Patent Publication Number: US-2011060242-A1

Title: Systems and methods for intra-operative stimulation within a surgical field

Description:
RELATED APPLICATIONS 
     This application 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. 
     This application also claims the benefit of U.S. Patent Application Ser. No. 61/338,312, filed Feb. 16, 2010, and entitled “Systems and Methods for Intra-Operative Stimulation,” which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     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 
     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. 
     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 
     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. 
     An embodiment of a method according to the present invention is a method of applying electrical stimulation to animal tissue. The method includes the step of identifying a three-dimensional surgical field comprising a targeted tissue region of an animal. The targeted tissue region may include muscle and/or nerve tissue. A device is provided, which includes a housing extending along a housing longitudinal axis between a housing proximal end and a housing distal end and electrical stimulation generation circuitry at least substantially contained within the housing. The device is preferably at least substantially sterile. Also provided are one or more user operable controls coupled to the housing and in operational communication with the electrical stimulation generation circuitry. Extending from the housing proximal end is an operative element comprising an electrode operatively coupled to the electrical stimulation generation circuitry. Also substantially contained within the housing is a power supply that is electrically coupled to the electrical stimulation generation circuitry. The device may be entirely inserted or introduced into the surgical field, and an electrical stimulation, generated by the electrical stimulation generation circuitry and delivered through the electrode may be applied to at least a portion of the targeted tissue region. This applying step may be carried out while the entire device or device housing is placed entirely within the surgical field. 
     According to one aspect of the invention, the surgical field, which may be at least substantially sterile, may extend from the targeted tissue region for a maximum length of thirty centimeters. Additionally or alternatively, the surgical field may be about 20 to about 50 millimeters wide, about 18 to about 22 centimeters long, and about 20 to about 50 millimeters deep. 
     According to another aspect of the invention, a method may further include the step of carrying the device by a single human hand. Preferably, the single human hand may be used to manipulate the device to change an electrical stimulation parameter of a stimulation to be generated by the electrical stimulation generation circuitry. Even more preferably, the manipulation may be carried out while the entire housing is positioned within the surgical field. 
     According to still another aspect of the present invention, the provided device may further include an electronic visual indicator operatively coupled to the stimulation circuitry. In performing a method according to the present invention, a first visual indication provided by the visual indicator may be observed, where the first visual indication is indicative of electrical power supplied to the stimulation circuitry by the power supply. Further, a second visual indication provided by the visual indicator may be observed, where the second visual indication is indicative of electrical stimulation flowing at least partially through the targeted tissue region. Where two visual indications may be observed, they may be different. For example, the first visual indication may be an illumination of a first color and the second visual indication may be an illumination of a second color, the second color being different from the first color. Additionally, or alternatively, the illuminations may be of a different flash pattern, such as being illuminated continuously, or having a flashing pattern. 
     According to yet another aspect of the present invention, the visual indicator may be an illumination device that is radially visible from 360 degrees around the longitudinal axis of the handle, and it may be situated between one of the user operable controls and the electrode. 
     In another embodiment of a method according to the present invention, a method of applying electrical stimulation to a targeted animal tissue region includes the step of receiving, into a single human hand, a device. The device includes a housing extending along a housing longitudinal axis between a housing proximal end and a housing distal end, electrical stimulation generation circuitry at least substantially contained within the housing, and one or more user operable controls coupled to the housing and in operational communication with the electrical stimulation generation circuitry. Extending from the proximal end of the housing is an operative element which includes an electrode operatively coupled to the electrical stimulation generation circuitry. Also contained at least substantially within the housing is a power supply that is electrically coupled to the electrical stimulation generation circuitry. The method further includes the step of generating a first indication, which is indicative of electrical power being supplied to the electrical stimulation generation circuitry. In another step, a first electrical stimulation is provided from the stimulation generation circuitry to the electrode. A second indication may be generated, which is indicative of the first stimulation is being provided to the stimulating tip and is further indicative of the first stimulation being prevented from being received by the device through a return electrode. While the method may end here, it is preferred to again apply the first electrical stimulation to a targeted animal tissue region and generate a third indication, which is indicative of the first stimulation being received by the device through the return electrode. 
     According to another aspect of the present invention, all of the indications are generated within a three-dimensional surgical field including the targeted tissue region. One or more of the indications may be visual or audio indications. Visual indications may be generated by a visual indicator disposed between the stimulating tip and all user operable controls. 
