Low profile instrument immobilizer

Description of equivalent WO 2004026161 A2

LOW PROFILE INSTRUMENT IMMOBILIZER

CROSS REFERENCE TO RELATED APPLICATIONS This patent application claims the benefit of priority, under 35 U.S.C. Section 119(e), to Skakoon et al. U.S. Provisional Patent Application Serial Number 60/411309, entitled "LOW PROFILE INSTRUMENT IMMOBILIZER," filed on September 17, 2002 (Attorney Docket No. 723.066PRV).

FIELD OF THE INVENTION This document relates generally to instrument immobilizers, and more specifically, but not by way of limitation, to a low profile instrument immobilizer.

BACKGROUND Neurosurgery sometimes involves inserting an electrode (for recording brain signals or providing stimulating pulses) or other instrument (for example, a catheter for fluid aspiration or drug infusion) through a burr hole or other entry portal into a subject's brain toward a target region of the brain. In certain applications, there is a need to secure the electrode or other instrument in place after it has been introduced, potentially for an extended period of time. Moreover, in certain applications, other equipment (such as a trajectory guide and any associated equipment) is mounted to the patient's skull about the burr hole.

For these and other reasons, which will become apparent upon reading the following detailed description and viewing the drawings that form a part thereof, the present inventors have recognized an unmet need for low profile instrument immobilizer devices, tools, and methods that reduce or avoid patient discomfort and also better retain instruments. BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which are not necessarily drawn to scale, like numerals describe substantially similar components throughout the several views. Like numerals having different letter suffixes represent different instances of substantially similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

Figure 1 is a top view illustrating generally, by way of example, but not byway of limitation, portions of a first instrument immobilizer. Figure 2 is a top view illustrating generally an example of portions of the first instrument immobilizer after cover pieces have been partially inserted into respective slots in opposing sides of a hoop.

Figure 3 is a perspective view illustrating generally an example of portions of the first instrument immobilizer after the cover pieces have been partially inserted into the respective slots of the hoop.

Figure 4 is a side view illustrating generally an example of portions of the first instrument immobilizer after the cover pieces have been almost fully inserted into the respective slots of the hoop.

Figure 5 is a top view illustrating generally an example of portions of the first instrument immobilizer after the cover pieces have been fully inserted into the respective slots of the hoop.

Figure 6 is a perspective view illustrating generally, by way of example, but not by way of limitation, portions of a second instrument immobilizer.

Figure 7 is a side view of the second instrument immobilizer with a latch piece in an open position.

Figure 8 is a perspective view of the second instrument immobilizer with the latch piece in a closed position.

Figure 9 is a side view of the second instrument immobilizer with the latch piece in a closed position. Figure 10 is a top view of a third instrument immobilizer.

Figure 11 is a top view of the third instrument immobilizer with a clasp in a closed position.

Figure 12 is a perspective view of the third instrument immobilizer with the clasp in its closed position. Figure 13 is a side view of the third instrument immobilizer with the clasp in its open position.

Figure 14 is a side view of the third instrument immobilizer with the clasp in its closed position. Figure 15 is a perspective view of a fourth instrument immobilizer with base pieces in an open position.

Figure 16 is a top view of the fourth instrument immobilizer with base pieces in a closed position, grasping and immobilizing a laterally bent electrode.

Figure 17 is a top view of a fifth instrument immobilizer. Figure 18 is a top view illustrating the fifth instrument immobilizer where the first retaining member and second retaining member immobilize an instrument.

Figure 19 is a top view of a sixth instrument immobilizer.

Figure 20 is a top view illustrating the sixth instrument immobilizer where the socket slot and socket immobilize an instrument.

Figure 21 is a perspective view of another example of the lid for the sixth instrument immobilizer having multiple slots and corresponding sockets.

Figure 22 is a top view illustrating generally the first instrument immobilizer where the cover pieces immobilize an instrument. Figure 23 is a perspective view of the second instrument immobilizer with the latch piece in the closed position where the latch piece immobilizes an instrument.

Figure 24 is a perspective view of the third instrument immobilizer with the clasp in the closed position where the clasp immobilizes an instrument. Figure 25 is a block diagram illustrating generally, by way of example, and not by way of limitation, a first method to immobilize an instrument.

