(12) United States Patent
`Black et al.
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006216045Bl
`US 6,216,045 Bl
`Apr. 10, 2001
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54)
`
`IMPLANTABLE LEAD AND METHOD OF
`MANUFACTURE
`
`(75)
`
`Inventors: Damon Ray Black, Dallas; Terry
`Daglow, Allen; John Erickson, Plano;
`Robert Earl Jones, Wylie; B. Reno
`Lauro, Murphy, all of TX (US)
`
`(73) Assignee: Advanced Neuromodulation Systems,
`Inc., Plano, TX (US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/299,702
`
`(22) Filed:
`
`Apr. 26, 1999
`
`Int. Cl? ....................................................... A61N l/05
`(51)
`(52) U.S. Cl. ............................................. 607/122; 607/373
`(58) Field of Search ..................................... 607/116, 119,
`607/122; 600/373-375, 381, 377
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,285,347
`4,369,791
`4,374,527
`4,379,462
`4,432,377
`4,437,474
`4,458,695
`4,549,556
`
`8/1981 Hess ..................................... 128/785
`1!1983 Friedman ......................... 128/419 P
`2/1983 Iversen ................................. 128/785
`4/1983 Borkan et a!. ....................... 128/786
`2/1984 Dickhudt .............................. 128/786
`3/1984 Peers-Trevarton ................... 128/784
`7/1984 Peers-Trevaton .................... 128/786
`10/1985 Tarjan et a!. ......................... 128/785
`
`4,592,372
`4,699,157
`5,121,754
`5,330,521 *
`5,374,285
`5,417,208
`5,458,629
`5,555,618
`5,562,722
`5,897,584 *
`
`6/1986
`10/1987
`6/1992
`7/1994
`12/1994
`5/1995
`10/1995
`9/1996
`10/1996
`4/1999
`
`Beranek ............................... 128/786
`Shonk .................................. 128/786
`Mullet .................................. 128/786
`Cohen .................................. 607/122
`Vaiani et a!. ... ... .... ... ... ... ... ... 607/117
`Winkler ................................ 128/642
`Baudino eta!. ..................... 607/116
`Winkler .................................. 29/825
`Racz et a!. .. ... ... .... ... ... ... ... ... 607/117
`Herman ................................ 607/122
`
`FOREIGN PATENT DOCUMENTS
`
`12/1988 (EP) .
`0 293 499
`8/1989 (EP) .
`0 329 112
`11/1994 (EP) .
`0 622 089
`wo 95 22371
`8/1995 (WO) .
`wo 98 34678
`8/1998 (WO) .
`wo 98 47560
`10/1998 (WO) .
`* cited by examiner
`
`Primary Examiner-Jeffrey R. Jastrzab
`(74) Attorney, Agent, or Firm---Sidley & Austin
`
`(57)
`
`ABSTRACT
`
`An implantable, substantially isodiametric, low resistance
`implantable lead having at least one electrode positioned in
`a stimulation/sensing portion of the lead. At least the
`stimulation/sensing portion is unitized through partially sur(cid:173)
`rounding and supporting insulation and conductive element
`(s) of the stimulation/sensing portion with a fused matrix of
`material having mechanical properties consistent with a
`body of the lead.
`
`14 Claims, 3 Drawing Sheets
`
`14
`\
`
`10
`~
`
`12
`~
`
`Nevro Corp.
`Ex. 1008
`U.S. Patent No. 7,891,085
`
`

`

`U.S. Patent
`U.S. Patent
`
`Apr.10, 2001
`Apr. 10, 2001
`
`Sheet 1 of 3
`Sheet 1 of 3
`
`US 6,216,045 B1
`US 6,216,045 Bl
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`U.S. Patent
`U.S. Patent
`
`Sheet 2 of 3
`Sheet 2 of 3
`
`US 6,216,045 Bl
`US 6,216,045 B1
`
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`Apr. 10, 2001
`Apr.10, 2001
`
`22,25
`
`

`

`U.S. Patent
`
`Apr. 10, 2001
`
`Sheet 3 of 3
`
`US 6,216,045 Bl
`
`30
`
`FIG. 8
`
`34
`
`FIG. 7
`
`32
`
`FIG. 9
`
`FIG. 10
`
`202
`
`FIG. 11
`
`

`

`US 6,216,045 Bl
`
`1
`IMPLANTABLE LEAD AND METHOD OF
`MANUFACTURE
`
`BACKGROUND OF THE INVENTION
`
`5
`
`25
`
`30
`
`Implantable leads having ring electrodes can be used in a
`variety of applications, including delivery of electrical
`stimulation to surrounding tissue, neural or otherwise, as
`well as measuring electrical energy produced by such tissue.
