Abstract:
A medical instrument for obtaining access to a site within the body directly inserted through the skin or through an incision in the skin to enable introduction of further medical instruments to the percutaneously accessed site or from the percutaneously accessed site to a more remote site in the body. The instrument comprises a combined medical probe and flexible guide wire for introduction of the further elongated diagnostic or surgical or therapy delivery devices over the guide wire and probe. The combined medical probe and flexible guide wire further comprises a stiff tissue penetrating probe having a probe length between a probe proximal end and a probe distal end, the probe length shorter than the elongated medical device length, and a flexible guide wire body having a guide wire length between a guide wire body proximal end and a guide wire body distal end, the guide wire distal end coupled to the probe proximal end, the guide wire length sufficiently long to support the elongated medical device to enable its over-the-wire advancement over the guide wire body and probe.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a medical instrument for obtaining access to a site within the body directly inserted through the skin or through an incision in the skin to enable introduction of further medical instruments to the percutaneously accessed site or from the percutaneously accessed site to a more remote site in the body, and more particularly to a combined medical probe and flexible guide wire (or guidewire) for introduction of the further elongated diagnostic or surgical or therapy delivery devices over the guide wire and probe. 
     2. Description of Related Art 
     Numerous medical procedures have come into common usage for accessing a site within the body in a minimally invasive manner that avoids surgical exposure of the site to perform a wide variety of diagnostic and therapeutic procedures involving use of a small diameter probe (defined herein as including a needle, a stiff wire, a trocar or the like). Such medical procedures generally involve use of the probe to create a percutaneous (also referred to in the art as transcutaneous or trans-dermal) pathway through the skin and subcutaneous tissue. The probe is either pushed or stuck directly through the patient&#39;s skin or is inserted through a small surgical incision in the skin to a particular percutaneously accessed site of interest or to a starting point of an access pathway to a remote site of interest. Then, the percutaneous pathway is expanded in a variety of ways to enable insertion of larger diameter diagnostic, surgical or therapeutic devices. In the course of such procedures, it is common to advance introducers, dilators, and other tubular instruments over the probe and over one another in a prescribed sequence to enlarge the percutaneous pathway by spreading tissue apart. The probe is removed at a particular point in the procedure depending upon the selection of instruments that are used in the sequence of enlarging the percutaneous pathway. 
     In one approach, the percutaneous pathway that is finally created is defined by the lumen of a hollow tubular catheter or introducer or the like extending from the skin to the accessed site to enable passage of therapeutic or diagnostic or surgical devices therethrough to the accessed site. In another approach, the percutaneous pathway is defined by the outer guiding surface of a hollow or solid core stylet or guide wire extending from the skin to the accessed site to enable over-the-wire advancement of therapeutic or diagnostic or surgical devices to the percutaneous access site. 
     When the percutaneously accessed site is the site of interest, a diagnostic, surgical or therapeutic device is introduced through the expanded percutaneous pathway in the through-the-lumen or over-the wire manner to perform a procedure or deliver a therapy to the accessed site. 
     When a more remote site is the site of interest, the same or a further accessing instrument or tool, e.g. an elongated catheter or cannula or guide wire (or a combination of the same used in a predetermined sequence), is advanced through the percutaneous pathway and from the percutaneously accessed site through a remote access pathway to the remote site of interest. The access pathway may be a vascular pathway from an incision into a vein or artery at the percutaneously accessed site that is employed to introduce cardiac catheters and leads or vascular instruments for diagnostic, therapeutic or surgical procedures at remote sites in the heart or in the vascular system. Or the access pathway may be through or into a body organ or cavity or lumen or other structure to the remote site of interest. 
     Usually, the percutaneous pathway is relatively straight, but the access pathway twists and turns following the anatomy of the body. Typically, the accessing instrument that is left in place extending to the remote site comprises a flexible guide wire or guide catheter that can bend to follow the access pathway. The flexible guide wire or guide catheter then extends from an accessible proximal end left outside the patient&#39;s body through the percutaneous pathway and the access pathway to a distal end advanced to the remote site. Then, a diagnostic or surgical or therapeutic instrument is introduced over-the-wire or through-the-lumen to enable a diagnostic or surgical procedure or to provide a therapy at the remote site. 
