Abstract:
A catheter assembly for intracranial treatment of a patient is disclosed. The assembly comprises outer and inner catheters. The outer catheter has an exterior surface, an inflatable balloon mounted upon the exterior surface, at least one element distal to the balloon, at least one aperture and a lumen. The inner catheter is sized to be received within the lumen and has a passageway extending between a proximal end and at least one port. The lumen is adapted to guide the inner catheter to the desired tissue region in the brain. Each element is adapted to monitor brain activity within the tissue region, to electronically stimulate the tissue region, or to provide information on a precise position of the element when the element is entirely within the brain. The elements are mounted proximal to the distal end of the outer catheter upon the exterior surface of its distal portion. The assembly can facilitate the administration of drugs to the tissue region or the removal of fluid from the brain through the inner catheter.

Description:
RELATED APPLICATION  
       [0001]     This is a divisional application claiming the benefit of U.S. patent application Ser. No. 10/423,587, filed on Apr. 25, 2003, hereby incorporated by reference. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates to the intracranial transfer of fluids and, in particular, to devices for affecting such transfer.  
       BACKGROUND OF THE INVENTION  
       [0003]     Movement disorders such as epilepsy and Parkinson&#39;s disease have been estimated to affect some 1-2% of the developed world&#39;s population and up to 10% of people in underdeveloped countries. Currently, approximately 75% of those who suffer from movement disorders are responsive in some degree to drugs.  
         [0004]     Electrical stimulation has also been utilized to treat some movement disorders. In the treatment of epilepsy, studies have been performed in which awake patients undergoing temporal lobe surgery underwent cortical stimulation. Such stimulation of the visual and hearing areas of the brain reproducibly caused the patients to experience visual and auditory phenomena. This discovery was made possible by the identification that certain brain subregions served specific functions, such as sight, hearing, touch and movement of the extremities and proved that direct electrical stimulation of the brain regions could cause partial reproduction or suppression of the functions.  
         [0005]     As suggested by these results, it is known that certain types of treatment of specific portions of the brain are able to suppress certain unwanted behavior which results from movement disorders. This behavior may include seizures such as those suffered by epileptics. However, the studies faced a major problem in that there was an inability to precisely electrically stimulate very small volumes of the brain.  
         [0006]     The advent of needle-shaped penetrating depth electrodes helped to overcome this obstacle faced by electrical stimulation. Depth electrodes can be placed within the brain tissue itself, enabling optimal surface contact with elements of the brain that are targeted for stimulation. This allowed for safe, chronic electrical stimulation of very small discrete volumes of brain.  
         [0007]     In treatment, electrical stimulation has been used with the recording and analysis of changes in brain activity to predict the occurrence of epileptic seizures. The time of onset of such seizures is often predictable by neural discharge monitoring, even when the exact causal nature of precipitating dysfunction is not understood. Electrodes have been used to obtain signals representative of current brain activity along with a signal processor for continuous monitoring and analysis of these electrical signals in order to identify important changes or the appearance of precursors predictive of an impending change.  
         [0008]     While the electrical stimulation of brain tissue has been somewhat effective in the treatment of migraines, epilepsy and other neurological problems, patients often experience diminishing returns with such treatment. Furthermore, because each patient reacts differently to electrical stimulation, substantial time must be spent to determine the specific amplitude, frequency, pulse width, stimulation duration, etc. which may result in effective treatment. In addition, such parameters often require continual adjustment in order to remain effective.  
         [0009]     The combination of drug delivery and electrical stimulation and/or monitoring has been shown to be more effective in some intracranial treatments. Such drug delivery and stimulation or monitoring is typically performed by instruments which are inserted into the brain at different locations or along different tracks. Other systems employ a single device which must be removed and reinserted to provide for delivery of multiple drugs or use of different electrical devices.  
         [0010]     Since the introduction of probes or other similar devices into the brain is common in many surgical procedures today, there are a variety of probes available. Such probes typically include ports for drug delivery or electrical, chemical, electrochemical, temperature and/or pressure contacts which enable the observation and analysis of the brain state or contacts providing stimulation. These ports and contacts must typically be positioned at specific points or regions in the brain.  
