Abstract:
A shunt system for controlling the flow of fluid from one region of a patient to a different region of the patient&#39;s body. The shunt system includes endoscopic placement features so that the system can be placed endoscopically in a minimally invasive surgery. Also provided is a single fluid flow control device having flow control characteristics previously obtainable only by connecting in series two or more shunt system components. In addition, the shunt system includes a selectively engageable locking mechanism that allows the system to be assembled quickly and easily, without the need for sutures or adhesives. The present assembly process minimizes the possibility of any unintended fluid leakage from the device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
   Not Applicable. 
   FIELD OF THE INVENTION 
   The present invention relates to medical devices for directing bodily fluids from one region of a patient to another region. More specifically, this invention relates to a shunt system having endoscopic placement features that allow its minimally invasive placement within a patient, and apparatus to facilitate such endoscopic placement. 
   BACKGROUND OF THE INVENTION 
   Hydrocephalus is a condition afflicting patients who are unable to regulate cerebrospinal fluid flow through their body&#39;s own natural pathways. Produced by the ventricular system, cerebrospinal fluid is normally absorbed by the body&#39;s venous system. In a patient suffering from hydrocephalus, the cerebrospinal fluid is not absorbed in this manner, but instead accumulates in the ventricles of the patient&#39;s brain. If left untreated, the increasing volume of fluid elevates the patient&#39;s intracranial pressure and can lead to serious medical conditions such as subdural hematoma, compression of the brain tissue, and impaired blood flow. 
   The treatment of hydrocephalus has conventionally involved draining the excess fluid away from the ventricles and rerouting the cerebrospinal fluid to another area of the patient&#39;s body, such as the abdomen or vascular system. A drainage system, commonly referred to as a shunt, is often used to carry out the transfer of fluid. In order to install the shunt, typically a scalp incision is made and a small hole is drilled in the skull. The proximal end of the shunt, which usually includes a proximal, or ventricular, catheter, is installed in the ventricular cavity of the patient&#39;s brain. The distal end of the shunt, which includes a distal, or drainage, catheter, is installed in that portion of the patient&#39;s body where the excess fluid is to be reintroduced. To regulate the flow of cerebrospinal fluid and maintain the proper pressure in the ventricles, a pump or valve can be placed between the proximal and distal catheters. If the pump or valve is not equipped with anti-siphon features and such features are desirable, a siphon control device can be separately included. The siphon control device can be positioned within the fluidic pathway, usually between the shunt valve and the drainage catheter. The siphon control device avoids overdrainage caused by the siphoning effect of hydrostatic pressure in the distal shunt catheter, which can be created by the elevation of the proximal catheter inlet with respect to the distal catheter outlet, i.e., when the patient sits or stands. 
   In most conventional shunt systems, the various components that form the shunt system, i.e., proximal and distal catheters, shunt valve, anti-siphon device, tubing, etc., are manufactured separately and then connected together during implantation to form the complete drainage pathway. During a typical surgical procedure, the proximal catheter is inserted directly into the ventricle cavity, after which the shunt valve and a pre-attached distal catheter are then implanted near the surface of the skull at an approximately 90° angle with respect to the proximal catheter. The proximal catheter is then attached by means of suturing surgical tubing to an inlet port on the shunt valve, thereby forming a right angle with respect to the shunt valve. With the current increase in popularity of endoscopic surgeries, some neurosurgeons have now attempted rigid endoscopic placement of ventricular catheters into the ventricles of the brain. In some cases endoscopic placement of shunt valves having domed silicone reservoirs with attached pre-cut catheters has even been attempted. 
   Because of the limited space available for the surgeon to perform the suturing after the proximal catheter is advanced into the ventricles, the assembly procedure after endoscopic implantation of the shunt system components can be extremely difficult. Also, shunts having domed reservoirs are not easily occluded for flushing distally. Given the amount of time necessary to suture the surgical tubing that connects the ventricular catheter to the shunt valve, the length of the surgical procedure can prove to be less than desirable. An added setback to using these conventional shunt systems is the compatibility problems that arise when the various components are produced by different manufacturers. Furthermore, currently available shunt systems can be prone to shunt separation and/or leakage at the sites where the separate components are connected to one another via the surgical tubing. 
