Abstract:
In one embodiment, an apparatus comprises: a base structure adapted to be inserted within the burr hole; a lead securing member for securing the lead, the lead securing member comprising a first arm structure and a second arm structure, at least one spring loaded structure adapted to exert a force to bring the first arm structure and the second arm structure together; and a positioning tool having a distal end adapted to be inserted within the lead securing member. When the positioning tool is positioned within the lead securing member, the distal end holds the first and second arm structures a sufficient distance apart to receive a lead between the first and second arm structures; wherein the positioning tool comprises a control structure at a proximal end that, when engaged, causes the distal end of the positioning tool to be released from between the first and second arm structures.

Description:
RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. application Ser. No. 12/847,948 , filed Jul. 30, 2010, now Pat. No. 7,887,550, which is a divisional of U.S. application Ser. No. 11/738,227, filed Apr. 20, 2007, now Pat. No. 7,766,922, which claims the benefit of U.S. Provisional Application No. 60/794,326, filed Apr. 21, 2006, which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present application is generally related to an apparatus for holding a stimulation lead, catheter, or cannula within a burr hole. 
       BACKGROUND 
       [0003]    Deep brain stimulation (DBS) refers to the delivery of electrical pulses into one or several specific sites within the brain of a patient to treat various disorders. For example, DBS has been proposed as a clinical technique for treatment of chronic pain, essential tremor, Parkinson&#39;s disease (PD), dystonia, epilepsy, depression, obsessive-compulsive disorder, and other disorders. 
         [0004]    A DBS procedure typically involves first obtaining preoperative images of the patient&#39;s brain (e.g., using computer tomography (CT) or magnetic resonance imaging (MRI)). The imaging process sometimes involves first affixing to the patient&#39;s skull fiducial markers that are discernable on the images produced by the imaging process. The fiducial markers assist in registering the preoperative images to the actual physical position of the patient in the operating room during the subsequent surgical procedure. Using the preoperative images, the neurosurgeon can select a target region within the brain, an entry point on the patient&#39;s skull, and a desired trajectory between the entry point and the target region. The entry point and trajectory are carefully selected to avoid intersecting or otherwise damaging critical brain structures. 
         [0005]    In the operating room, the patient is immobilized and the patient&#39;s actual physical position is registered. The physician marks the entry point on the patient&#39;s skull and drills a burr hole at that location. A mechanism is provided to precisely control the path through the patient&#39;s brain to the desired location. Specifically, a positioning error on the order of a millimeter can have a significant negative effect on the efficacy of the DBS therapy. Stereotactic instrumentation and trajectory guide devices are commercially available products that facilitate the control of the trajectory and positioning of a lead during the surgical procedure. 
         [0006]    A microdrive introducer can be used to insert a deep brain stimulation lead toward the selected region of the brain along the selected trajectory. The lead provides one or several conductive paths to deliver stimulation pulses to the selected region. The lead includes a very small diameter insulative lead body with one or several conductors (e.g., stranded wires) embedded in the insulative material. The lead also includes one or several electrodes at a distal end of the lead that are electrically coupled to respective conductors. The electrodes can be used to record signals within the brain and/or to deliver electrical stimulation pulses to brain tissue. Often, the electrical activity adjacent to one or several electrodes is analyzed to determine whether the recorded signals are consistent with the targeted region of the brain. If the recorded signals are not consistent with the targeted region, an adjustment to the lead&#39;s position can be made as appropriate. 
         [0007]    A burr hole plug or cap structure is typically utilized to retain the lead in the desired position. A burr hole structure generally includes (i) a ring or grommet-like element that is inserted into the hole first so as to protect the edges of the burr hole and (ii) a cap or plug device that is inserted into the ring or grommet-like element to secure the lead and plug the hole. 
         [0008]    By way of example, in U.S. Pat. No. 6,044,304, a burr ring is disclosed that is secured to the skull. The burr hole plug of the &#39;304 patent also has an upper flange portion and circumferential ribs used to position the plug in the cranium. Also, the burr hole plug described in the &#39;304 patent includes an aperture capable of accepting a lead through a septum. 