         [0011]     Probes used in intracranial penetration are typically fabricated so that their introduction to the brain is as minimally traumatic as possible. In addition to being minimally traumatic during insertion, certain inserted probes must also be able to remain implanted without causing injury through unintended movement. In some uses, a probe may be implanted and remain in the patient&#39;s brain for weeks or longer. Changes in the positioning of the probe often occur during placement or during such extended periods. Therefore, the probe must be capable of precise placement and as biocompatible as possible. In response to these requirements, state of the art intracranial probes are typically thin, flexible pieces with smooth surfaces to minimize the amount of brain tissue contacted and to minimize damage to contacted brain tissue.  
         [0012]     While such thin, flexible probes are sufficiently biocompatible, they are delicate and often difficult to insert along specific trajectories or lines of insertion. During typical implantation, a surgeon feeds the probe into the brain through an aperture in the skull. In this process, the surgeon has very little control over the distal end of the probe. In order to provide more rigidity to the probe to overcome this problem, a removable stylet may be inserted into the probe before implantation. Still, veering from the intended line of insertion is not altogether prevented by introduction of a stylet to the probe.  
         [0013]     While typical intracranial probes have smooth surfaces so as to not cut any contacted tissue, many such probes are made of elastomers or other such materials which, although smooth, do not easily slide through brain tissue. The drag encountered by these types of probes can result in injury to the contacted brain tissue.  
         [0014]     Therefore, there is a continuing significant need in the field of intracranial treatment, particularly with insertion of probes into the interior of the brain, for improvements in accuracy of insertion and avoidance of injury, while retaining efficiency and ease of use.  
         [0015]     In addition, there is a need in the field of intracranial treatment to minimize the invasiveness of intracranial treatment and to reduce the number of instruments which penetrate brain tissue or the number of times a single instrument must penetrate brain tissue.  
         [0016]     Furthermore, there is a need in the field of intracranial treatment to provide the ability to precisely locate the position of a probe during insertion to ensure proper positioning.  
       OBJECTS OF THE INVENTION  
       [0017]     It is an object of the invention to provide an improved intracranial insertion device which prevents injury to the patient.  
         [0018]     Another object of the invention is to provide a catheter assembly which is simple in structure and operation in order to facilitate intracranial procedures.  
         [0019]     Another object of the invention is to provide a catheter assembly which allows for the precise insertion of drug delivery ports or contacts in the brain while avoiding extensive trauma to and scarring of brain tissue.  
         [0020]     Another object of the invention is to provide an outer catheter which includes contacts for stimulation and/or monitoring the brain and which receives and guides a drug delivery catheter to the targeted brain tissue for drug delivery.  
         [0021]     Another object of the invention is to provide an outer catheter which includes contacts for stimulation and/or monitoring the brain and which receives and guides a cerebral spinal fluid recovery catheter to the targeted brain tissue for sampling cerebral spinal fluid through a dialysis membrane.  
         [0022]     Another object of the invention is to provide an outer catheter which includes location markers for allowing the positioning of the outer catheter to be determined during or after insertion of the catheter into the brain and which receives and guides an inner catheter for delivering or removing fluid from the targeted brain tissue.  
         [0023]     Another object of the invention is to provide a depth electrode which receives and guides an inner catheter for delivering or removing fluid from the targeted brain tissue and remains in position when the inner catheter is removed, allowing for further insertions of the inner catheter without further extended contact with brain tissue during insertion.  
         [0024]     Another object of the invention is to provide an outer catheter including an inflatable balloon for sealing any insertion tract to permit effective drug delivery to the targeted brain tissue region.  
         [0025]     Still another object of the invention is to provide a method of safely inserting, through use of an outer catheter, a catheter in a patient&#39;s brain which provides for drug delivery and/or cerebral spinal fluid withdrawal as well as stimulation and/or monitoring of brain activity.  
         [0026]     Yet another object of the invention is to provide a trajectory catheter which can be mounted to the patient&#39;s skull and connected to an inner catheter such that the inner catheter is positioned and held at the targeted brain tissue region.  
         [0027]     These and other objects of the invention will be apparent from the following descriptions and from the drawings.  
       BRIEF SUMMARY OF THE INVENTION  
       [0028]     In accordance with the present invention, an intracranial catheter assembly is provided for precise treatment of brain tissue. The catheter assembly of this invention overcomes certain problems and shortcomings of the prior art, including those noted above, and provides a unique structure satisfying a number of specific intracranial treatment needs.  