   SUMMARY OF THE INVENTION 
   The present invention provides a shunt system for controlling the flow of fluid from one region of a patient to a different region of the patient&#39;s body. The shunt system includes endoscopic placement features so that the system can be placed endoscopically for implantation in a minimally invasive surgery. Also provided is a single, fluid flow control device having flow control characteristics previously obtainable only by connecting in series two or more shunt system components. In addition, the shunt system can be assembled quickly and easily, without the need for suturing. The present assembly process minimizes the possibility of any unintended fluid leakage from the device, and preferably requires no adhesive to secure any of the components forming the shunt system to one another. 
   In an exemplary embodiment of the present invention, the shunt system comprises a shunt device contained within a housing. The shunt device is comprised of a valve mechanism for regulating fluid flow into and out of the shunt system, a pump chamber in fluid communication with the valve mechanism, and a reservoir which is also connected to and in fluid communication with the pump chamber. The reservoir includes a top section and a base section that terminates in a catheter connector. At least a portion of the connector extends out of the housing, and in one exemplary embodiment both the base section including the connector extends out of the housing. The shunt system also includes an inflow catheter and an outflow catheter, each catheter having first and second ends, and a channel extending between the first and second ends for carrying fluid within the catheter. The first end of each catheter is configured as an attachment end for connection to the shunt device to thereby form a fluidic pathway for transferring fluid from one region of the patient to another region. The second end of the inflow catheter serves as the fluid uptake end of the shunt system (i.e., where fluid enters the system), while the second end of the outflow catheter serves as the fluid release end of the shunt system (i.e., where fluid exits the system.) In addition, the first end of the inflow catheter is configured to be secured to the connector of the reservoir, and can include a locking mechanism for maintaining the attachment end around the connector. 
   In one aspect of the present invention, the connector includes a flange while the inflow catheter includes an attachment end that fits over the flange. The inner diameter of the attachment end is configured to be slightly smaller than the largest outer diameter of the flange, thereby enabling an interference fit to be formed when the attachment end is urged over the connector and flange. Included with the inflow catheter is a selectively engageable locking mechanism that is adapted to secure the attachment end of the inflow catheter to the connector. The locking mechanism comprises a retaining ring for maintaining the attachment end of the inflow catheter onto the connector. Once fully assembled, the inflow catheter extends at approximately 90° with respect to the outflow catheter. The ventricular catheter can have either an open or a closed second end configured for fluid uptake. If the fluid uptake end is closed, a pre-slit can be provided so as to allow an endoscope to pass through the second end. A series of apertures can be provided near the second end to facilitate the entry of fluid into the catheter. 
   In one exemplary embodiment, the retaining ring can be provided on the inflow catheter, and can be configured to slide along the inflow catheter and towards the attachment end of the inflow catheter when the attachment end is fitted onto the connector. When advanced over the flange, the retaining ring compresses the attachment end around the flange and thereby secures the inflow catheter onto the connector. The inflow catheter can also include indicia on the outer surface of the catheter to designate corresponding lengths. The marks can aid the surgeon in pre-sizing the ventricular catheter to individual patients once the specific catheter size desired has been determined by either CT scan or other known imaging techniques. This way, the surgeon can adjust the length, i.e., by cutting the catheter to the required size, intraoperatively. After the inflow catheter has been cut to the desired size, the retaining ring can be advanced near the attachment end prior to assembly. 
   In another exemplary embodiment of the present invention, rather than being slidable with respect to the inflow catheter, the retaining ring can be firmly secured to the inflow catheter at the attachment end. In yet another exemplary embodiment, the retaining ring can be secured to the inner diameter of the inflow catheter at the attachment end. 