`Whether serving in a stimulation capacity or a sensing
`capacity, such leads are commonly implanted along periph- 10
`eral nerves, within the epidural or the intrathecal spaces of
`the spinal column, about the heart, and in the brain.
`Notwithstanding the application, the common require(cid:173)
`ments for such implantable leads include flexibility,
`strength, and durability. The extent of such qualities, of 15
`course, is dependent upon the nature of the use, for example,
`temporary or permanent implantation. While material selec(cid:173)
`tion and certain construction techniques can be tailored to
`assist in meeting these prescribed characteristics, an over(cid:173)
`riding consideration in the design of such leads is achieving 20
`at least an isodiametric stimulation/pacing portion thereof.
`The benefits of achieving desired levels of flexibility,
`strength, and durability are intuitive. The isodiametric char(cid:173)
`acteristic is likely less obvious. Depending upon the
`application, an isodiametric lead can reduce the potential for
`damage to the lead during insertion (for example, when a
`lead is passed through an insertion needle to reach a patient
`epidural space) and/or placement, improve the ability of the
`lead to pass through tissue or a vascular system, and is more
`resistant to being immobilized by tissue growth at a perma(cid:173)
`nent implantation site.
`Differing techniques have been used to produce isodia(cid:173)
`metric leads. One such technique concerns adhering a plu(cid:173)
`rality of elements (i.e., conductive electrodes, conductive 35
`terminals, and spacing insulative tubing material) to produce
`a generally integral body. Tubing material separates a
`stimulation/sensing portion (i.e., alternating insulative tub(cid:173)
`ing material and electrodes) from a terminal portion (i.e.,
`alternating insulative tubing material and terminals). The 40
`electrodes, terminals, and tubing are independently formed
`but are intended to be isodiametric. Understandably, dimen(cid:173)
`sion variances in any one element can result in a lead having
`a varying diameter.
`Of further interest, to strengthen the plurality of element 45
`interfaces found in the stimulation/sensing portions and
`terminal portions of these leads, a composition, for example,
`medical grade epoxy, is injected within an interior of the
`leads in and about the stimulation/sensing portions and the
`terminal portions. While this technique does typically effect 50
`stabilization and strengthening of these critical regions, the
`end result can also be that these regions are too rigid and
`even brittle.
`Other techniques include applying a ring electrode(s)
`about an exterior surface of insulative tubing that forms the 55
`main body of the lead. The insulative tubing may be
`prepared to receive the electrode, for example, milled to
`remove an amount of material substantially equal to the
`material thickness of the ring electrode. Alternatively, the
`insulative tubing may be unprepared, for example, a ring 60
`electrode is simply "crimped" to a diameter substantially
`equal to the otherwise unadulterated diameter of the tubing.
`For all of the methods described above, a finished lead is
`still comprised of a plurality of independent components
`brought together in an effort to form an isodiametric cross- 65
`section. Element misalignment, inaccuracies in grinding,
`variances in electrode material thickness or individual ele-
`
`2
`ment dimensions, or over/under-crimping could respectively
`result in at least undesirable variances in lead diameter.
`Accordingly, a need exists for a lead, as well as a method
`of fabricating such lead, that provides a requisite level of
`flexibility, strength, and durability, while further providing a
`true isodiametric body for at least the stimulation/sensing
`portion of the lead.
`
`SUMMARY OF THE INVENTION
`One aspect of the present invention is directed to an
`implantable lead including a lead body, having a distal end
`and a proximal end, whereas the lead body is formed of a
`material having prescribed mechanical properties. Extend(cid:173)
`ing from the distal end of the lead body, a first region
`includes a plurality of electrodes. A first insulative material,
`having mechanical properties consistent with the material of
`the lead body, separates adjacent electrodes. Extending from
`the proximal end of the lead body, a second region includes
`at least one terminal. A second insulative material, having
`mechanical properties consistent with the material of the
`lead body, separates adjacent terminals. A conductor couples
`each terminal to at least one corresponding electrode of the
`plurality of electrodes, wherein the conductor(s) extends
`along an interior passage defined by the lead body, first
`region, and second region. In addition to the at least one
`conductor, the interior passage of the first region is substan(cid:173)
`tially filled with a third insulative material having mechani(cid:173)
`cal properties consistent with the material of the lead body.