         [0009]    In U.S. Pat. No. 5,954,687, a device is disclosed for securing a catheter within a burr hole. The device has a series of spaced septum elements that can be selectively penetrated for fluid communication with a reservoir in the apparatus. The main objective of the device is to allow fluid access to the patient&#39;s brain through a burr hole. Anchoring of the device is not taught and there are a limited predetermined number of septum holes that can be accessed. 
         [0010]    U.S. Pat. No. 5,927,277 describes a burr hole ring for retaining a probe relative to the skull. The burr hole ring has an engaging member with holes to receive a probe. The &#39;277 patent also describes a method for securing a device at a desired orientation within the burr hole. Since a fixed spacing between holes is described, the device can be placed in a limited number of locations through the burr hole. 
         [0011]    U.S. Pat. No. 5,865,842 discloses a system and method for anchoring a lead in a burr hole. The disclosed system consists of a base-plate, adaptor, seal, and screw cap. The lead is anchored mechanically at the burr hole at a 90 degree angle relative to the burr hole. 
         [0012]    U.S. Pat. No. 5,843,150 discloses an annular clamping means with a compressible feed-through member for receiving a lead. The described order for anchoring the lead includes making the burr hole, inserting the plug ring, inserting the lead, and engaging the clamping member. 
         [0013]    Other burr hole plug assemblies and features of burr hole plugs are taught in U.S. Pat. No. 5,464,446 (burr hole plug with a central lumen and a cap that engages with the flange of the plug); U.S. Pat. No. 4,998,938 (a device that facilitates insertion of an instrument into a patient&#39;s cranial cavity); U.S. Pat. No. 4,328,813 (a burr hole plug with a cap that anchors the lead); and U.S. Pat. No. 4,245,645 (a probe and system that is used to perform stereoelectroencephalographic exploration). 
       SUMMARY 
       [0014]    In one embodiment, an apparatus for securing a lead within a burr hole, comprises: a base structure adapted to be at least partially inserted within the burr hole; a lead securing member for securing the lead within the burr hole, the lead securing member comprising a first arm structure and a second arm structure, at least one spring loaded structure adapted to exert a force to bring the first arm structure and the second arm structure together; and a positioning tool having a distal end adapted to be inserted within the lead securing member; wherein when the distal end of the positioning tool is positioned within the lead securing member, the distal end holds the first and second arm structures a sufficient distance apart to receive a lead between the first and second arm structures; wherein the positioning tool comprises a control structure at a proximal end that, when engaged, causes the distal end of the positioning tool to be released from between the first and second arm structures thereby allowing further contraction of the first and second arm structures to secure the lead. 
         [0015]    The foregoing has outlined rather broadly certain features and/or technical advantages in order that the detailed description that follows may be better understood. Additional features and/or advantages will be described hereinafter which form the subject of the claims. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the appended claims. The novel features, both as to organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  depicts a burr hole assembly according to one representative embodiment. 
           [0017]      FIG. 2  depicts an outer ring structure adapted to be placed within the burr hole of the patient according to one representative embodiment. 
           [0018]      FIG. 3  depicts a grasping member adapted to fit around the lead and to be placed within the outer ring of  FIG. 2  according to one representative embodiment. 
           [0019]      FIG. 4  depicts a wedge member structure for placement around the grasping member of  FIG. 3 . 
           [0020]      FIG. 5  depicts burr hole device that enables a lead to be secured within a burr hole according to another representative embodiment. 
           [0021]      FIG. 6  burr hole device according to another representative embodiment. 
           [0022]      FIG. 7  depicts a placement tool coupled to a burr hold device for use in moving and manipulating a burr hole device according to one representative embodiment. 
           [0023]      FIG. 8  depicts the placement tool in isolation according to one representative embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Although a number of burr hole devices have been made commercially available, many burr hole cap devices suffer from various limitations. For example, some commercially available burr hole devices are too simple in design and do not provide adequate stabilization of the lead with the burr hole. Alternatively, other commercially available burr hole devices that achieve the desired stabilization of the lead within the burr hole are quite cumbersome during the placement and manipulation to capture the lead within the burr hole. Specifically, burr holes are relatively small, e.g., typically about 14 mm. Accordingly, the individual elements of a burr hole device can be quite small. Thus, when burr hole devices require precise manipulations, the lead securing process can be quite tedious. In contrast, representative embodiments provide burr hole devices that provide a desired amount of stabilization of the lead without requiring undue and cumbersome manipulation of small constituent elements. 
