CA2218986A1

CA2218986A1 - Securing device for intercranial infusion port with filter and catheter

Info

Publication number: CA2218986A1
Application number: CA002218986A
Authority: CA
Inventors: Michael D. Baudino
Original assignee: Medtronic Inc
Current assignee: Individual
Priority date: 1995-04-28
Filing date: 1996-04-15
Publication date: 1996-10-31
Also published as: EP0822844A1; DE69636682D1; US5954687A; DE69632819D1; EP1426074A1; WO1996033766A1; EP0822844B1; EP1426074B1; AU5545196A; DE69632819T2; DE69636682T2; JPH11504231A

Abstract

A burr hole ring with a catheter for use as an injection port comprises a modified burr hole ring adapted to engage the skull at a burr hole drilled therein. The interior of the burr hole ring defines a fluid reservoir that may be accessed by a needle or stylet inserted through a septum positioned over the top of the burr hole ring. The reservoir is in fluid communication with the central lumen of a catheter. The assembly comprises a fluid flow path suitable for the transfer of fluids to or from selected location at, near or within the brain. A filter layer may be provided to prevent contamination of the drug infusion site.

Description

W 096/33766 . PCTrUS96/05159 SECURING DEVICE FOR INTERCRANIAL INFUSION PORT WITH FILTER AND ~ATHETE~
BACKGROUND
The present invention relates genPr~lly to methods and a~alaLus for providing â low profile access port est~hli~hing fluid co""~ ,iri~ n with the brain, such as for the ~l.";.~ inn of drugs or other liquids to specific loe-l;o,-~ within the body; and fu~er relates to brain i..r. ~iO.. plucedul~s, such as, for ~ r, supplying .h,.. ",~re~ltir~l agents such as peptides, poly~~i,Li~le~ pluLtillS, ~Iy-;o~luL~i~, lipoproLei~s, oligonucleotides, olignmlrlPosi(1Pc~ hnrrnnn~l agents, and/or other biologically derived trophic agents to the lateral ventricle of t_e brain. ~lth(~ h t_is particular application is the one described in detail herein, it should be nn~lpr~tood that the invention is not IlPCe~ l ily SO limited.
Plly~ici~ls today often use a CaLl~ placed to extend to â selçcted loc~tinn with~n a patient's brain for both the ~ inn of fluids and the l~c~ivhlg offluids. Using conventional â~dl~l~US to deliver lJh,.""~r~ ir~l agents to a c~
for delivery to a specific location within the brain, however, has ~i~.. ir~drawbacks. For example, the c~llRL~r will typically extend ou~waldly from the burr hole. Where only periodic ~ lalion of fluids are ~PCPS~ ly~ the ~
catheter P1~S~11L~ an llnnPcec~ llblallce. It would be desirable to remove this encumbrance.
ACCOLdi11g1Y~ the present invention provides a new method and a~dLus for establishing fluid co-.---.. ir~ion through a caLllel~l to a se.lectecl point within a patient's brain, which maybe selectively arrPc~ed to inject fluid into, or WillldldW
fluid from, the brain through the cdLllcl~l.
SUMMARY OF THE INVENTION
AS explained in more detail below, the present invention overcomes the above-noted and other shortcomings of prior devices and mPthntl~ for f~rilit~ting the infusion of drugs to the brain. Three s~p~dL~ exemplary embo~limPnt~ of the present invention are described herein.
The first exemplary embodiment generaliy collll)lises a burr hole ring modified to act as a catheter access port. The device may be integrally ~tt~rhPd to a catheter of a length sllffiriPnt for delivering drugs to a desired location within the skull, or may be att~rhPcl following c~LheL~l pl~rPmPnt Preferably, in accordance W 096/33766 2 PCTrUS96/05159 with the present invention, a Calh~t~ integ~lly ~ h~d to a m~ifito~l burr hole ring assembly is inserted to a desired depth and ~l~r~ l within the brain, typically being placed with the use of a stylet (a thin, solid wire or similar relatively non-flexible e,) inserted through the ~;dlll~,t~,. access port and into the Cal~c~l to Ill~;--l 1;~ its S rigidity. Once the ca~ ,L~ is placed, the stylet is wi~ awll and the .. ~l;ri~oA burr ring or cap assembly is secured within the burr hole in the skull. .Secnri~ the cap assembly may be ~rcsmplich~od with screws inserted through the assembly and intothe skull. More preferably, though, the morlifi.o-l burr ring assembly is adapted with threads or ridges for eng~ging the skull at the burr hole. A septum positioned on top of the burr ring or cap assembly isolates the interior