Figure 26 is a block diagram illustrating generally, by way of example, and not by way of limitation, a second method to immobilize an instrument.

Figure 27 is a block diagram illustrating generally, by way of example, and not by way of limitation, a third method to immobilize an instrument.

Figure 28 is a block diagram illustrating generally, by way of example, and not by way of limitation, a fourth method to immobilize an instrument.

Figure 29 is a block diagram illustrating generally, by way of example, and not by way of limitation, a fifth method to immobilize an instrument. Figure 30 is a block diagram illustrating generally, by way of example, and not by way of limitation, a sixth method to immobilize an instrument.

DETAILED DESCRIPTION In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents. hi this document, the terms "a" or "an" are used, as is common in patent documents, to include one or more than one. Furthermore, all publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this documents and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.

Example 1 Figures 1 — 5 and 22 illustrate various views of a first embodiment of a low-profile instrument immobilizer for securing a flexible recording or stimulating electrode or the like, or other instrument (such as a catheter for fluid aspiration or drug, cell, or substance infusion) after it has been introduced through a burr hole or other entry portal to a desired target location in the brain. Figure 1 is a top view illustrating generally, by way of example, but not by way of limitation, portions of instrument immobilizer 100. In this example, instrument immobilizer 100 includes a hoop-like base 102 (also referred to herein as a "hoop"). The hoop 102 is sized and shaped for being circumferentially disposed about a burr hole (which, in this document, is understood to include a twist drill hole) or other entry portal of a desired size. Burr holes typically range in diameter between about 6 millimeters to about 14 millimeters. In this example, hoop 102 includes holes 104A-B or other passages for receiving corresponding bone screws or the like therethrough for securing hoop 102 to a subject's skull (or other desired location upon the subject). In this example, hole 104 A is located on an opposite side of hoop 102 from hole 104B. In operation, hoop 102 is secured to the skull before the electrode or other instrument is inserted to the desired location in the patient's brain. The electrode or other instrument (for example an aspiration catheter or an infusion catheter) is inserted through the circular center passage defined by hoop 102. In this example, instrument immobilizer 100 includes a two-piece sliding cover including cover pieces 106A-B. Each cover piece 106A-B is sized and shaped to be inserted through a corresponding side slot 108A-B in an opposing side of hoop 102. Each piece of cover piece 106A-B also has a snap-fit or other catch 109 A-B, such as a deformable tab, that engages a portion of hoop 102 when that cover piece 106 A or 106B has been fully inserted. Catches 109 A-B hold their corresponding cover piece 106A-B in place after it has been fully inserted. Alternatively, the instrument immobilizer includes a one-piece sliding cover that, in one example, the single cover piece substantially covers the circular center passage when fully inserted through a corresponding side slot. Figure 2 is a top view illustrating generally an example of portions of instrument immobilizer 100 after cover pieces 106 A-B have been partially inserted into respective slots 108A-B in opposing sides of hoop 102. Figure 3 is a perspective view illustrating generally an example of portions of instrument immobilizer 100 after cover pieces 106A-B have been partially inserted into respective slots 108A-B of hoop 102. Figure 4 is a side view illustrating generally an example of portions of instrument immobilizer 100 after cover pieces 106A-B have been almost fully inserted into respective slots 108A-B of hoop 102. Figure 5 is a top view illustrating generally an example of portions of instrument immobilizer 100 after cover pieces 106 A-B have been fully inserted into respective slots 108A-B of hoop 102.