   In other aspects of the present invention, the reservoir can be a domed reservoir while the housing can include a domed cap for accommodating the domed reservoir. Within the reservoir, a check valve mechanism is provided in the base portion to prevent occlusion of the shunt device during pumping of the valve mechanism. The check valve mechanism can comprise a free floating ball. The reservoir also includes surface features that provide the valve mechanism with anti-siphon properties. For example, the base portion can be provided with a central flow channel that connects to peripheral flow channels. Helically arranged ridges can be included within the peripheral flow channels to provide a tortuous fluid flow pathway with greater resistance to prevent siphoning. Also, the domed cap can include an endoscope port comprising a pre-formed slit that connects to the top portion of the reservoir. The endoscope port can be formed from a resealable silicone to allow an endoscope to pass through the housing and down into the reservoir base portion itself. The endoscope port can also be radiopaque to allow easy visualization and identification. The free-floating ball of the check valve mechanism can be pushed aside or manipulated aside with the endoscope. 
   The present invention also provides an instrument for assembling the ventricular catheter to the shunt device. The instrument has a first arm having a proximal end including a gripping section configured for holding a portion of the housing, and a distal end including a handle portion. Pivotally connected to the first arm is a second arm which has a proximal end including a platform section configured to sit around the inflow catheter and adjacent to the retaining ring. Upon the application of force to move the handle portions towards each other, the gripping section and the platform section of the arms push against the housing and the retaining ring, sliding the retaining ring over the attachment end of the ventricular catheter and over the flange of the connector. 
   Further features of the invention, its nature and various advantages, will be more apparent from the accompanying drawings and the following detailed description of the drawings and the preferred embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1A  is a top-down view of the shunt system of the present invention; 
       FIG. 1B  is an exploded view of the shunt system of  FIG. 1A ; 
       FIG. 1C  is an enlarged view of the reservoir and attached inflow catheter; 
       FIG. 2A  is an exploded view of another embodiment of a locking mechanism and inflow catheter of the present invention; 
       FIG. 2B  is an exploded view of yet another embodiment of a locking mechanism and inflow catheter of the present invention; 
       FIG. 3  is a side view of a domed reservoir of the prior art; 
       FIG. 4  is a cutaway side view of the shunt device during distal pumping; 
       FIG. 5A  is a cutaway side view of the shunt device of  FIG. 3  during normal erect flow; 
       FIG. 5B  is a cutaway side view of the shunt device of  FIG. 3  during endoscopic placement or ventricular injection; 
       FIG. 6A  is a cutaway side view of another embodiment of the base section during distal pumping; 
       FIG. 6B  is a cutaway side view of the base section of  FIG. 5A  during normal erect flow; 
       FIG. 6C  is a cutaway side view of the base section of  FIG. 5A  during anti-siphon flow; 
       FIG. 6D  is a cutaway side view of the base section of  FIG. 5A  during prone flow; 
       FIG. 6E  is a cutaway side view of the base section of  FIG. 5A  during endoscopic placement or ventricular injection; and 
       FIG. 7  is a perspective view of an instrument for assembling the shunt system of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention provides a shunt system having endoscopic placement features which allow the system to be surgically implanted and easily assembled using minimally invasive techniques. Turning now to the drawings and particularly to  FIGS. 1A and 1B , a shunt system  10  in accordance with the present invention is shown. In an exemplary embodiment of the present invention, the shunt system  10  comprises a shunt device  20  contained within a housing  12 . The shunt device  20  includes a valve mechanism  22  for regulating fluid flow into and out of the shunt device  20 . The valve mechanism  22  can comprise any typical valve mechanism, such as the ball-in-cone valve illustrated and as described in U.S. Pat. Nos. 3,886,948, 4,332,255, 4,387,715, 4,551,128, 4,595,390, 4,615,691, 4,772,257, and 5,928,182, all of which are hereby incorporated by reference. Of course, it is understood that the valve mechanism  22  can also comprise other suitable valves including programmable valves for controlling fluid flow in a shunt device as are known in the art. 