of the callleL~l access port to help prevent c~ lisn of fluids within the assembly. A needle fixed to an a~ploplidle device may be used to pr~ the septum as desired to either withdraw or inject fluid. In accor~ ce with the present invention, filtration of injectrd fluids also may be ~rcomrli.ch~ Preferably, filtration is achieved by a filter ~ lllbel that is bacterial retentive so as to prevent c~ ;on of the cerebral spinal fluid. The cap assembly may be adapted so that there is a filt~ring layer above the central tube which permits direct fluid c~ .;r~ on between the interior of the catheter and the interior of the cap assembly. Above the filtering layer is positioned a needle stop, so that the injection or withdrawal of fluid is accomplished by the needle pt~ d~illg the septum until it hits the needle stop rnaterial. Any injected fluid then passes through the filter, central tube and catheter to the desired location within the patient's body.
As compared to the first exemplary embodiment described above, in a second exemplary embodiment the ca~llcL~ access port assembly further cc,ll.~lises a direct-feed, generally tubular lll~lllb~l ÇXlt?.~ g through the septum and into the central tube. The direct-feed tubular .. ~ .. h~l allows direct, unfiltered, fluid access from a location at the top of the septum through the central tube an into the interior of the catheter. Fluid within the interior of the Calll~L~l access port assembly may still flow along a path through the filter m~ lm to the annular space between the central tube and the direct-feed tubular member. The second exemplary embodiment thus affordsthe physician more than one fluid path option for the injection or withdrawal of fluids.
In a third exemplary emboflim~nt~ a burr hole cap having an integrally coupled catheter is placed in engagement with the skull at a burr hole. A septum mounting W 096/33766 3 PCTrUS96/05159 ".~ f ~, c~....l.. ;~;;.~ a genf rAlly .~ collar-like ~ I)er, ~lef~,.ably snaps through use of split-flanged collets into the burr hole cap, ~lth...lgh other means for s~
the septum ...u~ -..h~ to the burr hole cap may be used, e.g. edge rA~r~lf ~;, clamps, adhesives, etc. The septum secured in the top portion of the septum wullLillg ~-~f~ hfel again fArilitAt-f~s ;~OlAt;~n of, yet selective access through a needle to, the filtered fluid path through which fluids may be injectecl or wiLl~ d~vu. The septum Illll~llllill~ nlc~ c~ ~lcr~.ably also is adapted with ~ llr~ lLial snap fittings and a ~.ruldlcd base to f~rilitAte insertion into the me~l~el of one or more selPctrd pieces of filter mf ~ lm The filtf rjng mAtf riAl is placed on the ~~clruldLcd base of the Illrlllhel, and a l~clr~ldLed filter cap is then snapped into the .. f ,.. hf l to hold the f,lter in place. The p~.rulalcd filter cap also may act as a needle stop. Preferably, the filter assembly also is ~lrtArhAhlr, thus having the advantage that the filter mr~lillm could be removed or the filter assembly replaced to l~,i,ull~,c,L a non-filnrti~nin~ port (e.g., a port having a dirty or clogged filter that overly l~tli~;~ fluid flow).
Examples of the more illl~olL~ulL Lalulcs of this-invention have been broadly outlined above in order that the fll-tAil~d des~ tion that follows may be betterunderstood and so that collL,il,uLiolls which this invention provides to the art may be better a~lcCiaLcd. There are, of course, At~litic)nAl features of the invention which will be described herein and which will be inr~ d within the subject matter of the claims appended hereto.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustration of an eYr~ lA~ burr hole cap assembly in accolddllce with the present invention.
FIG. 2 is an illustration of an exemplary m---lifil-d burr ring assembly in mrrhAnir~l long7l~mrnt with a caLIl~l in accordance with the present invention, depicted in a vertical cross-sectinn~l view.
FIG. 3 is an illustration of an exemplary burr hole cap assembly in accordance with the present invention with an exemplary direct-feed tubular member defining an exemplary additional fluid flow path, depicted in a vertical cross-sectional view.
FIG. 4 is an illustration of an exemplary burr hole cap assembly with a catheter for use as an injection port in accordance with the present invention, depicted in a cross-sectional view.

