US20080103572A1 - Implantable medical lead with threaded fixation - Google Patents

Abstract

The disclosure is directed to securing electrodes of a medical lead adjacent to a target tissue site. The medical lead may include one or more threaded fixation structures disposed circumferentially about the outer surface of the lead body, or elongated member, that resembles a “screw” or “auger.” During implantation, a clinician may rotate the entire lead to “screw” the lead into the tissue of the patient until electrodes of the lead reside adjacent to a target tissue. In this manner, the threaded fixation structure secures the lead within the patient to resist lead migration and improper therapy and provide a fine adjustment for depth of placement. The threaded fixation structure may be disposed on a portion of the lead proximal to or distal to the electrodes of the lead or over the portion of the lead that includes the electrodes.

Description

TECHNICAL FIELD
• The invention relates to stimulation systems and, more particularly, to stimulation leads in stimulation systems.
BACKGROUND
• Electrical stimulation systems may be used to deliver electrical stimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, multiple sclerosis, spinal cord injury, cerebral palsy, amyotrophic lateral sclerosis, dystonia, torticollis, epilepsy, pelvic floor disorders, or gastroparesis. An electrical stimulation system typically includes one or more stimulation leads coupled to an external or implantable electrical stimulator. The stimulation lead may be percutaneously or surgically implanted in a patient on a temporary or permanent basis such that at least one stimulation electrode is positioned proximate to a target stimulation site. The target stimulation site may be, for example, a spinal cord, pelvic nerve, pudendal nerve, stomach, muscle, or within a brain or other organ of a patient. The electrodes located proximate to the target stimulation site may deliver stimulation therapy to the target stimulation site in the form of electrical signals.
• Electrical stimulation of a sacral nerve may eliminate or reduce some pelvic floor disorders by influencing the behavior of the relevant structures, such as the bladder, sphincter and pelvic floor muscles. Pelvic floor disorders include urinary incontinence, urinary urge/frequency, urinary retention, pelvic pain, bowel dysfunction, and male and female sexual dysfunction. The organs involved in bladder, bowel, and sexual function receive much of their control via the second, third, and fourth sacral nerves, commonly referred to as S2, S3 and S4 respectively. Thus, in order to deliver electrical stimulation to at least one of the S2, S3, or S4 sacral nerves, a stimulation lead is implanted proximate to the sacral nerve(s).
• Electrical stimulation of a peripheral nerve, such as stimulation of an occipital nerve, may be used to induce paresthesia. Occipital nerves, such as a lesser occipital nerve, greater occipital nerve or third occipital nerve, exit the spinal cord at the cervical region, extend upward and towards the sides of the head, and pass through muscle and fascia to the scalp. Pain caused by an occipital nerve, e.g. occipital neuralgia, may be treated by implanting a lead proximate to the occipital nerve to deliver stimulation therapy.
• In many stimulation applications, including stimulation of a sacral nerve, it is desirable for a stimulation lead to resist migration following implantation. For example, it may be desirable for the electrodes disposed at a distal end of the implantable medical lead to remain proximate to a target stimulation site in order to provide adequate and reliable stimulation of the target stimulation site. In some applications, it may also be desirable for the electrodes to remain substantially fixed in order to maintain a minimum distance between the electrode and a nerve in order to help prevent inflammation to the nerve and in some cases, unintended nerve damage. Securing the stimulation lead at the target stimulation site may minimize lead migration.
SUMMARY
• In general, the disclosure is directed toward securing electrodes of a medical lead adjacent to a target tissue site with a threaded fixation structure configured to engage tissue within a patient to resist migration of the medical lead. The medical lead may be similar to a “screw” or “auger-like.” The threaded fixation structure defines one or more threads disposed circumferentially about the outer surface of a lead body. Specifically, the threads of the threaded fixation structure may be arranged in a helical pattern. During implantation, a clinician may rotate the entire lead to “screw” the lead into the tissue of the patient until electrodes of the lead reside adjacent to a target tissue. In this manner, the threaded fixation structure secures the lead within the patient to resist lead migration. In addition, the threaded fixation structure may allow a fine adjustment mechanism for the depth of the elongated member within the tissue. The threaded fixation structure may be disposed on a portion of the lead proximal to or distal to the electrodes of the lead or over the portion of the lead that includes the electrodes. In some cases, the entire distal end of the lead may include the threaded fixation structure to engage a greater area of tissue. In other embodiments, the threaded fixation structure may be used with drug delivery catheters instead of electrical stimulation leads.
• In one embodiment, the disclosure is directed to a medical lead that includes an elongated member having a proximal end and a distal end, at least one stimulation electrode disposed closer to the distal end of the lead than the proximal end of the lead, and at least one threaded structure extending around a portion of an outer surface of the elongated member and configured to engage tissue within a patient to resist migration of the medical lead.
• In another embodiment, the disclosure is directed to method that includes inserting a medical lead into a patient, wherein the lead comprises at least one stimulation electrode and at least one threaded fixation structure extending around a portion of an outer surface of the lead, and rotating the lead to engage the threaded fixation structure with tissue of the patient to resist migration of the lead.
• In an additional embodiment, the disclosure is directed to a system that includes a medical lead having an elongated member having a proximal end and a distal end, at least one stimulation electrode disposed closer to the distal end of the lead than the proximal end of the lead, and at least one threaded structure extending around a portion of an outer surface of the elongated member and configured to engage tissue within a patient to resist migration of the medical lead. The system also includes a stimulator that delivers electrical stimulation therapy to a patient via the medical lead within the patient.
• In another additional embodiment, the disclosure is directed to an apparatus that includes an elongated member having a proximal end and a distal end, a conduit disposed within the elongated member, an exit port disposed on an outer surface of the elongated member in fluidic communication with the conduit, and at least one threaded fixation structure extending around a portion of an outer surface of the elongated member and configured to engage tissue within a patient to resist migration of the medical lead.
• The disclosure may provide one or more advantages. The threaded fixation structure may be engaged to the adjacent tissue of the patient and still allow the clinician to advance or retract the lead to finely adjust the lead position. A sheath may also be used to cover the threaded fixation structure until the clinician desires to expose the threaded fixation structure to the adjacent tissue, and the sheath may collapse the threaded fixation structure to reduce the lead diameter until lead fixation is desired. In addition, the clinician may remove the lead by rotating the lead and reducing tissue trauma.
• The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
BRIEF DESCRIPTION OF DRAWINGS
• FIG. 1A is a schematic perspective view of a therapy system including an electrical stimulator coupled to a stimulation lead that has been implanted in a body of a patient proximate to a target stimulation site.
• FIG. 1B is an illustration of the implantation of a stimulation lead at a location proximate to an occipital nerve.
• FIG. 2 is a block diagram illustrating various components of an electrical stimulator and an implantable lead.
• FIGS. 3A and 3B are perspective drawings of a sheath that covers a lead prior to implantation and is removed after the lead is correctly positioned in a patient.
• FIGS. 4A-4C are perspective drawings illustrating exemplary stimulation leads with varying configurations of threaded fixation mechanisms.
• FIGS. 5A-5B are perspective drawings illustrating exemplary stimulation leads with varying threaded fixation mechanisms over electrodes of the lead.
• FIG. 6 is a perspective drawing illustrating an exemplary stimulation lead with threads from the distal tip to a location proximal to electrodes.
• FIG. 7 is a perspective drawing illustrating an exemplary stimulation lead with torsional reinforcement members within the elongated member.
• FIGS. 8A and 8B are perspective drawings illustrating exemplary stimulation leads with foldable threads.
• FIG. 9 is a flow diagram illustrating an exemplary process for securing a threaded lead to a tissue of a patient.
• FIG. 10 is a flow diagram illustrating an exemplary process for removing a threaded lead from a tissue of a patient.
• FIG. 11 is a flow diagram illustrating an exemplary process for securing a lead with folding threads to a tissue of a patient.
• FIGS. 12A and 12B are perspective drawings illustrating exemplary medical catheters with a helical threaded structure.
• FIGS. 13A and 13B are cross-sectional end views of a keyed stylet and reciprocally keyed medical lead.
DETAILED DESCRIPTION