     Many therapeutic and/or diagnostic procedures have been developed that involve obtaining access to a desired percutaneous access site or remote site in the body as described above and the implantation of a temporary or permanent electrical stimulation lead, sensor bearing lead or drug delivery catheter that is coupled with a permanently implanted or external pulse generator and/or monitor or drug delivery device. In many procedures, it is desirable to insert a therapeutic or diagnostic lead or catheter having as small an outside diameter as is possible to locate a distal segment thereof at a desired site while minimally displacing body tissue. The electrical stimulation lead, sensor bearing lead or drug delivery catheter is implanted via such a percutaneous pathway and typically extends through an access pathway to locate electrical sensing and/or stimulation electrodes or sensors or drug delivery outlets at the remote site. In permanent implantation procedures, the proximal ends of such sensor and/or electrode bearing leads or catheters are coupled to implantable pulse generators and/or monitors or drug delivery devices that are implanted subcutaneously near the percutaneous pathway or at a distance from the percutaneous pathway. In the latter case, the lead or catheter is relatively long or is attached to a relatively long lead or catheter body that is implanted through a subcutaneous tunnel to the remote medical device. 
     For example, access to the epidural space of the spinal column and to introduce a stimulation lead into the epidural space is disclosed in commonly assigned U.S. Pat. No. 5,255,691. An epidural needle assembly is employed to reach a percutaneously accessed site in the epidural space, and a stylet stiffened stimulation lead is introduced through the needle lumen and advanced past the percutaneously accessed site through an access pathway in the epidural space to position the lead electrodes at a remote site still within the epidural space. The needle and stylet are withdrawn, and the lead connector elements are connected with an implantable neurostimulator that is implanted subcutaneously in the body. 
     As noted above, the initial step in forming a percutaneous pathway typically involves use of a probe, such as a stiff, sharp tip or blunt tip, straight needle, that is advanced by a clinician from the skin or skin incision to the percutaneously accessed site. In most cases, the probe is aimed in a carefully determined direction from the skin to the site so that the distal tip of the needle reaches the site of interest with the needle axially aligned to body feature that must be accessed. For example, percutaneous pathways are formed to allow miniaturized neurostimulation leads to be advanced into the spinal column as disclosed, for example, in the above-referenced &#39;691 patent, or through a foramen of the sacrum (as disclosed, for example, in commonly assigned U.S. Pat. Nos. 5,957,965, 6,104,960 and 6,055,456) in carefully determined and particularly sensitive directions. 
     The direction of advancement of the needle or other probe in three-dimensional space is determined in advance by use of radiographic imaging or palpation of tissue or stealth station technology. The probe is then carefully held and advanced from the skin so that it is axially aligned with the predetermined direction. This procedure is most easily accomplished using a probe that is no longer than necessary to extend from the skin to the percutaneously accessed site. It is easier to accurately aim and advance a short probe than a long probe that extends away from the skin. The probe is necessarily small in diameter and stiff, and such a probe tends to flex and bend in direct relation to its length. Thus, a long probe can bend as it is advanced and depart from the intended direction. Moreover, the probe becomes more difficult to aim and hold to a desired direction as its length increases, because slight deviations from the intended direction are magnified through the length of the probe. 
     Therefore, relatively short probes are employed having a shorter exposed length extending from the skin than the length of a lead or catheter or instrument that is to be advanced through the percutaneous pathway. Typically, the probe length is shorter than the overall length of the lead or catheter which usually includes a proximal segment that is to be extended to an external or implanted device located or implanted at a distance from the percutaneous pathway. Thus, it is not possible to grasp the proximal end of the probe if an attempt is made to advance any such lead or catheter or instrument over the probe to maintain the carefully determined direction of insertion of the probe. 
     We have found that it would be desirable to be able to employ the probe itself to guide longer dilators or surgical instruments or leads or catheters or the like in an over-the-wire manner to a remote site or just to the percutaneous access site to minimize the number of instruments used and steps in the procedure. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention recognizes and provides a solution to the problems associated with defining a percutaneous pathway for over-the-wire advancement of a therapeutic or diagnostic instrument or a pathway expanding instrument. 
     In accordance with a preferred embodiment of the invention, a combined percutaneous medical probe and guide wire is employed to form a percutaneous pathway to a percutaneously accessed site and enables over-the-wire advancement of an elongated medical device to the percutaneously accessed site and into an access pathway. The combined medical probe eliminates the need to introduce a separate guide wire to the percutaneously accessed site. 