W 096/33766 4 PCTrUS96/05159 FIG. 5 is an illustration of an eY~ burr hole cap assembly with a Call~ l for use as an; . .je~ port, adapted with an r Y r~ . .l.l~ . ~ filter assembly, depicted in a cross-se.;l~ 1 view.
FIG. SA is an il~ ;ol~ of the assembly shown in FIG. S, depicted in a three~im~on~inI~I exploded view.
FIG. 6 is an ill--~ of the assembly shown in FIG. 5, depicted in a cross-secti~ n~l view taken along the line 6-6 in FIG. S.
FIG. 7 is an illustration of the filter mounting m~omh~r of the assembly shown in FIG. S, depicted in a bottom view.
DETAILED DESCRIPTION OF THE INVENTION
As illustrated in Fig. 1, the present invention is a fluid c~ n port genPr~lly labeled 10. In particular, the invention has particular application with an att~rh~(l calllel~l 12 for use to çst~hli~h fluid c~ ion with a location inside a patient's brain 1. The fluid c.).. ~.. ;r~tion port 10 may be used as an injection port lS in connection with the infusion of drugs to specific locations within the brain S.
pl~r~m~?nt of the fluid c(.. ~.. iri~lion port 10 is facilitated through the use of a stylet 14 placed through the fluid co.. -.. i~tion port 10 and within the catheter 12 to enh~nre its rigidity during insertion into the brain 1. One advantage of the present invention is that following the withdrawal of stylet 14, the positioned fluid c~ ir~tion port 10 has a low, relatively unobtrusive profile.
The first embodiment of the present invention is depicted in Fig. 2. This embodiment colll~lises a burr hole ring 16 having an upper flange portion 18, a lower burr hole eng;~ging portion 20, and a central connection tube 22 which permits fluid c~-,.. "-i~ti~ln between a catheter 12 and a fluid reservoir 24 within the burr hole ring 16. Central connection tube 22 is connected to burr hole ring 16 and has anupper opening 26 that is in fluid co"..,..l..i~;.l;~ n with fluid reservoir 24. C~th~ter 12 is ~tt~-'h~d to central c~ nn~cti-)n tube 22. This may be done by conventional telescoping or bayonet engagement. Preferably, the inner surface 28 of the lowerportion 20 is tapered, facilitating the flow of any liquid within fluid reservoir 24 into the central connection tube 22.
The outer surface of lower portion 20 preferably is adapted with a m~çh~ni~m for mt~ch~nir~lly eng~ging a burr hole drilled through the skull. As shown in Fig. 2, -W 096/33766 5 PCTrUS96/05159 the burr hole ~ ;u~ means l~lcf~bly colI.prises threads or ridges 30 ~(hr~ed to engage the irmer sides of the burr hole. However, screws or other suitable d~clK~ g means may be used to secure the burr hole ring 16 to a patient's skull.
The central conn~oction tube 22 extends within the caLl~cLcr 12 as a means of fzlrilit~tin~ fluid delivery to within the calllcl~. The central connPctinT~ tube 22 also may act as a guide to ease the entry of â stylet 14 into the central lumen of caLL~
12.
A septum 32 placed in the top portion of the mn~ifil-~l burr hole ring 16 isolates the fluid l.,sel VOil 24 from the ~libicllL e~lvilullm~llL. Providing a desired ph~. ".~r~ ;r~l agent to the fluid reservoir 24 for delivery to a specific loc~tion within the body may be accom~ h~d by hlsc~ , a hypodermic needle 34 or other similar device through the septum 32 to inject the fluid agent. The septum 32 will lJlerclably be formed of a silicone ~ ....e. selPct~d to be self-sealing to ~u~ ules by a needle or stylet of the size ~.~ cd to be utilized for fluid delivery to fluid reservoir 24.
In use, cdll~Lcr 12 is cut to a pre(lrlr~ ",;,-P~l length and ~tt~rh~o~l to central connection tube 22. A stylet 14 is inserted through septum 32 into central connPetirJn tube 22 and llltim~tt-ly into catheter 12. Stylet 14 adds rigidity to c~Lhet~, 12.
('~theter 12 is then inserted into the patient's brain 1 and moved to a desired location wl~lcu~on, burr hole ring 16 moves into the burr hole formed in the patient's skull.
The addition of stylet 14 facilitates pl~r~mPnt of the catheter 12 within the patient's brain 1.
An ~ltern~te embodiment of the present invention is shown in Fig. 3. This embo~liment similar to the previous emborlimPnt, has a burr hole ring 16, an upper flange portion 18, a lower burr hole ~ging portion 20 and a central tube 22. In this embodiment, a fltering means is added to filter the infusate. The filtering means conl~lises a filtering layer 36, a needle stop 38 and l~e.rol~L~d base 40 which forms a filter assembly. Filtering layer 36 is positioned within burr hole ring 16. In this embo-liment a lower fluid reservoir 42 is formed below filtering layer 36. Central tube 22 is in fluid collllllllllir~tion with lower fluid l~SelvOil 42. In this way, fluids from upper lescl ~uil 24 are filtered prior to entering central tube 22.