• The medical leads described herein include a threaded fixation mechanism that secures the medical lead within a tissue of a patient. The threaded fixation mechanism prevents the electrodes of the lead from migrating away from the target stimulation tissue, which may lead to a reduction in therapy efficacy. Specifically, the threaded fixation mechanism includes a thread structure disposed around the outer surface of the elongated member, such that the lead resembles a “screw” or “auger” device that advances or retreats when rotated. The threaded fixation mechanism may allow the clinician to finely adjust the elongated member location, in contrast to other medical lead fixation structures such as tines or adhesives. Generally, the threads may be arranged in a helical pattern, but other types of thread patterns may also be used to secure the lead. Hence, the threaded fixation mechanism may be referred to as a threaded fixation structure for purposes of illustration. In addition, other non-helical thread patterns may be used in some embodiments. The thread structure may be disposed distal to the electrodes, proximal to the electrodes, and/or at the same axial position of the electrodes. In addition, in some embodiments, the threaded fixation structure may be disposed on a tapered tip at the distal end of the elongated member to begin the engagement and tunneling of the lead through the tissue when the lead is rotated to secure the threaded fixation structure.
• In some embodiments, the thread structure may not engage the adjacent tissue until the user, e.g. a clinician, desires the structure to do so. For example, a sheath may be configured to cover the elongated member and thread structure for lead insertion and be removed to allow the threaded fixation structure to contact the adjacent tissue. In addition, the thread structure may fold down against the elongated member outer surface when constricted by the sheath. When the clinician removes the sheath, the threaded fixation structure extends away from the elongated member and returns to its original thread shape to secure the lead. In this case, the thread structure may have elastic, super-elastic, or shape memory properties that cause it to assume an extended position when a sheath or other restraint mechanism is removed to expose the thread structure.
• Alternatively, the medical lead may not include electrodes on the elongated member. In this case, the medical lead may be a catheter that delivers a therapeutic agent through one or more lumens in the elongated member, while the threaded fixation structure secures the location of the catheter. The lumen may end at one or more exit ports near the distal end of the elongated member, and the exit ports may be disposed in an axial or longitudinal outer surface of the elongated member.
• FIG. 1A a schematic perspective view oftherapy system10, which includeselectrical stimulator12 coupled tostimulation lead14, which has been implanted inbody16 of a patient proximate to targetstimulation site18.Electrical stimulator12 provides a programmable stimulation signal (e.g., in the form of electrical pulses or substantially continuous-time signals) that is delivered to targetstimulation site18 bystimulation lead14, and more particularly, via one or more stimulation electrodes carried bylead14.Electrical stimulator12 may be either implantable or external. For example,electrical stimulator12 may be subcutaneously implanted in the body of a patient16 (e.g., in a chest cavity, lower back, lower abdomen, or buttocks of patient16).Electrical stimulator12 may also be referred to as a pulse or signal generator, and in the embodiment shown inFIG. 1A,electrical stimulator12 may also be referred to as a neurostimulator. In some embodiments, lead14 may also carry one or more sense electrodes to permitstimulator12 to sense electrical signals fromtarget stimulation site18. Furthermore, in some embodiments,stimulator12 may be coupled to two or more leads, e.g., for bilateral or multi-lateral stimulation.
• Lead14 further includes a lead body, or elongated member, and one or more threaded fixation structures (not shown inFIG. 1) which engage with tissue proximate to targetstimulation site18 to substantially fix a position oflead14 proximate to targetstimulation site18. The threaded fixation structure is rotated during implantation to engage with tissue adjacent to targetstimulation site18.Proximal end14A oflead14 may be both electrically and mechanically coupled toconnector13 ofstimulator12 either directly or via a lead extension. In particular, lead14 may include electrical contacts nearproximal end14A to electrically connect conductors disposed within the elongated member to stimulation electrodes (and sense electrodes, if present) at a position adjacent todistal end14B oflead14 tostimulator12.Lead14 may be connected directly or indirectly (e.g., via a lead extension) tostimulator12.
• In the example embodiment oftherapy system10 shown inFIG. 1A,target stimulation site18 is proximate to the S3 sacral nerve, and lead14 has been introduced into the S3sacral foramen22 ofsacrum24 to access the S3 sacral nerve. Stimulation of the S3 sacral nerve may help treat pelvic floor disorders, urinary control disorders, fecal control disorders, interstitial cystitis, sexual dysfunction, and pelvic pain.Therapy system10, however, is useful in other stimulation applications. Thus, in alternate embodiments,target stimulation site18 may be a location proximate to any of the other sacral nerves inbody16 or any other suitable nerve inbody16, which may be selected based on, for example, a therapy program selected for a particular patient. For example, in other embodiments,therapy system10 may be used to deliver stimulation therapy to pudendal nerves, perineal nerves, or other areas of the nervous system, in which cases, lead14 would be implanted and substantially fixed proximate to the respective nerve. As further alternatives, lead14 may be positioned for temporary or chronic spinal cord stimulation for the treatment of pain, for peripheral neuropathy or post-operative pain mitigation, ilioinguinal nerve stimulation, intercostal nerve stimulation, gastric stimulation for the treatment of gastric mobility disorders and obesity, muscle stimulation (e.g., functional electrical stimulation (FES) of muscles), for mitigation of other peripheral and localized pain (e.g., leg pain or back pain), or for deep brain stimulation to treat movement disorders and other neurological disorders. Accordingly, although sacral nerve stimulation will be described herein for purposes of illustration, astimulation lead14 in accordance with the invention may be adapted for application to a variety of electrical stimulation applications.
• Migration oflead14 following implantation may be undesirable, and may have detrimental effects on the quality of therapy delivered to apatient16. For example, migration oflead10 may cause displacement of electrodes carried bylead14 to atarget stimulation site18. As a result, the electrodes may not be properly positioned to deliver the therapy, possibly undermining therapeutic efficacy of the stimulation therapy fromsystem10. Substantially fixinglead14 to surrounding tissue may help discourage lead14 from migrating fromtarget stimulation site18 following implantation, which may ultimately help avoid harmful effects that may result from a migratingstimulation lead14.
• To that end, the invention provides lead14 with a thread structure (not shown inFIG. 1) disposed around the elongated member oflead14 to provide fixation betweenlead14 andtissue surrounding lead14, such as tissue withinsacrum16 in the example ofFIG. 1A. The thread structure may have a helical pattern that permits lead14 to be, in effect, screwed into a tissue site. In comparison to some existing methods of fixing implanted medical leads, such as suturing lead14 to surrounding tissue or applying a cuff electrode, using a threaded fixation structure to securelead14 inpatient16 may be beneficial in a minimally invasive surgery, which may allow for reduced pain and discomfort forpatient16 relative to invasive surgery, as well as a quicker recovery time. As described in further detail below, the threaded fixation structure is disposed around the outer surface of the elongated body near the distal end oflead14 and configured to engage with the adjacent tissue to preventlead14 movement.
• Implantinglead14 with the threaded fixation structure may be completed via a few methods. First, the clinician may rotate lead14 to advancelead14 towardtarget stimulation sire18 and utilize the threaded fixation structure to engage the adjacent tissue. Second, a sheath (not shown inFIG. 1A) may be used initially to coverlead14 and the included threaded fixation structure to allow the clinician to insertlead14 intopatient16 until direct insertion is no longer possible. At this point, the clinician may remove the sheath to expose the threaded fixation structure and then rotatelead14 to advancelead14 the rest of the distance towardstarget stimulation site18.
• The rotation oflead14 may be achieved directly by rotating the lead body, or by a stylet or other device that is inserted into an inner lumen of the lead to engage the lead. In some embodiments, the stylet may have a keyed structure, such as one or more longitudinal flanges, ribs, teeth or grooves that engage reciprocal structure in the inner lumen of the lead. For example, a keyed stylet may be inserted to engage the distal end of the lead and lock into interior grooves or teeth to facilitate the rotation of the lead. In particular, reciprocal teeth or grooves, or the like, may rotationally bear against each other such that rotation of the stylet causes rotation of the lead in the same direction.
• In addition, the threaded fixation structure may be foldable against the elongated member oflead14 when covered by the sheath. When the sheath is removed, the threaded fixation structure may stand up, or extend, away from the elongated member to its original shape. The clinician may then rotatelead14 to advancelead14 to targetstimulation site18. In either case, the thread tends to “bite” into the surrounding tissue to resist migration of the lead from the target stimulation site.