As illustrated generally in Figures 1 - 5, when cover pieces 106A-B have been fully inserted and pressed against each other, they substantially cover the center passage defined by hoop 102, except for a small circular opening 500 formed by aligned semi-circular cutouts 110A-B of cover pieces 106A-B. Also, when cover pieces 106A-B have been fully inserted and their respective beveled edges 112 A-B are pressed against each other, a resulting trough, channel or groove 502 is formed. In this example, groove 502 aligns with exit grooves 11 A-B in hoop 102, however, this is not required. In another example, one or more exit grooves 114A-B are disposed elsewhere about hoop 102, such as, for example, exit grooves 114 distributed about hoop 102 at regular intervals (e.g., every 30 degrees, etc.). Moreover, such differently disposed exit grooves 114 are also applicable to all of the other examples depicted and/or described in this document. Figure 22 is a top view illustrating an instrument immobilizer 100 retaining at least one wire electrode or other introduced instrument 2200 (e.g., a catheter). Once the instrument 2200 is retained by cover pieces 106A-B so as to immobilize the instrument, a portion of the instrument 2200 may be bent into a portion of groove 502 and one of exit grooves 114 A-B to laterally exit hoop 102. In the above described example having multiple exit grooves 114A-B, the instrument 2200 may be bent into any one of the exit grooves 114 A-B. The introduced instrument 2200 is retained and immobilized by the snug fit through opening 500. Additionally the instrument 2200 is further retained by snug positioning of a portion of the instrument 2200 within the groove 502 and one of the exit grooves 114 A-B. Where the instrument 2200 is positioned within an exit groove 114 A-B the instrument immobilizer 100 and instrument 2200, in one example, are covered by a cap that provides a semi-permanent fixture for both.

Example 2 Figures 6 - 9 and 23 illustrate various views of a second embodiment of a low-profile instrument immobilizer for securing a flexible recording or stimulating electrode or the like (or other instrument, such as a catheter) after it has been introduced through a burr hole or other entry portal to a desired target location in the brain.

Figure 6 is a perspective view illustrating generally, by way of example, but not by way of limitation, portions of instrument immobilizer 600. In this example, instrument immobilizer 600 includes a base 602 sized and shaped for being secured above and covering a similarly-sized burr hole or other entry portal. In this example base 602 includes a pair of semicircular pieces 602A-B. Base 602 includes holes 604A-B or other passages for receiving corresponding bone screws or the like therethrough for securing base 602 to a subject's skull (or other desired location upon the subject). In this example, hole 604A is located on an opposite side of base 602 from hole 604B. The holes 604 A-B are, in this example, located on members 605A-B, which extend radially outward from base 602. In one example of operation, base 602 is secured to the skull by inserting a screw through one of the holes 604A-B. This permits the instrument immobilizer 600 to rotate about the axis of the screw through the one of the holes 604 A-B. The instrument immobilizer 600 is rotated away from the burr hole in this manner, thereby providing access to the burr hole. The electrode or other instrument is inserted through the burr hole to the target location, as desired. The instrument immobilizer is then rotated back toward the burr hole about the axis of the screw through the one of the holes 604A-B such that the instrument extends through an access slot 606. The instrument can then be further secured, such as discussed below. hi this example, the access slot 606 extends across base 602, except for the presence of connecting member 608. The slot 606 permits access to the underlying burr hole or other entry portal, except for the obstruction of connecting member 608. Connecting member 608 provides a mechanical connection between two semicircular portions 602A-B of base 602. The semicircular portions 610A-B are separated by slot 606 and connecting member 608.

In this example, a latch 610 is eccentrically coupled to base 602 by coupling the latch to the base at a point offset from the center of the base. In the example of Figure 6, the latch includes a semicircular latch piece 610 having a post 616 that is snap-fit into semicircular piece 602 A of base 602. Figure 6 illustrates latch piece 610 in an eccentrically-mounted open position, i this example, latch piece 610 includes a semicircular notch or cutout 612 that is sized to retain the electrode or other instrument snugly within slot 606 when latch piece 610 is moved to the closed position. After the instrument is axially positioned as desired within the slot 606, then the latch piece 610 is moved to the closed position and immobilizes the instrument. Figure 7 is a side view of instrument immobilizer 600 with latch piece 610 in the open position. Figure 8 is a perspective view of instrument immobilizer 600 with latch piece 610 in the closed position. Figure 9 is a side view of instrument immobilizer 600 with latch piece 610 in the closed position.

In Figures 6 - 9, when latch piece 610 is in the closed position the semicircular shape of latch piece 610 aligns and conforms with the circumference of base 602 such that the peripheral profile of the latch piece 610 is coextensive with the peripheral profile of the base 602 when the immobilizer 600 is viewed from above.