     According to an aspect of a visual indicator according to the present invention, the visual indicator may include a light ring having a proximal surface and a distal surface coupled by an oblique annular surface. Either or both of the proximal and/or distal surfaces may include a circular perimeter. In a preferred configuration, the distal perimeter is smaller than the proximal perimeter. Light may be transmitted through the light ring annular surface, distally away from the electrode. A visual indicator according to the present invention may further include a reflective element mounted adjacent the proximal surface of the light ring. 
     In another embodiment of a method according to the present invention, a method of applying electrical stimulation to a targeted animal tissue region includes the step of receiving, into a single human hand, a device. The device includes a housing extending along a housing longitudinal axis between a housing proximal end and a housing distal end, electrical stimulation generation circuitry at least substantially contained within the housing, and one or more user operable controls coupled to the housing and in operational communication with the electrical stimulation generation circuitry. Extending from the proximal end of the housing is an operative element which includes an electrode operatively coupled to the electrical stimulation generation circuitry. Also contained at least substantially within the housing is a power supply that is electrically coupled to the electrical stimulation generation circuitry. The housing may further include a gripping portion comprising a location channel extending longitudinally distally from one of the user operable controls. The method may include using a finger of the hand, preferably the index finger, to identify the location channel. One of the user operable controls which is proximal the location channel may be located and then manipulated. The user operable control may be located by sliding the finger proximally along the location channel. All of the steps of this method may be performed within a three-dimensional surgical field. Alternatively, one or more of the steps, such as the step of receiving the device, may be performed outside of a surgical field. 
     According to an aspect of a relationship between the operative element and the location channel provided on the device, the operative element may include an angled or curvilinear portion, thereby defining an operative element plane. The location channel and/or the located user operable control may be disposed substantially coplanar with the operative element plane. 
     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 
         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. 
         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. 
         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. 
         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. 
         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. 
         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. 
         FIG. 4B  is a side view of the stimulation probe of  FIG. 4A , showing the users hand flexing the flexible nose cone. 
         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. 
         FIG. 6  is a graphical view of a desirable biphasic stimulus pulse output of the stimulation device. 
         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. 
         FIG. 8  is a block diagram of a circuit that the stimulation control device shown throughout the FIGS. can incorporate. 
         FIGS. 9A and 9B  are perspective views showing the stimulation control device in use with a cutting device. 
         FIGS. 10A and 10B  are perspective views showing the stimulation control device in use with a drilling or screwing device. 
         FIGS. 11A and 11B  are perspective views showing the stimulation control device in use with a pilot auger device. 
         FIGS. 12A and 12B  are perspective views showing the stimulation control device in use with a fixation device. 
         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. 
         FIG. 14  is a perspective view of the stimulation probe shown in  FIG. 3C . 
         FIG. 15  is an exploded view of the stimulation probe shown in  FIG. 14 . 
         FIG. 16  is a side elevation view of a light permeable ring which may be used as a part of a visual indicator according to the present invention. 
         FIG. 17  is a distal elevation view of the ring of  FIG. 16 . 
         FIG. 18  is a partial assembly view of an embodiment of a device according to the present invention using the ring of  FIG. 16 . 
         FIG. 19  is a perspective view of an embodiment of a device according to the present invention depicting a relationship between a location channel, a user operable control, a visual indicator, and a user operable element. 
     
    
    
     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 
     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. 
     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. 
     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 
       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 . 
     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. 
     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 
     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 
       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. 
     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. 
     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). 
     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 . 
     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. 
     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 . 
     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. 
     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 . 
     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. 
     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. 
     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. 
     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 . 
     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. 
     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. 
     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 . 
     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. 
     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. 
     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 ). 
     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. 
       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. 
     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. 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. 
     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 
     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. 
     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. 
     C. Incorporation with Surgical Devices 
     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 
     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 . 
     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). 
     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 . 
     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 . 
     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). 
     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. 
     Additionally, the device  200  may incorporate a visual or audio indicator for the surgeon, as previously described. 
     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 
     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 . 
     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). 
     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). 
     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 . 
     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 . 
     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. 
     Additionally, the device  300  may incorporate a visual or audio indicator for the surgeon, as previously described. 
     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 
     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. 
     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). 
     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 . 
     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 . 
     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. 
     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. 
     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. 
     D. Incorporation with Fixation Devices 
     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. 
     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). 
     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 . 
     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 . 
     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. 
     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 . 
     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 
     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 
     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. 
     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 
     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 
     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). 