• Therapy system10 also may include aclinician programmer26 and apatient programmer28.Clinician programmer26 may be a handheld computing device that permits a clinician to program stimulation therapy forpatient16, e.g., using input keys and a display. For example, usingclinician programmer26, the clinician may specify stimulation parameters for use in delivery of stimulation therapy.Clinician programmer26 supports telemetry (e.g., radio frequency telemetry) withstimulator12 to download stimulation parameters and, optionally, upload operational or physiological data stored bystimulator12. In this manner, the clinician may periodically interrogatestimulator12 to evaluate efficacy and, if necessary, modifies the stimulation parameters.
• Likeclinician programmer26,patient programmer28 may be a handheld computing device.Patient programmer28 may also include a display and input keys to allowpatient16 to interact withpatient programmer28 andimplantable stimulator12. In this manner,patient programmer28 providespatient16 with an interface for control of stimulation therapy bystimulator12. For example,patient16 may usepatient programmer28 to start, stop or adjust stimulation therapy. In particular,patient programmer28 may permitpatient16 to adjust stimulation parameters such as duration, amplitude, pulse width and pulse rate, within an adjustment range specified by the clinician viaclinician programmer28, or select from a library of stored stimulation therapy programs.
• Stimulator12,clinician programmer26, andpatient programmer28 may communicate via cables or a wireless communication, as shown inFIG. 2.Clinician programmer26 andpatient programmer28 may, for example, communicate via wireless communication withstimulator12 using radio frequency (RF) telemetry techniques known in the art.Clinician programmer26 andpatient programmer28 also may communicate with each other using any of a variety of local wireless communication techniques, such as RF communication according to the 802.11 or Bluetooth specification sets, or other standard or proprietary telemetry protocols.
• FIG. 1B is a conceptual illustration of an alternative implantation site to the implantation ofFIG. 1A.Therapy system10 may also be used to provide stimulation therapy to other nerves of apatient16. For example, as shown inFIG. 1B, lead14 may be implanted and fixated with the two or more threaded fixation members proximate to anoccipital region29 ofpatient30 for stimulation of one or more occipital nerves. In particular, lead14 may be implanted proximate to lesseroccipital nerve32, greateroccipital nerve34, and thirdoccipital nerve36. InFIG. 1B, lead14 is aligned to be introduced intointroducer needle38 and implanted and anchored or fixated with fixation elements proximate tooccipital region29 ofpatient30 for stimulation of one or moreoccipital nerves32,34, and/or36. A stimulator (e.g.,stimulator12 inFIG. 1A) may deliver stimulation therapy to any one or more ofoccipital nerve32, greateroccipital nerve34 or thirdoccipital nerve36 via electrodes disposed adjacent todistal end14B oflead14. In alternate embodiments, lead14 may be positioned proximate to one or more other peripheral nerves proximate tooccipital nerves32,34, and36 ofpatient30, such as nerves branching fromoccipital nerves32,34, and36, as well as stimulation of any other suitable nerve, organ, muscle, muscle group or other tissue site withinpatient30, such as, but not limited to, nerves within a brain, pelvis, stomach or spinal cord ofpatient30.
• Implantation oflead14 may involve the subcutaneous placement oflead14 transversely across one or moreoccipital nerves32,34, and/or36 that are causingpatient30 to experience pain. In one example method of implantinglead14 proximate to the occipital nerve, using local anesthesia, avertical skin incision33 approximately two centimeters in length is made in the neck ofpatient30 lateral to the midline of the spine at the level of the C1 vertebra. The length ofvertical skin incision33 may vary depending on the particular patient. At this location, patient's skin and muscle are separated by a band of connective tissue referred to as fascia.Introducer needle38 is introduced into the subcutaneous tissue, superficial to the fascia and muscle layer but below the skin.Occipital nerves32,34, and36 are located within the cervical musculature and overlying fascia, and as a result,introducer needle38 and, eventually, lead14 are inserted superior tooccipital nerves32,34, and36.
• Onceintroducer needle38 is fully inserted, lead14 may be advanced throughintroducer needle38 and positioned to allow stimulation of the lesseroccipital nerve32, greateroccipital nerve34, thirdoccipital nerve36, and/or other peripheral nerves proximate to an occipital nerve. Upon placement oflead14,introducer needle38 may be removed. In some embodiments,introducer needle38 may be used to removelead14 after stimulation therapy is no longer needed.
• Accurate lead placement may affect the success of occipital nerve stimulation. Iflead14 is located too deep, i.e., anterior, in the subcutaneous tissue,patient30 may experience muscle contractions, grabbing sensations, or burning. Such problems may additionally occur iflead14 migrates after implantation. Furthermore, due to the location of implantedlead14 on the back of patient's30 neck, lead14 may be subjected to pulling and stretching that may increase the chances of lead migration. For these reasons, lead14 may employ the threaded fixation structure to securelead14 withinpatient16. In locations near the skin ofpatient16, the threaded fixation structure may only extend from the elongated body of lead14 a small distance to minimize patient detection of the threaded fixation structure at superficial implant locations. In other words, the thread structure may be sized so as not to protrude excessively into the superficial tissues, thereby avoiding skin deformations and potential tissue erosion and damage.
• Althoughlead14 has been generally described as an electrical lead that includes electrodes, lead14 may, in other embodiments, be a drug delivery catheter that delivers therapeutic agents to target stimulation site18 (FIG. 1A) oroccipital nerves32,34 or36. In this case,stimulator12 is a drug pump that controls the delivery of therapeutic agent topatient16. The drug delivery catheter embodiment oflead14 may include an exit port for the therapeutic agent that is disposed on any surface oflead14, adjacent to or within the threaded fixation structure.
• FIG. 2 is a block diagram illustrating various components ofimplantable stimulator12 and animplantable lead14.Stimulator12 includestherapy delivery module40,processor42,memory44,telemetry module46, andpower source47. In some embodiments,stimulator12 may also include a sensing circuit (not shown inFIG. 2). Implantable lead14 includes elongatedmember48 extending betweenproximal end48A and distal end48B.Elongated member48 may also be described as an elongated member.Elongated member48 may be a cylindrical or may be a paddle-shaped (i.e., a “paddle” lead).Electrodes50A,50B,50C, and50D (collectively “electrodes50”) are disposed on elongatedmember48 adjacent to distal end48B ofelongated member48. In the example ofFIG. 2, threaded fixation structures are omitted fromlead14 for ease of illustration.
• Stimulator12 delivers stimulation therapy via electrodes50 oflead14. In particular, implantable signal generator withintherapy delivery module40 delivers electrical signals to patient16 (FIG. 1A) via at least some of electrodes50 under the control of aprocessor42. The stimulation energy generated bytherapy delivery module40 may be formulated as stimulation energy, e.g., for treatment of any of a variety of neurological disorders, or disorders influenced by patient neurological response. The signals may be delivered fromtherapy delivery module40 to electrodes50 via a switch matrix and conductors carried bylead14 and coupled to respective electrodes50.
• In some embodiments, electrodes50 may be ring electrodes. In other embodiments, electrodes50 may be segmented or partial ring electrodes, each of which extends along an arc less than 360 degrees (e.g., 90-120 degrees) around the circumference ofelongated member48. In embodiments in which lead14 is a paddle lead, electrodes50 may extend along a portion of the periphery defined byelongated member48. Electrodes50 are electrically coupled to atherapy delivery module40 ofstimulator12 via conductors withinelongated member48.
• Electrodes50 extending around a portion of the circumference oflead body48 or along one side of a paddle lead may be useful for providing an electrical stimulation field in a particular direction/targeting a particular therapy delivery site. For example, in the electrical stimulation application shown inFIG. 1B, electrodes50 may be disposed alonglead body48 such that the electrodes face towardoccipital nerves32,34, and/or36, or otherwise away from the scalp ofpatient30. This may be an efficient use of stimulation because electrical stimulation of the scalp may provide minimally useful therapy, if any, topatient30. In addition, the use of segmented or partial ring electrodes50 may also reduce the overall power delivered to electrodes50 bystimulator12 because of the efficient delivery of stimulation tooccipital nerves32,34, and/or36 (or other target stimulation site) by eliminating or minimizing the delivery of stimulation to unwanted or unnecessary regions withinpatient30. The configuration, type, and number ofelectrodes28 illustrated inFIG. 2 are merely exemplary.
• In embodiments in which electrodes50 extend around a portion of the circumference oflead body48 or along one side of a paddle lead, lead14 may include one ormore orientation markers45 proximate toproximal end14A that indicate the relative location of electrodes50.Orientation marker45 may be a printed marking onlead body48, an indentation inlead body48, a radiographic marker, or another type of marker that is visible or otherwise detectable (e.g., detectable by a radiographic device) by a clinician.Orientation marker45 may help a clinician properly orientlead14 such that electrodes50 face the desired direction (e.g., towardoccipital nerves32,34, and/or36) withinpatient16. For example,orientation marker45 may also extend around the same portion of the circumference oflead body48 or along the side of the paddle lead as electrodes50. In this way,orientation marker45 faces the same direction as electrodes, thus indicating the orientation of electrodes50 to the clinician. When the clinician implants lead14 inpatient16,orientation marker45 may remain visible to the clinician.