Figure 23 is a perspective view illustrating the instrument immobilizer retaining a wire electrode or other introduced instrument 2200 (for example a catheter as described above). In the closed position, the instrument 2200 is snugly retained within the semicircular cutout 612 between latch piece 610 and connecting member 608. In this example, the latch piece 610 is securable in the closed position by a detent 616 that extends from a lower surface of the latch piece 610. As generally shown in Figure 6, the detent 616 engages the base 602 within a securing slot 618 defined by the base to secure the latch piece 610 in the closed position. The instrument 2200 may be laterally bent (e.g., such as at about a 90 degree angle, or otherwise) to laterally exit base 602. In this example, the laterally bent portion of the instrument 2200 may be wedged snugly under or along a tab (such as retaining member 614) disposed above slot 606. This further secures the instrument 2200 after immobilization by the latch piece 610.

Example 3 Figures 10 - 14 illustrate various views of a third embodiment of a low- profile instrument immobilizer for securing a flexible recording or stimulating electrode or the like, or other instrument, after it has been introduced through a burr hole or other entry portal to a desired target location in the brain.

Figure 10 is a top view illustrating generally, by way of example, but not by way of limitation, portions of instrument immobilizer 1000. In this example, instrument immobilizer 1000 includes a base 1002 sized and shaped for being secured such that it is cantilevered over at least a portion of a burr hole or other entry portal. In this example base 1002 includes a pair of approximately semicircular portions 1002 A-B connected by connecting member portions 1002C-D. Base 1002 includes holes 1004A-B or other passages for receiving corresponding bone screws or the like therethrough for securing base 1002 to a subject's skull (or other desired location upon the subject). An optional slot or lateral groove 1006 extends between semicircular portions 1002 A-B and comiecting member portions 1002C-D of base 1002. i this example, instrument immobilizer 1000 includes a semicircular shaped clasp 1008. The clasp 1008 is coupled at a first end to one of the semicircular portions 1002A-B by a hinge 1010. At a second end, the clasp 1008 includes a fastener 1012, hi this example, the fastener 1012 includes a male snap-fitting, for securing to a mating female receptacle 1100 (Figure ll)in the other of the semicircular portions 1002 A-B when the clasp 1008 is moved from an open position to a closed position, i another example, the clasp 1008 is coupled at a first end to one of the semicircular portions 1002 A-B with a flexible element, including but not limited to deformable plastic, or a binge as described above. Figure 11 is a top view of instrument immobilizer 1000 with clasp 1008 in the closed position. Figure 12 is a perspective view of instrument immobilizer 1000 with clasp 1008 in its closed position. Figure 13 is a side view of instrument immobilizer 1000 with clasp 1008 in its open position. Figure 14 is a side view of instrument immobilizer 1000 with clasp 1008 in its closed position. Figure 24 is a perspective view of an instrument immobilizer retaining a wire electrode or other instrument 2200 (for example, a catheter for aspiration or substance infusion). The instrument immobilizer base 1002 is secured to the skull such that clasp 1008 is cantilevered over the burr hole or other entry portal. The electrode or other instrument is inserted through the burr hole or other entry portal to the desired location so the instrument is near the clasp 1008. hi one option, the instrument is adjacent a side surface of the instrument immobilizer 1000. The clasp 1008 is then closed around the electrode or other instrument to snugly retain it. The electrode or other instrument is laterally bent into lateral groove 1006 and positioned snugly under cantilevered retaining members 1014A-B extending from semicircular portions 1002A-B over lateral groove 1006. As shown in Figure 24, The electrode or other instrument is thereby immobilized by clasp 1008. Cantilevered retaining members 1014A-B and/or lateral groove 1006 are sized or otherwise configured to snugly conform to the electrode or other instrument. This provides additional snug retention of the electrode or other instrument. Example 4 Figures 15 - 16 illustrate various views of a fourth embodiment of a low- profile instrument immobilizer for securing a flexible recording or stimulating electrode or the like, or other instrument (a catheter, in one example), after it has been introduced through a burr hole or other entry portal to a desired target location in the brain.

