Abstract:
A device, kit and method for monitoring muscle activity. The device may include an electrode having an annular profile substantially similar to that of the muscle. During a monitoring operation, the electrode contacts a substantial portion of the muscle and detects the muscle activity. In some cases, the electrode may be positioned around a catheter device to facilitate advancing of the electrode to the desired muscle. The catheter device may then be advanced through a lumen of the body to the muscle to be monitored. A balloon of the catheter device may be expanded once the catheter device is properly positioned to secure the electrode against the muscle.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The application claims the benefit of the earlier filing date of U.S. Provisional Patent Application No. 61/576,750, filed Dec. 16, 2011 and incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     An apparatus and method for monitoring the activity of muscle tissues, in particular an electrode device for monitoring the electrical activity of muscle tissues of the bladder. Other embodiments are also described and claimed. 
     2. Background 
     Electromyography (EMG) involves testing the electrical activity of muscles. Electromyographic monitoring of muscle tissue within the lower extremities, bowel and bladder using an electromyograph is essential during most spinal cord surgeries. In particular, the electromyograph detects the electrical potential generated by muscle cells when the cells are electrically, mechanically or neurologically stimulated. Based on the activity of the muscle cells, the surgeon can determine whether the surgical operation on the spinal cord is putting the innervating nerve root itself or, in some cases, the innervated muscle at risk. In the case of intramuscular electromyographic monitoring, monitoring is done by inserting needle electrodes into specific muscle groups. Extremity muscles and even the rectal sphincter muscle can be monitored by intramuscular electromyography. For example, in the case of the rectal sphincter, monitoring can be achieved by inserting a needle percutaneously through the skin into the sphincter muscle. It is difficult, however, to monitor deeper muscle groups such as the bladder sphincter using intramuscular electromyography because it is difficult to advance a needle into this region. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following illustration is by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate like elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
         FIG. 1  illustrates a side cut out view of an embodiment of a monitoring device positioned within a bladder. 
         FIG. 2  illustrates a perspective view of the monitoring device of  FIG. 1 . 
         FIG. 3  illustrates a perspective view of another embodiment of a monitoring device. 
         FIG. 4  illustrates the use of a monitoring device on a patient. 
         FIG. 5  illustrates a flow chart of one embodiment of a method for monitoring using the monitoring device. 
     
    
    
     DETAILED DESCRIPTION 
     In this section we shall explain several preferred embodiments with reference to the appended drawings. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not clearly defined, the scope of the embodiments is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments may be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this description. 
       FIG. 1  illustrates a side cut out view of an embodiment of a monitoring device positioned within a bladder. As previously discussed, it is challenging to monitor the electrical activity of deep muscle groups such as the bladder sphincter during surgery using EMG because this area is difficult to reach with a needle. In particular, as can be seen from  FIG. 1 , bladder sphincter  108  is found between bladder  106  and urethra  110 . Bladder sphincter  108  is a circular muscle that constricts the orifice between bladder  106  and urethra  110  and is therefore an important muscle group in preventing conditions such as urinary incontinence. During surgery, particularly a spinal surgery, it is important for the surgeon to be able to monitor bladder sphincter  108  to ensure they are not performing any operations that may compromise the functionality of this muscle. 
     Monitoring device  100  includes electrode  102  that is configured to allow for monitoring of muscle groups such as bladder sphincter  108 . In particular, in one embodiment, electrode  102  may be a ring shaped electrode that can be placed within bladder  106  and contact bladder sphincter  108 . In the preferred embodiment, electrode  108  is a monopolar electrode device. It is contemplated, however, that in other embodiments, electrode  108  may be a bipolar electrode device. In embodiments where electrode  102  is to be used to monitor bladder sphincter  108 , electrode  102  may have a diameter substantially similar to that of bladder sphincter  108 . Since electrode  102  has a similar shape as that of bladder sphincter  108 , electrode  102  can contact a substantial area of bladder sphincter  108  thereby providing an accurate reading of the electrical activity of the entire muscle area. It is important that the electrode  102  contact a substantial area of bladder sphincter  108  as this results in a more accurate EMG signal. 