• Stimulator12 delivers stimulation therapy via electrodes50 oflead14. In one embodiment, an implantable signal generator or other stimulation circuitry withintherapy delivery module40 delivers electrical signals (e.g., pulses or substantially continuous-time signals, such as sinusoidal signals) to targets stimulation site18 (FIG. 1A) via at least some of electrodes50 under the control of aprocessor42. The stimulation energy generated bytherapy delivery module40 may be formulated as stimulation energy, e.g., for treatment of any of a variety of neurological disorders, or disorders influenced by patient neurological response. The signals may be delivered fromtherapy delivery module40 to electrodes50 via a switch matrix and conductors carried bylead14 and electrically coupled to respective electrodes50. The implantable signal generator may be coupled topower source47.Power source47 may take the form of a small, rechargeable or non-rechargeable battery, or an inductive power interface that transcutaneously receives inductively coupled energy. In the case of a rechargeable battery,power source47 similarly may include an inductive power interface for transcutaneous transfer of recharge power.
• Processor42 may include a microprocessor, a controller, a DSP, an ASIC, an FPGA, discrete logic circuitry, or the like.Processor42 controls the implantable signal generator withintherapy delivery module40 to deliver stimulation therapy according to selected stimulation parameters. Specifically,processor42 controlstherapy delivery module40 to deliver electrical signals with selected amplitudes, pulse widths (if applicable), and rates specified by the programs. In addition,processor42 may also controltherapy delivery module40 to deliver the stimulation signals via selected subsets of electrodes50 with selected polarities. For example, electrodes50 may be combined in various bipolar or multi-polar combinations to deliver stimulation energy to selected sites, such as nerve sites adjacent the spinal column, pelvic floor nerve sites, or cranial nerve sites.
• In addition,processor42 may controltherapy delivery module40 to deliver each signal according to a different program, thereby interleaving programs to simultaneously treat different symptoms or provide a combined therapeutic effect. For example, in addition to treatment of one symptom such as sexual dysfunction,stimulator12 may be configured to deliver stimulation therapy to treat other symptoms such as pain or incontinence.
• Memory44 ofstimulator12 may include any volatile or non-volatile media, such as a RAM, ROM, CD-ROM, NVRAM, EEPROM, flash memory, and the like. In some embodiments,memory44 ofstimulator12 may store multiple sets of stimulation parameters that are available to be selected bypatient16 or a clinician for delivery of stimulation therapy. For example,memory44 may store stimulation parameters transmitted by clinician programmer26 (FIG. 1A).Memory44 also stores program instructions that, when executed byprocessor42,cause stimulator12 to deliver stimulation therapy. Accordingly, computer-readable media storing instructions may be provided to causeprocessor42 to provide functionality as described herein.
• In particular,processor42controls telemetry module170 to exchange information with an external programmer, such asclinician programmer26 and/or patient programmer28 (FIG. 1A), by wireless telemetry. In addition, in some embodiments,telemetry module46 supports wireless communication with one or more wireless sensors that sense physiological signals and transmit the signals tostimulator12.
• In some embodiments, wherelead14 is a drug delivery catheter,therapy delivery module40 may include a fluid pump or other release mechanism to dispense a therapeutic agent throughlead14 and intopatient16. Therapy delivermodule40 may also, in this case, include a fluid reservoir which contains the therapeutic agent. Possible therapeutic agents may include pharmaceutical agents, insulin, a pain relieving agent or a gene therapy agent. Refilling the fluid reservoir may be accomplished by inserting the needle of a syringe through the skin ofpatient16 and into a refill port in the housing ofstimulator12. In addition, more than one lead may be coupled totherapy delivery module40.
• FIGS. 3A and 3B are perspective drawings of a sheath that covers a lead prior to implantation and removed after the lead is correctly positioned in a patient, which includes a lead that includes a threaded fixation structure. As shown inFIG. 3A, lead52 is capable of delivering electrical stimulation to numerous tissue sites withinpatient16.Lead52 may be an embodiment of any lead described herein, includinglead14. Prior to delivering stimulation, elongatedmember54 oflead52 is covered completely around the longitudinal outer surface withsheath58.Sheath58 may be constructed to protectelectrodes56 and threadedfixation structure57 from implantation stresses or damage of adjacent tissues. In addition,sheath58 may be a restraint mechanism that keeps threadedfixation structure57 from being deployed until the clinician removed the sheath.Electrodes56 are typically ring electrodes, but other types of electrodes may be used. For example, segmented electrodes, or multiple electrodes around the circumference ofelongated member54 may be employed. Alternatively, lead52 may be in a non-circular shape, such as a rectangular paddle lead. In some embodiments, lead52 may also include one or more radio-opaque markers that allow the clinician to image the lead in real time to determine the exact position of the lead within patient after rotating the lead.
• Sheath58 may be constructed of a flexible polymer that provides a smooth interface between the sheath andelongated member54.Sheath58 may be dimensioned just larger thanelongated member54, or the sheath may be shrunk to fitelongated member54 snugly for implantation. In some embodiments,sheath58 may constructed to assist the clinician in guidinglead52 withinpatient16. In this case,sheath58 may be rigid or semi-rigid and similar to a lead introducer or a cannula introduction device.
• FIG. 3B showslead52 withsheath58 being removed fromelongated member54 in the direction of the arrow. Oncelead52 is positioned such thatelectrodes56 are adjacent to a target tissue for stimulation, the clinician may begin removinglead52 as shown. Assheath58 is removed, threadedfixation structure57 is exposed to the adjacent tissue to fixelongated member54 in position. In other embodiments, the clinician may removesheath58 in sections as fixation elements need to be deployed or as necessary to ensure proper fixation withinpatient16. As will be described in detail below, threadedfixation structure57 may have different dimensions, sizes, locations, and properties than shown inFIGS. 3A and 3B.
• FIGS. 4A-4C are perspective drawings illustrating exemplary stimulation leads with varying configurations of threaded fixation mechanisms. As shown inFIG. 4A, lead60 includes elongatedmember62,electrodes64, taperedtip68, and threadedfixation structure70. The distal end oflead60 is shown.Elongated member62 is substantially cylindrical in shape, but the elongated member may also be configured into any other shape.Electrodes64 are ring electrodes disposed at the distal end ofelongated member62. At the distal tip oflead60, tapered,conical tip68 is attached to, or integrally formed with, elongatedmember62. Threadedfixation structure70 is disposed distal toelectrodes64 and around the outer surface of taperedtip68.
• Tapered tip68 is formed in the shape of a cone to facilitate the tunneling oflead60 through tissue in order to reach the target tissue. Threadedfixation structure70 is disposed around the outer surface of taperedtip68 from adjacent to the distal end of the tapered tip to the distal end ofelongated member62. In this manner, threadedfixation structure70 engages with the adjacent tissue ofpatient16 as taperedtip68 pierces through the tissue. As a user, e.g., a clinician, rotateslead60, threadedfixation structure70 advances the lead through the adjacent tissue and moveselectrodes64 increasingly closer to a target tissue with each turn of the lead. In other embodiments threadedfixation structure70 may only be disposed along a portion of taperedtip68.
• Threadedfixation structure70 may be constructed of a material similar to or different fromelongated member62 or taperedtip68. The material of threadedfixation structure70 may be substantially biologically inert, e.g., biocompatible, and may include any of metals, metal alloys, composites, or polymers. Some example materials may include stainless steel, titanium, nitinol, polypropylene, polyurethane, polycarbonate, polyethylene, nylon, silicone rubber, or expanded-polytetrafluoroethylene. The material selection of threadedfixation structure70 may be based upon whether the structure is desired to be rigid, semi-rigid, or flexible properties, which could affect the engagement of the structure to the adjacent material. In addition, threadedfixation structure70 may be a combination of different materials depending on the implantation site. For example, threadedfixation structure70 may have a flexible distal portion that changes to a rigid portion for precise engagement with the adjacent tissue. Threadedfixation structure70 may be adhered to taperedtip68 through a glue, an epoxy, welding, soldering, or any other attachment mechanism. In other embodiments, threadedfixation structure70 may be an overmold that is fitted to a snug fit around elongatedmember62. Alternatively, threadedfixation structure70 may be formed with taperedtip68.
• In addition, threadedfixation structure70 may have a cross-sectional shape configured to assist the advancement oflead60 through the adjacent tissue. The cross-sectional shape of each thread may generally be a triangle, but other shapes are possible. For example, the cross-sectional shape of threadedfixation structure70 may be a rounded triangle, a semi-circle, a square, a rectangle, a trapezoid, or any other shape desired by the clinician. In addition, the cross-sectional shape may be angled in a direction non-perpendicular to the outer surface of taperedtip68. For example, threadedfixation structure70 may be tilted toward the proximal end oflead60. In other words, the angle between the outer surface of taperedtip68 and the proximal side of threadedfixation structure70 may be less than 90 degrees. Alternatively, the angle between the outer surface of taperedtip68 and the proximal side of threadedfixation structure70 may be greater than 90 degrees.