     The combined percutaneous medical probe and guidewire comprises a stiff tissue penetrating probe having a first length adapted to provide the percutaneous pathway to the percutaneously accessed site of interest. The tissue penetrating probe is coupled with a flexible guide wire body that remains entirely or substantially outside the body having a second length sufficiently long to support the full length of the elongated medical device to enable its over-the-wire advancement. The tissue penetrating probe is adapted to be manually grasped, aligned axially in a predetermined direction, and advanced from the skin to the percutaneously accessed site while the flexible guide wire droops away from the attachment with the proximal end of the probe. Thus, the relatively short probe is more readily and accurately aligned to the predetermined direction to facilitate accurate advancement. Then, a further instrument, e.g. a dilator having a through-lumen, can be advanced over the flexible guide wire body and distally over the probe to dilate the tissue surrounding it if necessary. An elongated medical device having a through-lumen comprising one of a lead or a catheter or a surgical instrument can be inserted over the combined flexible guide wire body and the probe to locate a distal end thereof at the percutaneously accessed site or through the percutaneously accessed site to a remote site in the body. 
     The percutaneously accessed site is typically within a vessel or organ lumen or within the brain or within a body cavity that is reached by the distal end of the probe that is passed through the skin and subcutaneous tissue. The combined medical probe can be employed as a test stimulation or electrical sensing lead to apply electrical stimulation to responsive tissue, e.g., muscle or nerve fibers or brain cells, or to receive electrical signals from tissue at the percutaneously accessed site. The probe is preferably formed of conductive metal and electrically insulated along its length except for a stimulation or sense electrode area at or adjoining the probe distal tip. The flexible guide wire is preferably formed of an electrical conductor that is electrically insulated along its length except for a proximal electrode connector element. 
     Preferably, the probe is formed of a needle with a closed distal tip to prevent coring of tissue. The flexible guide wire body is preferably formed of a coiled wire within an insulating sheath having a guide wire body diameter about equal with the diameter of the needle. An inextensible core wire is fixed to and extends from the exposed proximal end of the coiled wire through the coiled wire lumen and the needle lumen to the beveled needle distal tip and thereby inhibits stretching of the guide wire body and coring of tissue by the needles distal tip. Alternatively, the core wire can be affixed more proximally within the needle lumen or otherwise fixed to the needle proximal end, and the needle lumen can be filled with a further wire or filler material to provide an equivalent structure. The continuous core wire provides a continuous electrical conductor that is relatively noise free when the combined medical probe and guide wire is used as a stimulation or electrical sensing lead. 
     One preferred use of the combined percutaneous medical probe and guide wire is to form a percutaneous pathway to a sacral nerve that can be accessed in a posterior approach through a foramen of the patient&#39;s sacrum where the sacral nerve extends anteriorly and inferiorly so as to place an implantable neurostimulation lead electrode in operative relation with the sacral nerve. In this procedure, it is important to accurately insert the probe tip into the foramen at a prescribed angle to access the sacral nerve without damaging it. The sacral nerve response to applied electrical test stimulation can be assessed at differing depths of insertion of the exposed distal tip electrode to map the optimal location of the lead electrode. 
     If necessary, dilation of tissue around the probe can be undertaken. A dilator can be advanced over the guide wire body until the guide wire proximal end is exposed from the dilator lumen at the lead body proximal end. The guide wire body can be straightened to enable advancement of the dilator over the probe and withdrawal of the dilator. 
     A neurostimulation lead can be advanced over the guide wire body until the guide wire proximal end is exposed from the lead body lumen at the lead body proximal end. 
     The guide wire body can be straightened to enable advancement of the lead over the probe until the neurostimulation lead electrode(s) is optimally advanced into operative relation to the sacral nerve. The sacral nerve response to applied electrical test stimulation can also be tested using the neurostimulation lead as the lead electrode is advanced. The combined probe and guide wire can be retracted from the lead body lumen when the testing is completed and the distal stimulation electrode(s) is optimally placed. The implantation procedure of the present invention employing the combined percutaneous medical probe and guide wire to form a percutaneous pathway for implanting a neurostimulation lead allows more rapid placement of the stimulation electrodes near the sacral nerves. 
     A similar procedure can be undertaken using the to implant leads and catheters or to guide tissue expanding introducers or dilators to other percutaneously accessed sites using the combined percutaneous medical probe and guide wire is to form a percutaneous. pathway. For example, the combined percutaneous medical probe and guide wire can be used to form a percutaneous pathway into the epidural space of the spinal column, into or adjacent to the stomach wall for the treatment of stomach disorders such as gastroparesis, into the large intestine for treatment of a paralyzed bowel condition or delayed bowel. Moreover, the combined percutaneous medical probe and guide wire can be used to form a percutaneous pathway through chest wall into the pericardial sac to provide a pathway to advance a cardiac pacing lead for treatment of bradycardia or a lead bearing a physiologic sensor to the pericardium. The lead may have a fixation mechanism for affixing pace/sense electrodes against the pericardium or into the myocardium. 