     Electrode  102  may be held against a substantial area of bladder sphincter  108  by balloon  116 , which in some embodiments is a balloon of a urinary catheter. Representatively, since electrode  102  is positioned near the base of balloon  116 , when balloon  116  is positioned within urethra  106  and pulled toward urethra  110 , it pushes electrode  102  against bladder sphincter  108 . In addition, electrode  102  may have a coiled configuration to increase the electrode&#39;s contact surface with bladder sphincter  108 . For example, electrode  102  may be made of a conductive wire type material that may be coiled and connected at each end to form a coiled structure in the shape of a ring. It is noted, however, that in some embodiments the wire need not be connected at each end to maintain the ring shape. In addition, it is contemplated that electrode  102  may have a modifiable size so that it can monitor muscle groups having a variety of shapes and sizes. For example, the coiled wire forming electrode  102  may have a resiliency similar to a spring that allows it to expand or contract thereby changing or modifying a diameter of electrode  102 . In this aspect, electrode  102  can be securely placed, in one instance, within a muscle group having a large diameter (e.g., larynx) and, in another instance, contracted so that it can be placed within a muscle group having a smaller diameter (e.g., bladder sphincter). The conductive material may be any type of material suitable for insertion within the body. For example, the conductive material may be a nickel alloy, titanium alloy, nickel titanium alloy, stainless steel, or other corrosion resistant alloy. Lead  104  may be connected to electrode  102  and extend out urethra  110  to a monitoring station that can analyze and display the monitoring results to the care provider. For example, lead  104  may be an EMG lead which can transmit electrical signals detected by electrode  102  to an electromyograph. 
     In some embodiments, catheter device  112  may be used to advance monitoring device  100  into bladder  106  and position device  100  against bladder sphincter  108 . Representatively, catheter device  112  may include cannula  114  which is dimensioned to be inserted through urethra  110  and into bladder  106 . Catheter device  112  may include expandable balloon  116  having a proximal portion  118  and distal portion  120 . Balloon  116  can be expanded once positioned within bladder  106  to hold catheter device  112  in place. Electrode  102  is positioned around cannula  114  next to proximal portion  118  of balloon  116 . Electrode  102  may be held at this position around cannula  114  by a clip, adhesive or other similar technique suitable for securing one object to another. In other embodiments, a diameter of ring shaped electrode  102  may be substantially similar to that of cannula  114  such that electrode  102  fits snuggly around cannula  114  and is held in place by frictional forces. In still further embodiments, electrode  102  may be built into an outer surface of the wall forming cannula  114 , for example molded around the outer surface. Additionally, in some embodiments, electrode  102  may be removably attached to cannula  114  so that once electrode  102  is in position, catheter device  112  may be removed from the patient and electrode  102  may remain within the patient for further monitoring. Such a configuration may be desirable, where electrode  102  is used to monitor the electrical activity of a muscle group through which it is desirable to maintain fluid flow (e.g., the esophagus, the larynx etc.). 
     Catheter device  112  is then inserted into urethra  110  with electrode  102  attached and advanced into bladder  106 . Once balloon  116  is positioned within bladder  106 , balloon  116  is expanded. Balloon  116  has a larger diameter than bladder sphincter  108  and therefore prevents catheter device  112  from being removed from bladder  106 . In addition to preventing removal of catheter device  112 , the expansion of balloon  116  secures electrode  102  against bladder sphincter  108 . Lead  104  runs along a side of cannula  114  and out of the patient&#39;s body to a monitoring station. In some embodiments, catheter device  112  is a catheter such as a Foley catheter that is typically inserted into the bladder during surgical operations. In other embodiments, catheter device  112  may be any type of catheter configured to be inserted within the body. 
       FIG. 2  illustrates a perspective view of the monitoring device of  FIG. 1 .  FIG. 2  illustrates monitoring device  100  outside of the bladder so that the various structural components may be more clearly seen. In particular, it can be seen from this view that electrode  102  is made of a coiled wire that has a ring like shape. Lead  104  is attached to electrode  102  and transmits the electrical signals obtained by electrode  102  to a monitoring station. As previously discussed, monitoring device  100  may be positioned within the desired body area, for example the bladder sphincter, using catheter device  112 . In this aspect, electrode  102  may be positioned around a portion of cannula  114  next to proximal portion  118  of balloon  116 . Once catheter device  112  is advanced into bladder  106 , balloon  116  is expanded to hold catheter device  112  and electrode  102  in place against bladder sphincter  108 . It is contemplated, however, that in some embodiments once electrode  102  is at the desired position, balloon  116  may be contracted so that catheter device  112  can be removed while electrode  102  remains in position. 