• Threadedfixation structure70 may also be configured to advance through tissue at a predetermined rate or extend into the tissue a predetermined distance. The pitch of threadedfixation structure70 may be defined by thedistance lead60 is advanced with each full 360 degree rotation of the lead, i.e., the axial distance between two peaks of the threaded fixation structure. Threadedfixation structure70 may have a pitch between approximately 0.5 millimeters (mm) and 3 mm. The pitch may be less than approximately 0.5 mm or greater than 3 mm. The height of threadedfixation structure70 is the distance between the outer surface of taperedtip68 and the top edge of the threaded fixation structure. Generally, the height is between approximately 0.1 mm and 3 mm. However, other embodiments of threadedfixation structure70 may include heights smaller than approximately 0.1 mm or greater than 3 mm. While threadedfixation structure70 may have a constant height, the threaded fixation structure may increase in height as the threaded fixation structure moves away from the distal end of taperedtip68. Generally,elongated member62 may have an outside diameter between approximately 0.5 mm and 5 mm. The wall thickness ofelongated member62 may be between approximately 0.1 mm and 2 mm. In addition, the ratio of diameter to thread height may be between approximately 1 and 50, depending on the application oflead60.
• FIG. 4B showslead72, which is an embodiment of lead60 (FIG. 4A).Lead72 includes elongatedmember74,electrodes76, taperedtip80, and threadedfixation structure82.Lead72 differs fromlead60 in the shape of taperedtip80. While taperedtip68 is constructed as a cone shape, taperedtip80 is a parabolic shape with an atraumatic, rounded distal end.Tapered tip80 may be beneficial if the clinician does not want a tip that may damage adjacent tissue during extreme bends ofelongated member74. In other embodiments, taperedtip80 may be configured into a different shape. For example, taperedtip80 may be curved in any parabolic shape different from that shape of the tapered tip shown inFIG. 4B. In addition, taperedtip80 may be asymmetrical or bent in a predetermined direction to facilitate creating a curved path forlead72.
• FIG. 4C illustrates lead84 with threadedfixation structure90 disposed proximal toelectrodes88.Lead84 includes elongatedmember86,electrodes88 and threadedfixation structure90. Threadedfixation structure90 is disposed around the longitudinal outer surface ofelongated member86, proximal to the location ofelectrodes88. In other embodiments, threadedfixation structure90 may be disposed around the longitudinal outer surface ofelongated member86 at a location distal toelectrodes88. The distal position of threadedfixation structure90 may be instead of or in addition to the proximal position of the threaded fixation structure.
• Threadedfixation structure90 may include any number of turns around elongatedmember86. For example, threadedfixation structure90 may include 3 complete turns as shown inFIG. 4C. However, threadedfixation structure90 may include more than 3 or less than 3 turns, as desired by the clinician for a particular implantation site. In addition, threadedfixation structure90 may include partial turns, or even continuous structures with less than one complete turn. In other embodiments, multiple threadedfixation structures90 may be disposed proximal to or distal toelectrodes88. In alternative embodiments, lead84 may include a tip that has a threaded fixation structure such astapered tips68 and80 ofleads60 and72, respectively.
• Threadedfixation structure90 may be constructed of a material similar to or different fromelongated member86. The material of threadedfixation structure90 may be substantially biologically inert, e.g., biocompatible, and may include any of metals, metal alloys, composites, or polymers. Some example materials may include stainless steel, titanium, nitinol, polypropylene, polyurethane, polycarbonate, polyethylene, nylon, silicone rubber, or expanded-polytetrafluoroethylene. The material selection of threadedfixation structure90 may be based upon whether the structure is desired to be rigid, semi-rigid, or flexible properties. Threadedfixation structure90 may be adhered to elongatedmember86 through a glue, an epoxy, welding, soldering, or any other attachment mechanism. In other embodiments, threadedfixation structure90 may be an overmold that is fitted to a snug fit around elongatedmember86. Alternatively, threadedfixation structure90 may be integrally formed withelongated member86, e.g., by injection molding and/or insert molding.
• In addition, threadedfixation structure90 may have a cross-sectional shape configured to assist the advancement oflead84 through the adjacent tissue. The cross-sectional shape may generally be a triangle, but other shapes are possible. For example, the cross-sectional shape of threadedfixation structure90 may be a rounded triangle, a semi-circle, a square, a rectangle, a trapezoid, or any other shape desired by the clinician. In addition, the cross-sectional shape may be angled in a direction non-perpendicular to the outer surface ofelongated member86. For example, threadedfixation structure90 may be tilted toward the proximal end oflead84. In other words, the angle between the outer surface ofelongated member86 and the proximal side of threadedfixation structure90 may be less than 90 degrees. Alternatively, the angle between the outer surface ofelongated member86 and the proximal side of threadedfixation structure90 may be greater than 90 degrees.
• Threadedfixation structure90 may also be configured to advance through tissue at a predetermined rate or extend into the tissue a predetermined distance. The pitch of threadedfixation structure90 may be defined by thedistance lead84 is advanced with each full 360 degree rotation of the lead, i.e., the axial distance between two peaks of the threaded fixation structure. Threadedfixation structure90 may have a pitch between approximately 0.5 millimeters (mm) and 3 mm. In some embodiments, the pitch may be less than approximately 0.5 mm or greater than 3 mm. The height of threadedfixation structure90 is the distance between the outer surface ofelongated member86 and the top edge of the threaded fixation structure. Generally, the height is between approximately 0.1 mm and 3 mm. However, other embodiments of threadedfixation structure90 may include heights smaller than approximately 0.1 mm or greater than 3 mm. As threadedfixation structure90 increases in height, the surface area of the threaded fixation structure increases as well. A larger surface area of threadedfixation structure90 may increase theaxial force lead84 may be able to incur without allowing the lead to migrate in the direction of the axial force. In other words, a larger height of threadedfixation structure90 may be desired in cases wherelead84 is subjected to greater movement. While threadedfixation structure90 may have a constant height, the threaded fixation structure may increase in height as it moves towards the proximal end of the threaded fixation structure.Elongated member62 may have an outside diameter between approximately 0.5 mm and 5 mm. The wall thickness ofelongated member62 may be between approximately 0.1 mm and 2 mm. In addition, the ratio of diameter to thread height may be between approximately 1 and 50, depending on the application oflead60.
• Implantation of all leads60,72, and84, may vary depending on the target stimulation site withinpatient16 or implant preferences of the clinician. For example, a sheath (shown inFIGS. 3A and 3B) may be used to cover any threaded fixation structures to allow insertion of the lead without requiring rotation of the lead. Upon positioning the lead near the stimulation site, the clinician may remove the sheath and begin rotating the lead to engage to recently exposed threaded fixation structure. Alternatively, the clinician may guide and rotate the lead through a substantial length of the insertion of the lead without the use of a sheath.
• FIGS. 5A-5B are perspective drawings illustrating exemplary stimulation leads with varying threaded fixation mechanisms over electrodes of the lead. As shown inFIG. 5A, lead92 includes elongatedmember94,electrodes96, and threadedfixation structure98, a fixation structure. Threadedfixation structure98 is shown to be disposed around the same portion ofelongated member94 that includeselectrodes96. In this manner, threadedfixation structure98 is located over a portion of the surface of eachelectrode96 as the threaded fixation structure rotates from the proximal end of the threaded fixation structure to the distal end of the threaded fixation structure. Utilizing threadedfixation structure98 overelectrodes96 may provide for reduced movement ofelectrodes96 with respect to the target tissue, compared to threaded fixation structures located elsewhere along the longitudinal outer surface oflead92. Threadedfixation structure98 may be constructed similar to and have similar physical properties of threadedfixation structure90 ofFIG. 4C. Threadedfixation structure98 may attached toelectrodes96 with an adhesive or other bonding technique, while some embodiments may not have the threaded fixation structure attached to the electrodes.
• While threadedfixation structure98 is shown to be substantially disposed around the entire portion ofelongated member94 that includeselectrodes96, the threaded fixation structure may also be disposed further in the proximal or distal direction along the elongated member. In some embodiments, threadedfixation structure98 may only be disposed on a portion of thesurface including electrodes96. In other words, threadedfixation structure98 may not be disposed around allelectrodes96, e.g., the threaded fixation structure may only be disposed around the proximal two electrodes. In other embodiments, lead92 may include threadedfixation structure98 at locations along elongated body similar toleads60,72, or84 ofFIGS. 4A,4B, and4C, respectively.
