Method for applying pulsed radio frequency energy to the spinal canal

Abstract

A flexible catheter includes two electrical contacts in a distal region of the catheter and a distal aperture of a hose line. The electrical contacts are connected to a high frequency pulse generator for applying pulsed radio frequency energy for nerve stimulation. A temperature sensor is located in the distal region of the catheter. The flexible catheter is inserted into a region in the spinal canal and the pulsed radio frequency generator is operated, thereby applying pulsed radio frequency energy to a localized region to be treated. The temperature at the distal region of the catheter can also be monitored, and the pulsed radio frequency energy is applied in dependence on the monitored temperature. With the catheter, pain and other medical conditions being related to and influenced by a nervous system are treated.

Claims

1. A method for applying pulsed radio frequency energy to a region in the spinal canal, comprising the steps of: inserting a flexible epidural catheter into a spinal space, said flexible epidural catheter having at least one first electrical contact in a distal region of the catheter, said flexible epidural catheter also including a hose line that defines an aperture in the distal region of said hose line for injecting pain killing drugs through the aperture in the distal region of said hose line from a syringe or drug pump; operating a pulsed radio frequency generator, the pulsed radio frequency generator being coupled to said first electrical contact; thereby applying pulsed radio frequency energy via said first electrical contact to a localized region to be treated; detecting a temperature in the spinal space by a temperature sensor at the distal region of the catheter; automatically changing at least one parameter of the pulsed radio frequency energy supplied to the localized region when a specific temperature is detected, automatically switching off or temporarily suppressing of the pulsed radio frequency energy to the localized region when an upper temperature limit of 42 C. is reached to thereby avoid thermal damage to tissue, and whereby in said localized region at least one of a nerve, nerve root, a nerve ganglion and a part of the spinal cord is treated.

2. A method as claimed in claim 1, further comprising the step of probing a position of the catheter by applying a test stimulation via said electrical contact to detect a sensual response to the test stimulation signal.

3. A method as claimed in claim 2, wherein the test stimulation signal has a voltage in the range of 0 to 12 V, a frequency in the range of 50 to 150 Hz, and a pulse width in the range of 150 to 400 microseconds.

4. A method as claimed in claim 1, further comprising the step of repeatedly adjusting the catheter to different positions.

5. A method as claimed in claim 1, wherein the step of detecting the temperature comprises using a temperature sensor that is thermally connected to the first electrical contact.

6. A method as claimed in claim 1, wherein the step of inserting the flexible epidural catheter into the spinal canal comprises disposing an aseptic guide wire within the hose line, pushing the catheter to the desired position in the spinal canal, and retreating the guide wire.

7. A method as claimed in claim 1, wherein the applied pulsed radio frequency energy has a voltage in the range of 20 to 30 V, a frequency of 500 kHz and a pulse width of 20 ms.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only and thus are not limiting of the present invention and wherein

(2) FIG. 1 is a schematic view of an epidural catheter having two contacts, a thermocouple, and a hose line;

(3) FIG. 2 is a schematic longitudinal sectional view of a tip of a first embodiment of an epidural catheter;

(4) FIG. 3 is a transverse sectional view of the catheter of FIG. 2;

(5) FIGS. 4 and 5 show a second embodiment of a catheter in views corresponding to FIGS. 2 and 3;

(6) FIGS. 6 and 7 show a third embodiment of a catheter in views corresponding to FIGS. 2 and 3;

(7) FIG. 8 is a schematic view of an embodiment of an epidural catheter having a transducer with a coil within a flat casing being subcutaneously implantable, as well as an external device having an antenna;

(8) FIG. 9 is another view of the casing and the transducer with the coil;

(9) FIG. 10 is a schematic view of a stimulation lead passing through an endoscopic probe; the lead having one electrical contact and a thermocouple;

(10) FIG. 11 is a cross-sectional anatomical view of a spinal cord in a spinal column; and

(11) FIG. 12 is a sectional view of a spine taken along the length of the spine;

(12) For reasons of clarity, the drawings are not drawn to scale.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(13) FIG. 1 shows an epidural catheter 10 comprising in its distal region a distal contact 12 and a proximal contact 14 between which a lateral aperture 16 of a hose line 18 is disposed. Contacts 12 and 14 are drawn with hatching. The distal contact 12 forms a cap encasing the end of the catheter 10. The proximal contact 14 forms an annular strip encircling the catheter 10. The edges of the contacts 12 and 14 are flush with a mantle 20 of the catheter 10 made of silicone rubber.