Filtering layer 36 filters bacteria and other particulate matter from the liquidbeing infused into the patient. Preferably, filtering layer 36 CullllJliSeS a bio,cle~ re W O 96/33766 6 PCTrUS96/05159 m~tPri~l. An e~c",~l~uy m~tPri~l would be a polyv"lylidene flnori~1P ,l,c",~ldl~e having a ~ - pore si_e of .22 ll~iclol~.. Such a filter should retain its filtering cl~a~;lcli~,lics after subjection to a stPrili7~tinn process.
A needle stop 38 is pn~itinnP~l above filtering layer 36 and ~clruldlcd base 40 is positioned below filt~ring layer 36. The co,lll,i~lion of needle stop 38 above and ~clruldlcd base 40 below holds fihPring layer 36 in place and forms a seal around filt.oring layer 36 so that all fluid e~lcli-~ Cdlh~,t~,l 12 must pass through filtering layer 36. Needle stop 38 is preferably a highly porous, preferably p~,.r~"dlcd, generally rigid ~lc~l)el. This ~)lCVCllki passage of a needle through filt~ring layer 36, but allows passage of the infusate to filtering layer 36. Pclruldlcd base 40 should also be porous to allow fluid to pass into lower l~SGIVoil 42. In a~l-lition ~clÇuldLcd base 40 should be rigid enough to act as a support for filttq.ring layer 36. This configuration of needle stop 38 and pclr~ldlcd base 40 assures that any injected fluid will pass through the filter material of filt~.rin~ layer 36 prior to entering central tube 22.
Septum 32 covers fluid reservoir 24 and isolates fluid ,csc, voiL 24 from the çxtPrn~l cllvilulllllclll to prevent co..~ lion of the fluid within fluid reservoir 24.
A stylet tube 44 extends through septum 32 into central cnnnPctinn tube 22. The stylet tube 44 acts as a guide for an inserted stylet 14, ~ g accurate pl~remP.nt of stylet 14 within the catheter 12.
Stylet tube 44 is in sealing cn~ tion with both septum 32 and needle stop 38 and filtering layer 36. This ensures fluid from fluid Icscl ~oi I 24 must pass through filtering layer 36 before çntPring lower reservoir 42. However, it is e~sPnti~l that fluid in lower reservoir 42 be able to enter central connPction tube 22. This may be accomplished by making stylet tube 44 l~OWC~ that the inner ~ r~rl of centralconnection tube 22 so that fluid may enter central connPction tube 22 by flowingaround stylet tube 44. This may also be accomplished by p~lÇu,d~ g stylet tube 44 only within lower reservoir 42 so that fluid in lower reservoir 42 may enter stylet tube 44 through the perforations. Fluid entering stylet tube 44 through the l elrolc"iorls flows into central collnecLion tube 22 by flowing through and out of the end of stylet tube 44.
In use, as above, catheter 12 is cut to a pre(lclr~ ...i.~P~ length and ~tt~rnP(l to central connection tube 22. A stylet 14 is inserted through stylet tube 44 into central W 096133766 7 PCTrUS96/05159 co....~elion tube 22 and llltim~t~ly into c~Lll~te. 12. The addition of filttorin~ layer 36 ensures that the fluid delivered to the patient's brain 1 is fi~tered. Stylet tube 44 allows a stylet 14 to be used with the filt~ng layer 36 so that the advantages of both having a filter and a stylet are realized in a single device. ~'~thpt~r 12 is then placed in the patient's brain 1 as rlesrrihe(l above.
Upon Wi~ ldWi~ll of the sty-let 14, a sealing plug 46 or other suitable device is uls~L~d into the stylet tube 44 to prevent any unfiltered flow from ~ ;"g ~ll~
12. Preferably, sealing plug 46 is made of a bioco...~ m~tt~ri~l such as lil ..,i.....
or other biocn-.-~ le metal or a hard bioco--.~ ;hle polymer such as poly~urone.Regardless of the m~t-ri~l chosen for sealing plug 46, sealing plug 46 should beiu~p~ dldble by a needle.
FIGS. 4-7 show a third and fourth embodiment in accol~~e with the present invention. The key to both of these elllbo~ ; is that the s~Lullls or filters or both are removable As i~ ~d in FIG. 4, the invention collll lises a central cr.. Pcl;nn tube 22, a burr hole ring 16, a septum lllUUlltillg member 48, and a septum 32. The central connPction tube 22 is ~tt~h~d to the lower portion 50 of burr hole ring 16 to provide fluid co.. ~ lion benveen a fluid reservoir 20 within burr hole ring 16 and the central lumen of a cdLl~ . 12.
Septum mounting lllellll)er 48 is mountable to burr hole ring 16. Septum 32 is rigidly ~tt~rhPd to septum mounting lllclllbel 48. The septum mounting member 48can be det~r.h~kly coupled to burr hole ring 16. Removability allows direct access to the inside of burr hole ring 16. This in turn allows access to the central lumen of cdLll~Lt:l 12. Although septum mounting ~-~ h~- 48 is rlet~h~hly coupled to burrhole ring 16, a fluid seal must be formed between the two. This fluid seal is n~cess~ry to prevent fluid leakage from fluid reservoir 24 to undesired loc~tinn.~.
In use, septum mounting mPmher 48 is l~nloved from contact with burr hole ring 16. Stylet 14 is placed through burr hole ring 16 into cdLll~L~l 12. Catheter 12 is placed in a patient's brain 1 as described above. Once catheter 12 is in position, stylet 14 is removed. Then septum mmmting ll~mbel 48 is mollnt~d to burr hole ring 16, thereby sealing burr hole ring 16 and forming a fluid reservoir 24 within burr hole ring 16.