`Another aspect of the present invention concerns a
`method of forming a substantially isodiametric lead.
`Specifically, such lead has a prescribed diameter and
`includes at least one electrode separated from at least one
`terminal by a lead body, wherein the at least one electrode
`is electrically coupled to the at least one terminal by a
`conductor passing through a passage defined by at least the
`lead body. The forming steps include assembling the at least
`one electrode and the at least one terminal relative to the lead
`body to form an assembly, including connecting the at least
`one electrode to the at least one terminal via the conductor.
`The assembly is subjected to an over-molding process that
`over molds the assembly with a first material to form an
`intermediate assembly. This first material is compatible with
`and has mechanical properties consistent with a material of
`the lead body. Ultimately, the intermediate assembly is
`processed to remove all material of the intermediate assem(cid:173)
`bly in excess of the prescribed diameter.
`An object of the present invention is to avoid the short(cid:173)
`comings of known leads and manufacturing techniques for
`the same.
`Another object of the present invention is to provide a
`method of forming a lead having a true isodiametric body for
`at least the stimulation/sensing portion of the lead.
`Another object of the present invention is to provide a
`lead having a true isodiametric body for at least the
`stimulation/sensing portion of the lead.
`Another object of the present invention is to provide a
`lead having a low resistance from a terminal to a coupled
`electrode to reduce energy consumption during system
`operation.
`Other aspects, objects, and advantages of the present
`invention will be apparent to those of ordinary skill in the art
`having reference to the following Specification together with
`the provided drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`In reference to the following figures, like reference
`numerals and letters indicate corresponding elements:
`
`

`

`US 6,216,045 Bl
`
`5
`
`3
`FIG. 1 is a perspective view of a multi-electrode lead in
`accordance with the present invention;
`FIG. 2 is a plan view of another embodiment of a
`multi-electrode lead in accordance with the present inven(cid:173)
`tion;
`FIG. 3 is a sectional view of the lead of FIG. 2, taken
`along line III-III;
`FIG. 4 is a perspective view of a preferred conductor;
`FIG. 5 is a plan view of an assembly of elements on a 10
`mandrel used to form a lead in accordance with the present
`invention;
`FIG. 6 is a sectional view of a transitional element;
`FIG. 7 is a perspective view of an electrode spacer;
`FIG. 8 is a perspective view of a terminal spacer;
`FIG. 9 is a sectional view of a stylet guide;
`FIG. 10 is a sectional view of a cap electrode; and
`FIG. 11 is a schematic representation of one embodiment
`of an assembly fixture used to assemble a lead in accordance
`with the present invention.
`
`DETAILED DESCRIPTION OF 1HE
`PREFERRED EMBODIMENTS
`
`4
`approximately 0.055 inches, conductor 20 could be on the
`order of approximately 0.0065 inches.
`While stranded bundles of stainless steel, MP35N,
`platinum, platinum-iridium alloy, drawn-brazed silver
`(DES) or the like can be used, the preferred embodiment of
`conductors 20 utilizes wires formed of multi-strands of
`drawn-filled tubes (DFT), as illustrated in FIG. 4. Each
`strand is formed of a low resistance material 20a and is
`encased in a high strength material 20b (preferably, metal).
`A selected number of strands (seven, for this example) are
`wound and coated with an insulative material 20c. With
`regard to the operating environment of the present invention,
`insulative material20c protects the individual conductors 20
`if body 22 were breached during use. Wire formed of
`15 multi-strands of drawn-filled tubes to form conductors 20, as
`discussed here, is available from Temp-Flex Cable, Inc.
`(City, State).
