Patent Publication Number: US-2011071418-A1

Title: Apparatus for diagnosing muscular pain and method of using same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/663,125 filed Mar. 18, 2005, entitled “Dynamic Mode Surface Electra-Neural Stimulator for Diagnosis of Muscle Pain,” the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to apparatus for diagnosing muscle pain and, more particularly, to apparatus that employ electrical stimulation to accurately diagnose the source of muscle pain. 
     BACKGROUND OF THE INVENTION 
     A common type of musculoskeletal pain is myofascial pain syndrome, which is pain that emanates from muscles and corresponding connective tissue. Myofascial pain syndrome is often caused by myofascial pain generators called “trigger points.” Trigger points are discrete, focal, irritable spots located in a taut band of skeletal muscle, i.e., a ropey thickening of the muscle tissue. A trigger point is often characterized by a “referred pain” pattern that is similar to the patient&#39;s pain complaint. Referred pain is felt not at the site of the trigger point origin, but remote from it. The pain is often described as spreading or radiating. A trigger point develops due to any number of causes, such as sudden trauma or injury to musculoskeletal tissue, fatigue, excessive exercising, lack of activity, tension or stress, and nutritional deficiencies. 
     A problem in treating myofascial pain syndrome is locating the trigger point, since pain is typically felt remote from the trigger point. A common technique for locating a trigger point is palpation. That is, a physician palpates a muscle region suspected of having a trigger point by applying manual pressure to the region with his finger tips and kneading the muscles. As the physician palpates the muscles, the patient verbally indicates the existence of any pain or sensitivity and whether it increases or decreases as the physician moves his fingers within the suspected region. A shortcoming of this manual technique is that it can only locate a trigger point with a slight degree of certainty, and cannot typically locate the specific muscle that contains the trigger point. In addition, there is no standard unit of pressure to exert when palpitating a muscle, which could lead to a misdiagnosis. 
     Other techniques to locate trigger points include the use of a palpation index, pressure threshold meters, thermographic measuring devices, and electromyographic identification. However, these techniques are difficult to learn and use and are not always reliable. 
     U.S. Pat. No. 6,432,063 to Marcus (hereinafter “the Marcus &#39;063 Patent”), the entirety of which is incorporated herein by reference, discloses a method for locating myofascial trigger points (the “Marcus Method”) by applying an electrical stimulus in a suspected muscle area containing a trigger point. As the electrical stimulus is moved about the muscle area, the patient indicates an increase or decrease in the level of pain and sensitivity. Once the maximum pain location has been located, the trigger point has been identified and, thus, it can be treated appropriately. However, the Marcus &#39;063 Patent does not disclose in detail a particular electrical stimulator device that can be appropriately used in connection with the Marcus Method. 
     There are numerous trans-cutaneous electroneural stimulation (TENS) portable devices available in the marketplace. However, the leads (i.e., the electrodes) of these devices are designed for static and therapeutic purposes, rather than dynamic diagnosis purposes. As a result, TENS devices are not appropriate for locating myofascial trigger points. 
     U.S. Pat. No. 4,697,599 to Woodley et al. (the “Woodley &#39;599 Patent”) discloses a handheld meter for locating and detecting pain based on the measurement of conductance of skin in the area of perceived pain. The meter includes a housing, two concentric electrodes that extend from the housing, an electrical circuit connected to the electrodes, and a speaker. The electrodes are placed against a patient&#39;s skin at the location where a measurement is desired. The electrical circuit generates an electrical signal having a pulse frequency that varies according to the measured conductance of the skin. The conductance is measured aurally by a speaker, which translates the pulses into audible sounds, i.e., “clicks”. The clicks increase in frequency as the conductance of the patient&#39;s skin increases, which indicates the location of pain. However, the Woodley &#39;599 Patent does not disclose any correlation between increased conductance and the location of myofascial trigger points; and, therefore, the device is not effective at locating same. 
     U.S. Pat. No. 5,558,623 to Cody (the “Cody &#39;623 Patent) discloses a therapeutic ultrasonic device, which includes a hammer-shaped applicator having a head with two diametrically-opposed diaphragms. A piezoelectric crystal is connected to each of the diaphragms, which convert electrical energy into ultrasonic energy. The handle is connected electrically (i.e., hard-wired) to a control console, which allows a user to control the operational functions of the applicator, such as frequency, intensity, mode of operation, etc. The Cody &#39;623 Patent relates to the THERAMINI™ 3C brand clinical stimulator/ultrasound combination unit manufactured by Rich-Mar Corporation. However, the device disclosed in the Cody &#39;623 Patent utilizes ultrasound signals for therapeutic purposes, and is not equipped for diagnostic purposes. In addition, the device is not portable; and, therefore, its ease of use in a clinical setting is limited. 