         [0029]     The catheter assembly comprises (a) an outer catheter having a proximal opening, at least one aperture and a lumen connecting the opening and the at least one aperture, and at least one element; and (b) an inner catheter adapted to be received within the lumen and including a passageway and at least one port for delivering fluids to a tissue region within the patient&#39;s brain. In preferred embodiments the assembly further comprises a rigid stylet received within the lumen for insertion into the patient&#39;s brain (since the preferred outer catheter is flexible) and removed before insertion of the inner catheter into the lumen.  
         [0030]     In certain embodiments, the aperture is preferably axially aligned with the inner lumen. hI such embodiments, the inner catheter can extend through the aperture when the inner catheter is received within the lumen.  
         [0031]     In other embodiments, the outer catheter has a closed end which blocks passage of the inner catheter therethrough. In such embodiments the aperture is located along a side of the outer catheter. The outer catheter can include more than one aperture which are preferably radially and axially spaced about the outer catheter. In still other embodiments, the outer catheter has an aperture axially aligned with the inner lumen and other apertures which are located along a side which may be radially or axially spaced.  
         [0032]     In certain preferred embodiments, the outer catheter further includes a conduit extending from the proximal end to an inflatable balloon which is adapted to be inflated to seal a tract created during insertion of the assembly into the brain. The inflatable balloon may be inflated with a fluid which does not come in contact with brain tissue; however, in some embodiments, the balloon is inflated with a fluid which is then introduced to the tissue region surrounding the balloon. Such a fluid can be any type of medicament, and will be referred to herein as a “drug,” such term including other types of medicaments. Introduction of the fluid can occur at a slow or fast rate as fluid permeates through or otherwise leaves the balloon and can occur before, simultaneous with, or after transfer of fluid through the lumen or passageway such that multiple fluids may be administered separately through the catheter assembly.  
         [0033]     The inner catheter preferably has at least one port. In some embodiments, the ports are designed to be in communication with the apertures of the outer catheter when the inner catheter is inserted into the lumen to a preferred position. In other embodiments, the position of the ports do not correspond with the apertures—particularly when an aperture is axially aligned with the lumen and the distal portion of inner catheter passes through the aperture. In certain preferred embodiments there are at least two ports which are axially spaced on a side of the inner catheter along a line parallel to the passageway. In other embodiments, the ports are radially and axially spaced about the inner catheter. In yet other embodiments, the inner catheter includes a port axially aligned with passageway and at least one port positioned on its side.  
         [0034]     The preferred port is adapted to deliver or remove fluids from the surrounding brain tissue. In certain embodiments, the port includes a dialysis membrane adapted to receive cerebral spinal fluid.  
         [0035]     In some embodiments, the outer catheter and inner catheter preferably have proximal ends with one of the proximal ends including a luer fitting and the other of the proximal ends configured for connection to the luer fitting. In such embodiments, the outer catheter is inserted into the patient&#39;s brain to a desired position, then the inner catheter is inserted into the lumen and the catheters are connected to one another via the luer fitting such that the inner catheter is secured at the desired position in the brain.  
         [0036]     In some embodiments, the outer catheter is preferably adapted to connect to the patient&#39;s skull when inserted to the targeted portion. In such embodiments, the inner catheter is preferably adapted to connect to the outer catheter when inserted to the targeted portion. Therefore, during use, the outer catheter may be inserted to the targeted position and secured to the skull while the inner catheter is inserted into the lumen and then secured to the outer catheter. Such connections are preferably performed by screwing the outer catheter to the skull and the inner catheter to the outer catheter, i.e., via threads on each of the catheters.  
         [0037]     In certain embodiments, the at least one element is a contact which monitors activity in the brain. In such embodiments, the outer catheter can be considered as a depth electrode. The contact may be of the type which senses electrical, chemical or electrochemical activity in the brain. The contact preferably senses brain function in the tissue region. In other embodiments the contact provides electrical stimulation to the tissue region. The contact may be a collar circumscribing the outer catheter, a micro contact, a macro contact, or other types of contacts. The depth electrode preferably includes an electrical lead corresponding to each contact.  