     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 
     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. 
     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. 
     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 .   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.       

     The problems prior to introduction of embodiments of the device disclosed herein were that current tissue stimulators did not provide an adequate range of stimulus intensity, could not reliably reproduce the stimulus, and did not have an intuitive feel and ergonomic form factor. 
     An intuitive feel and ergonomic form factor allows a surgeon to operate the device with one hand without diverting attention from the surgical field, which is where the surgeon&#39;s attention must be focused at substantially all times. A surgical field perimeter may be conventionally defined physically by a surgical drape, for example. A three-dimensional surgical field may be surrounded by such perimeter, and include a targeted tissue region to receive electrical stimulation. The three-dimensional field further extends away from the animal body, substantially perpendicular to a tangent of the body portion surrounded by the surgical drape. While a method of defining a surgical field has been disclosed, it is to be understood that embodiments of methods according to the present invention may be performed in a surgical field including a targeted tissue region, wherein the surgical field is preferably a maximum size of about 5 centimeters wide, by about 5 centimeters deep, by about 30 centimeters long. 
     Prior devices are large and bulky and frequently require a remote console controlled by a second physician or technician. This results in the inability by the surgeon to coordinate the application of the stimulus and the observation of the area being stimulated and the response. Such remotely operated units do not afford the surgeon adequate control and are unwieldy and costly to operate because of the extra manpower required. 
     An embodiment of a hand-held tissue stimulation system including features as disclosed herein is advantageous to allow a surgeon to remain focused and concentrated on a targeted tissue region, while at the same time altering electrical stimulation parameters and receiving substantially simultaneous or instantaneous situational feedback, both of which may occur within an established operating, or surgical, field. Procedures in which devices such as that disclosed may be performed under a microscope upon structures of very small size; therefore, the ability to manipulate and precisely control such device with only one hand without having to look away from the microscope may be highly desirable because movement of the tip (stimulation probe) by, for example, less than 1 millimeter may completely change the response. 
     Preferred methods according to the present invention include the placement of an entire handheld electrical stimulation device into a surgical, operating field, manipulating electrical stimulation parameters, and observing visual feedback from the device. The manipulation of electrical stimulation parameters preferably occurs manually within the surgical, operating field, and the feedback is preferably generated within the operating field, which may consist of visual feedback to be perceived by a surgeon&#39;s peripheral vision or audio feedback to be heard by the surgeon. 
     Several features of the present invention assist in providing an improved, intuitive, successful experience for the surgeon. 
     One aspect of embodiments of the present invention adding to ergonomic methods of intraoperative neural stimulation are the user operable controls  155 ,  160 . Both the type and positioning of the user operable controls  155 ,  160  are thought to improve operability. First, the housing  112  and/or overmolding  68  has a circumferential surface  73  formed about a housing longitudinal axis  75 , as can be seen in  FIG. 5 . At least one user operable control, such as the pulse control device  160 , preferably protrudes radially away from the housing longitudinal axis  75  beyond the housing surface  73  to enable the pulse control device  160  to be located by touch. 
     Another aspect of embodiments of the present invention that assists an ergonomic intraoperative neural stimulation is the gripping base portion  60 . As noted above, gripping base portion  60  of the housing  112  may also include an overmolded portion  68 . The overmolded portion  68 , which is preferably formed from a material that is softer than the housing  112 , may comprise the full length of the gripping base portion  60 , or only a portion of the gripping base  60 , such as that shown on  FIG. 19 . The softer 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 ribs  70  are preferably disposed distally from at least one user operable control, such as the pulse duration control  160 . Additionally, the overmolded portion  68  may include a location channel  77 , which may extend longitudinally towards the user operable control  160 , and be circumferentially aligned with the user operable control  160 . Accordingly, while the overmolded portion  68  is generally provided to improve grip, the location channel  77  may serve to provide the surgeon with the ability to, by touch only, determine in which rotational position the device is in his or her hand. Furthermore, because the softer, overmolded portion  68  is not present in the channel  77 , and the preferably harder plastic housing  112  is located therein, a surgeon&#39;s finger may more readily slide along the channel  77  towards the user operable control  160 . The result is that the surgeon is provided with a mechanism to more easily determine both the rotational position and the location of the user operable control  160  to be adjusted during stimulation. It is preferred that, if the location channel  77  is provided, that the ribs  70  are provided on either side of the channel  77  to allow engagement with, for example, a surgeon&#39;s thumb on one side and another finger, such as the middle or ring finger, on the other side. 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 . 
