Abstract:
Systems and methods according to the present invention provide a means for determining, as an example, the health or location of nerves. Generally, embodiments according to the present invention may be used to verify the absence of nerve tissue along a prospective incision location to avoid damage caused by such incision. Alternatively or additionally, embodiments according to the present invention may be used to locate and/or hone in on a more precise location of one or more nerves. Electrical stimulation may be applied to tissue in an iterative fashion in one or more desired patterns and at one or more stimulation intensities to determine one or more regional neural responses and one or more focused neural responses.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of co-pending U.S. patent application Ser. No. 12/806,698, filed Aug. 19, 2010, and entitled “Systems and Methods for Intra-Operative Stimulation,” which claims the benefit of U.S. Patent Application Ser. No. 61/338,312, filed Feb. 16, 2010, entitled “Systems and Methods for Intra-Operative Stimulation, and is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/651,165, filed Jan. 9, 2007, and entitled “Systems and Methods for Intra-Operative Stimulation,” which is a continuation-in-part of U.S. patent application Ser. No. 11/099,848, filed Apr. 6, 2005, and entitled “Systems and Methods for Intra-Operative Stimulation,” which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/657,277, filed Mar. 1, 2005, and entitled “Systems and Methods for Intra-Operative Stimulation,” each of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates generally to tissue identification and integrity testing, and more particularly to systems and methods for safeguarding against nerve and muscle injury during surgical procedures, location and stimulation of nerves and muscles, identification and assessment of nerve and muscle integrity following traumatic injuries, and verification of range of motion and attributes of muscle contraction during reconstructive surgery. 
       BACKGROUND OF THE INVENTION 
       [0003]    Even with today&#39;s sophisticated medical devices, surgical procedures are not risk-free. Each patient&#39;s anatomy differs, requiring the surgeon to be ever vigilant to these differences so that the intended result is accomplished. The positioning of nerves and other tissues within a human or animal&#39;s body is one example of how internal anatomy differs from patient to patient. While these differences may be slight, if the surgeon fails to properly identify one or several nerves, the nerves may be bruised, stretched, or even severed during an operation. The negative effects of nerve damage can range from lack of feeling on that part of the body to loss of muscle control. 
         [0004]    Traumatic injuries often require surgical repair. Determining the extent of muscle and nerve injury is not always possible using visual inspection. Use of an intra-operative stimulator enables accurate evaluation of the neuromuscular system in that area. This evaluation provides valuable knowledge to guide repair/reconstructive surgery following traumatic injury, and when performing a wide range of surgeries. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention provides devices, systems, and methods for intra-operative stimulation. The intra-operative stimulation enables accurate evaluation of the neuromuscular system to guide repair or reconstructive surgery. 
         [0006]    An embodiment of a method according to the present invention includes a method of avoiding nerve tissue in a surgical procedure. The targeted tissue in a first application step, a first electrical stimulation is applied with an electrode to a first tissue region along the first potential incision length. The first tissue region may be cutaneous or subcutaneous. During the first application step, a neural response may be observed. In the event that a neural response is observed, a second incision location and a second potential incision length may be identified, so as to avoid damage to the nerve which was stimulated during the first application step. In a second application step, a second electrical stimulation may be applied with the electrode to a second tissue region along the second potential incision length. During the second application, a neural response may or may not be observed. If no neural response is observed, a surgical procedure may be performed on or through the second tissue region. The surgical procedure may include the step of incising a portion of the second tissue region along a portion of the second potential incision length. 
         [0007]    According to one aspect of a method according to the present invention, if no neural response is observed in response to a stimulation, a parameter of the stimulation may be adjusted and, in a third application step, a third electrical stimulation may be applied with an electrode to the first tissue region along the first potential incision length. The adjustment to the stimulation parameter may be a decrease in stimulation intensity by reducing one or both of stimulation pulse duration and stimulation amplitude. Alternatively, the adjustment to the stimulation parameter may be an increase in stimulation intensity by increasing one or both of stimulation pulse duration and stimulation amplitude. 
         [0008]    Another embodiment of a method according to the present invention includes a method of locating nerve tissue to perform a surgical procedure, perhaps in the area of or on the nerve tissue. The method includes identifying a first potential incision location and a first potential incision length. In a first application step, a first electrical stimulation is applied with an electrode to a tissue region along the first potential incision length. The tissue region may include tissue that is cutaneous or subcutaneous. During the first application step, a neural response may or may not be observed. If no desired neural response is observed, a parameter of the electrical stimulation may be altered, and, in a second application step, a second stimulation may be applied with the electrode to the tissue region. During the second application step, a neural response may or may not be observed. If a neural response is observed, after the first and second application steps, an incision may be made along at least a portion of the first potential incision length, and a surgical procedure may be performed through or accomplished by the incision. The method may further include, in a third application step, applying the first stimulation to the tissue region, and observing the desired neural response during the third application step. 
         [0009]    According to an aspect of a method according to this embodiment, the first application step may be performed before the altering step and the second application step may be performed after the altering step. The altering step may include the step of increasing or decreasing electrical stimulation intensity, which may be accomplished by increasing or decreasing, respectively, at least one of electrical stimulation amplitude and/or pulse duration. 
         [0010]    According to another aspect of a method according to the present invention, the application steps may include the step of translating the electrode along at least a portion of an incision length while the electrode is in contact with the tissue. Thus, the electrical stimulation may be applied while the electrode is moving in contact with the tissue. 
         [0011]    According to yet another aspect of a method according to the present invention, the surgical procedure may include the step of removing scar tissue, which may be removed through or caused by the incision. In one embodiment two devices are used for stimulation and surgery, respectively. For instance embodiments of systems disclosed herein may be used for electrical stimulation, and a scalpel may be used for performing the surgical procedure. 
         [0012]    Another embodiment of a method according to the present invention is a method for honing in on nerve fibers disposed below or innervating animal tissue, which may be cutaneous or subcutaneous tissue. The method includes the step of applying a first electrical stimulation to animal tissue, at a first stimulation intensity, within an identified stimulation region, the first electrical stimulation being applied with an electrode in contact with the tissue. A plurality of first active stimulation locations may be identified within the stimulation region. The active stimulation locations are locations of the electrode in contact with tissue at which one or more neural responses are generated in response to the first electrical stimulation. The plurality of first active stimulation locations is disposed about a perimeter of a focused stimulation region. At a reduced stimulation intensity, a second electrical stimulation may be applied within the focused stimulation region. In a second identifying step, at least one second active stimulation location may be identified within the focused stimulation region. The reduced stimulation intensity may be generated by a step of altering an electrical stimulation parameter of the electrical stimulation. The step of altering may include reducing at least one of electrical stimulation pulse duration and electrical stimulation pulse amplitude. 
         [0013]    According to an aspect of such embodiment, the first identifying step may include the step of translating the electrode across the tissue while applying the first electrical stimulation. The electrode may be translated in a desired pattern, such as a star pattern, a zig-zag pattern, or a spiral pattern. 
         [0014]    According to another aspect of an embodiment of honing in on nerve fibers, the second identifying step may include the step of translating the electrode across the tissue while applying the second electrical stimulation. The electrode may be translated in a desired pattern, such as a star pattern, a zig-zag pattern, or a spiral pattern. 
         [0015]    Yet another embodiment of a method according to the present invention includes a method of seeking a neural response to electrical stimulation. The method includes the step of identifying a prospecting location on animal tissue, which may be cutaneous or subcutaneous. This location may be selected based on prior experience with other patients or prior experience with a specific patient. Alternatively, the location may be randomly selected. An electrical stimulation maybe applied to the tissue at the prospecting location with an electrode to determine whether a neural response is generated. A neural response may or may not be observed. 
         [0016]    If no neural response is observed, the electrode may be translated while in contact with the tissue radially outward from the prospecting location in a first direction for a first honing distance. The method may further include the step of translating the electrode in a second direction back to the prospecting location. The electrode may then be translated radially outward from the prospecting location in a third direction for a second honing distance, and a neural response to the electrical stimulation may be observed. The third direction may be substantially the same as the second direction, and the second honing distance may be substantially the same as the first honing distance. 
         [0017]    According to an aspect of such embodiment, the step of translating in the first direction may be performed while applying the electrical stimulation to the tissue. Alternatively or additionally, one or more of the translating steps may be performed while the electrode is in contact with the tissue. The second direction may be opposite the first direction. 
         [0018]    According to another aspect of an embodiment of seeking a neural response, the method may include the step of identifying an active stimulation location on the tissue. 
         [0019]    According to yet another aspect of an embodiment of seeking a neural response, one or more of the following steps may be repeated: identifying a prospecting location; applying electrical stimulation to the tissue at the prospecting location with an electrode to determine whether a neural response is generated; and identifying an active stimulation location on the tissue. 
         [0020]    Features and advantages of the inventions are set forth in the following Description and Drawings, as well as the appended description of technical features. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a diagrammatic view of a system usable in association with a family of different monitoring and treatment devices for use in different medical procedures. 
           [0022]      FIG. 2  is a perspective view showing an exemplary embodiment of the system shown in  FIG. 1 , the stimulation control device being removably coupled to a stimulation probe, and showing the stimulation signal path through the system. 
           [0023]      FIG. 3A  is a side view with a portion broken away and in section showing the stimulation probe having the stimulation control device embedded within the stimulation probe. 
           [0024]      FIG. 3B  is a side view with a portion broken away and in section showing the stimulation probe having the stimulation control device embedded within the stimulation probe, and showing an optional needle-like return electrode. 
           [0025]      FIG. 3C  is a side view with a portion broken away and in section showing an additional embodiment of the stimulation probe having a housing that includes a gripping base and a flexible nose cone, and an illuminating ring indicator. 
           [0026]      FIG. 4A  is a side view of the stimulation probe of  FIG. 3   c , showing the users hand in a position on the stimulation probe to move the flexible nose cone. 
           [0027]      FIG. 4B  is a side view of the stimulation probe of  FIG. 4A , showing the users hand flexing the flexible nose cone. 
           [0028]      FIG. 5  is a side view with a portion broken away and in section showing elements of the flexible nose cone, the ring indicator, and the gripping base. 
           [0029]      FIG. 6  is a graphical view of a desirable biphasic stimulus pulse output of the stimulation device. 
           [0030]      FIG. 7  is a view showing how the geometry of the stimulation control device shown in  FIG. 2  aids in its positioning during a surgical procedure. 
           [0031]      FIG. 8  is a block diagram of a circuit that the stimulation control device shown throughout the Figs. can incorporate. 
           [0032]      FIGS. 9A and 9B  are perspective views showing the stimulation control device in use with a cutting device. 
           [0033]      FIGS. 10A and 10B  are perspective views showing the stimulation control device in use with a drilling or screwing device. 
           [0034]      FIGS. 11A and 11B  are perspective views showing the stimulation control device in use with a pilot auger device. 
           [0035]      FIGS. 12A and 12B  are perspective views showing the stimulation control device in use with a fixation device. 
           [0036]      FIG. 13  is a plane view of a kit used in conjunction with the stimulation probe shown in  FIG. 3C , and including the stimulation probe and instructions for use. 
           [0037]      FIG. 14  is a perspective view of the stimulation probe shown in  FIG. 3C . 
           [0038]      FIG. 15  is an exploded view of the stimulation probe shown in  FIG. 14 . 
           [0039]      FIG. 16  is a flow chart of a first embodiment of a method according to the present invention. 
           [0040]      FIG. 17  is a flow chart of a second embodiment of a method according to the present invention. 
           [0041]      FIGS. 18A-18F  depict a first series of steps according to the embodiment of  FIG. 17 . 
           [0042]      FIG. 19  depicts an alternate stimulation, relocation and identification pattern to be used in the embodiment of  FIG. 17 . 
       
    
    
       [0043]    The invention may be embodied in several forms without departing from its spirit or essential characteristics. The scope of the invention is defined in the appended claims, rather than in the specific description preceding them. All embodiments that fall within the meaning and range of equivalency of the claims are therefore intended to be embraced by the claims. 
       DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0044]    This Specification discloses various systems and methods for safeguarding against nerve, muscle, and tendon injury during surgical procedures or confirming the identity and/or location of nerves, muscles, and tendons and evaluating their function or the function of muscles enervated by those nerves. The systems and methods are particularly well suited for assisting surgeons in identification of nerves and muscles in order to assure nerve and muscle integrity during medical procedures using medical devices such as stimulation monitors, cutting, drilling, and screwing devices, pilot augers, and fixation devices. For this reason, the systems and methods will be described in the context of these medical devices. 
         [0045]    The systems and methods desirably allow the application of a stimulation signal at sufficiently high levels for the purposes of locating, stimulating, and evaluating nerve or muscle, or both nerve and muscle integrity in numerous medical procedures, including, but not limited to, evaluating proximity to a targeted tissue region, evaluating proximity to a nerve or to identify nerve tissue, evaluating if a nerve is intact (i.e., following a traumatic injury) to determine if a repair may be needed, evaluating muscle contraction to determine whether or not the muscle is innervated and/or whether the muscle is intact and/or whether the muscle is severed, and evaluating muscle and tendon length and function following a repair or tendon transfer prior to completing a surgical procedure. 
         [0046]    Still, it should be appreciated that the disclosed systems and methods are applicable for use in a wide variety of medical procedures with a wide variety of medical devices. By way of non-limiting example, the various aspects of the invention have application in procedures requiring grasping medical devices and internal viewing devices as well. 
       I. Overview of the System 
       [0047]      FIG. 1  shows an illustrative system  20  for locating and identifying tissue and safeguarding against tissue and/or bone injury during surgical procedures. In the illustrated embodiment, the system  20  is configured for locating, monitoring, and stimulating tissue and other structures throughout the body. The system  20  includes a stimulation control device  22  operating individually or in conjunction with one or more of a family of stimulating medical devices including, for example, a stimulation monitor or probe  100 , a cutting device  200 , a drilling or screwing device  300 , a pilot auger  400 , and a fixation device  500 . 
         [0048]    In an exemplary embodiment, and as can be seen in  FIG. 2 , the stimulation control device  22  functions in the system  20  to generate an electrical stimulation signal  29 . The stimulation signal  29  flows from the stimulation control device  22  through a lead  24  to a medical device (e.g., stimulation probe  100 ). The stimulation signal  29  then flows through a predefined insulated path  124  within the stimulation probe  100  and to an operative element, such as an electrically conductive surface, i.e., a coupled electrode  110 . The electrode  110  is to be positioned on or near a region of a patient to be stimulated. In monopolar operation, a return electrode (or indifferent electrode)  38  provides an electrical path from the body back to the control device  22 . The stimulation control device  22  may operate in a monopolar or bipolar configuration, as will be described in greater detail later. 
         [0049]    The stimulation signal  29  is adapted to provide an indication or status of the device. The indication may include a physical motor response (e.g., twitching), and/or one or more visual or audio signals from the stimulation control device  22 , which indicate to the surgeon the status of the device, and/or close proximity of the electrode  110  to a nerve, or a muscle, or a nerve and a muscle. The stimulation control device may also indicate to the surgeon that the stimulation control device is operating properly and delivering a stimulus current. 