         [0038]     In other preferred embodiments, the element is a location marker for allowing the position of the outer catheter to be located within the brain. The location marker is preferably adapted to be located by magnetic resonance imaging or computerized x-ray tomography such that such imaging devices can be used to locate the position of the catheter in the patient&#39;s brain during or after insertion or implantation.  
         [0039]     In yet other preferred embodiments, multiple elements on the outer catheter include both at least one contact and at least one marker.  
         [0040]     The invention also includes a method of treating a tissue region in the brain of a patient comprising (a) inserting into the brain an outer catheter having at least one element, at least one aperture and a lumen, (b) inserting into the lumen an inner catheter having a passageway extending between a proximal end and at least one port, and (c) transferring fluids between the tissue region and the proximal end through the passageway. In the inventive method the outer catheter guides the inner catheter to the tissue region. Therefore, the inner catheter may be non-rigid or otherwise ill-designed to be precisely inserted into a patient&#39;s brain and still be precisely positioned at the desired position in the brain. The method preferably includes positioning a stylet in the lumen during insertion of the outer catheter into the brain and removing the stylet from the outer catheter before the inner catheter is inserted into the lumen. The method also preferably includes connecting the outer catheter to the patient&#39;s skull and connecting the inner catheter to the outer catheter. The catheters may be connected by screwing reciprocal threaded parts together, by use of a luer fitting or other connecting members.  
         [0041]     In certain embodiments, the element is a location marker and the method further includes locating the position of the location marker in the brain. The location marker is preferably located by magnetic resonance imaging or by computerized x-ray tomography.  
         [0042]     In other embodiments, the element is a contact and the method further comprises monitoring the tissue region via the contact. The contact preferably provides electrical stimulation to the tissue region, senses brain activity in the tissue region, or multiple contacts allow for performance of each of these functions. The preferred monitoring action includes sensing chemical changes at the tissue region and/or sensing electrical changes at the tissue region. The contact is preferably a collar-type contact, a micro contact for monitoring cells or neurons, a macro contact for monitoring tissue, or a fiber optic contact.  
         [0043]     In preferred methods, the inner catheter has a distal end which passes through the aperture into the tissue region beyond the outer catheter during the insertion of the inner catheter into the lumen. In other preferred embodiments, the inner catheter has a distal end and the outer catheter has a closed lumen so that the distal end is contained within the outer catheter when the inner catheter is inserted into the lumen.  
         [0044]     The transferring action preferably includes delivering drugs to the tissue region through the at least one port and/or withdrawing cerebral spinal fluid through the at least one port. In certain embodiments, the inner catheter includes a micro-dialysis membrane at the at least one port and cerebral spinal fluid passes through the membrane during the withdrawing action.  
         [0045]     In certain preferred embodiments, the outer catheter includes an inflatable balloon and the method further comprises inflating the balloon to seal a tract created during insertion of the assembly into the brain. The balloon is preferably inflated with a drug which is delivered to the tissue region through the balloon. The preferred method further comprises delivering a second drug to the tissue region through the at least one port.  
         [0046]     Some preferred embodiments of the invention include a first inner catheter having a first length for delivering fluids to a first tissue region and a second inner catheter having a second length greater than the first length for delivering fluids to a second tissue region within the patient&#39;s brain. More preferably, the assembly comprises a third inner catheter having a third length greater than the second length for delivering fluids to a third tissue region within the patient&#39;s brain. As is understood the assembly can include many inner catheters of different lengths and having different arrangements of ports to provide for treatment of specific desired tissue regions in the brain.  