`In addition to providing the requisite strength, flexibility,
`and resistance to fatigue, conductors 20 formed of multi-
`20 strands of drawn-filled tubes, in accordance with the pre(cid:173)
`ferred embodiment, provide a low resistance alternative to
`other conventional materials. Specifically, a stranded wire,
`or even coiled wire, of approximately 60 em and formed of
`MP35N or stainless steel or the like would have a measured
`resistance in excess of 30 ohms. In contrast, for the same
`length, a wire formed of multi-strands of drawn-filled tubes,
`as illustrated in FIG. 4, could have a resistance less than 4
`ohms. Accordingly, in a preferred embodiment, each con(cid:173)
`ductor 20, having a length equal to or less than 60 em, has
`30 a resistance of less than 25 ohms. In a more preferred
`embodiment, each conductor 20, having a length equal to or
`less than 60 em, has a resistance equal to or less than 10
`ohms. In a most preferred embodiment, each conductor 20,
`having a length equal to or less than 60 em, has a resistance
`35 of less than 4 ohms.
`As an alternative embodiment, body 22 can further
`encompass stylet tubing 24 (FIG. 3). Stylet tubing 24
`extends from the proximal end 12 to a point within a distal
`portion of lead 10; however, in a preferred embodiment,
`40 stylet tubing 24 extends to cap electrode 34. In cooperative
`reference to FIG. 2, stylet tubing 24 operatively receives
`stylet 100 for purposes of allowing better control over lead
`10 during placement.
`
`Various embodiments, including preferred embodiments, 25
`will now be described in detail below with reference to the
`drawings.
`FIG. 1 illustrates a preferred embodiment of multi(cid:173)
`electrode lead 10. While the leads illustrated and generally
`discussed here have eight electrodes, lead 10 of the present
`invention may be constructed having any number of elec(cid:173)
`trodes (i.e., one or more).
`Lead 10 includes a proximal end 12 and a distal end 14.
`The proximal end 12 includes a plurality of electrically
`conductive terminals 16, and the distal end 14 includes a
`plurality of electrically conductive electrodes 18. While
`typically each terminal 16 is electrically connected to a
`single electrode 18 via a conductor 20 (FIG. 3), a terminal
`16 can be connected to two or more electrodes 18.
`Terminals 16 and electrodes 18 are preferably formed of
`a non-corrosive, highly conductive material. Examples of
`such material include stainless steel, MP35N, platinum, and
`platinum alloys. In a preferred embodiment, terminals 16
`and electrodes 18 are formed of a platinum-iridium alloy.
`Spanning between electrodes 18 of the distal end 14 and
`terminals 16 of the proximal end 12, body 22 is formed from
`a medical grade, substantially inert material, for example,
`polyurethane, silicone, or the like. While the specific mate(cid:173)
`rial used for body 22 is not critical to the present invention, 50
`body 22 must be non-reactive to the environment of the
`human body, provide a flexible and durable (i.e., fatigue
`resistant) exterior structure for the components of lead 10,
`and insulate adjacent terminals 16 and/or electrodes 18.
`Serving as a sheath, body 22 substantially provides the 55
`exterior structure that contains the internalized elements of
`lead 10. Specifically, body 22 provides an enclosure for each
`conductor 20 that connects a terminal 16 with one or more
`electrodes 18. Each conductor 20 is formed of a conductive
`material that exhibits the desired mechanical properties of
`low resistance, corrosion resistance, flexibility, and strength.
`For consideration, however, it should be appreciated that in
`the context of a multiple electrode lead 10, a plurality of
`conductors 20 are required to fit within the interior of body
`22. Accordingly, the cross-sectional area of each conductor
`20 is restricted. As but one example, for a lead in accordance
`with the present invention that has an outer diameter of
`
`45
`
`Lead Assembly
`While the following discussion provides but one example
`of a sequence of steps to form a lead similar to that
`illustrated in FIGS. 2 and 3. One having ordinary skill in this
`art shall appreciate that the following steps may be per(cid:173)
`formed in a differing order or otherwise inconsequentially
`modified to still yield the present invention. Consequently,
`such minor variations are still regarded as being within the
`scope of the present invention and should be construed in
`such manner.
`Furthermore, for purposes of illustration, the following
`example includes certain physical dimensions to illustrate
`the relationship between elements as well as effects of
`differing processes. Accordingly, the provided physical
`dimensions are used merely for example and shall not
`60 restrict the scope of the present invention.
`The following illustrative example concerns the construc(cid:173)
`tion of an eight electrode, epidural lead that accommodates
`a stylet. One skilled in the art shall appreciate, however, that
`a lead in accordance with the present invention may have
`65 more than or less than eight electrodes and/or have a larger
`or smaller diameter than the following example and remain
`within the scope of this disclosure.