     Until now, there is no current device that effectively locates a myofascial trigger point. As a result, this has contributed to ignoring muscles as a major cause of most common pain problems and, unfortunately, has led to unnecessary testing, injections and medications, and surgeries. Accordingly, there is a need for a device that can accurately diagnose and locate trigger points, which is portable and ergonomically designed. 
     SUMMARY OF THE INVENTION 
     The problems and disadvantages associated with the prior art are overcome by the present invention, which includes an electro-neural stimulator for locating myofascial pain trigger points. The stimulator includes a housing, an electrical signal generator mounted within the housing, and a pair of electrodes, one of which is mounted to one end of the housing and the other of which is mounted to an opposite end of the housing. Each of the electrodes stimulates muscles with an electrical signal generated by the generator. A patient&#39;s response to such stimulus (i.e., whether such stimulus causes pain or sensitivity) is indicative of the existence or lack of a trigger point within the muscle. One of the electrodes has a relatively small surface area for diagnosing smaller muscles or muscle groups, while the other electrode has a relatively large surface area for diagnosing, larger muscles or muscle groups. The stimulator is a self-contained, wireless unit and is highly maneuverable. These characteristics allow a user to quickly and easily diagnose a source of muscle pain. 
     In accordance with another aspect of the present invention, the housing is sized and shaped for mounting on a user&#39;s arm, while one of the electrodes is attached to a ring that is worn on the user&#39;s finger. This configuration allows the user to alternate quickly and easily between manual palpation of the subject muscle with his hand and fingertips and electrical stimulation of the muscle with the electrode. 
     In accordance with another aspect of the present invention, the generator may include an analog waveform generator or a digital signal processor. The properties of the electrical signal generated by the generator, such as waveform, amplitude, frequency and duty cycle, is selectable by the user. 
     Specifically, the present invention has been adapted for use in diagnosing the existence of myofascial trigger points. However, the present invention can be utilized to diagnose other sources of muscle pain, such as muscle tender points and tension. 
     Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of the exemplary embodiments of the invention, which are given below by way of example only with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, reference is made to the following detailed description of the exemplary embodiments considered in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a top perspective view of an electro-neural stimulator constructed in accordance with one exemplary embodiment of the present invention; 
         FIG. 2  is a top plan view of the stimulator shown in  FIG. 1 , with an access panel employed by the stimulator removed therefrom and a grounding electrode employed by the stimulator attached thereto; 
         FIG. 3  is a perspective view of the stimulator shown in  FIG. 1  being applied to a patient&#39;s forearm; 
         FIG. 4  is a perspective view of an electro-neural stimulator constructed in accordance with another exemplary embodiment of the present invention; 
         FIG. 5  is a perspective view of the stimulator shown in  FIG. 4  strapped to a physician&#39;s arm and being applied to a patient&#39;s forearm; and 
         FIG. 6  is an electrical block diagram of a digital signal processor (DSP) employed by the stimulators shown in  FIGS. 1-5  in accordance with another exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring to  FIGS. 1 and 2 , an electro-neural stimulator  10  includes a hexagonal-shaped housing  12  having a first end  14  and a second end  16  opposite the first end  14 . A first electrode  18  is mounted on the first end  14  of the housing  12 , while a second electrode  20  is mounted on the second end  16  of the housing  12 . With particular reference to  FIG. 2 , the first electrode  18  includes a circular-shaped head  22  having a contact surface  24  and a centrally located cylindrical-shaped pin  26  extending outwardly from the head  22 . Similarly, the second electrode  20  includes a circular-shaped head  28  having a contact surface  30 , and a centrally located cylindrical-shaped pin  32  extending outwardly from the head  28 . The first end  14  of the housing  12  includes a cylindrical-shaped aperture  34  that extends axially therethrough  12 . Similarly, the second end  16  of the housing  12  includes a circular-shaped aperture  36  that extends axially therethrough. The aperture  34  is sized and shaped to receive the pin  26  of the first electrode  18 , while the aperture  36  is sized and shaped to receive the pin  32  of the second electrode  20 . The first and second electrodes  18 ,  20  are secured to the housing  12  by friction fit or an adhesive. Alternatively, each of the pins  26 ,  32  of the first and second electrodes  18 ,  20 , respectively, may include external threads, and each the apertures  34 ,  36  of the housing  12  may include internal threads such that the pins  26 ,  32  threadedly engage the apertures  34 ,  36 , respectively (not shown in the Figures). 
     Preferably, the diameter of the head  28  of the second electrode  20  is greater than the diameter of the head  22  of the first electrode  18 . Alternatively, the diameter of the head  28  of the second electrode  20  can be smaller than the diameter of the head  22  of the first electrode  18 , or the diameters of both heads  22 ,  28  can be equal. The functions of the electrodes  18 ,  20  will be described hereinafter. 
     Referring to  FIG. 2 , the housing  12  includes a compartment  38  having a rectangular-shaped first chamber  40 , a rectangular-shaped second chamber  42  positioned intermediate the first chamber  40  and the aperture  34 , and a rectangular-shaped third chamber  44  positioned intermediate the first chamber  40  and the aperture  36 . The aperture  34  extends from the first end  14  of the housing  12  to the second chamber  42  and the aperture  36  extends from the second end  16  of the housing  12  to the third chamber  44 . Alternatively, the second chamber  42  need not be included and, in such case, the aperture  34  may extend from the first end  14  of the housing  12  to the first chamber  40 . 
     Referring to  FIG. 1 , the housing  12  includes a hexagonal-shaped access panel  46  that is sized and shaped to enclose the compartment  38 . Referring to  FIG. 2 , the housing  12  includes a plurality of apertures  48  having internal threads (not shown in the Figures), while the panel  46  includes a plurality of apertures (not shown in the Figures), each of which correspond with one of the apertures  48  of the housing  12 . Each of the apertures  48  of the housing  12  and each of a corresponding one of the apertures of the panel  46  receives one of a plurality of screws  50 , which secure the panel  46  to the housing  12  (not shown in  FIG. 2 , but see  FIG. 1 ). Alternatively, the panel  46  can be secured to the housing  12  by other means known in the art, such as adhesives or by the use of snap-tabs formed on the panel  46  and corresponding tab slots formed in the housing  12  (not shown in the Figures). 
     Referring to  FIG. 2 , the stimulator includes a printed circuit board  52  that is positioned within the first chamber  40  of the housing  12 , and a power supply  54  that which is positioned within the third chamber  44  of the housing  12  and is connected electrically to the printed circuit board  52 . A wire  56  runs through the aperture  34  and the second chamber  42  and electrically connects the first electrode  18  to the printed circuit board  52  and the power supply  54 . Similarly, a wire  58  runs through the second aperture  36  and the third chamber  44  and electrically connects the second electrode  20  to the printed circuit board  52  and the power supply  54 . 
     Still referring to  FIG. 2 , the printed circuit board  52  includes a first potentiometer  60  and a second potentiometer  62  that extend upwardly therefrom, a third potentiometer  64  and a fourth potentiometer  66  that extend outwardly from one side  68  of the housing  12 , and a slide switch  70 . The potentiometer  64  is connected electrically to the first electrode  18  and the printed circuit board  52 , while the potentiometer  66  is connected electrically to the second electrode  20  and the printed circuit board  52 . The functions of the potentiometers  60 ,  62 , the potentiometers  64 ,  66 , and the switch  70  shall be described hereinafter. 
     Referring to  FIGS. 1 and 2 , a first light emitting diode (LED)  72  and a second LED  74  are mounted on the printed circuit board  52 . Each of the LEDs  72 ,  74  protrude through a corresponding aperture formed within the panel  46  (not shown in the Figures) when the panel  46  is fastened to the housing  12  (not shown in  FIG. 2 , but see  FIG. 1 ). The stimulator  10  includes a grounding wire  76 , one end of which is connected to the printed circuit board  52 , and the other end of which includes a connecting pin  78 . A grounding electrode  80 , which includes a rectangular-shaped pad  82  and a wire  84  having a connecting pin  86 , is connected to the grounding wire  76 , such that the pins  78 ,  86  are sized and shaped to mechanically and electrically connect with one another. Preferably, the pad  82  of the grounding electrode  80  has a self-adhesive surface (not shown in the Figures). The function of the grounding electrode  80  shall be described hereinafter. 
     Preferably, the housing  12  and the panel  46  are each hexagonal in shape. However, the housing  12  and the panel  46  may each consist of other shapes and sizes, such as rectangular, elliptical or conical in shape. The electrodes  18 ,  20  are, preferably, circular, in shape, but they can consist of other shapes and sizes, such as square, rectangular, elliptical or triangular in shape. 
     Preferably, the housing  12  is manufactured from an injection-molded polymer plastic material. Alternatively, the housing  12  can be manufactured from other materials. The electrodes  18 ,  20  are preferably manufactured from an electrically conductive and biocompatible material, such as stainless steel or aluminum. Alternatively, the electrodes  18 ,  20  can be made from other materials. 
     Preferably, the printed circuit board  52  is obtained commercially from Johari Digital Healthcare Ltd.&#39;s (of Rajasthan, India; web site joharidigital.com) TENS 2500 device, model number ZZA250T. Alternatively, the printed circuit board  52  can be supplied by other manufacturers and/or be characterized by other model and part numbers. 
     Preferably, the power supply  54  consists of a standard 9-volt battery. Alternatively, the power supply  54  can consist of other types of batteries, such as, for example, a button style “watch” battery, which can be mounted on or off the printed circuit board  52 . 
     The grounding electrode  80  is commercially available and may be obtained from a healthcare supplier or pharmacy. Alternatively, the grounding electrode  80  may consist of other brands and models and/or may be obtained from other manufacturers. The pad  82  of the grounding electrode  80  should be at least 2″×2″ and flat, but it may consist of other shapes and sizes. 
     Referring to  FIGS. 1 through 3 , the stimulator  10  is implemented in conjunction with the Marcus Method disclosed in the Marcus &#39;063 Patent, which patent has been incorporated by reference herein in its entirety. In this regard, the settings of the stimulator  10  are adjusted by a user by employing the potentiometer  60  to adjust the frequency of the applied electrical stimulus waveform, while employing the potentiometer  62  to adjust of the duty cycle of the applied stimulus waveform. The switch  70  enables a user to change the “mode” of operation of the stimulator  10  between a continuous waveform output, a burst mode which delivers a short burst of a waveform, and a modulation mode in which a continuous waveform carrier signal is amplitude modulated. 
     The output current of the stimulator  10  can vary from 0 mA to about 200 mA. Experiments have shown that optimal detection of pain varies from person to person, with generally larger and heavier people requiring more current to obtain the same results as a smaller and lighter person. Experiments have also shown that the waveform that produces the best response (i.e., the most accurate location of the pain source) is a continuous square wave, with a 50% duty cycle and a frequency in the range from about 100 Hz to about 150 Hz. The output waveform frequency of the stimulator  10  can be adjusted over a range of 0 Hz to about 200 Hz with variable duty cycle. 
     The electrical signal generated by the stimulator  10  is not limited to the shape of a square wave for the output waveform. For instance, the output waveform can be any periodic waveform, such as square waveform, a triangular waveform, a sinusoidal waveform, or a saw tooth waveform, or any combination thereof. In addition, the output waveform can be amplitude modulated. For example, the carrier frequency can be a sinusoidal waveform falling within a frequency range of about 1500 Hz to about 5000 Hz amplitude modulated with a sinusoidal waveform which produces a beat frequency in the range of about 1 Hz to about 200 Hz. Alternatively, the carrier waveform can be any periodic waveform, such as a square waveform, a triangular waveform, a sinusoidal waveform, or a saw tooth waveform, and likewise the amplitude modulating waveform can be any periodic waveform, such as a square waveform, a triangular waveform, a sinusoidal waveform, or a saw tooth waveform, or any combination thereof. 
     Next, the pin  86  of the grounding electrode  80  is attached to the pin  78  of the grounding wire  76 . The pad  82  is adhered to the skin of a patient, such as on the patient&#39;s arm  88  (see  FIG. 3 ). Preferably, the grounding electrode  80  is placed in the vicinity of the suspected trigger point and should be properly secured in order to maximize patient comfort. The grounding electrode  80  acts as a negative terminal for the stimulator  10 . 
