulation regimen defines the duration and rate at which a stimulation session is applied to the body tissue, said stimulation regimen requiring that the stimulation session have a duration of T 3  minutes, wherein T 3  is at least 10 minutes, and a rate of occurrence of once every T 4  minutes, wherein the ratio of T 3 /T 4  is no greater than 0.05;   a coin-cell type primary battery residing inside the housing that provides the operating power for the stimulation circuitry, wherein the primary battery has an internal impedance that is greater than 5 ohms, and wherein the coin-cell primary battery has sufficient capacity to power the operation of the EA device in accordance with the prescribed stimulation regimen for at least two years;   wherein the total surface area of the at least one cathodic electrode is sufficiently large to allow a desired current density to flow through it without causing electrode corrosion, and further   wherein the at least one cathodic electrode is positioned sufficiently far from the at least one anodic electrode to prevent current shunting between the at least one cathodic electrode and the at least one anodic electrode.   
     
     
         18 . The EA device of  claim 17  wherein the at least one cathodic electrode comprises a single cathodic electrode located in the center of a bottom surface of the disc-shaped housing. 
     
     
         19 . The EA device of  claim 18  wherein the stimulation circuitry generates monophasic stimulation pulses having a magnitude of between 2 to 25 ma, a pulse width of between 100 to 600 msec, and a frequency of between 1 and 5 Hz. 
     
     
         20 . The EA device of  claim 19  wherein the disc-shaped housing has a diameter of no greater than 25 mm, a thickness no greater than 3 mm.