`
`

`

`US 6,216,045 Bl
`
`5
`In reference to FIG. 5, stylet tubing 24 is positioned over
`mandrel 150. Stylet tubing 24 has an outer diameter of
`approximately 0.02 inches.
`Depending on the quantity of conductors 20 required
`(e.g., for this illustration, eight) and the size (i.e., diameter) 5
`of such conductors 20, arranging and securing conductors 20
`can be problematic when they are being arranged and
`secured about an element having the dimensions of stylet
`tubing 24.
`While any number of techniques may be used to achieve
`such arrangement of conductors 20 relative to stylet tubing
`24, FIG. 11 illustrates an example of a fixture 200 that can
`assist in this task. Specifically, fixture 200 includes first
`irotary clamp 202, iris 204, iris 206, second rotary clamp
`208, and clamp 210. Rotary clamps 202 and 208 each 15
`include a corresponding plurality of conductor clamps 203.
`While not required, it is preferred that the plurality of
`conductor clamps 203 of each rotary claim 202 and 208 be
`positioned within an arbitrary perimeter 205, whereas
`perimeter 205 should be equal to or greater than a fully- 20
`opened inner diameter of either iris 204 or 206.
`As illustrated, mandrel 150, including stylet tubing 24,
`passes through irises 204 and 206 and second rotary clamp
`208 and is secured between clamps 202 and 210. Each
`conductor 20 similarly passes through irises 204 and 206 25
`and is secured between respective clamps 203 of rotary
`clamps 202 and 208.
`Conductors 20 secured within fixture 200 are prepared for
`assembly in that a prescribed amount of insulative material
`20c is removed at or about the proximal and distal ends of
`each conductor 20 to expose conductive material 20a and
`20b. As will be discussed later, this exposed conductive
`material20a and 20b of the proximal and distal ends of each
`conductor 20 is eventually joined to an electrode 18 and a
`terminal 16. Accordingly, the exposed conductive material
`20a and 20b is arranged at differing positions relative to
`stylet tubing 24 to accommodate the serial arrangement of
`terminals 16 and electrodes 18.
`The rotational nature of rotary clamps 202 and 208
`provides unobstructed access to the in-process lead 10.
`Specifically, upon securing a single conductor 20 between
`opposing (or non-opposing) clamps 203, the rotary clamps
`202 and 210 are simply rotated to allow access to unoccu(cid:173)
`pied clamps 203.
`When all of the conductors 20 are strung between claims
`202 and 208, irises 204 and 206 are actuated to close and
`draw conductor(s) 20 closely about the outer diameter of
`stylet tubing 24. When conductorts) 20 are resting against
`the outer diameter of stylet tubing 24, conductor(s) 20 are
`secured in place. Conductor(s) 20 may be secured using
`adhesive and/or subjected to a force applied through use of
`a temporary or permanent restraint, for example, one or
`more crimped collars.
`While the illustration of FIG. 11 shows but one embodi(cid:173)
`ment of fixture 200, one skilled in the art should appreciate
`that other techniques/structures may be employed to position
`conductors 20 adjacent an exterior surface of stylet tubing
`24. Specifically, clamps 203 of each rotary clamp 202 and
`208 could be moveable along respective radial paths (not
`shown) that would allow strung conductors 20 to be moved
`from a first position to a second position adjacent the
`exterior surface of stylet tubing 24. Alternatively, conductors
`20 could initially be secured to one end of stylet tubing 24
`and only a single iris could be used to draw the unsecured
`portions of conductors 20 toward stylet tubing 24. As yet
`another alternative, while the various alternatives offered
`
`6
`provide some mechanism to control the rate of movement
`and relative positioning of conductors 20, an operator could
`simply manipulate the conductor(s) 20 to manually position
`and secure them relative to stylet tubing 24.
`Once all conductors 20 are secured to stylet tubing 24,
`transitional element 26, electrode(s) 18, electrode spacer(s)
`28, outer tubing 23, terminal spacer(s) 30, terminal(s) 16,
`and stylet guide 32 are positioned over, and concentrically
`arranged with, stylet tubing 24. The arrangement of these
`10 elements is in accordance with that illustrated in FIG. 5.
`Transitional element 26 is illustrated in FIG. 6. As will be
`discussed later, transitional element 26 provides a platform
`to receive cap electrode 34 (FIG. 10). Transitional element
`26 further provides a durable guide 26a to direct a distal end
`(not shown) of stylet 100 to cap electrode 34 via passage
`26b. Transitional element 26 is preferably formed of a
`conductive material, for example, the same material used to
`form electrodes 18.