       II. Medical Devices 
       [0050]    The configuration of the stimulating medical devices that form a part of the system can vary in form and function. Various representative embodiments of illustrative medical devices will be described. 
       A. Stimulation Probe 
       [0051]      FIGS. 3A to 3C  show various embodiments of a hand held stimulation monitor or probe  50  for identification and testing of nerves and/or muscles during surgical procedures. As shown, the stimulation probe  50  may accommodate within a generally tubularly housing  112  the electrical circuitry of a stimulation control device  22 . The stimulation probe  50  is desirably an ergonomic, sterile, single use instrument intended for use during surgical procedures to identify nerves and muscles, muscle attachments, or to contract muscles to assess the quality of surgical interventions or the need for surgical interventions, or to evaluate the function of nerves already identified through visual means. The stimulation probe  50  may be sterilized using ethylene oxide, for example. 
         [0052]    The stimulation probe  50  is preferably sized small enough to be held and used by one hand during surgical procedures, and is ergonomically designed for use in either the left or right hand. In a representative embodiment, the stimulation probe  50  may have a width of about 20 millimeters to about 30 millimeters, and desirably about 25 millimeters. The length of the stimulation probe  50  (not including the operative element  110 ) may be about 18 centimeters to about 22 centimeters, and desirably about 20 centimeters. The operative element  110  may also include an angle or bend to facilitate access to deep as well as superficial structures without the need for a large incision. The operative element  110  will be described in greater detail later. A visual or audio indicator  126  incorporated with the housing  112  provides reliable feedback to the surgeon as to the request and delivery of stimulus current. 
         [0053]    In one embodiment shown in  FIGS. 3C and 14 , the stimulation probe  50  includes a housing  112  that comprises a gripping base portion  60  and an operative element adjustment portion  62 . The operative element  110  extends from the proximal end of the adjustment portion  62 . In order to aid the surgeon in the placement of the operative element  110  at the targeted tissue region, the adjustment portion, as will be described as a nose cone  62 , may be flexible. This flexibility allows the surgeon to use either a finger or a thumb positioned on the nose cone  62  to make fine adjustments to the position of stimulating tip  111  of the operative element  110  at the targeted tissue region (see  FIGS. 4A and 4B ). The surgeon is able to grasp the gripping base  60  with the fingers and palm of the hand, and position the thumb on the nose cone  62 , and with pressure applied with the thumb, cause the stimulating tip  111  to move while maintaining a steady position of the gripping base portion  62 . This flexible nose cone  62  feature allows precise control of the position of the stimulating tip  111  with only the movement of the surgeon&#39;s thumb (or finger, depending on how the stimulating probe is held). 
         [0054]    The flexible nose cone  62  may comprise a single element or it may comprise at least an inner portion  64  and an outer portion  66 , as shown in  FIG. 5 . In order to facilitate some flexibility of the proximal portion  114  of the stimulation probe  50 , the inner portion  64  of the nose cone  62  may be made of a thermoplastic material having some flexibility. One example may be LUSTRAN® ABS 348, or similar material. The outer portion  66  may comprise a softer over molded portion and may be made of a thermoplastic elastomer material having some flexibility. One example may be VERSAFLEX™ OM 3060-1 from GLS Corp. The nose cone  62  is desirably generally tapered. For example, the nose cone  62  may be rounded, as shown in  FIGS. 3A and 3B , or the nose cone may be more conical in shape, as shown in  FIG. 3C . 
         [0055]    The nose cone  62  may also include one or more features, such as ribs or dimples  72 , as shown in  FIG. 14 , to improve the gripping, control, and stability of the stimulation probe  50  within the surgeon&#39;s hand. 
         [0056]    The gripping base portion  60  of the housing  112  may also include an overmolded portion  68 . The overmolded portion  68  may comprise the full length of the gripping base portion  60 , or only a portion of the gripping base  60 . The soft overmolded portion  68  may include one or more features, such as dimples or ribs  70 , as shown, to improve the gripping, control, and stability of the stimulation probe  50  within the surgeon&#39;s hand. The overmolded portion  68  may comprise the same or similar material as the thermoplastic elastomer material used for the outer portion  66  of the flexible nose cone  62 . 
         [0057]    In one embodiment, the stimulation probe  50  includes a housing  112  that carries an insulated lead  124 . The insulated lead  124  connects the operative element  110  positioned at the housing&#39;s proximal end  114  to the circuitry  22  within the housing  112  (see  FIG. 3A ). It is to be appreciated that the insulated lead is not necessary and the operative element  110  may be coupled to the circuitry  22  (see  FIG. 3C ). The lead  124  within the housing  112  is insulated from the housing  112  using common insulating means (e.g., wire insulation, washers, gaskets, spacers, bushings, and the like). The conductive tip  111  of the operative element  110  is positioned in electrical conductive contact with at least one muscle, or at least one nerve, or at least one muscle and nerve. 
         [0058]    As shown, the stimulation probe  50  is mono-polar and is equipped with a single operative element (i.e., electrode)  110  at the housing proximal end  114 . A return electrode  130 ,  131  may be coupled to the stimulation probe  50  and may be any of a variety of electrode types (e.g., paddle, needle, wire, or surface), depending on the surgical procedure being performed. As shown, the various return electrodes  130 ,  131  are coupled to the housing distal end  118 . In an alternative embodiment, the stimulation device  50  itself may be bipolar by including a return electrode in the operative element  110 , which precludes the use of a return electrode coupled to the stimulation probe  50 . 
         [0059]    As shown and described, the stimulation probe  50  may accommodate within the housing  112  the electrical circuitry of a stimulation control device  22 . In this arrangement, the stimulation probe  50  may have one or more user operable controls. Two are shown— 155  and  160 . Power switch  155  serves a dual purpose of turning the stimulation probe  500 N and OFF (or standby), and also can be stepped to control the stimulation signal amplitude selection within a predefined range (e.g., 0.5, 2.0, and 20 mA). In this configuration, the switch may be a four position switch. Before the first use of the stimulation probe  50 , the power switch  155  is in the OFF position and keeps the stimulation probe off. After the stimulation probe  50  has been turned ON—by moving the switch  155  to an amplitude selection—the OFF position now corresponds to a standby condition, where no stimulation would be delivered. In one embodiment, once the stimulation probe  50  has been turned on, it cannot be turned off, it can only be returned to the standby condition and will remain operational for a predetermined time, e.g., at least about seven hours. This feature is intended to allow the stimulation probe  50  to only be a single use device, so it can not be turned OFF and then used again at a later date. 
         [0060]    The pulse control device  160  allows for adjustment of the stimulation signal pulse width from a predefined range (e.g., about zero to about 200 microseconds). In one embodiment, the pulse control  160  may be a potentiometer to allow a slide control to increase or decrease the stimulation signal pulse width within the predefined range. 
         [0061]    The stimulation pulse may have a non-adjustable frequency in the range of about 10 Hz to about 20 Hz, and desirably about 16 Hz. 
         [0062]    As a representative example, the stimulation pulse desirably has a biphasic waveform with controlled current during the cathodic (leading) phase, and net DC current less than 10 microamps, switch adjustable from about 0.5 milliamps to about 20 milliamps, and pulse durations adjustable from about zero microseconds up to about 200 microseconds. A typical, biphasic stimulus pulse is shown in  FIG. 6 . 
         [0063]    The operative element  110  exits the housing  112  at the proximal end  114  to deliver stimulus current to the excitable tissue. The operative element  110  comprises a length and a diameter of a conductive material, and is desirably fully insulated with the exception of the most proximal end, e.g. about 1.0 millimeters to about 10 millimeters, and desirably about 4 millimeters to about 6 millimeters, which is non-insulated and serves as the stimulating tip or surface (or also referred to as active electrode)  111  to allow the surgeon to deliver the stimulus current only to the intended tissue. The small area of the stimulating surface  111  (the active electrode) of the operative element  110  ensures a high current density that will stimulate nearby excitable tissue. The insulation material  113  may comprise a medical grade heat shrink. 