• FIG. 5B showslead100 that is substantially similar to lead92 ofFIG. 5A.Lead100 includeselongated member102,electrodes104, and threadedfixation structures106A,106B,106C,106D and106E (collectively “threaded fixation structures106). Threaded fixation structures106 are disposed at the portion ofelongated member102 which also includeselectrodes104. However, none of threaded fixation structures106 are located over the surface of any ofelectrodes104. Instead, each of threaded fixation structures106 are only attached toelongated member102 and stop before covering any portion ofelectrodes104. In other words, threaded fixation structures106 may be substantially similar to threadedfixation structure98 ofFIG. 5B, but have any portion of the threaded fixation structure overelectrodes96 removed. In this manner, threaded fixation structures106 are arranged in sections to avoid interference with the electrical field produced byelectrodes104 that provides therapy to the target tissue ofpatient16. Threaded fixation structures106 may be constructed similar to and have physical properties similar to threadedfixation structure90 ofFIG. 4C. In some embodiments, one or more of threaded fixation structures106 may be constructed of different materials to the other threaded fixation structures.
• Threadedfixation structures106B-D are located betweenelectrodes104, threadedfixation structure106A is disposed proximal toelectrodes104 and threadedfixation structure106E is disposed distal to the electrodes. In some embodiments, threadedfixation structure106A may include more turns and be disposed along a greater proximal portion ofelongated member102. Alternatively, threadedfixation structure106E may include more turns and be disposed along a greater distal portion ofelongated member102. In other embodiments, one or more of threaded fixation structures106 may not be included inlead100. For example, lead100 may only include threadedfixation structures106A-C. In additional embodiments, lead100 may include threaded fixation structures at locations along elongated body similar toleads60,72, or84 ofFIGS. 4A,4B, and4C, respectively.
• FIG. 6 is a perspectivedrawing illustrating lead108 with threaded fixation structure extending from the distal end of the lead to a location proximate toelectrodes112. As shown inFIG. 6, lead108 includeselongate member110,electrodes112, taperedtip114, and threadedfixation structure116. Threaded fixation structure begins at the distal tip of taperedtip114 and continues to wrap aroundelongate member110past electrodes112 to a location of the electrode member proximal to the electrodes. Lead108 may be a combination of threaded fixation structures described with respect to leads60,72,84,92, or100 ofFIGS. 4 and 5. In addition, threadedfixation structure116 may have similar properties to any of threadedfixation structures70,82,90,98, or106. In other embodiments threadedfixation structure116 may be broken into two or more threaded fixation structures at any location along taperedtip114 orelongated member110, including threaded fixation structures that do not cover the surface ofelectrodes112. In alternative embodiments, lead108 may include threaded fixation structures at the proximal and/or intermediate locations ofelongate member110 instead of or in addition to threadedfixation structure116.
• FIG. 7 is a perspectivedrawing illustrating lead118 that includes a reinforcement member.Lead118 is substantially similar to lead108 ofFIG. 6 and includeselongate member120,electrodes122, taperedtip124, and threadedfixation structure126. In contrast to lead108, lead118 includeshelical reinforcement member128 which resides withinelongated member120.Helical reinforcement member128 is provided to add torsional rigidity to lead118 which resists twisting ofelongated member120 when the clinician rotates the lead to engage threadedfixation structure126.
• Helical reinforcement member128 may be provided in a variety of methods. First,helical reinforcement member128 may be a metal or polymer wire. Second,helical reinforcement member128 may be a metal or polymer ribbon that creates a substantially contiguous cylinder. Other fibers, materials, or members may be used to constructhelical reinforcement member128, in some embodiments. Whilehelical reinforcement member128 is shown as extending withinelongate member120 in a direction opposite threadedfixation structure126, some embodiments may employ the helical reinforcement member in the same direction as the threaded fixation structure. Alternatively,helical reinforcement member128 may include two helical reinforcement members in which one helical reinforcement member is arranged in one direction and the second helical reinforcement member is arranged in a second direction opposite the first direction.Helical reinforcement member128 may extend throughout the entire length oflead118 or only a small portion of the lead.
• FIGS. 8A and 8B are perspective drawings illustrating exemplary stimulation leads with foldable threads.FIG. 8A illustrates lead130 prior to the removal ofsheath138.Lead130 includeselongated member132,electrodes134, threadedfixation structure136, andsheath138. Lead130 may be similar to any ofleads60,72,84,92,100,108 or118; however, threadedfixation structure136 is foldable, or compliant, such thatsheath138 prevents the threaded fixation structure from extending away fromelongated member132. While threadedfixation structure136 is shown to be disposed around the portion ofelongated member132 that includeselectrodes134, the threaded fixation structure may be disposed at any portion of the elongated member as described herein.
• Sheath138 is provided to facilitate implantation oflead130. Withsheath138 coveringelongated member132 and collapsing threadedfixation structure136, the diameter oflead130 is smaller to allow the clinician to push the lead through a lead introducer (not shown) or through tissue ofpatient16. Once the clinician inserts lead130 to the desired position,sheath138 is removed to expose threadedfixation structure136 to the adjacent tissue. Threadedfixation structure136 extends away from the outer surface ofelongated member132 to the originally formed threaded fixation structure dimensions.Rotating lead130 may help threadedfixation structure136 to extend away from the surface ofelongated member132 and engage the surrounding tissue. The extended angle of threadedfixation structure136 may be less than 90 degrees between the outer surface ofelongated member132 and the proximal surface of the threaded fixation structure. While threadedfixation structure136 is foldable towards the proximal end oflead130, the threaded fixation structure may be foldable towards the distal end of the lead in other embodiments.
• Threadedfixation structure136 may be constructed of any bendable, pliable, elastic, or superelastic material that is biocompatible. For example, a polymer such as expanded-polytetrafluoroethylene or a shape memory metal alloy such as nitinol may be used to construct threadedfixation structure136.Sheath138 may be constructed of a thin polymer membrane that may slide over the surface ofelongated member132 and threadedfixation structure136 while maintaining sufficient circumferential stiffness that retains the threaded fixation structure before deployment.Sheath138 may be initially configured to coverelongated member132 and threadedfixation structure136 by sliding the sheath from the distal end oflead130 to the proximal end of the lead. Alternatively,sheath138 may loosely coverlead130 and be heated to shrink the circumference of the sheath and collapse threadedfixation structure136.
• FIG. 8B showslead130 withsheath138 being removed in the proximal direction ofarrow140. The distal portion of threadedfixation structure136 has already extended away fromelongated member132 in the direction ofarrow142. The proximal portion of threaded fixation structure, indicated byarrow144, is still restricted bysheath138 that has not been fully removed. Oncesheath138 is fully removed fromlead130, the clinician may rotate the lead to engage threadedfixation structure136 with the adjacent tissue. In addition, oncesheath138 is removed fromlead130, the clinician may not be able to slide the sheath back over threadedfixation structure136.
• In alternative embodiments,sheath138 may not be necessary for threadedfixation structure136 to fold down againstelongated member132. Threadedfixation structure136 may fold down from force from adjacent tissue when the clinician inserts lead130 intopatient16. Whenlead130 is properly positioned, the clinician may pull back on the lead to cause threadedfixation structure136 to engage with the adjacent tissue and extend the threaded fixation structure away fromelongated member132. The clinician can then begin to rotatelead130 to screw the lead into the tissue andsecure electrodes134 to the desired location.
• FIG. 9 is a flow diagram illustrating an exemplary process for securing a threaded lead to a tissue of a patient. Any of leads60,72,84,92,100,108 or118, or130 may be implanted with this procedure, but lead60 will be used as an example. The clinician beings by inserting the lead introducer into the target stimulation site of patient16 (146). Next, the clinician inserts lead60 into the lead introducer until the lead is positioned correctly (148). The clinician then withdraws the sheath that covers lead60 (150) and rotates the lead in the direction of threadedfixation structure68, e.g., clockwise, to secure the lead at the target tissue (152). Iflead60 is not correctly placed (154), the clinician continues to rotate the lead (152). Iflead60 is positioned correctly (154), the clinician may attach the proximal end of the lead to the stimulator and proceed with beginning therapy (156).
• In some embodiments, the clinician may not need to remove a sheath to expose the threaded fixation structure. In other embodiments, the clinician may require a keyed stylet or other device that engages into the distal end of the lead and locks into interior grooves or teeth to facilitate the rotation of the lead and engagement of the threaded fixation structure. Alternatively, the stylet may be inserted through a channel extending withinlead60 that attaches to grooves, slots, or teeth near the proximal end of the lead to facilitate lead rotation that engages the threaded fixation structure to the adjacent tissue.