`Electrode spacer 28 is illustrated in FIG. 7. Similarly,
`terminal spacer 30 is illustrated in FIG. 8. Functionally,
`electrode spacer 28 and terminal spacer 30 accurately
`defines a space between adjacent electrodes 18 and terminals
`16, respectively. Electrode spacer 28 and terminal spacer 30
`are preferably formed of the same material as outer tubing
`23. However, spacers 28 and 30 may be formed of a material
`that differs from that of outer tubing 23; provided however,
`any differing material used for electrode spacer 28 and/or
`terminal spacer 30 must be compatible with and possess
`largely the same mechanical properties (e.g., non-reactive to
`the environment of the human body, flexible and durable) as
`outer tubing 23. At least for purposes of this example,
`spacers 28 and 30 are formed of a polyurethane material, for
`example, Bionate 75D (Polymer Tech. Group, City, State).
`As is noted in FIG. 5, spacers 28 and 30 should have an outer
`diameter greater than lead 10.
`Outer tubing 23 separates electrodes 18 from terminals
`16. In a preferred embodiment, outer tubing 23 has a
`diameter substantially equal to a diameter of lead 10.
`40 Alternatively, outer tubing 23 may have a diameter less than
`lead 10, or a diameter greater than lead 10. In regard to the
`latter alternative, outer tubing 23 must have a wall thickness
`greater than a differential between a radius of lead 10 and a
`radius (to the outer diameter) of outer tubing 23. For this
`45 particular example, outer tubing 23 has a nominal outer
`diameter of approximate 0.055 inches.
`Stylet guide 32 is illustrated in FIG. 9. Stylet guide 32
`provides an inlet to stylet tubing 24. Stylet guide 32 is
`preferably formed of a conductive material, for example, the
`50 same material used to form electrodes 18. Stylet guide 32, as
`well as terminals 16, electrodes 18, and transitional element
`26, preferably each have an outer diameter equal to or
`greater than a nominal diameter of lead 10. In a more
`preferred embodiment, these elements each have an outer
`55 diameter greater than a nominal diameter of lead 10.
`Following the assembly of each of the elements described
`above, terminals 16 and electrodes 18 are joined to their
`respective conductors 20. Generally, each terminal16 (and
`each electrode 18) is positioned relative to exposed conduc-
`60 tive material 20a and 20b of a conductor 20 and is joined in
`a manner that facilitates a transfer of electrical energy, for
`example, resistance weld or laser weld. Once all terminals
`16 and electrodes 18 are secured, stylet guide 32 is secured
`to a proximal-most terminal16, and transitional element 26
`65 is secured to a distal-most electrode 18. Provided transi(cid:173)
`tional element 26 and stylet guide 32 are formed a conduc(cid:173)
`tive material, these elements may be secured using a process
`
`30
`
`35
`
`

`

`US 6,216,045 Bl
`
`15
`
`7
`consistent with that used to join terminals 16 and electrodes
`18 with conductors 20. Otherwise, transitional element 26
`and stylet guide 32 can be joined using an adhesive, cement
`or the like.
`The completed assembly (FIG. 5) is then over-molded, 5
`using well known injection molding techniques, using a
`material having mechanical properties consistent with a
`material(s) used to form outer tubing 23, electrode spacer
`28, and terminal spacer 30. In a preferred embodiment, the
`over-molding material and the material of outer tubing 23, 10
`electrode spacer 28, and terminal 28 are the same.
`This process has the beneficial effect of unitizing the
`element assembly to form lead 10. Moreover, electrode
`spacers 28 and terminal spacers 30 are placed in a state of
`flow, which, at least in part, results in a filling of regions
`between terminals 16/electrodes 18 and stylet guide 24.
`Consequently, terminals 16 and electrodes 18 are partially
`surrounded (i.e., along an interior surface) and supported by
`a fused matrix of material. Importantly, as electrode spacers
`28 and terminal spacers 30 are formed of a material
`mechanically equivalent to that of body 22/outer tubing 23, 20
`the stimulation/sensing portion and terminal portion of lead
`10 are stabilized and strengthened while also retaining their
`flexible properties.