   Also included in the shunt device  20  is a pump chamber  24  that is connected to and in fluid communication with the valve mechanism  22 . The pump chamber  24  can comprise a flexible diaphragm  26  that enables selective occlusion of fluid flow into and out of the pump chamber  24 , thereby allowing bidirectional pumping of fluid between the pump chamber  24  and an attached reservoir  30  that is in fluid communication with the pump chamber  24 . The reservoir  30  comprises a top section  32  and a base section  34  which terminates in a catheter connector  36 . A portion of the base section  34  including the connector  36  extends out of the housing  12  as shown in  FIG. 1B . However, it is understood that only the connector  36  need be located outside of the housing  12  for ease of assembly, and the base section  34  itself may be wholly contained within the housing  12  if desired. The top section  32  of the reservoir  30  which connects to the pump chamber  24  serves as a second pump chamber. Preferably, the reservoir  30  can be a “domed” reservoir. That is, the top section  32  of the reservoir  30  is situated under a domed cap  14  that forms a part of the housing  12 , much like in the prior art Rickham pump chamber  2  of  FIG. 3  in which there is shown a pump chamber  4  attached to a reservoir  6  seated underneath a domed housing  8 . In the present invention, both the top section  32  of the reservoir  30  and the pump chamber  24  are each configured to handle approximately 0.08 cc of fluid volume, thereby allowing in total about four times the fluid volume as compared to the Rickham pump chamber  2  of the prior art. However, the length of the housing  12  itself is approximately  4  cm so the overall dimensions of the shunt device  20  are still relatively small. 
   To form the complete fluid flow pathway, catheters  40 ,  60  are connected to the shunt device  20  of the present invention. Provided with the shunt system  10  is an inflow catheter  40  having a first end  42 , a second end  44 , and a channel  46  extending between the first end  42  and second end  44 . The first end  42  of the inflow catheter  40  is configured to attach to the base section  34  of the reservoir  30  by way of the catheter connector  36 , while the second end  44  serves as the fluid uptake end, thereby providing a pathway for fluid to enter the shunt system  10 . In a hydrocephalus shunt system, the inflow, or ventricular, catheter  40  is placed in a ventricle of the patient so that cerebrospinal fluid can enter the shunt device  20 . After the cerebrospinal fluid enters the shunt device  20 , the fluid is regulated by the valve mechanism  22  and, according to the patient&#39;s physiological condition, excess cerebrospinal fluid is released from the shunt device  20  through an outflow, or drainage, catheter  60 . The excess fluid is carried out through a channel  66  extending between a first end  62  of the outflow catheter  60 , which first end  62  is configured to attach to the valve mechanism  22 , and a second, fluid release end  64  where the fluid exits the shunt system  10 . 
   As shown in  FIG. 1B , the catheter connector  36  includes a flange  38  at its free end. The first, attachment end  42  of the inflow catheter  40  has an inner diameter ID which is slightly smaller than the largest outer diameter of the flange  38 . This inner diameter ID can be the diameter of the channel  46  extending from the first, attachment end  42  to the second, fluid uptake end  44  of the inflow catheter  40  provided the channel  46  has a consistent diameter throughout the inflow catheter  40 . However, it is understood that the inner diameter ID of the channel  46  need only be smaller than the largest outer diameter of the flange  38  at a section near the first, attachment end  42  of the inflow catheter  40 . This smaller inner diameter ID enables the attachment end  42  to form a tight, interference fit with the connector  36  when the attachment end  42  is urged onto the connector  36  and flange  38 . The inflow catheter  40  can be formed from a resilient and flexible material such as medical-grade silicone to allow the first, attachment end  42  to deform and fit over the connector  36  and flange  38  as the inflow catheter  40  is advanced towards the base section  34 . 
   To secure the first, attachment end  42  of the inflow catheter  40  to the connector  36 , a selectively engageable locking mechanism  50  is provided with the inflow catheter  40 . The locking mechanism  50  can comprise a retaining ring  52  for maintaining the attachment end  42  of the inflow catheter  40  onto the connector  36 . In one exemplary embodiment, the retaining ring  52  is able to move, or slide over the inflow catheter  40  and beyond the flange  38  when the inflow catheter  40  is attached to the connector  36 . As illustrated in  FIG. 1C , the retaining ring  52  can be situated adjacent to the attachment end  42  in an unlocked state. After the attachment end  42  is urged onto the connector  36  and flange  38 , the retaining ring  52  can be moved towards the attachment end  42  such as by sliding, twisting, or other similar advancing action until the retaining ring  52  passes over the flange  38  held within the attachment end  42 . In this locked state as shown, the retaining ring  52  compresses the flexible attachment end  42  over the connector  36 . The retaining ring  52  is configured such that the inner diameter is smaller than the largest outer diameter of the attachment end  42  with the flange  38  therein, thereby preventing the retaining ring  52  from sliding out of its locked state back to its unlocked state. 