• FIG. 10 is a flow diagram illustrating an exemplary process for removing a threaded lead from a tissue of a patient. Any of leads60,72,84,92,100,108 or118, or130 may be implanted with this procedure, but lead60 will be used as an example. After stimulation therapy has been completed or lead60 needs to be removed for any other reason, the clinician mayready patient16 for removal of the lead from stimulator12 (158). If the threaded fixation structure is foldable (160), the clinician inserts a sheath down to the proximal end of the threaded fixation structure (162). If the threaded fixation structure oflead60 is not foldable, or the sheath has been inserted to the foldable threads, the clinician begins to rotate the lead in the opposite direction of the threaded fixation structure, e.g., counter-clockwise (164). If the threaded fixation structure is not released from tissue (166), the clinician continues to rotate lead60 (164). If the threaded fixation structure has been released from tissue (166), the clinician may pull lead60 from patient16 (168). Releasing the threaded fixation structure from the tissue may include either backing the threaded fixation structure into the sheath such that the structure folds under the sheath or rotating the lead enough that the threaded fixation structure is free from being engaged from any tissue ofpatient16.
• Similar toFIG. 9, some embodiments may require that the clinician use a keyed stylet or other device that engages into the distal end of the lead and locks into interior grooves or teeth to facilitate the rotation of the lead and disengagement of the threaded fixation structure. Alternatively, the stylet may be inserted through a channel extending withinlead60 that attaches to grooves, slots, or teeth near the proximal end of the lead to facilitate lead rotation that disengages the threaded fixation structure from the adjacent tissue.
• FIG. 11 is a method of implanting a lead inpatient12 with a different threaded fixation structure than the leads implanted in with the technique ofFIG. 9. Any of leads60,72,84,92,100,108 or118, or130 with a foldable threaded fixation structure may be implanted with this procedure, but lead130 will be used as an example. The clinician beings by inserting the lead introducer into the target stimulation site of patient16 (169), which causes threadedfixation structure136 to fold down against the surface oflead130. Next, the clinician inserts lead130 into the lead introducer until the lead is positioned correctly (171). The clinician then removes the lead introducer that covers lead130 (173) and pulls back on the lead to engage, or extend, the folded threaded fixation structure with the adjacent tissue (175). The clinician then rotates the lead in the direction of threadedfixation structure136, e.g., clockwise, to secure the lead at the target tissue (177). Iflead130 is not correctly placed (179), the clinician continues to rotate the lead (177). Iflead130 is positioned correctly (179), the clinician may attach the proximal end of the lead to the stimulator and proceed with beginning therapy (181).
• In some embodiments, the clinician may be able to insertlead130 directly intopatient16 without the use of a lead introducer. In this case, foldable threadedfixation structure136 folds down with the force of the adjacent tissue aslead130 is inserted intopatient16. In other embodiments, the clinician may require a keyed stylet or other device that engages into the distal end of the lead and locks into interior grooves or teeth to facilitate the rotation of the lead and engagement of the threaded fixation structure. Alternatively, the stylet may be inserted through a channel extending withinlead130 that attaches to grooves, slots, or teeth near the proximal end of the lead to facilitate lead rotation that engages the threaded fixation structure to the adjacent tissue.
• FIGS. 12A and 12B are perspective drawings illustrating exemplary medical catheters with a helical threaded structure. Threadedfixation structures174 and184 may be similar to the threaded fixation structures of any ofleads60,72,84,92,100,108 or118, or130. However, a conduit is used to deliver a therapeutic agent to the tissue instead of electrodes that deliver stimulation.FIG. 12A showslead170 that includeselongated member172, threadedfixation structure174,conduit176, andexit port178. Threadedfixation structure174 is disposed about the outer surface ofelongated member172 at the distal end of the elongated body. A drug pump may be attached to the proximal end oflead170 for delivering a therapeutic agent throughconduit176 and out ofexit port178 into the adjacent target tissue.Conduit176 resides withinelongated member172, and may or may not have a common central axis to the elongated member. In other embodiments, more than one threadedfixation structure174 may be provided to secure the location oflead170 and ensure that the therapeutic agent is delivered to the appropriate tissue ofpatient16.
• FIG. 12B showslead180 which is similar to lead170 ofFIG. 12A.Lead180 includeselongated body182, threadedfixation structure184,conduit186, andexit port188.Exit port188 is disposed on a longitudinal outer surface ofelongated member182, within threadedfixation structure184.Conduit186 resided withinelongated member182, and may or may not have a common central axis with the elongated member. In other embodiments,exit port188 may be located outside of threadedfixation structure184 either distal to or proximal to the threaded fixation structure. In alternative embodiments,conduit186 may be in fluidic communication with more than one exit port, where the multiple exit ports are located at various longitudinal or circumferential positions ofelongated member182 or in the axial surface of the elongated member. In addition, lead180 may include multiple conduits withinelongated member182.
• FIGS. 13A and 13B are cross-sectional end views of akeyed stylet200 and a reciprocally keyedmedical lead202. As discussed previously, rotational movement of a lead may be accomplished by simply rotating the lead body. In some embodiments, however, it may be desirable to rotate the lead body with the aid of a stylet inserted in an inner lumen of the lead body. For example, a stylet may provide added structural integrity relative to a flexible lead. The stylet may be sized to frictionally engaged the inner wall of the inner lumen such that rotation of the stylet causes rotation of the lead body. Alternatively, the stylet and the lead body may be formed with a reciprocal key structure, such as any combination of slots, grooves, teeth, ribs, rails, or the like.
• In the example ofFIGS. 13A and 13B,stylet200 includes astylet body203 withmultiple teeth204A-204D. The teeth may run longitudinally substantially the entire length of thestylet body203, or be provided only near a distal end of the stylet body, e.g., over the last 2 to 6 centimeters at the distal end of the stylet. In either case,teeth204A-204D may be sized and shaped to engagereciprocal grooves210A-210D in alead body206 oflead202. Thegrooves210A-210D may be formed by molding, extruding, scribing or other techniques. In any event,teeth204A-204D engagecorresponding grooves210A-210D so that the teeth can bear against the grooves to transmit rotational force fromstylet200 to lead202.
• Also shown inFIG. 13B arerepresentative portions212A,212B of a threaded fixation structure. Any thread fixation structure, as described herein, may be combined with a lead202 including slots, grooves, or the like. Moreover, the number of slots or grooves may be subject to wide variation. Also, in some embodiments, lead202 may include teeth whilestylet200 includes grooves. The exact combination, arrangement, size, and number of slots, grooves, teeth or the like is subject to variation provided thelead202 andstylet200 include reciprocal structure to impart rotational movement from the stylet to the lead.
• Alternative to keyedstylet200, a cannula device that is configured to fit around the outside of the lead may be used to rotate the lead and engage the threaded fixation structure. The cannula device may be circumferentially locked to the lead via one or more slots, grooves, teeth, ribs, rails, or the like, disposed on the outside of the elongated member. In some embodiments, the cannula device may use a friction fit to lock to the lead. In either case, the cannula device may be slid down to the proximal end of the threaded fixation structure or some other location of the lead that still facilitates rotation of the lead.
• A lead including threaded fixation may be useful for various electrical stimulation systems. For example, the lead may be used to deliver electrical stimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, multiple sclerosis, spinal cord injury, cerebral palsy, amyotrophic lateral sclerosis, dystonia, torticollis, epilepsy, pelvic floor disorders, gastroparesis, muscle stimulation (e.g., functional electrical stimulation (FES) of muscles) or obesity. In addition, the helical fixation described herein may also be useful for fixing a catheter, such as a drug deliver catheter, proximate to a target drug delivery site.
• The preceding specific embodiments are illustrative of the practice of the invention. It is to be understood, therefore, that other expedients known to those skilled in the art or disclosed herein may be employed without departing from the invention or the scope of the claims. For example, the present invention further includes within its scope methods of making and using systems and leads for stimulation, as described herein. Also, the leads described herein may have a variety of stimulation applications, as well as possible applications in other electrical stimulation contexts, such as delivery of cardiac electrical stimulation, including paces, pulses, and shocks.
• Many embodiments of the invention have been described. Various modifications may be made without departing from the scope of the claims. These and other embodiments are within the scope of the following claims.