`The over-molded assembly (not shown) is then subjected
`to a grinding process to remove all excess material. In a
`preferred process, the over-molded assembly is subject to
`centerless grinding, wherein excessive material, including
`over-molded material, electrode material, terminal material,
`and the like, is removed. Pursuant to the described over-
`molding and grinding of the entire lead assembly, an iso(cid:173)
`diametric lead is obtained, which is further free of any gaps
`or voids between insulative material and conductive material
`that may otherwise exist in conventional devices.
`Following the grinding process, cap electrode 34 is affixed 35
`to transitional element 26 using conventional means, for
`example, resistance welding, laser welding, or the like.
`While addressed in part above, as the invention has been
`described herein relative to a number of particularized
`embodiments, it is understood that modifications of, and 40
`alternatives to, these embodiments, such modifications and
`alternatives realizing the advantages and benefits of this
`invention, will be apparent to those of ordinary skill in the
`art having reference to this specification and its drawings. It
`is contemplated that such modifications and alternatives are 45
`within the scope of this invention as subsequently claimed
`herein, and it is intended that the scope of this invention
`claimed herein be limited only by the broadest interpretation
`of the appended claims to which the inventors are legally
`entitled.
`What is claimed is:
`1. An implantable lead comprising:
`a lead body having a distal end and a proximal end,
`wherein the lead body is formed of a material having
`prescribed mechanical properties;
`a first region extending distally from the distal end of the
`lead body, wherein the first region includes a plurality
`of electrodes, and adjacent electrodes are separated by
`a first insulative material having mechanical properties
`consistent with the material of the lead body;
`a second region extending proximally from the proximal
`end of the lead body, wherein the second region
`includes at least one terminal, and when the implant(cid:173)
`able lead includes a plurality of terminals, adjacent
`terminals are separated by a second insulative material 65
`having mechanical properties consistent with the mate(cid:173)
`rial of the lead body; and
`
`50
`
`8
`at least one conductor electrically coupling each terminal
`with at least one corresponding electrode of the plu(cid:173)
`rality of electrodes, wherein each conductor extends
`along an interior passage defined within the lead body,
`first region, and second region,
`wherein in addition to the at least one conductor, the
`interior passage of the first region is substantially filled
`with a third insulative material having mechanical
`properties consistent with the material of the lead body.
`2. An implantable lead in accordance with claim 1,
`wherein the first insulative material, second insulative
`material, and third insulative material are the same.
`3. An implantable lead in accordance with claim 1,
`wherein the first insulative material, second insulative
`material, third insulative material, and the material of the
`lead body are the same.
`4. An implantable lead in accordance with claim 1,
`wherein each conductor is formed of stranded wire and has
`a resistance equal to or less than 25 ohms for a conductor
`length equal to or less than 60 em.
`5. An implantable lead in accordance with claim 1,
`wherein an outer diameter of the lead body is approximately
`0.050 inches.
`6. An implantable lead in accordance with claim 1, further
`comprising a stylet guide, positioned within the interior
`passage defined by the lead body, first region, and second
`region, wherein an inlet of the stylet guide is at the proximal
`end of the second region, and the third material substantially
`surrounds the stylet guide.
`7. An implantable lead in accordance with claim 1,
`wherein the implantable lead is substantially isodiametric.
`8. An implantable lead in accordance with claim 1,
`wherein the third insulative material is a fused matrix.
`9. An implantable lead in accordance with claim 1,
`wherein in addition to the at least one conductor, the interior
`passage of the second region is substantially filled with a
`fourth insulative material having mechanical properties con(cid:173)
`sistent with the material of the lead body.
`10. An implantable lead in accordance with claim 9,
`wherein the first insulative material, second insulative
`material, third insulative material, and fourth insulative
`material are the same.
`11. An implantable lead in accordance with claim 9,
`wherein the fourth insulative material is a fused matrix.
`12. An implantable lead comprising:
`a lead body having a distal end and a proximal end,
`wherein the lead body is formed of a material having
`prescribed mechanical properties;
`a first region extending distally from the distal end of the
`lead body, wherein the first region includes a plurality
`of electrodes, and adjacent electrodes are separated by
`a first insulative material having mechanical properties
`consistent with the material of the lead body;
`a second region extending proximally from the proximal
`end of the lead body, wherein the second region
`includes at least one terminal, and when the implant(cid:173)
`able lead includes a plurality of terminals, adjacent
`terminals are separated by a second in