         [0064]    The conductive material of the operative element  110  comprises a diameter having a range between about 0.5 millimeters to about 1.5 millimeters, and may be desirably about 1.0 millimeters. The length of the operative element  110  may be about 50 millimeters to about 60 millimeters, although it is to be appreciated that the length may vary depending on the particular application. As shown, the operative element  110  may include one or more bends to facilitate accurate placement of the stimulating surface  111 . In one embodiment, the conductive material of operative element  110  is made of a stainless steel 304 solid wire, although other known conductive materials may be used. 
         [0065]    As previously described, in monopolar operation, a return electrode (or indifferent electrode)  130  or  131 , for example, provides an electrical path from the body back to the control device  22  within the housing  112 . The return electrode  130  (see  FIG. 3A ) may be placed on the surface of intact skin (e.g., surface electrodes as used for ECG monitoring during surgical procedures) or it might be needle-like  131  (see  FIGS. 3B and 3C ), and be placed in the surgical field or penetrate through intact skin. The housing&#39;s distal end  118  can incorporate a connector or jack  120  which provides options for return current pathways, such as through a surface electrode  130  or a needle electrode  131 , having an associated plug  122 . It is to be appreciated that a return electrode and associated lead may be an integral part of the stimulation probe  50 , i.e., no plug or connector, as shown in  FIG. 3C . 
         [0066]    Additionally, the device  50  may desirably incorporate a visual or audio indicator  126  for the surgeon. This visual or audio indicator  126  allows the surgeon to confirm that the stimulator  50  is delivering stimulus current to the tissue it is contacting. Through the use of different tones, colors, different flash rates, etc., the indicator  126  (which can take the form, e.g., of a light emitting diode (LED)) allows the surgeon to confirm that the stimulating tip  111  is in place, the instrument is turned ON, and that stimulus current is flowing. Thus the surgeon has a much greater confidence that the failure to elicit a muscle contraction is because of lack of viable nervous tissue near the tip  111  of the stimulator  50  rather than the failure of the return electrode connection or some other instrumentation problem. 
         [0067]    As a representative example, in use the indicator  126  may be configured to illuminate continuously in one color when the stimulation probe  50  is turned on but not in contact with tissue. After contact with tissue is made, the indicator  126  may flash (i.e., blink) to indicate that stimulation is being delivered. If the stimulation has been requested, i.e., the stimulation probe has been turned on, but there is no stimulation being delivered because of a lack of continuity between the operative element  110  and the return electrode  130 , or an inadequate connection of the operative element  110  or the return electrode  130  to the patient tissue, the indicator  126  may illuminate in a different color, and may illuminate continuously or may flash. 
         [0068]    In one embodiment, as can be best seen in  FIGS. 3C and 5 , the indicator  126  comprises a ring indicator  128  that provides a visual indication around at least a portion, and desirably all of the circumference of the stimulation probe  50  generally near the flexible nose cone  62 . The visual ring indicator  128  may be an element of the gripping portion  60 , or it may be an element of the flexible nose cone  62 , or the ring indicator may positioned between the gripping portion  60  and the flexible nose cone  62 . The ring indicator  128  may also include a reflective element  129  to improve and focus the illumination effect of the light emitting source, e.g., one or more LEDs. The ring indicator  128  and the reflective element may be a single component, or more than one component (as can be seen in  FIGS. 5 and 15 ). 
         [0069]    Audio feedback also makes possible the feature of assisting the surgeon with monitoring nerve integrity during surgery. The insulated lead  124  connects to the operative element  110  that, in use, is positioned within the surgical field on a nerve distal to the surgical site. Stimulation of the nerve causes muscle contraction distally. The stimulation control device  22  incorporated within the housing  112  may be programmed to provide an audio tone followed by a stimulation pulse at prescribed intervals. The audio tone reminds the surgeon to observe the distal muscle contraction to confirm upon stimulation that the nerve is functioning and intact. 
         [0070]      FIG. 15  shows an exploded view of a representative stimulation probe  50 . As can be seen, the stimulation control device  22  is positioned within the housing  112 . A battery  34  is electrically coupled to the control device  22 . A first housing element  90  and a second housing element  92  partially encapsulate the control device  22 . The ring indicator  128  and the reflective element  129  are coupled to the proximal end of the housing  112 . The operative element  110  extends through the nose cone  62  and couples to the control device  22 . Desirably, the stimulation probe  50  will be constructed in a manner to conform to at least the IPX1 standard for water ingress. 
         [0071]    Alternatively, as  FIG. 2  shows, the stimulation control device  22  may be housed in a separate case, with its own input/output (I/O) controls  26 . In this alternative arrangement, the stimulation control device  22  is sized small enough to be easily removably fastened to a surgeon&#39;s arm or wrist during the surgical procedure, or otherwise positioned in close proximity to the surgical location (as shown in  FIG. 7 ), to provide sufficient audio and/or visual feedback to the surgeon. 
         [0072]    In this arrangement, the separate stimulation control device  22  can be temporarily coupled by a lead to a family of various medical devices for use. 
         [0073]    The present invention includes a method of identifying/locating tissue, e.g., a nerve or muscle, in a patient that comprises the steps of providing a hand-held stimulation probe  50 ,  100  as set forth above, engaging a patient with the first operative element  110  and the second electrode  130 , moving the power switch  155  to an activation position causing a stimulation signal  29  to be generated by the stimulation control device  22  and transmitted to the first operative element  110 , through the patient&#39;s body to the second electrode  130 , and back to the stimulation control device  22 . The method may also include the step of observing the indicator  126  to confirm the stimulation probe  50 ,  100  is generating a stimulation signal. The method may also include the step of observing a tissue region to observe tissue movement or a lack thereof. 
       B. The Stimulation Control Device 
       [0074]    As  FIG. 8  shows, the stimulation control device  22  includes a circuit  32  that generates electrical stimulation waveforms. A battery  34  desirably provides the power. The control device  22  also desirably includes an on-board, programmable microprocessor  36 , which carries embedded code. The code expresses pre-programmed rules or algorithms for generating the desired electrical stimulation waveforms using the stimulus output circuit  46  and for operating the visible or audible indicator  126  based on the controls actuated by the surgeon. 
         [0075]    In one form, the size and configuration of the stimulation control device  22  makes for an inexpensive device, which is without manual internal circuit adjustments. It is likely that the stimulation control device  22  of this type will be fabricated using automated circuit board assembly equipment and methods. 
         [0000]    C. Incorporation with Surgical Devices 
         [0076]    A stimulation control device  22  as just described may be electrically coupled through a lead, or embedded within various devices commonly used in surgical procedures (as previously described for the stimulation probe  50 ). 
       1. Cutting Device 
       [0077]    In  FIGS. 9A and 9B , a device  200  is shown that incorporates all the features disclosed in the description of the stimulation probe  50 ,  100 , except the device  200  comprises the additional feature of providing an “energized” surgical device or tool.  FIG. 9A  shows the tool to be a cutting device  200  (e.g., scalpel) removably coupled to a stimulation control device  22 . 
         [0078]    In the embodiment shown, the cutting device  200  includes a body  212  that carries an insulated lead  224 . The insulated lead  224  connects to an operative element, such as electrode  210 , positioned at the body proximal end  214  and a plug-in receptacle  219  at the body distal end  118 . The lead  224  within the body  212  is insulated from the body  212  using common insulating means (e.g., wire insulation, washers, gaskets, spacers, bushings, and the like). 