Figure 15 is a perspective view illustrating generally, by way of example, but not by way of limitation, portions of instrument immobilizer 1500 for securing an electrode 1502 or other instrument. In this example, instrument immobilizer 1500 includes a two-piece base 1504A-B. Base piece 1504A is sized and shaped for being disposed along a first side of a burr hole 1505 or other entry portal. Base piece 1504B is sized and shaped for being disposed along a second side of a burr hole or other entry portal. Each elongated base piece 1504A-B includes a corresponding hole 1506A-B, at a first end, for receiving a corresponding bone screw 1508 A-B or the like therethrough for securing the corresponding base piece 1504A-B to the subject's skull, hi one example, the bone screws 1508A-B and holes 1506A-B are disposed on opposite sides of the burr hole 1505. In another example, the base pieces 1504A-B are sized and shaped so bone screws 1508A-B and holes 1506A-B are disposed at non-opposed locations around the burr hole 1505. Each bone screw 1508A-B and corresponding hole 1506A-B provides a hinge about which the corresponding elongate base piece 1504A-B rotates, such as from the open position illustrated in Figure 15 to a closed position, in which base pieces 1504A-B retain and immobilize the electrode or other instrument. In one option, the base pieces 1504A-B rotate about parallel axes, h another option the base pieces 1504A-B rotate within the same plane. Figure 16 is a top view illustrating base pieces 1504A-B in a closed position, retaining and immobilizing a laterally bent electrode 1502.

In the example of Figures 15-16, base pieces 1504A-B are disposed such that when these pieces are rotated into the closed position of Figure 16, male couplers 1508A-B (for example snap fittings) on base piece 1504A engage corresponding mating couplers 1510A-B on base piece 1504B. This fastens base pieces 1504A-B together to retain electrode 1502 therebetween. Electrode 1502 is further laterally bent into the groove 1512 of base piece 1504A. Groove 1512 is sized and shaped to snugly grasp electrode 1502 therein to further retain and immobilize electrode 1502.

Example 5 Figure 17 is a top view illustrating generally, by way of example, but not by way of limitation, a fifth embodiment of an instrument immobilizer, such as instrument immobilizer 1700. hi this example, instrument immobilizer 1700 includes a hoop-like base 1702 (also referred to herein as a "hoop") sized and shaped for being circumferentially disposed about a burr hole or other entry portal of a desired size. In this example, hoop 1702 includes holes 1704A-B or other passages for receiving corresponding bone screws or the like therethrough for securing hoop 1702 to a subject's skull (or other desired location upon the subject). In this example, hole 1704A is located on an opposite side of hoop 1702 from hole 1704B. hi this example, hoop 1702 defines a center passage therewithin, into which an insert 1706 is disposed. Insert 1706 includes at least one snap-fitting feature that allows insert 1706 to be snapped into hoop 1702. In one example, insert 1706 is inserted into the circular center passage of hoop 1702 such that insert 1706 rotates therewithin with respect to hoop 1702. h this example, the insert 1706 includes at least one detent disposed about the insert bottom surface and projecting to the side of the insert. The hoop 1702 includes a corresponding grooved surface disposed upon an intermediate surface therein. The at least one detent engages the grooved surface. This engagement prevents unwanted rotation of the insert 1706 with respect to the hoop 1702.

In Figure 17, insert 1706 includes a rectangular or other access opening 1708. Retaining members 1710A-B are movably coupled to the insert 1706. In one example, the retaining members 1710A-B, include slidable retaining members carried substantially within access opening 1708. h one example, access opening 1708 includes opposing side slide rails that allow retaining members 1710A-B to slide toward and away from each other within access opening 1708. In the example of Figure 17, sliding retaining members 1710A-B each have beveled edges 1712 A-B and semicircular cutouts 1 14 A-B in center portions of beveled edges 1712A-B. When retaining members 1710A-B are positioned adjacent to each other, beveled edges 1712A-B form a lateral groove, and semicircular cutouts 1714 A-B are aligned to each other to form a circular opening. In an alternative example, however, the semicircular cutouts 1714A-B are omitted.