W 096/33766 PCTrUS96105159 Cc,~ P~ septum ,,,....,.~ g ",el"bcl 48 to burr hole ring 16 may be done by friction fitting or threading the illlr~ rh~e bcLwccll septum llluullLiug ...~..h ~ 48 and burr hole ring 16. In ~ltlitirm, septum ,,,,~ g lllc~ el 48 may be co~ P~-Ir~l to burr hole ring 16 by confi~lring the upper flanged section 52 of septum ...o~..l;..
... ~.. l-eL 48 with split-flanged collets 54. Burr hole ring 16 is COL~1~ ulcd with a plurality of holes 56 to receive the split-flanged collets 54 proLludillg from septum mollnting lll~llll~r 48. Further, other means for se~;~.. ;.. g the septum .. ~;.. g n,c",bel 48 to the burr hole cap 52 are available, e.g. an edge clamping l~ r~ "~;
screws; etc.
FIG. 5 shows an ~ .. ,.1;vc embodiment of the invention. In this emborlimPnt similar el~m~nt~ are referred to with similar lcr.,~ ce .. h~.~. In addition, unless stated otherwise, the ~c~cllced eleTnPnt~ operate as described above.
Septum llwullLing member 48 is adapted with filter means in the fluid flow path to the caLllt:lcl 12. The filter means cc",~,ises a needle stop 38, filtering layer 36 and a ~ro~Lcd base 40 that function as described above. Preferably, needle stop 38, filtering layer 36 and perforated base 40 are rigidly att~rhPd to mmlnting ...~...he 48. The rigid ~tt~rhmP,nt may be either ~ l or removable. This comle~;Lion may be accomplished by ultrasonic welding, adhesives, threads or other ".Pr~ ir~l means that will occur to those skilled in the art.
In this embodiment, mounting ~llclllbel 48 is ~let~rh~ble from burr hole ring 16with the corresponding advantages as described above. In addition, removability permits the P~ch~nge of one filter assembly for another when one assembly becomes clogged or uLllt;lvvise inoperable over time.
As will be app,-,ciaLcd, the devices described herein may be m~n~f~rtl-red from a variety of biocompatible materials, inrl~lrling a variety of plastics in~ 1ing, but not limited to, polyulclll~le, nylon or polysulfone. Although conventional telescoping or bayonet engagement has been depicted between burr hole ring 16 and catheter 12, other configurations could be lltili7Pd, inr,lll~ling forming catheter 12 integrally with the burr hole ring 16.
Although the l~lcrcll~d embodiment of this invention has been described hereinabove in some detail, it should be appreciated that a variety of embo-limPntc will be readily available to persons lltili7,ing the invention for a specific end use. The W O 96/33766 9 PCTrUS96/05159 desc~ ion of the d~palaLus and method of this ulvcllLioll is not i. .Ir~ e~l to be limiting on this ulvcllLioll, but is merely illustrative of the plef~led embo~limlont of this invention. Other d~alaLus and mPth~As which uleul~uldle m~ir.~ or rll~n~s to that which has been desL;libed herein are equally in~hlAed within ~is a~l~lir"liom 5, A<l~liti-m~l objects, Ç~aLule;, and advantages of the present invention will b~ecome dp~lalcllL by lcf~ g to the following ~ec~ of the invention in cc~ n with the ~c~ ..yillg dlawillg~.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for securing a catheter within a burr hole through a patient's skull, comprising:
a housing member configured to be mechanically coupled to said skull proximate said burr hole, said housing member including a generally interior portion, said interior portion being in fluid communication with said catheter;
a septum selectively coupleable to said housing to isolate said interior portionof said housing from a location exterior to said patient's skull, said septum selectively penetrable to provide fluid communication from said location exterior to said skull and said interior portion of said housing member.