         [0079]    In this embodiment, the electrode  210  performs the cutting feature (e.g., knife or razor). The electrode  210  performs the cutting feature in electrical conductive contact with at least one muscle, or at least one nerve, or at least one muscle and nerve. The cutting device  200  desirably includes a plug-in receptacle  216  for the electrode  210 , allowing for use of a variety of cutting electrode shapes and types (e.g., knife, razor, pointed, blunt, curved), depending on the specific surgical procedure being performed. In this configuration, the lead  224  electrically connects the electrode  210  to the stimulation control device  22  through plug-in receptacle  219  and lead  24 . 
         [0080]    In one embodiment, the cutting device  200  is mono-polar and is equipped with a single electrode  210  at the body proximal end  214 . In the mono-polar mode, the stimulation control device  22  includes a return electrode  38  which functions as a return path for the stimulation signal. Electrode  38  may be any of a variety of electrode types (e.g., paddle, needle, wire, or surface), depending on the surgical procedure being performed. The return electrode  38  may be attached to the stimulation device  22  by way of a connector or plug-in receptacle  39 . In an alternative embodiment, the cutting device  200  may be bipolar, which precludes the use of the return electrode  38 . 
         [0081]    In the embodiment shown in  FIG. 9B , the cutting device  200  accommodates within the body  212  the electrical circuitry of the stimulation control device  22 . In this arrangement, the cutting device  200  may have at least two operational slide controls,  255  and  260 . Power switch  255  serves a dual purpose of turning the stimulation signal to the cutting device  200  on and off, and also is stepped to control the stimulation signal amplitude selection from a predefined range (e.g., 0.5, 2.0, and 20 mA). The pulse control switch  260  allows for adjustment of the stimulation signal pulse width from a predefined range (e.g., zero through 200 microseconds). 
         [0082]    At the body distal end  218 , a second plug-in receptacle  220  may be positioned for receipt of a second lead  222 . Lead  222  connects to electrode  230  which functions as a return path for the stimulation signal when the cutting device  200  is operated in a mono-polar mode. 
         [0083]    Additionally, the device  200  may incorporate a visual or audio indicator for the surgeon, as previously described. 
         [0084]    The present invention includes a method of identifying/locating tissue, e.g., a nerve or muscle, in a patient that comprises the steps of providing cutting device  200  as set forth above, engaging a patient with the first electrode  210  and the second electrode  230 , moving the power switch  255  to an activation position causing a stimulation signal  29  to be generated by the stimulation control device  22  and transmitted to the first electrode  210 , through the patient&#39;s body to the second electrode  230 , and back to the stimulation control device  22 . The method may also include the step of observing the indicator  126  to confirm the cutting device  200  is generating a stimulation signal. The method may also include the step of observing a tissue region to observe tissue movement or a lack thereof 
       2. Drilling Device 
       [0085]    In  FIGS. 10A and 10B , a device  300  is shown that incorporates all the features disclosed in the description of the stimulation probe  50 ,  100 , except the device  300  comprises the additional feature of providing an “energized” surgical device or tool, which comprises a drilling device  300 . In  FIG. 10A  is drilling device  300  is removably coupled to a stimulation control device  22 . 
         [0086]    In the embodiment shown, the drilling device  300  includes a body  312  that carries an insulated lead  324 . The insulated lead  324  connects to an operative element, such as electrode  310 , positioned at the body proximal end  314  and a plug-in receptacle  319  at the body distal end  318 . The lead  324  within the body  312  is insulated from the body  312  using common insulating means (e.g., wire insulation, washers, gaskets, spacers, bushings, and the like). 
         [0087]    In this embodiment, the electrode  310  performs the drilling feature. The electrode  310  may also perform a screwing feature as well. The electrode  310  performs the drilling feature in electrical conductive contact with a hard structure (e.g., bone). 
         [0088]    The drilling device  300  desirably includes a plug-in receptacle or chuck  316  for the electrode  310 , allowing for use of a variety of drilling and screwing electrode shapes and sizes (e.g., ¼ and ⅜ inch drill bits, Phillips and flat slot screw drivers), depending on the specific surgical procedure being performed. In this configuration, the lead  324  electrically connects the electrode  310  to the stimulation control device  22  through plug-in receptacle  319  and lead  324 . 
         [0089]    In one embodiment, the drilling device  300  is mono-polar and is equipped with a single electrode  310  at the body proximal end  314 . In the mono-polar mode, the stimulation control device  22  includes a return electrode  38  which functions as a return path for the stimulation signal. Electrode  38  may be any of a variety of electrode types (e.g., paddle, needle, wire, or surface), depending on the surgical procedure being performed. The return electrode  38  may be attached to the stimulation device  22  by way of a connector or plug-in receptacle  39 . In an alternative embodiment, the drilling device  300  may be bipolar, which precludes the use of the return electrode  38 . 
         [0090]    In  FIG. 10B , the drilling device  300  is shown to accommodate within the body  312  the electrical circuitry of the stimulation control device  22 . The drilling device  300  may have at least two operational slide controls,  355  and  360 . Power switch  355  serves a dual purpose of turning the stimulation signal to the drilling device  300  on and off, and also is also stepped to control the stimulation signal amplitude selection from a predefined range (e.g., 0.5, 2.0, and 20 mA). The pulse control switch  360  allows for adjustment of the stimulation signal pulse width from a predefined range (e.g., zero through 200 microseconds). At the body distal end  318 , a second plug-in receptacle  320  may be positioned for receipt of a second lead  322 . Lead  322  connects to electrode  330  which functions as a return path for the stimulation signal when the drilling device  300  is operated in a mono-polar mode. 
         [0091]    Additionally, the device  300  may incorporate a visual or audio indicator for the surgeon, as previously described. 
         [0092]    The present invention includes a method of identifying/locating tissue, e.g., a nerve or muscle, in a patient that comprises the steps of providing a drilling device  300  as set forth above, engaging a patient with the first electrode  310  and the second electrode  330 , moving the power switch  355  to an activation position causing a stimulation signal  29  to be generated by the stimulation control device  22  and transmitted to the first electrode  310 , through the patient&#39;s body to the second electrode  330 , and back to the stimulation control device  22 . The method may also include the step of observing the indicator  126  to confirm the drilling device  400  is generating a stimulation signal. The method may also include the step of observing a tissue region to observe tissue movement or a lack thereof 
       3. Pilot Auger 
       [0093]    An additional aspect of the invention provides systems and methods for controlling operation of a family of stimulating devices comprising a stimulation control device electrically coupled to a pilot auger for hard surface rotary probing. 
         [0094]    This embodiment incorporates all the features disclosed in the description of the stimulation probe  50 ,  100 , except this embodiment comprises the additional feature of providing an “energized” surgical device or tool.  FIG. 11A  shows a pilot auger device  400  removably coupled to a stimulation control device  22 . In the embodiment shown, the pilot auger device  400  includes a body  412  that carries an insulated lead  424 . The insulated lead  424  connects to an operative element, such as an electrode  410 , positioned at the body proximal end  414  and a plug-in receptacle  419  at the body distal end  418 . The lead  424  within the body  412  is insulated from the body  412  using common insulating means (e.g., wire insulation, washers, gaskets, spacers, bushings, and the like). In this embodiment, the electrode  410  performs the pilot augering feature. The electrode  410  performs the pilot augering feature in electrical conductive contact with a hard structure (e.g., bone). 
         [0095]    The pilot auger device  400  desirably includes a plug-in receptacle or chuck  416  for the electrode  410 , allowing for use of a variety of pilot augering electrode shapes and sizes (e.g., 1/32, 1/16, and ⅛ inch), depending on the specific surgical procedure being performed. In this configuration, the lead  24  electrically connects the electrode  410  to the stimulation control device  22  through plug-in receptacle  419  and lead  24 . 