In one example, retaining members 171 OA-B include respective mating couplings to hold the retaining members in engagement with each other, hi one option, the mating couplings include snap-fit features to maintain engagement between the retaining members 1710A-B. In another example, at least one of the retaining members 171 OA-B includes an engagement coupling that secures the at least one of the retaining members 171 OA-B relative to insert 1706. In one option, the engagement coupling includes a "one-way" toothed surface disposed substantially upon the side slide rails of the insert 1706. Corresponding tabs are disposed along the bottom edge of the at least one of the retaining members 171 OA-B. The tabs engage the toothed surface and thereby allow slidable movement of the at least one of the retaining members 171 OA-B in one direction, typically toward the other retaining member, h another option, both retaining members 1710A-B have tabs that engage toothed surfaces on the rails. When retaining members 1710A-B contact each other, the tabs engaging the toothed rails maintain engagement between the retaining members 171 OA-B. The retaining members 171 OA-B do not disengage from each other because the tabs and teeth prevent sliding away in the other direction. If it is desirable to move the retaining members 171 OA-B in a direction counter to that allowed by the tabs and teeth the retainmg members 171 A-B are pulled out of engagement with the side rails, disengaged from each other and repositioned within the side slide rails.

Figure 18 is a top view illustrating instrument immobilizer 1700 retaining a wire electrode or other instrument 2200. In operation, hoop 1702 is secured and insert 1706 is inserted therein. An electrode or other instrument 2200 (for example an aspiration or infusion catheter) is inserted between retaining members 171 OA-B to the desired location in the patient's brain, hi one example, the insert 1706 is capable of being rotated about the instrument 2200. This provides added flexibility in the location for immobilization of the instrument. Retaining members 171 OA-B are moved against each other to snugly retain and immobilize a portion of the instrument 2200, such as within the circular opening defined by semicircular cutouts 1714A-B. In another example, the semicircular cutouts 1714A-B are omitted and the instrument 2200 is compressibly retained between the beveled edges 1712A-B at a desired position anywhere along the beveled edges. The retaining members 171 OA-B engage each other and/or the side rails (as discussed above) to immobilize the instrument 2200. If desired, the instrument 2200 can be bent into the lateral groove formed 1800 by beveled edges 1712A-B. In one example, the lateral groove 1800 aligns with one or more lateral exit grooves 1716A-B providing lateral access through hoop 1702, allowing the electrode or other instrument to laterally exit hoop 1702. h one example, the lateral groove 1800 and/or the lateral exit groove(s) 1716 A-B are sized and shaped to snugly grasp and retain the instrument 2200. h another example, once the instrument 2200 is immobilized by the retaining member

171 OA-B and grasped and retained by the lateral groove 1800 and/or lateral exit groove 1716A-B, a cap is affixed to the instrument immobilizer 1700.

Example 6 Figure 19 is a top view illustrating generally, by way of example, but not by way of limitation a sixth embodiment of an instrument immobilizer, such as instrument immobilizer 1900. In this example, instrument immobilizer 1900 includes a hoop-like base 1902 (also referred to herein as a "hoop") sized and shaped for being circumferentially disposed about a burr hole or other entry portal of a desired size. In this example, hoop 1902 includes holes 1904A-B or other passages for receiving corresponding bone screws or the like therethrough for securing hoop 1902 to a subject's skull (or other desired location upon the subject). In this example, hole 1904A is located on an opposite side of hoop <img file="WO2004026161A2_D0001.tif" />

In this example, hoop 1902 defines a center passage therewithin, into which a lid 1906 is disposed. Lid 1906 includes at least one snap-fitting feature that allows lid 1906 to be snapped into hoop 1902. h one example, lid 1906 rotates substantially within the circular center passage of hoop 1902. In another example, the lid 1906 includes at least one detent on its bottom surface, and the hoop 1902 includes a corresponding groove on or near its inner periphery. The at least one detent engages the groove. This prevents undesirable rotation of the lid 1906 with respect to the hoop 1902.