2. The apparatus of claim 1, wherein said septum is selectively penetrable to provide fluid communication from said location exterior to said skull to a first location within said interior portion of said housing, and wherein said apparatus furthercomprises a filter assembly in a flow path between said first location within said housing member and said catheter.

3. The apparatus of claim 1, wherein said housing member is configured to mechanically engage said skull adjacent the surfaces of said skull defining said burr hole.

4. The apparatus of claim 1, wherein said housing member is configured to be selectively secured to said skull through retaining members.

5. The apparatus of claim 4, wherein said retaining members comprise screws.

6. An apparatus for securing a catheter within a burr hole through a patient's skull, comprising:
a housing member configured to mechanically engage the surfaces of said skull defining said burr hole, said housing forming a fluid reservoir, said housing including a connection portion configured to mechanically engage said catheter assembly; and a septum configured to provide selective access to said fluid reservoir from a location exterior to said patient's skull.

7. The apparatus of claim 6, wherein a path of fluid communication is formed between said fluid reservoir and said catheter, and wherein said apparatus further comprises a filter member retained within said fluid communication flow path.

8. The apparatus of claim 6, wherein said septum is selectively penetrable to provide fluid communication from said location exterior to said patient's skull to said fluid reservoir.

9. The apparatus of claim 8, wherein said septum is formed of an elastomeric material which is selectively penetrable by a fluid delivery needle.

10. An apparatus for providing fluid access with a patient's brain through a burr hole, comprising.
a burr hole cap assembly engageable with said patient's skull, said burr hole cap assembly comprising a catheter coupled to a fluid exit of a burr hole cap, said catheter extending into said patient's brain, said burr hole ring comprising a fluid chamber and a filter chamber in a fluid path between said fluid chamber and said fluid exit;
a filter element within said filter chamber; and a septum generally isolating said fluid chamber from a location exterior to said patient's skull while allowing penetration by a needle.

11. The apparatus of claim 10, wherein said septum and said burr hole cap each include a stylet aperture providing access by a stylet into said catheter, and wherein said apparatus further comprises a closure member for closing at least said stylet access port in said septum.

12. The apparatus of claim 10, wherein said fluid chamber and said filter chamber are separated at least in part by a needle stop surface.

13. The apparatus of claim 10, wherein said catheter is selectively engageable with said burr hole cap.

14. The apparatus of claim 10, wherein said burr hole cap assembly comprises:
a housing member configured to engage the patient's skull; and an inner member which includes said filter chamber and which defines at least a portion of said fluid chamber.

15. A housing member engageable with a patient's skull, said housing member including a first fluid reservoir within said patient's skull, comprising:

a second fluid reservoir at a second location within the patient's body; and a filtering layer within a fluid flow path between said first and second fluid reservoirs, said filtering layer adapted to prevent contaminants within contaminated fluid following the fluid flow path from one reservoir to the other reservoir from passing from the one reservoir to the other reservoir.

16. The apparatus of claim 15, wherein said second fluid reservoir comprises thelumen of an implanted catheter.

17. The apparatus of claim 15, wherein said filtering layer comprises a bioretentive filter material secured within an implantable catheter access port.18. The apparatus of claim 15, wherein said filtering layer comprises a filter assembly detachably coupled within an implantable catheter access port.