     This summary of the invention has been presented here simply to point out some of the ways that the invention overcomes difficulties presented in the prior art and to distinguish the invention from the prior art and is not intended to operate in any manner as a limitation on the interpretation of claims that are presented initially in the patent application and that are ultimately granted. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention are illustrated in the drawings, wherein like reference numerals refer to like elements in the various views, and wherein: 
     FIG. 1 is a plan view of a preferred embodiment of the combined percutaneous medical probe and guide wire of the present invention. 
     FIG. 2 is a side cross-section view of the guide wire construction taken along lines  2 — 2  of FIG.  1 . 
     FIG. 3 is an end cross-section view of the guide wire construction taken along lines  3 — 3  of FIG.  1 . 
     FIG. 4 is an end cross-section view of the guide wire construction taken along lines  4 — 4  of FIG.  1 . 
     FIG. 5 is a schematic illustration of the percutaneous advancement of the medical probe of the combined percutaneous medical probe and guide wire to a percutaneously accessed site through a foramen of the sacrum. 
     FIG. 6 is a schematic illustration of the percutaneous advancement of the medical probe of the combined percutaneous medical probe and guide wire to a percutaneously accessed site through a foramen of the sacrum. 
     FIG. 7 is a schematic illustration of the straightening and insertion of the guide wire body proximal end into the through-lumen of an elongated neurostimulation lead. 
     FIG. 8 is a schematic illustration of the advancement of the elongated neurostimulation lead over the combined percutaneous medical probe and guide wire to locate the lead electrodes at the percutaneously accessed site adjacent to the sacral nerve. 
     FIG. 9 is a schematic illustration of the withdrawal of the combined percutaneous medical probe and guide wire through the through-lumen of the elongated neurostimulation lead leaving the lead electrodes at the percutaneously accessed site adjacent to the sacral nerve. 
     FIGS. 10 a - 10   c  illustrate a preferred dilator formed of the assembly of a dilator body and a dilator sheath usable in the procedure illustrated in FIGS. 5-9 to dilate the percutaneous pathway to facilitate introduction of the neurostimulation lead either over the combined percutaneous medical probe and guide wire of through the lumen of the dilator sheath. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of the combined probe and guide wire of the present invention is depicted in FIGS. 1-4, and a preferred use is depicted in FIGS. 5-9 optionally including the use of the dilator of FIGS. 10 a - 10   c  described further below. The combined probe and guide wire  100  comprises a stiff tissue penetrating probe  112  having a probe length between a probe proximal end  114  and a probe distal end  116  and a flexible guide wire body  120  having a guide wire length between a guide wire body proximal end  122  and a guide wire body distal end  124 . The guide wire body distal end  124  is coupled to the probe proximal end  114 . 
     The combined percutaneous medical probe and guide wire  100  is preferably covered along its length by an insulating coating  126  except for a distal exposed area providing an exposed electrode  128  for delivering stimulation to body tissue and an exposed electrical connector area of the guide wire body providing an exposed connector element  130 . The internal structure of the probe  112  and guide wire body  120  conducts electrical signals between the distal exposed electrode  128  and the electrical connector element  130 . 
     The flexible guide wire body  120  preferably comprises a coiled wire  132  extending between the guide wire body proximal end  122  and the guide wire body distal end  124  forming a coiled wire lumen  134  and an inextensible core wire  136 . The core wire  138  extends through the coiled wire lumen  134  and is affixed to the coiled wire  132  at the guide wire body proximal end  122  and the guide wire body distal end  124  to inhibit stretching of the guide wire body  120 . The core wire and the coiled wire can also conduct electrical signals generated by an electrical stimulator or electrical signals of the body from between the exposed electrode  128  and connector element  130 . 
     Preferably, the tissue penetrating probe  112  has a probe lumen  140  extending distally from the probe proximal end  114  toward the probe distal end  116 . The probe distal end  116  is preferably tapered to a sharpened tip, and the probe lumen  140  is filled at the tapered distal end  116 . Preferably, the inextensible core wire  136  and wire coil  132  extend into the probe lumen  140  and are affixed to the tissue penetrating probe therein by welding and/or crimping to attach the guide wire body distal end  124  to the probe proximal end  114  as shown in FIG.  4 . The core wire  136  can extend to the probe distal end  116  to fill the probe lumen at the tapered distal end  116 . 