In this example, the lid 1906 includes a slot 1908. hi one option, the slot 1908 has an arcuate geometry defined by the lid 1906 and extends across an angle of approximately 15 degrees. The slot 1908 extends from an outer edge 1920 of the lid 1906, tapering inward toward a center 1922 of the lid 1906. The slot includes at least one socket 1910. Figure 19 illustrates the socket 1910 extending through the center of the lid 1906. However, the socket 1910 may alternatively be offset from the center of the lid 1906 to provide added flexibility in positioning and immobilizing an instrument. In one example, the slot 1908 narrows as it extends from the outer edge 1920 of the lid 1906 toward the socket 1910. hi Figure 19, just before reaching the socket 1910, the slot 1908 is slightly more narrow than the socket 1910 is wide. This provides a lip 1912 on the slot 1908 adjacent the socket 1910. Figure 20 is a top view illustrating a wire electrode or other instrument

2200 (e.g., a catheter, such as for aspiration or infusion of drug(s), cell(s) or other substances) that is immobilized by the instrument immobilizer 1900. In one example of operation, hoop 1902 is first secured. The instrument 2200 is then inserted through the hoop 1902 to the desired location in the patient's brain. In one example, the lid 1906 is then inserted into the hoop 1902 such that the instrument 2200 is disposed within a slot 1908. Inserting the lid 1906 after positioning the instrument 2200 provides additional flexibility for positioning the slot around the instrument 2200 so as to reduce or minimize any unwanted movement of the instrument 2200. The instrument 2200 is then advanced laterally within the slot 1908 toward the socket 1910. Upon reaching the lip 1912, a portion of the instrument 2200 and/or the lip 1912 deforms slightly to permit the instrument 2200 to enter the socket 1910 for retention and immobilization by the socket 1910. In one example, the hoop 1902 includes at least one lateral exit groove 1916 and the lid 1906 includes at least one lateral exit groove 1918. The lid 1906 is positionable to permit groove 1918 to align with one of the lateral exit grooves 1916. A portion of the instrument 2200 is then bent and positioned within the groove 1918 and lateral exit groove 1916 where it is retained snugly therein. This further immobilizes the instrument 2200. In one example, a cap is affixed to the instrument immobilizer 1900. Figure 21 is a perspective view of another embodiment of a lid 2100 usable with the instrument immobilizer 1900 illustrating generally multiple slots 2102, sockets 2104 and lips 2106. The lid 2100, as illustrated in the example of Figure 21, is operable to retain and immobilize up to three instruments. Alternately, the lid 2100 is operable to retain an instrument in multiple positions for flexibility of immobilization. Similar configurations can be used to immobilize fewer or greater instruments.

Some Variations and Other Aspects of the Above Examples In the above examples (aspects of which can be combined with each other), the components of instrument immobilizers 100, 600, 1000, 1500, 1700, 1900, and lid 2100 may be manufactured from molded plastic and are MRI compatible. The bone screws used for securing the instrument immobilizers may be manufactured from stainless steel. In one example, such bone screws include imaging fiducial markers integral or attachable thereto. Additionally, in other embodiments of the above examples the exit grooves are disposed at various locations (for example, at regular intervals) about the instrument immobilizers 100, 600, 1000, 1500, 1700, and 1900 to provide flexibility in the placement of the instruments when immobilized. Instrument immobilizers 100, 600, 1000, 1500, 1700, 1900, and lid 2100 are not limited to use in conjunction with skull burr holes in neurosurgery, but may be secured at other locations of a patient for securing an electrode or other surgical instrument (for example catheters used for aspiration or infusion), or about an entry portal in other objects into which an instrument has been introduced, and which requires immobilization. The above examples provide instrument immobilizers that are designed to advantageously provide a low-profile (e.g., small height) above the patient's skull. By way of example, but not by way of limitation, in one embodiment, instrument immobilizer 100 provides a height of less than about 0.1 inches, instrument immobilizer 600 provides a height of less than about 0.08 inches, instrument immobilizer 1000 provides a height of less than about 0.08 inches, instrument immobilizer 1500 provides a height of less than about 0.065 inches, instrument immobilizer 1700 provides a height of less than about 0.1 inches, and instrument immobilizer 1900 and lid 2100 provide a height of less than about 0.1 inches

Method of Use Example 1 Figure 25 is a block diagram of a method 2500 for immobilizing an instrument, for example an electrode or catheter. At 2502, an instrument is disposed within a passage of an instrument immobilizer base. At 2504, a first cover piece and a second cover piece are advanced toward the instrument. At 2506 the first cover piece and the second cover piece are engaged against the instrument to immobilize the instrument therebetween.

Several variations are possible. One example includes sliding the first cover piece through a slot in the instrument immobilizer base and sliding the second cover piece through another slot in the instrument immobilizer base, includes grasping and/or retaining a portion of the instrument within a groove defined by the first and second cover piece.