(14) The outer diameter of the mantle 20 is 1.33 mm, corresponding to a specification of 4 French. In longitudinal direction of the catheter 10 the contacts 12 and 14 extend to a length approximately corresponding to the outer diameter of the mantle 20. The contacts 12 and 14 are offset to each other by approximately 4 mm in longitudinal direction of the catheter 10. The overall length of the shown epidural catheter 10 is 60 cm, however, other lengths are also conceivable.

(15) Within the catheter 10, a thermocouple 21 (FIG. 2) is thermally connected to the distal contact 12. Electrical leads 22 for the electrical contacts 12, 14 as well as connecting wires 23 and 24 of the thermocouple 21 run within the mantle 20 parallel to hose line 18 and are, like hose line 18, indicated with dashed lines in FIG. 1. Thermocouple 21 is of the type nickel-chromium/nickel, wire 23 being of nickel-chromium and wire 24 being of nickel. The internal configuration of catheter 10 will be further explained below with FIGS. 2 and 3.

(16) Catheter 10 comprises a fixation device 25 which can serve to fasten the catheter to a point where the catheter enters a body, the element 25 being configured like in a conventional implantable catheter. Furthermore, in a known manner an aseptic guide wire (not shown) is disposed within the hose line that serves to push the catheter 10 to the desired position in the spinal canal and is then retreated. The guide wire is slightly bendable in the region of its leading end.

(17) At a connecting member 26, the electrical leads 22 are led out of the mantle 20 of catheter 10 in form of electrically isolated wires 28, and wires 23 and 24 are led out of the mantle 20 into an isolated cord 29. The hose line 18 continues within a mantle 30, which is a continuation of mantle 20, to a connector 32. Said connector serves for connecting a syringe or a drug pump and is configured in a conventional manner. Between the connector 32 and connecting member 26 is disposed a clip 34 that allows to clamp hose line 18 and re-open it by releasing clip 34. The clip 34 is configured in a conventional manner, as well, and can also be disposed at the connection 32.

(18) Wires 28 are provided with electrical connectors 36 and 38. Connector 36 is connected to the distal contact 12, and a connector 38 is connected to the proximal contact 14 of the catheter. Connectors 36 and 38 are merely schematically shown in the drawing, and can be encoded in terms of color and/or in terms of the shape of contacts of the connectors. Said connectors are adapted to be directly or via an adapter (not shown) connected to a pulse generator 39 generating a pulsed high frequency current. The pulse generator 39 can, for example, be the device N50 of the company Stryker Howmedica, the device RFG-3C+ of the company Radionics, or the device Neurotherm of the company RDG Medical.

(19) The connectors 36, 38, wires 28, leads 22, and the contacts 12 and 14 are adapted both for application of pulses for a test stimulation of nerves or of a spinal cord having, for example, a voltage in the range of 0 to 12 V. a frequency in the range of 50 to 150 Hz, and a pulse width in the range of 150 to 400 microseconds, as well as for applying pulsed high frequency, for example, within a voltage ranging from 20 to 30 V and a pulsed frequency of 500 kHz and a pulse width of 20 ms. The numerical values given are only examples to illustrate the range of application of the catheter.

(20) A bipolar connector 40 of cord 29, being secured against connecting with the wrong polarity, is connected to the wires 23 and 24 of the thermocouple 21. Connector 40 is adapted for connecting to a measuring device 41, which measures the temperature in the region of the distal contact 12 of the catheter using the thermocouple 21.