     The outer diameter of the combined percutaneous medical probe and guide wire i  100  is selected in relation to the through-lumen of a medical device, e.g., a lead an introducer, a dilator, a catheter or the like, so that the medical device can be advanced over the combined percutaneous medical probe and guide wire  100  after it is inserted transcutaneously as described further below to form a percutaneous pathway. The length of the probe  112  is selected to traverse the desired percutaneous pathway and is shorter than the length of the elongated medical device to be introduced therethrough. The length of the guide wire body  120  is selected in relation to the length of the medical device to enable grasping the guide wire body proximal end  122  upon advancement of the elongated medical device over the guide wire body  120 . Then, the guide wire body  120  and elongated medical device overlying it can be axially aligned with the tissue penetrating probe  112  to enable advancement of the elongated medical device over the tissue penetrating probe  112  and through a percutaneous pathway . 
     The combined probe and guide wire  100  is therefore typically employed to form a percutaneous pathway to a percutaneously accessed site and to enable over-the-wire advancement of an elongated medical device having a device length and device through-lumen to the percutaneously accessed site or into an access pathway accessible from the percutaneously accessed site. The probe  112  is adapted to be manually grasped and advanced from the skin to the percutaneous access site to provide the percutaneous pathway to the percutaneously accessed site at the probe distal end. 
     One procedure for introducing a an elongated neurostimulation lead  10  over the combined percutaneous medical probe and guide wire  100  to locate the lead electrodes through a foramen  40  of the sacrum  50  at a percutaneously accessed site  30  adjacent to the sacral nerve (not shown) is depicted in FIGS. 5-9. The sacrum  50 , generally speaking, is a large, triangular bone situated at the lower part of the vertebral column, and at the upper and back part of the pelvic cavity. The sacrum  50  is perforated by the anterior and posterior sacral foramina, e.g., foramen  40 , that the sacral nerves pass through. The organs involved in bladder, bowel, and sexual function receive much of their control via the second, third, and fourth sacral nerves, commonly referred to as S 2 , S 3  and S 4  respectively. Electrical stimulation of these various nerves has been found to offer some control over these functions including control for bladder incontinence. Unlike other surgical procedures, sacral nerve stimulation using an imp lantable pulse generator is reversible by merely turning off the pulse generator. 
     The minimally invasive method of the present invention for inserting an elongated medical device, e.g., lead  10  or the dilator  70  shown in FIGS. 10 a - 10   c , having a device length and device through-lumen percutaneously to the percutaneously accessed site  30  commences in FIG.  5 . In these illustrations, the elongated medical device comprises a neurostimulation lead  10  shown most particularly in FIG.  8 . The neurostimulation lead  10  has a lead body  12  extending between a lead body proximal end  14  and a lead body distal end  16 . A plurality of stimulation electrodes  18  are arrayed along a distal segment of the lead body  12 , and a like plurality of in-line connector elements  20  are arrayed along a proximal segment of the lead body  14 . The lead body  12  encloses a like plurality of conductors that are insulated electrically from one another and extend between each of the plurality of connector elements  20  and electrodes  18 . A through-lumen extends within the lead body  12  from the lead body proximal end  14  to the lead body distal end  16 . The lead body through-lumen diameter is sized to receive the combined probe and guide wire  100  for over-the-wire advancement. 
     In FIG. 5, the probe  112  is grasped, aimed in alignment with a predetermined direction D and advanced from the skin  60  to the percutaneously accessed site  30 . The sharpened tip distal end  116  penetrates the surgically sterilized site on the skin or is advanced through a small skin incision toward the percutaneously accessed site  30  which is within or through the foramen  40  as the probe  112  is manually advanced in alignment with the direction D. Depth markings on the probe body and radiographic imaging can be employed to determine the depth of insertion and the location of the probe distal end  116 . 
     The probe distal end  116  is shown fully advanced to the percutaneously accessed site  30  in FIG.  6 . Test electrical stimulation can be applied at terminal  130  through the combined percutaneous medical probe and guide wire  100  to determine if stimulation applied through the probe distal end electrode  128  to the sacral nerve elicits a favorable response indicating optimal positioning. When testing is completed, the combined percutaneous medical probe and guide wire  100  depth provides the percutaneous pathway from the skin  60  to the percutaneously accessed site  30 . 