     In addition, although in one embodiment, electrode  102  includes a coiled, ring shaped structure, it is further contemplated that electrode  102  may have other shapes and sizes.  FIG. 3  illustrates a perspective view of another embodiment of a monitoring device. In this embodiment, monitoring device  300  includes electrode  302  connected to lead  304 . Similar to the electrode of  FIG. 1 , electrode  302  is made of a conductive material and has a ring like configuration, however, in this embodiment, a surface area of electrode  302  is increased by expanding a width (w) of electrode  302  instead of using the coil configuration. In particular, electrode  302  is formed by a thin plate of conductive material having a width (w). The width (w) may be any width suitable to increase a contact area between electrode  302  and the orifice within which it is positioned. For example, in some embodiments electrode  302  may have a width substantially similar to a width of proximal portion  318  of balloon  316  and a funnel like shape that conforms to the surface of balloon  316  such that balloon  316  essentially wedges electrode  302  within the desired orifice. It is further noted that electrode  302  may form a complete ring, a partial ring or may be made of segments that are mounted around catheter device  312 . 
       FIG. 4  illustrates the use of a monitoring device on a patient. The electrode of any of the previously discussed monitoring devices, for example monitoring device  100  or monitoring device  300 , is inserted into the bladder of patient  402  using any of the previously discussed catheter devices. Lead  402  of the monitoring device, which extends out of patient  402  and is connected to a monitoring station such as electronic device  406 , communicates signals from the electrode to electronic device  406 . Electronic device  406  in some cases may be an electromyograph capable of receiving signals (e.g., muscle membrane potential electrical signals) from the electrode and analyzing the signals to detect muscle activation levels. Electronic device  406  may, in some cases, process and display the results on a display screen interface to the health care provider. The health care provider can then review the display and monitor the electrical activity of the muscle tissues being monitored to ensure they are not putting any of the muscle tissues at risk throughout the surgical procedure. 
       FIG. 5  illustrates one embodiment of a process for monitoring muscle activity using any of the previously discussed monitoring devices. Representatively, in one embodiment the monitoring process  500  includes positioning an electrode for monitoring muscle activity around a catheter device (block  502 ). The electrode may be positioned around the catheter device prior to insertion within the patient by, for example, inserting the electrode around a free end of the catheter device cannula and advancing the electrode to a base of a balloon attached to the cannula. Alternatively, in some embodiments, the electrode may be separated along its annulus to form a gap in the ring and the cannula inserted through the gap. Once the electrode is positioned around the catheter, the catheter device can be advanced through a lumen of the body to the muscle to be monitored (block  504 ). Representatively, in the case of monitoring a bladder sphincter muscle, the catheter may be inserted through the urethra and into the bladder such that the balloon is positioned within the bladder while a portion of the cannula extends outside of the body to allow for inflation of the balloon. Once in position, the balloon can be expanded to secure the electrode against the muscle (block  506 ). In particular, since the electrode is positioned at the base of the balloon (portion of the balloon connected to the cannula), when the balloon is expanded the electrode is held affixed between the balloon and the bladder sphincter muscle. 
     In the preceding detailed description, specific embodiments are described. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the claims. For example, although an electrode having a ring shaped configuration for monitoring a bladder sphincter is described, it is further contemplated that the electrode may have any size and shape suitable for monitoring an electrical activity of any muscle tissue within a body cavity that is difficult to monitor. Representatively, the electrode may be configured to monitor muscle cells within the throat such as the larynx, esophagus, stomach, intestines, or rectum. For example, the electrode may be attached to an end of a cannula suitable for advancing through a body lumen connecting to the larynx, esophagus, stomach, intestines or rectum. The cannula can then be advanced through the lumen to the desired muscle group such that the electrode is positioned on or within the muscle group and can monitor the muscle activity. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense.