Patent Application
20050256541
The invention relates to neurostimulation therapy and, more particularly, to placement of a catheter for delivery of a therapeutic substance to the central nervous system.
Delivery of therapeutic substances such as pharmaceutical or biological therapies to the brain, spinal column or other part of the central nervous system have been used to treat a variety of neurological symptoms or conditions such as chronic pain, spasticity, dystonia, Parkinson's disease, or to provide pain relief during surgery. Delivery of electrical stimulation to targets in the central nervous system has also been used to treat these and a number of other neurological conditions. Electrical stimulation therapy may be delivered via a stimulation electrode on an electrical lead located proximate to target tissue in the brain, spinal column, pelvic nerves, stomach, or other organ of a patient. Therapeutic substances, such as pharmaceutical therapies (e.g., anesthetics or narcotics) biological therapies (e.g., gene therapy agents or growth factors) or other neuropharmacologic agents (i.e., agents that effect neurotransmitter activity or metabolism) may be delivered via a catheter inserted within or near the target tissue. The electrodes or the catheter are carefully positioned to ensure that the therapy is delivered to the intended target tissue.
Target verification in the case of therapeutic substances to target tissue within the brain first involves localization or mapping of functional brain structures. Anatomical localization of brain targets can be accomplished using anatomical brain atlases, imaging by means of positive contrast x-rays, CT or MRI under stereotactic conditions. Such standard well-known imaging techniques are used to make an initial determination of location coordinates for the target tissue to which the catheter will be directed during the surgical implant procedure.
After insertion of the catheter into the area of the brain identified as described above, small quantities of a therapeutic substance may then be delivered to achieve more precise target verification. If the delivered therapy has the desired effect, target verification can be achieved. However, because therapeutic substances often require an extended period of time to take effect, this technique may not be viable as a means of target verification during the surgical procedure.
Another method of achieving more precise target verification involves electrical test stimulation of the identified brain structures. The test stimulation is delivered via a electrical stimulation lead inserted into the target tissue. When the patient response to electrical test stimulation is consistent with appropriate lead placement, target verification can be achieved. The electrical stimulation lead is then removed from the body, and a catheter is inserted for delivery of the therapeutic substance.
In general, the invention is directed to devices and methods for positioning a medical catheter within the nervous system of a patient for delivery of therapeutic substances. A catheter having a lumen extending therethrough for delivery of therapeutic substances includes a stylet removably positioned within the lumen. The stylet includes at least one temporary stimulation electrode at its distal end. In use, the distal end of the catheter is positioned proximate target tissue within the brain or other part of the central nervous system of the patient, such as the spinal column. The temporary stimulation electrode can be used to deliver a test stimulation to verify whether the catheter is properly positioned with respect to the target tissue.
If the patient response to the test stimulation is consistent with accurate target localization, it may be determined that the catheter is properly positioned with respect to the target tissue. However, if the patient response to the test stimulation is not consistent with proper positioning of the catheter, the catheter may be repositioned and the temporary stimulation electrode may deliver additional test stimulations. After target verification is achieved, the stylet may be removed from the lumen, while leaving the catheter in place for delivery of the therapeutic substance.
In one embodiment, the invention provides a device comprising a catheter having a proximal end and a distal end and a lumen extending between the proximal end and the distal end of the catheter to deliver a therapeutic substance to target tissue, a stylet removably positioned within the lumen and having a proximal end and a distal end, wherein the distal end of the stylet extends beyond the distal end of the catheter, and at least one stimulation electrode disposed at the distal end of the stylet to verify proper positioning of the distal end of the catheter with respect to the target tissue.
In another embodiment, the invention provides a method comprising introducing a catheter having a temporary stimulation electrode removably positioned therein to target tissue within a body of a patient such that a distal end of the temporary stimulation electrode extends beyond a distal end of the catheter, delivering a test stimulation via the temporary stimulation electrode to produce a patient response, determining, based on the patient response, whether the catheter is properly positioned with respect to the target tissue, and removing the temporary stimulation electrode from the catheter when the catheter is properly positioned.
In another embodiment, the invention provides a device comprising a catheter having a proximal end and a distal end and a lumen extending between the proximal end and the distal end of the catheter to deliver a therapeutic substance to target tissue, a stiffening stylet removably positioned within the lumen and having a proximal end and a distal end, wherein the distal end of the stylet extends beyond the distal end of the catheter, and at least one stimulation electrode disposed at the distal end of the stylet to verify proper positioning of the distal end of the catheter with respect to the target tissue.
The invention may provide one or more advantages. For example, introduction of a test stimulation electrode via a catheter permits quick verification of proper catheter positioning. In particular, patient response to electrical test stimulation can be evaluated almost immediately, in comparison to evaluation of patient response to therapeutic substances, which may require an extended period of time and thereby prolong the placement procedure. In addition, the invention avoids the need to separately deploy the catheter and an electrode lead. Instead, if the test electrode introduced via the catheter indicates proper positioning, the electrode is withdrawn but the catheter simply remains in place at the target site.
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.
Stylet 23 is positioned within the lumen 21 of catheter 22. Stylet 23 may be fabricated from a semi-rigid material, such as titanium, tungsten or tungsten alloy, to provide some stiffening/structural rigidity to the catheter and aid in passing the catheter 22 into the body of the patient. Stylet 23 includes a proximal end 36 and a distal end 34. The distal end 34 of the stylet 22 includes shoulders 43 that are shaped to push against contact surfaces 43 of end cap 9. In this way, stylet 23 pushes the catheter 22 through the tissue toward its desired location. At least one temporary stimulation electrode 24 is disposed on distal end 34 of stylet 23. A stylet handle 18 is disposed on the proximal end 36 of the stylet 23, which may be used to remove the stylet from the catheter once proper placement of the catheter is achieved.
An extension 10 electrically connects the stylet 23 to a stimulator 28. The stimulator is the source of electrical pulses for electrical test stimulation of the target tissue. In one embodiment, stimulator 28 includes a device external to the body that may be used during a surgical procedure in which catheter 22 is inserted or implanted into the patient. In one embodiment, stylet 23 is electrically conductive and conducts electrical stimulation pulses from the stimulator 28 to the temporary stimulation electrode 24. Temporary stimulation electrode 24 then delivers the electrical test stimulation to the target tissue. Based on the response of the patient to the electrical test stimulation, a physician can determine whether catheter 22 is properly positioned with respect to the target tissue for delivery of a therapeutic substance.
Stylet 23 and its associated temporary stimulation electrode 24 is removably positioned within the lumen 21 of catheter 22. After verification of proper positioning of the catheter with respect to the target tissue, stylet 23 and its associated temporary stimulation electrode 24 are removed from the catheter, leaving catheter 22 in place with respect to the target tissue. Hence, placement of catheter 22 involves a single insertion of catheter 22, rather than insertion of an electrical stimulation lead followed by withdrawal of the lead and insertion of a catheter.
Introduction of a test electrode via a catheter permits quick verification of proper catheter positioning. In particular, patient response to electrical test stimulation can be evaluated almost immediately, in comparison to evaluation of patient response to therapeutic substances, which may require an extended period of time and thereby prolong the placement procedure. Moreover, the invention avoids the need to separately deploy the catheter and an electrode lead. Instead, if the test electrode introduced via the catheter indicates proper positioning, the electrode is withdrawn but the catheter simply remains in place at the target site. The therapeutic substance may then be delivered through the catheter lumen 21 directly to the target tissue.
The catheter 22 may be used to deliver any of a number of therapeutic substances. For example, the catheter 22 may deliver pharmaceutical therapies such as anesthetics or narcotics, biological therapies such as gene therapy agents or growth factors, or other neuropharmacologic agents (i.e., agents that effect neurotransmitter activity or metabolism) suitable for delivery to various parts of the central nervous system. The therapeutic substance delivered may be of a liquid, semi-liquid, or gel-type form which can flow through the lumen 21 of the catheter 22. The therapeutic substance exits one or more ports in or adjacent to the distal end 38 of the catheter 22. For example, the therapeutic substance may be delivered to the target tissue via the opening created by the lumen 21 at the distal end 38 of the catheter 22.
In one embodiment, temporary stimulation electrode 24 is formed by coating at least a portion of the distal end of stylet 24 with a conductive material. The conductive material may include, for example, platinum, platinum-iridium, stainless steel, or some other low impedance, biocompatible conductive material. Although
In one embodiment, the patient response to the test stimulation can include any one or more of symptom reduction, evoked potentials, subjective sensations, paraesthesia, subjective input from the patient or objective observation by the physician. If the test stimulation causes a patient response consistent with that which would result from proper positioning of catheter 22, it may be determined that catheter 22 is properly positioned with respect to the target tissue 8. If the patient response is not consistent with proper positioning of the catheter 22, catheter 22 may be moved to another position, and another test stimulation may be delivered. This process may be repeated until distal end of catheter 22 is properly positioned with respect to the target tissue. Once catheter 22 is positioned in the desired location, the stylet and its associated temporary stimulation electrode 24 may be withdrawn from the lumen extending through catheter 22, while leaving the catheter 22 in place with respect to the target tissue. At this point, the catheter 22 may deliver one or more therapeutic substances to target tissue 8.
The catheter with temporary stimulation electrode described herein provides more precise means of target verification before injection of a therapeutic substance. The catheter with temporary stimulation electrode therefore may increase the effectiveness of the therapeutic substance and decrease the potential for adverse side effects. Once target verification is achieved via the temporary stimulation electrode, the stylet and the temporary stimulation electrode may be removed without affecting the final placement of the catheter itself. Thus, there is no need to separately introduce a stimulation electrode, remove the stimulation electrode, and reintroduce a catheter once the location of the target tissue has been identified. This increases the accuracy of the catheter's final placement and reduces the number of times the brain or other tissue must be traversed for successful introduction of the catheter. This may result in a decreased risk to the patient and may also reduce patient recovery time.
The catheter with temporary stimulation electrode may be used in any of a number of surgical applications where therapeutic substances are to be delivered. For example, the device may be used for target verification for the delivery of anesthesia or narcotics for pain relief during surgery. The device may also be used for target verification for the delivery of biological agents, such as gene therapy agents or growth factors, into brain tissue during a surgical procedure. As another example, the device may be used for target verification for implantable drug delivery systems. An implantable drug delivery system includes a drug infusion pump implanted in the body of the patient and a catheter implanted in the intrathecal or epidural space of the spinal column, or a catheter implanted within the brain. Typically, the drug delivery system may be refilled periodically by inserting a needle percutaneously into a septum located on the drug infusion pump. It shall be understood that the catheter with temporary stimulation electrode described herein may be used for target verification for virtually any procedure in which a catheter is to be inserted into bodily tissue for the delivery of therapeutic substances, whether the insertion of the catheter into the bodily tissue is temporary (such as during a surgical procedure) or permanent (such as implantation).
In the embodiment of
It shall be understood that although particular monopolar and bipolar electrode arrangements have been shown and described, many other monopolar or bipolar arrangements known in the art may be substituted for those shown, and that the invention is not limited in this respect. It shall also be understood that alternative methods of stimulation, including multipolar stimulation (e.g., quadripolar, octapolar, etc.) may also be used without departing from the scope of the present invention.
If the patient response to the test stimulation is consistent with accurate target localization (46), i.e., if the test stimulation produced the desired patient response, it may be determined that the catheter is properly positioned with respect to the target tissue. However, if the patient response was not consistent with accurate target localization (46), the catheter may be repositioned (48) and another test stimulation may be delivered to the patient (42). In one embodiment, this process may be repeated until the catheter is properly positioned with respect to the target tissue.
After determining that the distal end of the catheter is positioned correctly, the stylet and its associated temporary stimulation electrode are withdrawn from the lumen of the catheter (50). The catheter remains in place in its proper position with respect to the target tissue. A therapeutic substance may then be delivered to the target tissue via the catheter (52).
The preceding discussion was directed to embodiments in which the catheter includes a single stylet that performs both the stiffening function (via the material with which the stylet is made, such as tungsten or titanium) and the stimulating function (via the temporary stimulation electrode at the distal end of the stylet). In another embodiment, two separate stylets, a stiffening stylet and a separate stimulation stylet, may be used. In that event, the tiffening stylet and the stimulating stylet could have different mechanical characteristics. For example, the stimulating stylet would not require the same mechanical characteristics, such as stiffness, as would the stiffening stylet. A flow diagram illustrating the two stylet system is shown in
If the patient response to the test stimulation is consistent with accurate target localization (68), i.e., if the test stimulation produced the desired patient response, it may be determined that the catheter is properly positioned with respect to the target tissue. However, if the patient response was not consistent with accurate target localization (68), the catheter may be repositioned (70) and another test stimulation may be delivered to the patient (66). In one embodiment, this process may be repeated until the catheter is properly positioned with respect to the target tissue.
After achieving accurate target localization, the stimulating stylet and its associated temporary stimulation electrode are withdrawn from the catheter (72). The catheter remains in place in its proper position with respect to the target tissue. A therapeutic substance may then be delivered to the target tissue via the catheter (74).
Various embodiments of the invention have been described. However, one skilled in the art will appreciate that various modifications may be made to these embodiments without departing from the scope of the invention. These and other embodiments are within the scope of the following claims.
This application claims the benefit of U.S. provisional application No. 60/566,955, filed Apr. 30, 2004, the entire content of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60566955 | Apr 2004 | US |