         [0025]      FIG. 1  depicts burr hole  100  assembly according to one representative embodiment. For the sake of clarity, the actual cap for the burr hole assembly is omitted to enable the interior details of assembly  100  to be shown in  FIG. 1 . As shown in  FIG. 1 , burr hole cap assembly comprises  100  outer ring  101 , wedge member  102 , and grasping member  103 . 
         [0026]    In one embodiment as shown in  FIG. 2 , outer ring  101  is adapted to be placed within the burr hole of the patient. Outer ring  101  possesses a small profile somewhat flat portion that is intended to remain on the patient&#39;s skull and an annular portion adapted to be inserted within the burr hole. Additionally, outer ring  101  is preferably fabricated from a bio-stable, bio-compatible polymer material. Outer ring  101  preferably possesses some amount of rigidity and strength to promote mechanical robustness and stability. Outer ring  101  includes apertures  201  for receiving bone screws to secure outer ring  101  to the patient&#39;s skull after outer ring  101  has been placed with the burr hole. In the embodiment shown in  FIG. 2 , outer ring  101  comprises securing members  202  into which a cap structure (not shown) can be coupled. 
         [0027]    In one embodiment as shown in  FIG. 3 , grasping member  103  is adapted to fit around the lead and to be placed within the outer ring  101  with relatively little difficulty. For the purpose of this application, the term “lead” is used in a broad sense and encompasses electrical stimulation leads, drug infusion catheters, cannulas, and any other similar elongated medical device to be stabilized within a burr hole of a patient. As shown in  FIG. 3 , grasping member  103  is a somewhat annular structure. Grasping member  103  could alternatively be tapered or possess a truncated cone-shape to facilitate the assembly of burr hole cap assembly  100 . Grasping structure  301  comprises gap  301  that runs along a substantial portion of the diameter of grasping member  103 . Preferably, grasping member  103  is a single integral structure and gap  301  is only completely open on only one side of grasping member  103 . Additionally, grasping member  103  is preferably fabricated of a bio-compatible and bio-stable material that possesses a relatively low durometer to cause grasping member  103  to be compressible. For example, grasping member  103  can be fabricated from a suitable silicone material. 
         [0028]    In use, when a lead is positioned within the burr hole of a patient, grasping member  103  is placed around the lead using gap  301 . When grasping member  103  is not compressed, gap  301  possesses a width that is sufficiently greater than the diameter of the lead to prevent application of an excessive frictional force on the lead. Thus, grasping member  103  can be placed on the lead at a distance away from the position where outer ring  101  is secured to the skull. Then, grasping member  103  can be slid along the lead and into the outer ring without dislocating the lead within the patient. The outside diameter of grasping member  103  is preferably smaller that the inside diameter of outer ring  101  thereby allowing the insertion of grasping member  103  into outer ring  101  to occur with little complication. 
         [0029]    After grasping member  103  is placed around the lead and within outer ring  101 , wedge member  102  (as shown in isolation in  FIG. 4 ) is placed around grasping member  103  and within outer ring  101  to form the assembly shown in  FIG. 1 . Wedge member  102  preferably possesses a durometer that is greater than the durometer of grasping member  103 . Additionally, wedge member  102  preferably possesses an inner diameter that is smaller than the outside diameter of grasping member  103 . Accordingly, when wedge member  102  is placed around grasping member  103 , wedge member  102  compresses grasping member  103  thereby narrowing gap  301  and securing the lead. 
         [0030]      FIG. 5  depicts another burr hole device that enables a lead to be secured within a burr hole with a relatively minimal amount of difficulty. As shown in  FIG. 5 , burr hole device  500  includes outer ring  501  which is preferably implemented in a manner similar to outer ring  101 . Inner disc  502  is adapted to be placed within outer ring  501  and around the lead. Preferably, outer ring  501  possesses interior flange or edge  506  to hold inner disc  502 . Also, inner disc  502  is preferably rotatable within outer ring  501  to enable the lead to be captured from substantially any position within the burr hole. Inner disc  502  preferably comprises a first arm structure  505  that is rigidly fixed on inner disc  502 . Second arm structure  503  is preferably attached to moveable curved projection element  504  which thereby allows a “window”  507  of space through burr hole device  500  to be opened and closed. 