     In FIG. 7, the guide wire body  120  is straightened, and the guide wire body proximal end  122  is inserted into the through-lumen of the elongated neurostimulation lead  10 . The elongated neurostimulation lead  10  is advanced over the over the guide wire body  120  as shown in FIG. 8 by grasping the guide wire body proximal end  122  upon advancement of the lead  10  over the guide wire body  120  to align the guide wire body  120  and elongated lead generally axially with the tissue penetrating probe  112  and in the direction D. 
     The elongated lead is then advanced over the tissue penetrating probe  112  as shown in FIG. 8 until the lead electrodes  18  are located at the percutaneously accessed site  30  as shown in FIG.  9 . The lead electrodes  18  can be moved back and forth to locate at least one or a pair of the electrodes in optimal location with respect to the sacral nerve to effect the desired response to test stimulation selectively applied through the electrodes. Then, the combined percutaneous medical probe and guide wire  100  is withdrawn through the through-lumen of the lead body  12  as shown in FIG.  9 . The lead body  12  is fixed in place to prevent movement of the electrodes in a manner described in commonly assigned U.S. Pat. No. 5,484,445, for example. The lead connector elements  20  can then be coupled to an implantable neurostimulator in a manner known in the art. 
     The percutaneous pathway effected by the relatively short stiff probe  112  can be expanded by use of a dilator  70  formed of the assembly of a dilator body  80  and a dilator sheath  90  as shown in FIGS. 10 a - 10   c . The dilator body  80  is preferably conductive, and the dilator sheath  90  is preferably non-conductive but may bear radiopaque and visually observable depth marks  96  along its length to facilitate radiographic imaging when it is extended into the paiient&#39;s body. The depth markings or marks  96  can be one centimeter or one-half centimeter bands or numerals or other indicia that indicate the depth of insertion to clinician from the exposed marking. The most distal mark is spaced from the distal tip of dilator sheath  90  to indicate a predetermined depth of the distal tip  84  of the dilator body  80  protruding distally during insertion as shown in FIG. 10 c.    
     Thus, when assembled as shown in FIG. 10 c , the dilator body distal end extends out of the dilator sheath distal end and is electrically exposed. Electrical stimulation of the sacral nerve to test placement can take place through the dilator body  80  while the dilator sheath  90  is in place 
     The dilator body  80  has a dilator body diameter, a dilator body length extending between a dilator body proximal end  82  and a dilator body distal end  84 , and a dilator body lumen  86  extending from the dilator proximal end to the dilator distal end. The dilator sheath  90  has a dilator sheath diameter, a dilator sheath length extending between a dilator sheath proximal end  92  and a dilator sheath distal end  94 . A dilator sheath lumen  98  extends from the dilator sheath proximal end to the dilator sheath distal end, the dilator sheath lumen having a dilator sheath lumen diameter sized in operative relation to the dilator body diameter to selectively receive the dilator body therein to assemble the dilator body and dilator sheath as the dilator as shown in FIG. 10 c . The dilator sheath lumen  98  is also sized in operative relation to the diameter of the neurostimulation lead body  12  so that the neurostimulation lead  10  can be advanced through the dilator sheath lumen  98  when the dilator body  80  is removed. 
     In this case, the dilator  70  is substituted for the lead  10  shown in FIG. 7, and the proximal end  122  of the combined percutaneous medical probe and guide wire  100  is inserted through the dilator body lumen  86 . The dilator  70  is advanced over the combined percutaneous medical probe and guide wire  100  as shown in FIGS. 8 and 9 to dilate the percutaneous path. Then, either the entire dilator  70  or just the dilator body  80  can be withdrawn to enable the advancement of the lead  10  over the combined percutaneous medical probe and guide wire  100 . Or, the dilator body  80  and the combined percutaneous medical probe and guide wire  100  can be withdrawn, and a neurostimulation lead that does not have a through-lumen can be advanced through the dilator sheath lumen  98 . 
     Thus, it will be seen that the combined percutaneous medical probe and guide wire  100  can be used in a variety of other ways that will be apparent to those of skill in the art to facilitate advancement of implantable leads, catheters, dilators, introducers, cannula and tubes to various percutaneously accessed sites and in certain cases, from the percutaneously accessed site to a more remote site through an access pathway. 
     All patents and other publications referenced herein are incorporated herein by reference. 
     The true spirit and scope of the inventions of this specification are best defined by the appended claims, to be interpreted in light of the foregoing specification. Other apparatus that incorporate modifications or changes to that which has been described herein are equally included within the scope of the following claims and equivalents thereof. Therefore, to particularly point out and distinctly claim the subject matter regarded as the invention, the following claims conclude this specification.