         [0047]     Each different inner catheter is preferably introduced to the brain through a single outer catheter such that an instrument penetrates a large portion of the brain tissue between the skull and the desired tissue regions only once. Such an assembly allows for inserting the outer catheter through the intervening brain tissue, precisely locating the outer catheter relative to a specific tissue region, inserting corresponding inner catheter (the inner catheter which would position a port at the tissue region when inserted into the lumen) in the lumen, treating the tissue region, withdrawing the used inner catheter from the lumen, inserting another inner catheter corresponding to another desired specific tissue region, treating that region, etc. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0048]     The drawings furnished herewith illustrate a preferred construction of the present invention in which the above advantages and features are clearly disclosed as well as others which will be readily understood from the following description of the illustrated embodiment. In the drawings:  
         [0049]      FIG. 1  is a perspective view of a catheter assembly and patient, shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0050]      FIGS. 2   a  and  2   b  are perspective views of an alternate outer catheter having a closed end, shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0051]      FIG. 3  is a perspective view of an outer catheter when receiving a stylet, shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0052]      FIG. 4  is a perspective view of an outer catheter when receiving an inner catheter, shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0053]      FIGS. 5   a,    5   b,    5   c  and  5   d  are perspective views of alternate inner catheters, shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0054]      FIG. 6  is a perspective view of an outer catheter having a balloon shown both deflated and inflated, with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0055]      FIG. 7  is a perspective view of an alternate version of the outer catheter shown in  FIG. 6 , shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0056]      FIG. 8  is a perspective view of an alternate version of the outer catheter shown in  FIGS. 6 and 7 , shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0057]      FIGS. 9   a,    9   b,    9   c  and  9   d  are perspective views of alternate versions of the outer catheters shown in  FIGS. 6-8 , shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0058]      FIG. 10  is a perspective view of a preferred outer catheter having a balloon and contacts with an electrical lead, shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0059]      FIG. 11  is a perspective view of an alternate version of the outer catheter shown in  FIG. 10 , shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0060]      FIG. 12  is a perspective view of an alternate version of the outer catheter shown in  FIGS. 10 and 11 , shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0061]      FIG. 13  is a perspective view of an alternate version of the outer catheter shown in  FIGS. 10-12 , shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0062]      FIGS. 14   a,    14   b,    14   c  and  14   d  are perspective views of alternate versions of the outer catheters shown in  FIGS. 10-13 , shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0063]      FIGS. 15 and 16  are perspective views of a preferred catheter assembly in which the inner catheter includes a dialysis membrane, shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
         [0064]      FIGS. 17   a  and  17   b  are perspective views of a preferred catheter assembly which provides for connection between the outer catheter and the patient&#39;s skull and includes a location marker and including a set of inner catheters, shown with dashed lines representing otherwise unseen internal features, in accordance with the invention.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0065]     Referring to  FIG. 1 , a catheter assembly in accordance with the present invention is generally designated by the reference numeral  10 . Catheter assembly  10  allows intracranial treatment of a patient by providing an outer catheter  30  and inner catheter  50  which cooperate to transfer fluids between a tissue region  81  in the patient&#39;s brain  80  and an external receptacle or device. Also shown with catheter assembly  10  is stylet  60  which can be received by outer catheter  30  to prevent the entrance of brain tissue into outer catheter  30  during insertion into the brain.  
         [0066]     Outer catheter  30  is preferably between about 0.6 and 1.5 millimeters, most preferably about 1.0 millimeter and is comprised of polyurethane, silicone, polyimide, or other biocompatible material. Outer catheter  30  includes a lumen  33  which extends from proximal opening  31  to aperture  32 . Outer catheter  30  also includes elements  40  which may provide for monitoring of brain tissue or for providing a location marker for determining the precise position of outer catheter  30  within the brain. As shown, elements  40  include distal contacts  41  which can sense brain activity in tissue region  81  via electrical, electrochemical, chemical or pressure changes within the brain. Preferred contacts  41  are platinum, platinum iridium or other biocompatible conductive material. For pressure sensing, contact  41  is a miniature pressure-sensing contact which is preferably a miniature optical pressure transducer less than about 2 millimeters long as discussed in U.S. patent application Ser. No. 09/948,153, filed Sep. 6, 2001 and incorporated herein by reference. Brain activity sensed by distal contacts  41  is transmitted to an external connector through proximal contacts  48  and then to a computer or instrument which records and/or analyzes such activity. During insertion or implantation proximal contacts  48  remain outside of the patient and allow for connection to such an instrument. Proximal contacts  48  are preferably stainless steel or other alloys or materials which are noncorrosive conductors which can endure the sterilization process.  
         [0067]     Inner catheter  50  is preferably polyimide, polyimide-coated glass or other similar material and includes a passageway  51  which extends from proximal end  53  to port  52 . Passageway  51  has an inner diameter which may vary depending on the desired flow rate of fluid therethrough but is preferably between about 25 microns and 0.5 millimeters. As shown, port  52  is axially aligned with passageway  51  (as is aperture  32  with lumen  33 ) such that fluids may be transferred to or from the tissue region  81  at port  52 , e.g., drugs may be administered to tissue region  81 , cerebral spinal fluid may be withdrawn, or both. Inner catheter  50  is shown as including a luer fitting  54  which provides for connection with outer catheter  30 .  