     At this stage, a user must determine which of the electrodes  18 ,  20  will be used for diagnosis. For example, the first electrode  18 , which is, preferably, the smaller of the electrodes  18 ,  20 , can be used to stimulate small muscles, such as the flexor digitorum superficialis muscle (which is located in the arm) or small muscle groups. The second electrode  20 , which is, preferably, the larger of the electrodes  18 ,  20 , can be used for stimulating large muscles, such as the trapezius muscle (which is located in the upper back) or larger muscle groups. In addition, the second electrode  20  can be used to establish the general location of a muscle group containing a potential myofascial pain trigger point, while the electrode  18  can be used to find a particular muscle within the muscle group that is the source of the myofascial pain trigger point. 
     It is noted that the heads  22 ,  28  of the electrodes  18 ,  20  are preferably sized and shaped to meet the present FDA approved contact area to field strength requirements. For example, the head  22  of the electrode  18  is, preferably, 1 inch in diameter and approximately 0.785 square inches in surface area, while the head  28  of the second electrode  20  is, preferably, 1.5 inches in diameter and approximately 1.767 square inches in surface area. These sizes are used in order to minimize the possibility of a patient experiencing a burning sensation as would be the case with an electrode having small surface area. However, it is noted that the diameter and surface area of the heads  22 ,  28  of the electrodes  18 ,  20  can each be greater or smaller than those previously listed. 
     If the first electrode  18  is to be used for diagnosis, then the user turns the potentiometer  64  in order to turn on and increase or decrease the power (i.e., current) of a signal to be applied to the first electrode  18 . Similarly, if the second electrode  20  is to be used for diagnosis, then the user turns the potentiometer  66  in order to turn on and increase or decrease the power (i.e., current) of a signal to be applied to the second electrode  20 . The power supply  54  generates an electrical current to each of the electrodes  18 ,  20 . Each of the electrodes  18 ,  20  act as a positive terminal of the stimulator  10 . 
     The LED  72  functions as an on/off indicator of the stimulator  10 , while the LED  74  functions as a low battery indicator. Alternatively, the stimulator  10  need not include either or both of the LEDs  72 ,  74 , or the stimulator may, include additional LEDs used for other types of indicators (not shown in the Figures). 
     Once the desired settings of the stimulator  10  are set, conductive gel (not shown in the Figures) is applied to the general area of suspected pain. The electrode  18  is placed on an easily contracted muscle (i.e., a reference muscle), which for large muscles, can be, for example, the trapezius (upper back muscle). The potentiometer  64  is turned in order to increase the amperage of the electrode  18  to the minimal amount to induce a muscle contraction from the reference muscle. Once this is determined, the user can utilize the Marcus Method of locating trigger points. More particularly, the user places the contact surface  24  of the electrode  18  on the skin of the patient in the suspected location of trigger points and moves the stimulator around the suspected area of pain. If a trigger point is within such area, the electrical stimulus from the stimulator  10  will prompt a pain response from the patient, which is then recorded. The stimulator  10  is then moved to a nearby area. If the patient indicates a decrease in pain, then the location of the trigger point has been determined. It is noted that the same technique is used in connection with the second electrode  20  when diagnosing trigger points in larger muscles or muscle groups. In addition, the second electrode  20  can be used to diagnose the general location of a trigger point within a muscle group, while the second electrode  18  can be used to diagnose the specific location of the trigger point within a particular muscle of the muscle group. 
     Because the stimulator  10  is wireless, it is highly maneuverable and can be placed on any part of the patient&#39;s body. Furthermore, the stimulator  10  is lightweight and ergonomically designed, thereby enabling a user to use it comfortably and easily in a clinical setting. The stimulator  10  allows a physician to easily detect the responses to electrical stimuli, resulting in an accurate diagnosis of the location of pain. This provides the physician with a better understanding of the pain conditions in a patient so that medicine, massage, injections, or other appropriate remedies can be more accurately directed. Medical physicians can use the stimulator  10  for performing routine checkups or when diagnosing complaints of muscle pain in patients. Pain management specialists and physical therapists can accurately and precisely pinpoint pain and accurately and precisely direct therapies (ultrasound, electro-neural stimulation therapy, thermal therapy, massage) and therapeutic exercises. Sports medicine practitioners and physical trainers can use the stimulator  10  to diagnose and characterize injuries sustained during rigorous physical activity either in a clinical setting or outdoor/athletic environments. Pharmaceutical researchers can utilize the stimulator  10  to accurately and precisely identify pain states in the source muscle in test subjects to achieve high levels of repeatability for analgesic/pain-killer drug development. 