   It is contemplated that the retaining ring  52  can be formed of a suitable biocompatible material such as titanium or titanium alloy, while the connector  36  and flange  38  are formed of a semi-deformable material such as nylon to allow enough compression for the retaining ring  52  to slide over the flange  38 . With this locking mechanism  50 , the inflow catheter  40  is able to be assembled to the shunt device  20  quickly and easily, without the need for sutures or adhesives. The retaining ring  52  also provides a more consistent joining force than current suturing methods. 
   The inflow catheter  40  of the present invention also provides features that enable its customization to a particular patient. On the outer surface of the inflow catheter  40  are marks or indicia  54  which correspond to the length of the inflow catheter  40 . These marks  54  can aid the surgeon in pre-sizing the inflow catheter  40  to the individual patient once the specific size of the ventricular tube needed has been determined by either CT scan or other known imaging techniques. This way, the surgeon can adjust the length, i.e., by cutting the catheter  40  to the required size, intraoperatively. If it is desirable to cut the inflow catheter  40  to size, the retaining ring  52  can be slid away from the area to be cut, near the second, fluid uptake end  44 . Alternatively, the retaining ring  52  can be taken off the inflow catheter  42  entirely, and placed back on after the inflow catheter  40  has been cut to size. Once the inflow catheter  40  has been cut to the desired size, the retaining ring  52  is advanced near the first, attachment end  42  prior to assembly. 
   In addition, the inflow catheter  40  can have either an open or a closed second end  44  for surgeon modification to allow visualization with an endoscope. If the second end  44  is closed, a pre-formed slit  56  can be provided so as to allow the endoscope to pass through the second end  44 . Since the second end  44  serves as the fluid uptake end, a series of apertures  58  can be provided near the closed second end  44  to facilitate fluid entry into the inflow catheter  40 . 
   Rather than having a sliding retaining ring  52  on the inflow catheter  40 ,  FIG. 2A  shows another exemplary embodiment of a locking mechanism  50 ′ comprising a retaining ring  52 ′ that is firmly secured to the inflow catheter  40  of the present system  10  at its attachment end  42 . The retaining ring  52 ′ can resemble the retaining ring  52  of  FIGS. 1B and 1C  in size, shape, and composition, except that the retaining ring  52 ′ is bonded to the outer diameter of the inflow catheter  40 .  FIG. 2B  shows yet another exemplary embodiment of a locking mechanism  50 ″ for use with the inflow catheter  40  of the present system  10 , in which a retaining ring  52 ″ is firmly secured such as by bonding to the inner diameter ID of the inflow catheter  40  at its attachment end  42 . The retaining ring  52 ″ can be formed from a semi-deformable material such as nylon. The retaining rings  52 ′,  52 ″ of the present invention can be used with pre-cut fixed length inflow catheters  40 . During assembly, the bonded retaining rings  52 ′,  52 ″ pop over the flange  38  of the connector  36  when the inflow catheter  40  is urged onto the connector  36 , thus retaining the inflow catheter  40  and the connector  36  together without the need for sutures or adhesives. 
   To allow pumping of the valve mechanism  22  distally while preventing occlusion of the shunt device  20  proximally, the base section  34  of the reservoir  30  can include a check valve mechanism  70  as illustrated in  FIG. 4 . Within the base section  34  are partitions  76  that form a funnel entrance  82  leading into a constricted region or central flow channel  78  that extends into the main chamber  84 . The partitions  76  can be held a distance apart from the base section  34  to thereby create peripheral flow channels  80  as well. The peripheral flow channels  80  lend anti-siphon properties to the check valve mechanism  70  by creating narrow structures that restrict fluid flow distally. A free floating ball  72  is provided with the check valve mechanism  70  to occlude fluid flow into the base section  34  from the inflow catheter  40  during distal pumping or anti-reflux as shown in  FIG. 4 . The free floating ball  72  can be pushed aside or manipulated aside by positioning the patient, such as in  FIG. 5A  where normal flow conditions are present and fluid flows from the inflow catheter  40  through the base section  34  of the reservoir  30  and to the valve mechanism  22  as indicated by the arrows. 