         [0068]      FIGS. 2   a  and  2   b  depict alternate embodiments of outer catheter  30  in which lumen  33  has a closed end  34 . In such embodiments, apertures  32  are positioned along the side or sides of the outer catheter. For instance,  FIG. 2   a  shows apertures  32  axially spaced along a line parallel to lumen  33 .  FIG. 2   b  shows apertures  32  axially and radially spaced about outer catheter  30 . In addition, outer catheter  30  is shown as including a luer fitting  36  providing for connection with inner catheter  50 .  
         [0069]      FIG. 3  shows stylet  60  received within lumen  33  for insertion into the patient&#39;s brain. Stylet  60  prevents brain tissue from entering lumen  33  during insertion and may provide rigidity to outer catheter  30  if outer catheter  30  is not rigid.  
         [0070]      FIG. 4  shows inner catheter  50  received within lumen  33 . As shown, distal portion  56  of inner catheter  50  extends through aperture  32  to reach the desired region in the brain. Port  52  is shown axially aligned with passageway  51  although additional ports  52  can be positioned along the sides of distal portion  56 .  
         [0071]      FIG. 5   a  shows inner catheter  50  while  FIGS. 5   b,    5   c  and  5   d  show alternate embodiments of distal end  56  of inner catheter  50  in which port  52  is axially aligned with passageway  51  ( FIG. 5   b ), multiple ports  52  are axially spaced along a line parallel to passageway  51  ( FIG. 5   c ), and multiple ports  52  are axially and radially spaced about inner catheter  50  ( FIG. 5   d ). It is understood that an inner catheter  50  can include both an axially aligned port  52  and ports  52  positioned along its side.  
         [0072]      FIGS. 6-14   d  pertain to a preferred embodiment of the catheter assembly  10  in which outer catheter  30  includes an inflatable balloon  38 . As shown in  FIG. 6 , a conduit  37  leads to balloon  38  to provide for the introduction of a fluid to inflate balloon  38  and, if necessary to withdraw fluid from balloon  38  to cause deflation (in certain embodiments fluid permeates through balloon  38  to treat the tissue region surrounding balloon  38 ). As shown, conduit  37  terminates at a plug which can be connected to another device to receive or dispense fluid. Conduit  37  runs alongside lumen  33  and terminates at balloon  38 .  FIGS. 6-8  show the alternate embodiments in which apertures  32  are variously positioned as discussed above. In each of  FIGS. 6-8  elements  40  are distal contacts  41 , and more specifically are macro contacts of the collar-type which circumscribe outer catheter  30 . Proximal contacts  48  connect to distal contacts  41  to communication brain activity from distal contacts  41  to a recording or analysis instrument. Proximal contacts  48  do not enter the patient&#39;s brain, instead they provide connection to such an instrument.  
         [0073]     Balloon  38  can be inflated to block any insertion tract created when catheter assembly  10  is inserted into the brain such that any drug administered to the brain cannot migrate through any tract. In addition, balloon  38  may be inflated with a drug or other fluid which is intended to be administered to the brain. In this manner, fluids may be transferred between the brain and the apertures  32  at the same time fluids are introduced to the brain through balloon  38  through permeation. Balloon  38  is particularly adept at administering fluids to the brain slowly over a period of time which may allow for effective introduction of the fluid to the brain.  
         [0074]      FIGS. 9   a,    9   b,    9   c  and  9   d  differ from  FIGS. 6-8  in that outer catheter  30  includes a distal portion which has a reduced diameter. Such an embodiment provides for minimized invasiveness at the targeted tissue region.  FIGS. 9   b,    9   c  and  9   d  are enlarged views of the distal portion about which apertures  32  may be variously positioned.  