         [0096]    In one embodiment, the pilot auger device  400  is mono-polar and is equipped with a single electrode  410  at the body proximal end  414 . In the mono-polar mode, the stimulation control device  22  includes a return electrode  38  which functions as a return path for the stimulation signal. Electrode  38  may be any of a variety of electrode types (e.g., paddle, needle, wire, or surface), depending on the surgical procedure being performed. The return electrode  38  may be attached to the stimulation device  22  by way of a connector or plug-in receptacle  39 . In an alternative embodiment, the pilot auger device  400  may be bipolar, which precludes the use of the return electrode  38 . 
         [0097]    As  FIG. 11B  shows, the pilot auger device  400  may accommodate within the body  412  the electrical circuitry of the stimulation control device  22 . At the body distal end  418 , a second plug-in receptacle  420  may be positioned for receipt of a second lead  422 . Lead  422  connects to electrode  430  which functions as a return path for the stimulation signal when the pilot auger device  400  is operated in a mono-polar mode. 
         [0098]    The pilot auger device  400  includes a power switch  455 . When moved to an activation position, a stimulation signal is generated by the stimulation control device  22 . Additionally, the device  400  may incorporate a visual or audio indicator for the surgeon, as previously described. 
         [0099]    The present invention includes a method of identifying/locating tissue, e.g., a nerve or muscle, in a patient that comprises the steps of providing a pilot auger device  400  as set forth above, engaging a patient with the first electrode  410  and the second electrode  430 , moving the power switch  455  to an activation position causing a stimulation signal to be generated by the stimulation control device  22  and transmitted to the first electrode  410 , through the patient&#39;s body to the second electrode  430 , and back to the stimulation control device  22 . The method may also include the step of observing the indicator  126  to confirm the pilot auger device  400  is generating a stimulation signal. The method may also include the step of observing a tissue region to observe tissue movement or a lack thereof. 
         [0000]    D. Incorporation with Fixation Devices 
         [0100]    An additional aspect of the invention provides systems and methods for controlling operation of a family of stimulating devices comprising a stimulation control device electrically coupled to a fixation device or a wrench or screwdriver for placing the fixation device. A fixation device (e.g., orthopedic hardware, pedicle screws) is commonly used during spinal stabilization procedures (fusion), and internal bone fixation procedures. 
         [0101]    This embodiment incorporates all the features disclosed in the description of the stimulation probe  50 ,  100 , except this embodiment comprises the additional feature of providing an “energized” fixation device or tool.  FIG. 12A  shows a fixation device  500  removably coupled to a stimulation control device  22 . In the embodiment shown, the fixation device  500  includes a rectangularly shaped body  512  that also serves as an operative element, such as electrode  510 . The fixation device  500  may take on an unlimited number of shapes as necessary for the particular procedure taking place. Pedicle screws  535  may be used to secure the fixation device to the bony structure. The electrode  510  performs the fixation feature in electrical conductive contact with a hard structure (e.g., bone). 
         [0102]    The fixation device  500  or wrench or screwdriver for placing the fixation device desirably includes a plug-in receptacle  519 . The fixation device  500  may take on an unlimited variety of shapes and sizes depending on the specific surgical procedure being performed. In this configuration, the lead  24  electrically connects the electrode  510  to the stimulation control device  22  through plug-in receptacle  519 . 
         [0103]    In one embodiment, the fixation device  500  is mono-polar and is equipped with the single electrode  510 . In the mono-polar mode, the stimulation control device  22  includes a return electrode  38  which functions as a return path for the stimulation signal. Electrode  38  may be any of a variety of electrode types (e.g., paddle, needle, wire, or surface), depending on the surgical procedure being performed. The return electrode  38  may be attached to the stimulation device  22  by way of a connector or plug-in receptacle  39 . In an alternative embodiment, the fixation device  500  may be bipolar, which precludes the use of the return electrode  38 . 
         [0104]    In yet an additional alternative embodiment (see  FIG. 12B ), the fixation device may be a pedicle screw  535 . The pedicle screw  535  is removably coupled to a stimulation control device  22 . In the embodiment shown, the pedicle screw  535  includes a head  570  and a shaft  572 , which both serve as an operative element, such as electrode  574 . The electrode  574  performs the fixation feature in electrical conductive contact with a hard structure (e.g., bone), as the pedicle screw  535  is being positioned within a bony structure. The lead  24  electrically connects the electrode  574  to the stimulation control device  22 , through a break-away connection or other similar electrical connective means. The fixation device  535  may take on an unlimited variety of shapes and sizes depending on the specific surgical procedure being performed. 
         [0105]    In the mono-polar mode, the stimulation control device  22  includes a return electrode  38  which functions as a return path for the stimulation signal. Electrode  38  may be any of a variety of electrode types (e.g., paddle, needle, wire, or surface), depending on the surgical procedure being performed. In an alternative embodiment, the fixation device  500  may be bipolar, which precludes the use of the return electrode  38 . 
         [0106]    The present invention includes a method of identifying/locating tissue, e.g., a nerve or muscle, in a patient that comprises the steps of providing a fixation device  500  as set forth above, engaging a patient with the first electrode  510  and the second electrode  38 , turning power on to the stimulation control device  22  through the I/O controls  26 , causing a stimulation signal  29  to be generated by the stimulation control device  22  and transmitted to the first electrode  510 , through the patient&#39;s body to the second electrode  38 , and back to the stimulation control device  22 . The method may also include the step of observing the indicator  126  to confirm the fixation device  500  is generating a stimulation signal. The method may also include the step of observing a tissue region to observe tissue movement or a lack thereof. 
       IV. Technical Features 
       [0107]    The stimulation control device  22 , either alone or when incorporated into a stimulation probe or surgical device, can incorporate various technical features to enhance its universality. 
       A. Small Size 
       [0108]    According to one desirable technical feature, the stimulation control device  22  can be sized small enough to be held and used by one hand during surgical procedures, or to be installed within a stimulation probe or surgical device. The angle of the stimulating tip facilitates access to deep as well as superficial structures without the need for a large incision. Visual and/or audible indication incorporated in the housing provides reliable feedback or status to the surgeon as to the request and delivery of stimulus current. 
         [0109]    According to an alternative desirable technical feature, the stimulation control device  22  may also be sized small enough to be easily removably fastened to a surgeon&#39;s arm or wrist during the surgical procedure, or positioned in close proximity to the surgical location (as shown in  FIG. 7 ), to provide sufficient audio and/or visual feedback to the surgeon. 
       B. Power Source 
       [0110]    According to one desirable technical feature, power is provided by one or more primary batteries  34  for single use positioned inside the housing and coupled to the control device  22 . A representative battery  34  may include a size “N” alkaline battery. In one embodiment, two size “N” alkaline batteries in series are included to provide a 3 volt power source. This configuration is sized and configured to provide an operating life of at least seven hours of operation—either continuous or intermittent stimulation. 
       C. The Microprocessor/Microcontroller 
       [0111]    According to one desirable technical feature, the stimulation control device  22  desirably uses a standard, commercially available micro-power, flash programmable microcontroller  36 . The microcontroller  36  reads the controls operated by the surgeon, controls the timing of the stimulus pulses, and controls the feedback to the user about the status of the instrument (e.g., an LED with 1, 2, or more colors that can be on, off, or flashing). 
         [0112]    The microcontroller operates at a low voltage and low power. The microcontroller send low voltage pulses to the stimulus output stage  46  that converts these low voltage signals into the higher voltage, controlled voltage, or controlled current, stimulus pulses that are applied to the electrode circuit. This stimulus output stage  46  usually involves the use of a series capacitor to prevent the presence of DC current flow in the electrode circuit in normal operation or in the event of an electronic component failure. 