Claims (34)

1. A medical lead comprising:

an elongated member having a proximal end and a distal end;

at least one stimulation electrode disposed closer to the distal end of the lead than the proximal end of the lead; and

at least one threaded structure extending around a portion of an outer surface of the elongated member and configured to engage tissue within a patient to resist migration of the medical lead.

2. The medical lead ofclaim 1, wherein the portion of the outer surface is proximal to the at least one stimulation electrode.

3. The medical lead ofclaim 1, wherein the portion of the outer surface is distal to the at least one stimulation electrode.

4. The medical lead ofclaim 3, further comprising a tapered tip at the distal end of the elongated member, wherein the tapered tip includes the portion.

5. The medical lead ofclaim 1, wherein the portion of the outer surface includes the at least one stimulation electrode.

6. The medical lead ofclaim 1, wherein a plurality of threaded fixation structures are formed around the portion of the outer surface of the elongated member to simulate a continuous threaded fixation structure.

7. The medical lead ofclaim 1, wherein the threaded fixation structure is foldable in one direction to allow the thread structure to lay substantially flat against the elongated member when restrained by a sheath.

8. The medical lead ofclaim 1, further comprising a helical reinforcement member disposed within an inner surface of the elongated member to provide torsional rigidity to the elongated member.

9. The medical lead ofclaim 8, wherein the helical reinforcement member is disposed in a direction different than the direction of the threaded fixation structure.

10. The medical lead ofclaim 1, wherein the threaded fixation structure comprises a pitch between adjacent threads or approximately 0.5 millimeters (mm) to approximately 3 mm.

11. The medical lead ofclaim 1, wherein the threaded fixation structure comprises a thread height between approximately 0.1 millimeters (mm) and approximately 3 mm.

12. The medical lead ofclaim 1, wherein the threaded fixation structure comprises at least one of a biocompatible metal alloy and a biocompatible polymer.

13. A method comprising:

inserting a medical lead into a patient, wherein the lead comprises at least one stimulation electrode and at least one threaded fixation structure extending around a portion of an outer surface of the lead; and

rotating the lead to engage the threaded fixation structure with tissue of the patient to resist migration of the lead.

14. The method ofclaim 13, further comprising removing a sheath from the lead to expose the at least one threaded fixation structure after the lead is inserted into the patient.

15. The method ofclaim 14, wherein removing the sheath allows the at least one threaded fixation structure to unfold and extend from the lead.

16. The method ofclaim 13, further comprising generating electrical stimulation with a stimulator and delivering the electrical stimulation to the patient via the at least one stimulation electrode of the lead.

17. The method ofclaim 13, further comprising rotating the lead to disengage the threaded fixation structure from the tissue in the patient.

18. The method ofclaim 13, further comprising sliding a sheath over the lead to cover the at least one threaded fixation structure with the sheath.

19. The method ofclaim 18, further comprising removing the lead and sheath from the patient

20. The method ofclaim 13, wherein inserting a medical lead into a patient comprises forcing the at least one threaded fixation structure to fold down against the outer surface of the lead in a first direction.

21. The method ofclaim 20, further comprising pulling the lead in the first direction to extend the at least one threaded fixation structure into the tissue, and wherein rotating the lead causes the at least one threaded fixation structure to advance the lead in a second direction opposite the first direction.

22. The method ofclaim 13, further comprising positioning the at least one electrode adjacent to at least one of a sacral nerve, a pudendal nerve, a spinal cord, and an occipital nerve.

23. A system comprising:

a medical lead comprising:

an elongated member having a proximal end and a distal end;

at least one stimulation electrode disposed closer to the distal end of the lead than the proximal end of the lead; and

at least one threaded structure extending around a portion of an outer surface of the elongated member and configured to engage tissue within a patient to resist migration of the medical lead; and

a stimulator that delivers electrical stimulation therapy to a patient via the medical lead within the patient.

24. An apparatus comprising:

an elongated member having a proximal end and a distal end;

a conduit disposed within the elongated member;

an exit port disposed on an outer surface of the elongated member in fluidic communication with the conduit; and

at least one threaded fixation structure extending around a portion of an outer surface of the elongated member and configured to engage tissue within a patient to resist migration of the medical lead.

25. The apparatus ofclaim 24, wherein the exit port is disposed on an axial outer surface of the distal end of the elongated member.

26. The apparatus ofclaim 24, wherein the exit port is disposed on a longitudinal outer surface of the elongated member.

27. The apparatus ofclaim 26, wherein the at least one threaded fixation structure is disposed at least one of proximal to the exit port and distal to the exit port.

28. The apparatus ofclaim 24, wherein the at least one threaded fixation structure is foldable in one direction to allow the thread structure to lay substantially flat against the elongated member when restrained by a sheath.

29. The apparatus ofclaim 24, further comprising a helical reinforcement member disposed within an inner surface of the elongated member to provide torsional rigidity to the elongated member.

30. The apparatus ofclaim 29, wherein the helical reinforcement member is disposed in a direction different than the direction of the at least one threaded fixation structure.

31. The apparatus ofclaim 24, wherein the threaded fixation structure comprises a pitch between approximately 0.5 millimeters (mm) and 3 mm.

32. The apparatus ofclaim 24, wherein the threaded fixation structure comprises a thread height between approximately 0.1 millimeters (mm) and 3 mm.

33. The apparatus ofclaim 24, wherein the threaded fixation structure comprises at least one of a biocompatible metal alloy and a biocompatible polymer.

34. The apparatus ofclaim 24, wherein the conduit delivers a therapeutic agent to the patient via the exit port.

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