     Referring now to  FIGS. 16-18 , yet another aspect of embodiments of the present invention, which assist in improved intraoperative stimulation, is the visual indicator  126 . Preferably, the visual indicator  126  is located between at least one user operable control, such as the pulse duration control  160 , and the stimulating tip  111  and/or the operative element  110 . Even more preferably, the visual indicator  126  is located between all user operable controls and the stimulating tip  111 . Such positioning places the visual indicator  126  in a surgeon&#39;s peripheral field of vision during an intraoperative stimulation, allowing the surgeon to remain focused on the targeted tissue region. 
     A preferred visual indicator  126  includes a light ring  128  and at least one light source  140 , which may comprise a light emitting diode (LED)  142 . More preferably, the visual indicator  126  includes a plurality of light sources  140 , which may include a plurality of LED&#39;s  142   a ,  142   b ,  142   c  arranged in a desirable pattern, preferably surface mounted to a printed circuit board  144 . The light ring  128  has a proximal surface  146 , which is preferably a planar surface having a first diameter  148 . The light ring  128  has a distal surface  150 , opposed from the proximal surface  146 . The distal surface  150  is preferably a planar surface having a second diameter  152 . The second diameter  152  is preferably smaller than the first diameter  148 . The distal surface  150  is preferably at least substantially parallel to the proximal surface  146 , and disposed at a ring thickness  154  therefrom. The light ring  128  further preferably includes an annular surface  156  disposed between the proximal surface  146  and the distal surface  150 , where the annular surface  156  is oriented at an angle  158  that is neither parallel to the housing axis  75 , when the device is assembled, nor orthogonal thereto. 
     The annular surface  156  may extend completely between the proximal surface  146  and the distal surface  150 , or only partially therebetween, as shown in  FIG. 16 . The annular surface  156 , disposed at such oblique angle, assists in transmitting a majority of the light generated by the light source  140  distally, away from the stimulating tip  111 . 
     The light ring  128  further includes support structure, to assist in coupling the ring  128  to the housing  112 . Preferably, the ring  128  is provided with a retention flange  162  spaced from but preferably parallel to the distal surface  150 . The retention flange  162  is coupled to the distal surface  150  and provides a mounting channel  164  between the flange  162  and the distal surface  150 . The mounting channel  164  is adapted to receive a portion of the housing  112  when the device is assembled so as to prevent longitudinal and radial displacement, and also rotation, of the ring  128  with respect to the housing  112 . Provided in addition to the retention flange  162  is an optional circuit board support tab  166 , extending preferably substantially orthogonally from the distal surface  150 , providing an extended circuit board support surface  168 . 
     A plurality of apertures may be provided through the light ring  128 . A first aperture  170  may provide a passageway to allow electrical coupling of the operative element  110  to the electrical stimulation generation circuitry  22  contained within the housing  112 , such as through a friction-fit connector  172  mounted on the printed circuit board  144 . The same opening  170  preferably provides a light shroud including a circuit board support surface  174  and a light receiving surface  176 . Once assembled onto the device, the light source(s)  140  are disposed substantially within the opening  170  between the circuit board support surface  174  and the light receiving surface  176 . The light receiving surface  176  is preferably disposed substantially perpendicular to the dominant viewing angle of the light source(s)  142 . For instance, a preferred light source  142  is a surface mount LED, such as PLCC surface mount LEDs available from Avago Technologies. Such LEDs have a dominant viewing angle which is substantially perpendicular to the surface onto which the LEDs are mounted. The LEDs have a viewing angle of about 120 degrees. A preferred arrangement of light sources  142  includes the use of three light sources  142   a ,  142   b ,  142   c . The three light sources are preferably aligned in a row on the printed circuit board  144 . While one or more colors of LEDs could be used, it is preferred that at least two colors are provided. For instance, light sources  142   a  and  142   c  could be amber LED&#39;s having a dominant wavelength of about 592 nanometers, and light source  142   b  could be a red LED having a dominant wavelength of about 630 nanometers. While the LEDs could be arranged in any desirable order, it is preferred to provide a balanced light output. Accordingly, it may be preferred to dispose the two amber LEDs  142   a ,  142   c , one on either side of the red LED  142   b , thereby preventing any light bias and providing a balanced light output. Thus, the LEDs  142   a ,  142   b ,  142   c  are disposed on the printed circuit board  144 , which is inserted into the aperture  170  to rest adjacent the circuit board support surface  174 . 