   The free floating ball  72  can also be pushed aside using an endoscope  90  such as in  FIG. 5B  during endoscopic placement of the shunt system  10  or during ventricular injection. To provide the endoscope  90  with access to the check valve mechanism  70 , the domed cap  14  of the housing  12  can include an endoscope port  16 . The endoscope port  16  can comprise a pre-formed slit comprising a resealable silicone and can extend into a portal  18  that connects to the top section  32  of the reservoir. Once the endoscope  90  has passed through the portal  18 , the endoscope can continue through the top section  32  and into the base section  34  past the central flow channel  78 . The endoscope  90  can extend all the way out through the catheter connector  36  to facilitate placement of the shunt device  20  with respect to the pre-inserted inflow catheter  40  and allow endoscopic visualization as needed. The endoscope port  16  can also include radiopaque markings to assist the surgeon in locating and targeting the port  16 . 
   Additionally, the peripheral flow channels  80  of the base section  34  can be made more tortuous with surface features such as helical ridges  86  as illustrated in  FIG. 6A  which shows the flow dynamics during distal pumping or anti-reflux. The helical ridges  86  within the peripheral flow channels  80  provide the shunt system  10  with higher resistance and even more anti-siphoning capabilities.  FIG. 6B  shows the flow dynamics during normal erect flow, while  FIG. 6C  shows the flow dynamics during anti-siphon flow in which fluid traveling distally is forced through the tortuous path of the peripheral flow channels  80  and is thereby drained from the shunt system  10  at a reduced rate. Finally, the flow dynamics during prone flow, or during distal pumping is illustrated in  FIG. 6D , while  FIG. 6E  shows the use of an endoscope  90  with the present shunt system  10  during endoscopic placement or ventricular injection. 
   The present invention also provides an instrument  100  for assembling the inflow catheter  40  quickly and easily to the shunt device  20 . The instrument  100  has a first arm  110  having a proximal end  112  and a distal end  114  including a handle portion  118 . Pivotally connected to the first arm  110  at pin  130  is a second arm  120  having a proximal end  122  and a distal end  124  including a handle portion  128 . The proximal end  112  of the first arm  110  includes a gripping section  116  that is configured to hold a portion of the housing  12 . As illustrated in  FIG. 7 , the gripping portion  116  is configured to seat against the domed cap  14  of the housing  12 . The proximal end  122  of the second arm also includes a platform section  126  that is configured to sit around the inflow catheter  40  and against the retaining ring  52  while resting on the patient&#39;s scalp. Upon compressing the handle portions  118 ,  128  together, the gripping section  116  and platform section  126  advance towards each other, in the process forcing the retaining ring  52  up towards the first, attachment end  42  of the inflow catheter  40 . The platform section  126  is configured to slide along the inflow catheter  40 . The use of the instrument  100  to connect these components enables the retaining ring  52  to slide over the attachment end  42  of the ventricular catheter  40  and over the flange  38  of the connector  36  without over advancement. 
   Typically, the outflow catheter  60  can be assembled to the shunt device  20  prior to implantation, while the inflow catheter  40  is assembled to the shunt device after the two components are separately implanted. In one exemplary embodiment of the shunt system  10 , when fully assembled the inflow catheter extends at approximately 90° with respect to the outflow catheter. 
   The endoscopic placement features just described for the shunt system  10  of the present invention allow the system  10  to be easily assembled and implanted using endoscopic placement so as to require only minimally invasive surgery. The assembly process for the present invention minimizes surgery time and avoids leakage at the connection sites, since the retaining ring eliminates the need for suturing methods. The endoscopic placement features of the present invention also provides the added benefits of revision on a minimally invasive basis, such as clearing or draining obstacles to improve cerebrospinal fluid flow, without major surgical intervention. Finally, the check valve mechanism of the reservoir also provides easy occlusion for distal flushing. All of these features make endoscopic placement more convenient for the surgeon, and provide a better and more effective shunt system for the patient. 
   It will be understood that the foregoing is only illustrative of the principles of the invention, and that various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. All references cited herein are expressly incorporated by reference in their entirety.