         [0075]      FIGS. 10-14   d  depict an outer catheter  30  which includes micro contacts  44  and/or macro contacts  45  and a lead  42  which communicates brain activity through connector  46 . As shown, lead  42  runs alongside conduit  37  and lumen  33  to distal contacts  41  (micro contacts  44  and/or macro contacts  45 ). It is noted that sensing contacts  41  may be positioned on both the distal and proximal sides of balloon  38 . Such a design allows for monitoring of brain tissue which is being treated with drugs simultaneous with monitoring of brain tissue which is not being treated. Micro contacts  44  and apertures  32  are shown variously positioned in  FIGS. 10-14   d  as apertures  32  were shown and discussed as being variously positioned above. For example,  FIGS. 14   b,    14   c  and  14   d  show the distal portions of outer catheter  30  and have an axially aligned aperture  32  and axially spaced micro contacts  44  in a line parallel to lumen  33  ( FIG. 14   b ), micro contacts  44  and apertures  32  axially spaced in a line parallel to lumen  33  ( FIG. 14   c ) and radially and axially spaced apertures  32  and axially spaced micro contacts  44  ( FIG. 14   d ).  
         [0076]      FIGS. 15 and 16  depict a catheter assembly  10  which includes a inner catheter  50  with a port  52  which is a micro dialysis membrane  55 . In such an embodiment, outer catheter  30  includes apertures  32  which allow cerebral spinal fluid to reach membrane  55 . Fluid moves through membrane  55  and is transferred through passageway  51  to external receptacles or analysis devices. In  FIG. 15 , proximal opening  31  is axially aligned with outer catheter  30  such that lumen  33  passes through proximal contacts  48 . In  FIG. 16 , lumen  33  branches off of outer catheter  30  through a flexible tubing before reaching proximal contacts  48  (proximal contacts  48  are connected to distal contacts  41  by an unshown connection). Inner catheter is received in lumen  33  and moves into outer catheter  30  to ports  32 . In such an embodiment, inner catheter is sufficiently flexible to navigate lumen  33 .  
         [0077]      FIG. 17   a  shows catheter assembly  10  including an outer catheter  30  which has a location marker  43  as element  40 . Location marker  43  is preferably comprised of a material which contains a mobile phase suitable for MRI imaging by commercial machines, and which is sufficiently X-Ray-opaque for adequate imaging on CT or X-ray. Catheters  30 , 50  also include threads  39 , 58  which provide for attachment to the patient&#39;s brain and between the catheters  30 , 50 . Such an outer catheter  30  can be called a trajectory catheter when used in this manner. In a preferred method of use, trajectory catheter  30  is inserted into the brain and positioned at a desired location in the brain by using marker  43 . Outer catheter  30  is then connected to the patient&#39;s skull by screwing threads  39  into the skull. Then inner catheter  50  is inserted through lumen  33  and connected to outer catheter  30  by threads  58 .  
         [0078]      FIG. 17   b  shows the distal portions  56  of a set  59  of inner catheters including ports  52  which are variously positioned on distal portions  56  as shown. In certain preferred embodiments, inner catheters  50  of different lengths, such as those shown, are supplied with an outer catheter  30  such that, after inserting outer catheter  30  into the patient&#39;s brain, an inner catheter  50  of a specific length is selected to treat a desired tissue region at a known location beyond outer catheter  30 . After treatment at that location, the inner catheter  50  can be removed and another inner catheter  50  of a different length and/or different port arrangement can be inserted into the patient&#39;s brain to treat a different desired tissue region. For instance, an inner catheter  50  which extends 0.5 cm beyond outer catheter  30  may be used to treat the tissue region 0.5 cm beyond outer catheter  30  and then removed from lumen  33  before another inner catheter  50  which extends 2.0 cm beyond outer catheter  30  is inserted through lumen  33  and used to treat the tissue region 2.0 cm beyond outer catheter  30 . A set of inner catheters  50  is preferably provided with an outer catheter  30  such that a physician may select specific inner catheters  50  to treat the desired tissue regions. Such a set allows for specific treatment of different tissue regions, such as those found in and around tumors, with the same or different drugs without requiring multiple insertions through the intervening brain tissue.  
         [0079]     In some embodiments, outer catheter has apertures on its side (not shown) which correspond to ports  52 . In other embodiments, outer catheter has only a open ended lumen  33  such that the aperture is aligned with lumen  33 , and inner catheter  50  includes ports  52  on its distal portion which extends out of lumen  33  when inserted into the patient&#39;s brain. Outer catheter  30  can further include contacts  41  as disclosed in the prior figures.  
         [0080]     While the invention has been described with respect to specific embodiments by way of illustration, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true scope and spirit of the invention.