     Directionality of light provided through the light ring  128  is thought to improve the usefulness of devices according to the present invention, especially in situations where light indications are to be observed in a surgeon&#39;s peripheral field of vision. While part of the light directionality is provided by the design of the light ring  128 , itself, such directionality may be enhanced by the inclusion of a reflective element  129  disposed adjacent to or formed as a part of the light ring  128 . The reflective element  129  preferably includes a white distal surface  178 , which is a preferably substantially planar surface adapted to rest adjacent the proximal surface  146  of the light ring  128 . The distal surface  178  of the reflective element  129  aids in directing light through the light ring  128  and out of the annular surface  156  thereof. The reflective element  129  also preferably includes an aperture  180  therethrough, which may mate with the aperture  170  formed through the light ring  128  to allow connectivity of the operative element  110  to the stimulation generation circuitry  22 . 
     The light ring  128  is preferably formed as a unitary member including the proximal surface  146 , the distal surface  150 , and the optional retention flange  162  and circuit board support tab  166 . The light ring  128  is preferably formed from a substantially optically clear material and preferably has a highly polished annular surface  156 , so as to provide a desired transmittance. 
     The operation of the visual indicator  126  is informational to a user. The visual indicator  126 , through various color and flash pattern indications, informs the surgeon more than just when a nerve has been stimulated, it informs the surgeon whether the electrical flow path of the stimulation signal is complete. That is, when the flow path is complete, the visual indicator  126  informs the surgeon that the stimulation circuitry  22  is generating a stimulation signal, the stimulation signal is being delivered to the stimulating tip  111 , the stimulation signal is passing through tissue at the targeted tissue region, and that the stimulation signal is being received at the stimulation circuitry  22  through the return electrode  130 . This status of the device, in combination with observation of the neural response to the applied stimulation, provides the surgeon the ability to assess the health of a nerve. 
     The visual indicator  126  provides stimulation system status conditions, the status conditions including (i) confirmation of electrical power provided to the stimulation generation circuitry  22 , such as by continuous amber or yellow lighting of LEDs  142   a  and  142   c , (ii) confirmation of stimulation availability at the stimulating tip  111 , such as by flashing of either the amber LEDs  142   a ,  142   c  or the red LED  142   b , and (iii) confirmation of stimulation delivery to the targeted tissue region, such as by flashing of either the amber LEDs  142   a ,  142   c  or the red LED  142   b . The power supply, including the battery  34 , is configured such that, once power is supplied to the circuitry  22 , the visual indicator  126  will illuminate for confirmation of such power provision, and the visual indicator  126  preferably cannot be turned off, until the battery charge dissipates completely, or is otherwise removed from the device. 
     Still another aspect of embodiments according to the present invention adding to the usability of intraoperative stimulation is the provision of stimulation parameters to allow for continuous stimulation during translation or relocation of the stimulating tip  111 , while maintaining contact with tissue or even during stimulation parameter adjustment without causing tissue damage. Indeed, stimulation pulse trains may continually be generated, at a desired frequency, while the electrode is in contact with a targeted tissue region, as well as during periods of stimulation parameter adjustment. Thus, a method according to the present invention includes providing an electrical stimulation device, such as embodiments described herein, including an operative element having an electrode stimulating tip disposed thereon. The electrical stimulation is started at a desired, predetermined, or established frequency, where electrical stimulation pulses having specified duration are supplied to the electrode at such frequency. Electrical stimulation is continued at the desired frequency while one or more electrical stimulation parameters, such as amplitude and duration, are adjusted. Alternatively, or additionally, electrical stimulation is applied to a targeted animal tissue region during the adjustment or alteration of the electrical stimulation parameters. Alternatively, or additionally, electrical stimulation is applied to a targeted animal tissue region during translation of the electrode across and in electrically communicative contact with the tissue region. Thus, while electrical stimulation is being delivered at a frequency, either or both of the following actions may be performed: (i) translating or moving of the electrode in contact with the tissue region; and (ii) adjusting or altering electrical stimulation parameters, such as amplitude and/or pulse duration. All of these actions may be performed while receiving feedback from the indicator  126  provided on the device. Accordingly, while allowing a surgeon to maintain focus on a targeted tissue region, methods according to the present invention improve the ergonomic and intuitive use of an electrical stimulator, by allowing substantially simultaneous electrode/tissue translation, adjustment of electrical stimulation parameter(s) and informational feedback. 
     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.