         [0031]    In use, with second arm structure  503  positioned such that window  507  is as wide as possible, inner disc  502  is placed within outer ring  501  such that the lead is positioned between arms  503  and  505 . Inner disc  502  is then rotated within outer ring  501  by pushing a suitable tool against rigid arm  505  until rigid arm  505  is positioned against the lead. By implementing rigid arm  505  to protrude above the main surface of inner disc  502 , rigid arm  505  can be used to rotate disc  502  within ring  501 . Thereby, the manipulation of disc  502  into the correct position can occur in an efficient manner and cumbersome precision movements are not required. Then, arm  503  is rotated toward arm  505  to secure the lead between arms  503  and  505 . 
         [0032]      FIG. 6  depicts burr hole device  600  according to another embodiment. Burr hole device  600  is similar to burr hole device  500  in that the lead is secured between arms  603  and  604 . Burr hole device  600  differs from burr hole device  500  in the manner in which arms  603  and  604  are brought together to secure the lead. 
         [0033]    As shown in  FIG. 6 , burr hole device  600  comprises annular structure  601  that is inserted within the burr hole of the patient and secured to the patient&#39;s skull. On the interior wall of annular structure  601 , a lower flange or edge can be provided to hold lead securing member  602 . Also, annular structure  601  may comprise ridges or other structures on its interior wall to limit the rotation of lead securing member  602 . 
         [0034]    In use, tool  609  is initially inserted within lead securing member  602 . Upper lever structures  605  and  606  (e.g., “dead bolts”) are spring loaded such that lever structures  605  and  606  exert an “inward” force against arms  603  and  604 , respectively. Although spring loaded lever structures are shown for one embodiment, other shape memory elements could be employed. For example, suitable shaped wire elements having spring characteristics could be employed in lieu of spring loaded lever structures. When the distal end of tool  609  is inserted within lead securing member  602 , arms  603  and  604  clamp against the distal end of tool  609  as shown in  FIG. 6 . The distal end of tool  609  maintains an opening  610  (between arms  603  and  604 ) large enough to accept the lead with or without a cannula with little difficulty. Also, the clamping force applied by arms  603  and  604  against tool  609  allows lead securing member  602  to be moved and manipulated into place by using tool  609  (see  FIG. 7 ). Additionally, when inserted within lead securing member  602 , the distal end of tool  609  maintains spring loaded lever structures  607  and  608  in a “closed” position. That is, lever structures  607  and  608  are spring loaded to automatically open and contact an inner shoulder of annular structure  601  when the distal end of tool  609  is removed. The expansion or opening of lever structures  607  and  608  causes securing member  602  to be secured within annular structure  601 . 
         [0035]      FIG. 7  depicts an expanded view of tool  609  inserted within securing member  602 . As shown, a surgeon can grasp tool  609  to pick-up and move securing member  602  for placement within annular structure  601  with relative ease. Once, lead securing member  602  is positioned around the lead and within the annular structure, the surgeon need only remove tool  609  from lead securing member  602  to secure the lead and lock member  602  into place against annular structure  601 . Specifically, as the distal end of tool  609  is removed, arms  603  and  604  clamp around the lead (or the cannula) due to the application of force exerted by spring loaded lever structures  605  and  606 . Also, as tool  609  is removed, spring load lever structures  607  and  608  expand to contact annular structure  601 . 
         [0036]      FIG. 8  depicts another view of tool  609 . As shown in  FIG. 8 , tool  609  comprises handles  801  and  802  at is proximal end. When handles  801  and  802  are compressed together, pin  803  is extended from the distal end of  609 . Pin  803  is used to remove the distal end of tool  609  from annular structure  601 . Specifically, when extended, pin  803  contacts an interior surface of annular structure  601  thereby pushing end  804  of tool  609  upward. When end  804  is pushed upward, arms  603  and  604  are no longer held apart by end  804  and arms  603  and  604  contract toward each other to clamp around the lead. Additionally, end  804  is tapered to allow end  804  to be re-inserted within annular structure  601  to push arms  603  and  604  apart and to retract lever structures  607  and  608 . Accordingly, lead securing member  602  can be removed from annular structure  601  as efficiently as it can be inserted with structure  601 . 
         [0037]    Although representative embodiments and advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from this disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized without departing from the scope of the appended claims. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.