     Another exemplary embodiment of the present invention is illustrated in  FIG. 4 . Elements illustrated in  FIG. 4  that correspond to the elements described above with reference to  FIGS. 1 through 3  have been designated by corresponding reference numerals increased by two hundred (200). In addition, elements illustrated in  FIGS. 1 through 3  that do not correspond to the elements described herein with reference to  FIGS. 1 through 3  are designated by odd reference numbers starting with reference numeral  211 . The embodiment of  FIG. 4  operates in the same manner as the embodiment of  FIGS. 1 through 3 , unless it is otherwise stated. 
     Referring to  FIG. 4 , an electro-neural stimulator  210  includes a rectangular-shaped housing  212  having a first surface  211  and a concave-shaped second surface  213  opposite the first surface  211 , whose function shall be described hereinafter. The housing  212  houses a printed circuit board (not shown in the Figures), the components of which are identical or similar to the components of printed circuit board  52  of the stimulator  10  described above. The first surface  211  of the housing  12  includes various controls and indicators, such as an LCD display  215 , an amperage toggle switch  217 , a mode select button  219 ; and a pair of LED indicators  272 ,  274 . 
     Still referring to  FIG. 4 , the stimulator includes a circular-shaped electrode  218  having a contact surface  224  mounted to a circular-shaped ring  221 . The functions of the electrode  218  and the ring  221  shall be described hereinafter. A wire  223  electrically connects the electrode  218  to the printed circuit board (not shown in the Figures). One end of a grounding wire  276  is connected to the printed circuit board (not shown in the Figures), while a connecting pin  278  is connected to the other end of the grounding wire  276 . A grounding electrode  280 , which includes a rectangular-shaped pad  282  and a wire  284  having a pin  286 , is connected to the grounding wire  276 , such that the pins  278 ,  286  are sized and shaped to mechanically and electrically connect with one another. 
     Still referring to  FIG. 4 , a strap  225  having a first end  227  and a second end  229  opposite the first end  227  is fastened to the housing  212 . The ends  227 ,  229  include VELCRO® brand fasteners  231  so that the ends  227 ,  229  may be fastened to one another. Other fastening means known in the art may be utilized to fasten the ends  227 ,  229  of the strap  225  to one another, such as snaps, adjustable belts and buckles, etc. 
     Referring to  FIGS. 4 and 5 , the stimulator  210  operates in the following manner. First, the stimulator  210  is attached to the forearm  233  of a user and is secured thereto by the fastening the ends  227 ,  229  of the strap  225 . The stimulator  210  can also be strapped any other portion of the user&#39;s body, such as around the tricep or the waist, as desired. Alternatively, the housing  212  may employ a belt clip for securing it to a user&#39;s belt (not shown in the Figures). The concave surface  213  of the housing  212  is sized and shaped so that it contours with the arm  231  of the user, thereby providing a more comfortable fit. Next, the ring  221  is slipped on a finger  233  of the user, whereby the contact surface  224  of the electrode  218  is positioned distal from the back side of the user&#39;s hand. Alternatively, the electrode  218  can be positioned on the palm side of the hand (not shown in the Figures). The wire  223  is of sufficient length such that the electrode  218  may be positioned on the user&#39;s hand in a comfortable manner. 
     Next, the settings of the stimulator  210  are adjusted. The output current of the stimulator  210  can vary from 0-200 mA and is manually selected by depressing the amperage toggle switch  217 . The output waveform frequency of the stimulator  210  can be set by depressing the mode selected button  219 . The LCD screen  215  provides a visual display of the selected amperage, mode, and other pertinent indicators. The LED  272  functions as an on/off indicator of the stimulator  210 , while the LED  274  functions as a low battery indicator. Alternatively, the stimulator  210  need not include either or both of the LEDs  272 ,  274  and such information can be displayed on the LCD screen  215 , or the stimulator may also include additional LEDs used for other types of indicators (not shown in the Figures). 
     Next, the pin  286  of the grounding electrode  280  is attached to the pin  278  of the grounding wire  276  of the housing  212 . The pad  282  is adhered to the skin of a patient, such as on the patient&#39;s arm  302 . Preferably, the grounding electrode  280  is placed in the vicinity of the suspected trigger point and should be properly secured in order to maximize patient comfort. 