Method of Use Example 2 Figure 26 is a block diagram of a method 2600 for immobilizing an instrument. At 2602, an mstrument is disposed within a passage of an instrument immobilizer base. At 2604, a latch including a notch is rotated toward the instrument. At 2600 the instrument is engaged against the latch to immobilize the instrument, where the surface defining the notch engages the instrument. Several variations are possible. One example includes retaining the latch against the instrument by engaging a portion of the latch to a mating portion of the instrument immobilizer base. In another example, a portion of the instrument is laterally positioned against the instrument immobilizer base, and the portion of the instrument is tucked under an overlying retaining member that holds the portion of the instrument against the instrument immobilizer base.

Method of Use Example 3 Figure 27 is a block diagram of a method 2700 for immobilizing an instrument. At 2702, an instrument immobilizer base is cantilevered above a burr hole. At 2704, the mstrument is disposed near a side of the instrument immobilizer base. In one example, the instrument is disposed adjacent a side of the instrument immobilizer base. At 2706 the clasp is advanced around the instrument by rotating the clasp about a first end of the clasp. At 2708, another end of the clasp is engaged with the instrument immobilizer base to immobilize the mstrument. Several variations are possible. One example includes positioning a portion of the instrument laterally against the instrument immobilizer base, and tucking the instrument under a retaining member overlying the instrument and a groove. Another example includes snap-fitting the clasp to the instrument immobilizer base. Method of Use Example 4 Figure 28 is a block diagram of a method 2800 for immobilizing an instrument. At 2802, an instrument is positioned between a first base piece and a second base piece. At 2804, the first base piece is rotatably advanced toward the instrument, h one example, the first base piece is rotatably coupled to a surface. At 2806, the first base piece and the second base piece are engaged against the instrument to immobilize the instrument therebetween.

Several variations are possible. One example includes rotatably advancing the second base piece toward the instrument, where the second base piece is rotatably coupled with the surface. Another example includes snapping the first base piece together with the second base piece. In still another example, a portion of the instrument is positioned within a groove defined by one of the first base piece or the second base piece.

Method of Use Example 5 Figure 29 is a block diagram of a method 2900 for immobilizing an instrument. At 2902, an instrument is disposed within a passage of an instrument immobilizer base. At 2904, a first retaining member and a second retaining member are advanced toward the instrument. At 2906, the first retainmg member and second retaining member are engaged against the mstrument to immobilize the instrument.

Several variations are possible. One example includes coupling an insert with an instrument immobilizer base. In another example, a portion of the instrument is received along edges of the first and second retaining member.

Method of Use Example 6 Figure 30 is a block diagram of a method 3000 for immobilizing an instrument. At 3002, an instrument is disposed within a tapered slot of an instrument immobilizer base. At 3004, the instrument is moved along the tapered slot until the instrument is grasped by the tapered slot and immobilized. Several variations are possible. One example includes disposing a second instrument within a second tapered slot of the mstrument immobilizer base, and moving the second instrument along the second tapered slot until the second instrument is grasped by the second tapered slot and immobilized. In another example, a portion of the instrument is received laterally along the instrument immobilizer base. Conclusion Although the above examples have discussed immobilizing an electrode, these examples are also applicable to immobilizing any other instrument, including, but not limited to instruments for surgical, therapeutic, or diagnostic use, including use in non-medical fields where immobilization of an instrument is advantageous. Some examples of such other medical instruments include, by way of example, but not by way of limitation, a catheter (e.g., for aspiration or for infusion of a drag, cells, or another substance), a probe for measuring pressure, temperature, or some other parameter, a biopsy or other needle. Moreover, certain of the above examples that provide a cover for a burr hole or other entry portal may be useful for serving this function as well, even without securing and immobilizing an instrument. Furthermore, in the above examples, one or more of such components may be coated, impregnated, or otherwise provided with a drug or other therapeutic agent for delivery to the site at which such component(s) are located. Examples of such agents include steroids or other anti-inflammatory agents, or anti-infection agents such as antibiotics or antiviral drugs.

It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments may be used in combination with each other. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein." Moreover, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.