       V. Representative Use of a Stimulation Probe 
       [0113]    The stimulation probe  50 ,  100 , as described, make possible the application of a stimulation signal at sufficiently high levels for the purposes of locating, stimulating, and evaluating nerve or muscle, or both nerve and muscle integrity in numerous medical procedures, including, but not limited to, evaluating proximity to a targeted tissue region, evaluating proximity to a nerve or to identify nerve tissue, evaluating if a nerve is intact (i.e., following a traumatic injury) to determine if a repair may be needed, evaluating muscle contraction to determine whether or not the muscle is innervated and/or whether the muscle is intact and/or whether the muscle is severed, and evaluating muscle and tendon length and function following a repair or tendon transfer prior to completing a surgical procedure. 
         [0114]    Instructions for use  80  are desirably included in a kit  82  along with a stimulation probe  50 . The kit  82  can take various forms. In the illustrated embodiment, kit  82  comprises a sterile, wrapped assembly. A representative kit  82  includes an interior tray  84  made, e.g., from die cut cardboard, plastic sheet, or thermo-formed plastic material, which hold the contents. Kit  82  also desirably includes instructions for use  80  for using the contents of the kit to carry out a desired therapeutic and/or diagnostic objectives. 
         [0115]    The instructions  80  guide the user through the steps of unpacking the stimulation probe  50 , positioning the electrodes, and disposing of the single use disposable stimulator  50 . Representative instructions may include, but are not limited to:
       Remove the stimulation probe  50  from sterile package  88 .   Remove cover  94  (e.g., a silicone cover) from the operative element  110 .   Remove protective cover  86  from the return electrode  131 .
           1. Position the return electrode  131  in contact with the patient such that: □1. The return electrode is desirably positioned in an area remote from the area to be stimulated.   2. The return electrode is desirably not positioned across the body from the side being stimulated.   3. The return electrode is desirably not in muscle tissue.   
           Turn the stimulation probe  500 N by moving the power switch  155  from OFF to the 0.5 mA setting (or greater). The stimulation probe  50  desirably is turned ON before the operative element  110  makes contact with tissue.   The indicator  126  will be illuminated yellow (for example) continuously if the stimulation probe  50  is ON, but not in contact with tissue.   Contact tissue with the operative element  110 .   Adjust the pulse control  160  gradually to increase the level of stimulation. The indicator  126  will flash yellow indicating that stimulation is being delivered.   A flashing red (for example) indicator  126  means that stimulation has been requested, but no stimulation is being delivered because of inadequate connection of the operative element  110  or the return electrode  131  to the patient tissue. Check the return electrode contact and position, and check the operative element  110  contact and position.   Placing the power switch  155  to the off/standby position will stop stimulation and the visual indictor  126  will be illuminated yellow continuously.   Placing the pulse control  160  at the minimum position will stop stimulation and the visual indictor  126  will be illuminated yellow continuously.   A low/depleted battery  34  will cause the stimulation probe  50  to automatically turn OFF and the visual indicator  126  will not be illuminated. No further use of the stimulator  50  will be possible.   At end of use, move the power switch  155  to the off/standby position and move the pulse control  160  to the minimum position.   Cut off and dispose of the return electrode  131  in an appropriate sharps/biohazard container.   Dispose of the stimulation probe  50  per hospital or facility guidelines.       
 
         [0133]    Nerve location may be performed for a variety of reasons, including location for identification prior to or during a “nerve cleaning” procedure, and location for avoidance of iatrogenic nerve injury. One problem that has long persisted in the field of reconstructive and microvascular surgery is the continued occurrence of iatrogenic nerve injury during surgery. Iatrogenic nerve injury during surgery is a deservedly feared complication, resulting in pain and possible permanent loss of function for the patient and malpractice litigation and probable liability for the physician. One retrospective study of 444 randomly sampled malpractice claims revealed that 14% were peripheral nerve injuries. 
         [0134]    Reported nerve injury rates are surprisingly high and, as with most complications, are probably underreported. 
         [0135]    While nerve injury is perhaps not totally avoidable, the capacity to stimulate nerves and muscles intraoperatively makes surgery safer and more predictable, and improves outcomes. This is difficult when operating through areas scarred by trauma, infection, tumors or previous surgery that obliterates the normal, anatomical landmarks. Distinguishing nerve from adjacent tissue is difficult or impossible by visual inspection. The ability to electrically stimulate tissue to elicit a response is frequently of crucial importance to identify and protect nerves whose identity and location are obscured by scarring and abnormal anatomy. 
         [0136]    While various nerve stimulators exist, they have been problematic for a number of reasons. For instance, scar is an effective insulator and it has been discovered that a lack of response to electrical stimulation from existing nerve stimulators may be due to inadequate stimulus intensity. Thus, failure to elicit a response with conventional intraoperative stimulation may have indicated that the structure in question was not a nerve and was, therefore, safe to cut. However, it may also have meant that the stimulator was not functioning properly or that the stimulus provided by the prior art stimulator was insufficient to stimulate the nerve due to, e.g., scar-related, or other, dysfunction. When there is a failure to elicit a response, and a surgeon is still suspicious, the surgeon must extend the surgical exposure time significantly or call for the operating microscope to dissect around the structure in question thought to be innervated by nerve tissue. These processes may take considerable time, will add to the service cost through extra operating room time and expensive billing codes for microsurgery, and are not processes that most orthopedic surgeons can actually perform. Existing stimulators have been unreliable and undependable (the Vari-Stim® by Medtronic Xomed, Inc., has been recalled; Recall # Z-0947-2009), which adds to the problem of uncertainty. 
         [0137]    Alternatively, rather than locating a nerve and then performing a surgical procedure remotely from the located nerve, it may be desirable to locate a nerve precisely to perform a surgical procedure adjacent to or on the nerve tissue. Very broad, but safe, stimulation capability, from stimulating entire muscle regions to individual nerve fibers, is desirable. These features enable the surgeon to avoid dangerous “false negative” responses, and allow the surgeon to perform threshold testing in a semi-quantitative manner. Indeed, wide-range, continuously-variable stimulus capability allows the surgeon to hone in on an area suspected of containing nerve tissue and then precisely localizing the nerve by beginning with a higher stimulus intensity and gradually lowering the intensity as the nerve is excavated from the scar tissue. This has allowed identification of nerves that were heavily scarred and indistinguishable from adjacent tissue and, in several cases, has avoided erroneous sacrifice of a critical nerve that would have significantly, detrimentally, affected the outcome of a surgery. 
         [0138]    A first embodiment  1600  of a method according to the present invention includes the steps depicted in  FIG. 16 . In one step or series of steps  1602 , a first potential incision location and a first potential incision length are determined and/or identified. A first electrical stimulation is applied  1604  to a tissue region located along at least a portion of the first potential incision length. During and in response to the first electrical stimulation  1604 , a neural response may or may not be observed  1606 . For example, where nerve fibers are activated by the first electrical stimulation, and such nerve fibers innervate muscle, the muscle may twitch and/or fully contract. For instance, sufficient stimulation of the axillary nerve will likely cause contraction of the deltoid muscle in a human shoulder, which can be visibly observed. Arthroscopically, stimulation may be visibly observed as a jump or movement of the innervated tissue within the field of an arthroscope. If a neural response is observed, an alternate potential incision location and associated desired incision length may be determined and/or identified  1608 . The operative element  110  of a stimulator  50  may be relocated  1610  to contact a second tissue region located along the alternate desired incision length. A stimulation may again be applied  1604 , this time to at least a portion of the second tissue region. Steps of this method may be repeated at a predetermined or desired stimulation level until no neural response is observed at a final incision location. Once no neural response to the subsequent stimulation(s) is observed, and if the surgeon is comfortable with the intensity of the electrical stimulation applied, the surgeon may be confident in incising the final incision location  1612 . 