     Once the desired settings of the stimulator  10  are set, conductive gel (not shown in the Figures) is applied to the general area of suspected pain. The contact surface  224  of the electrode  218  is placed on a reference muscle, such as the trapezius. The amperage toggle switch  217  is depressed in order to achieve the desired amperage of the electrode  218  to the minimal amount to induce a muscle contraction from the reference muscle. Once this is determined, the user can utilize the Marcus Method by placing the contact surface  224  of the electrode  218  on the skin of the patient in the suspected location of trigger points and move the stimulator around the suspected area of pain. If a trigger point is within such area, the electrical stimulus from the stimulator  210  will prompt a pain response from the patient, which is then recorded. The stimulator  210  is then moved to a nearby area. If the patient indicates a decrease in pain, then the location of the trigger point has been determined and appropriate treatment can be initiated. 
     The stimulator  210  is wireless, highly maneuverable and can be used to diagnose any part of the patient&#39;s body. Furthermore, the stimulator  210  is lightweight and ergonomically designed, thereby enabling a physician to use it comfortably and easily in a clinical setting. It is also noteworthy that the position of the electrode  218  on the physician&#39;s hand as shown in  FIG. 5  allows the physician to freely alternate between manual palpation of the patient&#39;s muscles with his fingertips and the application of the electrode  218  for applying electrical stimulus to the patient&#39;s muscles. Accordingly, the stimulator  210  gives the physician maximum flexibility in diagnosing trigger points. 
     Referring to  FIG. 6 , an alternate embodiment of the circuitry employed in the electro-neural stimulators  10 ,  210  shown in  FIGS. 1 through 5 . Elements illustrated in  FIG. 6  that correspond to the elements described above with reference to  FIGS. 1 through 3  have been designated by corresponding reference numerals increased by four hundred (400). In addition, elements illustrated in  FIG. 6  that do not correspond to the elements described herein with reference to  FIGS. 1 through 5  are designated by odd reference numbers starting with reference numeral  411 . The embodiment of  FIG. 6  operates in the same manner as the embodiment of  FIGS. 1 through 5 , unless it is otherwise stated. 
       FIG. 6  is an electrical block diagram of alternate electrical components of the stimulators  10 ,  210  constructed in accordance with another exemplary embodiment of the present invention. Instead of employing an analog circuit to implement a waveform generator, the stimulator includes a circuit  411  which employs a digital signal processor (DSP)  413  to simulate a digital version of the waveform generator. The circuitry surrounding the DSP  413  includes an analog multiplexer  415 , a frequency selector  417 , a duty cycle selector  419  and a mode selector  421 , each of which is electrically connected to the multiplexer  415 , an analog-to-digital converter (A/D)  423  electrically connected to the multiplexer  415 , an optional shift register  425  electrically connected to the A/D  423  and to the DSP  413 , a memory module  427  electrically connected to the DSP  413 , a digital-to-analog converter (D/A)  429  electrically connected to the DSP  413 , a filter bank  431  electrically connected to the D/A  429 , a pair of power amplifiers  433 ,  435  each of which is electrically connected to the filter bank  431 , a first amplitude selector  437  electrically connected to the power amplifier  433 , and a second amplitude selector  439  electrically connected to the power amplifier  435 . The power amplifier  433  is electrically connected to a first electrode  418 , while the power amplifier  435  is electrically connected to a second electrode  420 . 
     The output voltages of each of the frequency selector  417 , the duty cycle selector  419 , and the mode selector  421  are sampled in a time-division multiplexed fashion by the multiplexer  415 . The output of the multiplexer  415  is sampled by the analog-to-digital converter (A/D)  423 . The shift register  425  converts the parallel outputs of the A/D converter  423  to a serial bit stream, which is input to the DSP  413 . The DSP  413  interfaces with the memory  427 , which may be a combination of random access memory for storing intermediate calculations and executing a waveform generation program, and a non-volatile FLASH portion of the memory  427 , which may store waveforms and/or a program for forming the waveforms. The output of the DSP  413 , applies a discrete version of the waveforms to be applied, which is converted to analog form by the D/A converter  429 . The output of the D/A converter  429  is fed to the filter bank  431 , which can filter out quantization noise and other distortions. The output of the filter bank  431  is fed to the power amplifiers  433 ,  435 , which outputs a signal capable of applying RMS currents in the range of 0-200 mA to the electrodes  418 ,  420  by adjusting the amplitude selectors  437 ,  439 . 
     It will be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make many variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the present invention as defined in the appended claims.