         [0139]    The method may further include the steps of altering electrical stimulation parameters, such as by increasing or decreasing the electrical stimulation pulse current amplitude and/or the pulse time duration. Such altering of stimulation parameters may occur, for example, after it has been determined whether a neural response was generated by previous stimulation. For instance, it may be desirable to confirm the neural response to determine whether the observed response or lacking response were false. Such confirmation may be made by adjusting stimulation parameters  1614 , 1616  and then again applying a stimulation  1604  to the same tissue region that was stimulated when the neural response determination  1606  was made. For example, if no neural response was observed, it may be desirable to adjust electrical stimulation parameters  1614  to increase stimulation intensity (pulse duration and/or amplitude) of the electrical stimulation to confirm that the lacking neural response was not a false negative. Additionally, if a neural response was observed, it may be desirable to adjust electrical stimulation parameters  1616  to decrease stimulation intensity (pulse duration and/or amplitude) to confirm that the neural response was not a false positive. The stimulation pulse train is preferably provided continuously once it has started, but it may optionally be paused or stopped. 
         [0140]    A second embodiment  1700  of a method according to the present invention is shown in  FIG. 17 . Reference may also be had to  FIGS. 18A-18F  to aid in understanding the following description. The second method embodiment  1700  generally includes a method for honing in on a precise location of one or more nerve fibers  1802 , perhaps not for the purpose of avoiding fibers  1802 , but for the purpose of operating directly on one or more of the fibers  1802 . The nerve fibers  1802  may innervate muscle tissue  1803 , which may be disposed beneath a tissue layer  1810  to be stimulated. In one step  1702 , a target stimulation tissue region  1804  is identified. In that tissue region  1804 , using an operative element  110  of a handheld stimulator  50 , a first electrical stimulation is applied  1704  along a first stimulation path  1806 , across a first tissue stimulation width  1808 . Preferably, this first electrical stimulation may be provided at a maximum stimulation intensity to be used during the prospecting or honing method, such as an amplitude of 20 mA and a pulse duration of greater than zero and less than or equal to 200 μs. The first electrical stimulation may also be provided at a minimal stimulation intensity and increased until some neural response is detected, and then the level could be altered from that point to be further increased, but preferably decreased. Furthermore, this first electrical stimulation may be provided while translating the electrode  111  along the stimulation path  1808  while in contact with tissue  1810  in the tissue region  1804 . In response to the applied electrical stimulation applied at various stimulation locations, a neural response may be generated and observed. If no response is generated and/or observed, the electrode  111  or operative element  110  of the stimulator  50  may be relocated  1706  to a different position, within or without the stimulation region  1804 , and a subsequent stimulation  1704  applied. If a neural response is generated and/or observed, the surgeon may identify, measure, and/or document  1708  one or more active stimulation locations  1812  at which such a response is observed. In other words, one or more positions of the electrode  111 , at which a neural response is generated in response to an electrical stimulation, is or are identified, measured, and/or documented  1708 . 
         [0141]    Since the first stimulation is provided at a maximum stimulation level, an active region  1814  including active stimulation locations  1812  is likely to be identified for a given nerve or set of nerve fibers  1802 . This active region  1814  is likely to be smaller in size in at least one dimension than the tissue region  1804  identified to be at least partially stimulated prior. That is, a tissue region  1804  is swept to identify a smaller, or focused, active region  1814 . The sweeping of a stimulation path may be done continuously, or interruptedly, and may be of any pattern, though a zig-zag or spiral pattern is preferred. Once an active region  1814  is identified, which may include one or more of the identified active stimulation locations  1812 , a parameter of the electrical stimulation to be applied is modified or adjusted  1710 . For instance, the stimulation intensity (pulse duration and/or amplitude) could be reduced. After the modification of the stimulation parameter  1710 , then a second electrical stimulation  1704  is applied to the tissue region  1804 . The second stimulation  1704  may be confined to the active region  1814  within the tissue region  1804 , or may extend beyond the active region  1814 . Preferably, the second stimulation  1704  is confined to a second stimulation path  1816  located entirely within the previously identified active region  1814  so as to minimize the stimulation area and reduce the time in which a nerve is located. In response to the second electrical stimulation  1704  applied at various stimulation locations, preferably all contained within the previously identified active region  1814 , a second neural response may be generated and observed. The second neural response may be generated by stimulation of the same nerve or nerve fibers  1802  that were stimulated by the first stimulation. The surgeon may identify, measure, and/or document  1708  one or more active stimulation locations  1822  at which such response is observed. In other words, one or more positions of the electrode  111 , at which a neural response is generated in response to the second stimulation  1704 , is or are identified, measured, and/or documented. 
         [0142]    The process of modifying at least one stimulation parameter and then applying stimulation may be repeated as many times as desired to achieve an active region of a desired size, indicative of present neural fibers. In such iterative application, a previously identified active region preferably becomes the next stimulation region, such that with each iteration, the area of tissue  1810  to be stimulated decreases. If the active region is of a desired size or a given stimulation intensity has been reached, thereby possibly limiting the narrowness of the active region, the method may be ended having identified an active region of a desired size or the method may continue with, for example, an incision that may be made  1712  near the active region in an attempt to, for example, expose the nerve or nerve fibers  1802 . 
         [0143]    In a variation of the second embodiment  1700 , the identification step  1702 , in which a stimulation region  1804  is identified, may be eliminated and replaced by, or supplemented with, a prospecting step. Reference to  FIGS. 17 and 19  may assist in understanding the following explanation. For instance, a surgeon may be completely unaware of a path or paths of nerve fibers  1802  that run beneath or within a tissue  1810  to be stimulated. To determine a desired stimulation region  1804  or active region  1814 , one or more prospecting points  1830  located on or in the tissue  1810  may be selected. An electrical stimulation is applied at one of the prospecting points  1830  using an electrode  111  disposed on an operative element  110  of a stimulation probe  50 . Preferably while in contact with the tissue  1810 , the electrode ill may be moved in a desired pattern to attempt to identify active stimulation locations  1812 . While zig-zag and spiral patterns have already been mentioned, when prospecting a star pattern may prove beneficial. Such pattern may be traced by the electrode  111  in contact with the tissue  1810  in the following manner. Electrical stimulation may be applied at a prospecting location  1830  to determine whether neural response is generated. If no neural response is detected, the electrode  111 , preferably while in contact with the tissue  1810 , may be translated radially outwardly in a first direction  1832  for a first honing distance  1834 . If a neural response is detected, an active stimulation location  1812  may be identified or noted. If no neural response is detected, the electrode  111 , preferably while in contact with the tissue  1810 , may be translated radially inwardly in a second direction  1836  opposite the first direction  1832  through the first honing distance  1834 , back to the prospecting location  1830 . The radially outward translation can then be repeated until at least one active stimulation location  1812  is determined. Subsequent honing translations may be done at through different honing distances  1834  and in different directions, though similar or the same honing distances  1834  are preferred from a given prospecting location. While more than one active stimulation location  1812  may be determined from the process originating at a single prospecting location  1830 , it is preferred that once a first active stimulation location  1812  is located, the electrode  111  may be disengaged from the tissue  1810 , and moved to a subsequent prospecting location  1830 , to continue the prospecting process. After one or more active stimulation locations  1812  have been identified, thereby establishing an active region  1814 , the method embodiment  1700  may then proceed as desired, such as by reducing the stimulation intensity  1708 , and so on. 
         [0144]    The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.