(21) The measuring device 41 can be integrated into the pulse generator 39 in form of an appropriate circuit, for example, or can be connected to the pulse generator, so as to automatically effect a switching off or a change of parameters of pulse generation when a specific temperature is reached; said specific temperature being adjustable. For example, an adaptive or stepwise control of pulse generation can be provided that reduces the power and/or frequency of the pulses when an intended upper temperature limit is approached. Alternatively or, if the temperature is too high, additionally the pulse generation can be temporarily stopped until a sufficiently low temperature is reached again.

(22) FIG. 2 shows the tip of the catheter 10 of FIG. 1 as a longitudinal sectional view, though the catheter 10 as well as the leads 22 and wires 23, 24 disposed in front of and behind the plane of the drawing are shown in a sectional view.

(23) The electrical leads 22 and wires 23, 24 each comprise an isolation 42. Leads 22 are internally soldered to the distal contact 12 and the proximal contact 14 respectively. The thermocouple 21 is formed by a contact point of the nickel-chromium wire 23 and the nickel wire 24 and is connected to the contact 12 via the wire 23 in immediate proximity. Thus, a good heat conduction between the contact 12 and the thermocouple 21 is accomplished.

(24) The mantle 20 of the catheter 10 comprises an internal partition wall 44 dividing the inside of the catheter 10 into a first hollow space forming the hose line 18 and a second hollow space 46. The leads 22 and wires 23, 24 run within this second hollow space 46. The electrical contacts 12 and 14 are separated from the hose line 18 by the mantle 20. The lateral aperture 16 of the mantle 20 opens the hose line 18 to the outside.

(25) FIG. 3 shows a cross-sectional view of the catheter 10 along the line of FIG. 2. The arrangement of leads 22 and wires 23, 24 within the second hollow space 46 of the mantle 20 is shown.

(26) FIGS. 4 and 5 show a second embodiment, wherein the mantle 20 has no internal partition wall 44 forming a second hollow space 46. Instead the electrical leads 22 and the wires 23, 24 with their respective isolations 42 run within a thickened area of the wall of the mantle 20 of the catheter 10. The hose line 18 is formed inside the mantle 20 in a way similar to the first embodiment.

(27) FIGS. 6 and 7 show a third embodiment which differs from the second embodiment in that inside the mantle 20, there is an additional internal tubular layer 48 forming the hose line 18. The mantle 20 encloses the tube formed by the internal layer 48 as well as the Isolations 42 of the electrical leads 22 and wires 23, 24. At least at the aperture 16, which penetrates the layer 48 and the mantle 20, the internal layer 48 is tightly connected to the mantle 20. However, the internal layer 48 can also be a part of a mantle of the catheter constituted of two or more layers.

(28) The tube formed by the inner layer 48 ends on the other side of the aperture 16. It can, however, also extend into the cap formed by the distal contact 12 as indicated by chain dotted lines. The internal layer 48 is isolated by the mantle 20 from the contacts 12 and 14.

(29) The shown embodiments. are meant to demonstrate a possible arrangement and contacting of the electrical leads 22 and of the thermocouple 21 and its wires 23, 24 and to present possible constructions of the hose line 18. It is to be understood that the catheter of the invention can also have a configuration that differs from these embodiments, for example a combination of the inner layer 48 of FIG. 7 with the two hollow spaces of the mantle 20 of FIG. 3, or a different location of the thermocouple 21.

(30) Alternatively, the electrical contact 12 can also be configured having the shape of an annular strip. It goes without saying that more than the two shown contacts can be provided.

(31) FIGS. 8 and 9 show another embodiment of the catheter 10 the distal part of which is constituted similar to the catheter of the third embodiment shown in FIGS. 6 and 7.

(32) As the proximal end of the catheter 10, the catheter is seamlessly connected to a flat casing 52. The upper region of the casing 52 contains an injection chamber 54 which is connected to the hose line 18. The upper wall of the injection chamber 24 comprises a bulge forming a port 56 in form of an injection septum. Via the port 26, the injection chamber of the implanted catheter is accessible from external by way of an injection needle, for example. The injection septum is made in a known manner such that its wall is sufficiently dense and elastic so as to provide a reliable sealing after an injection needle previously inserted through the septum is retracted.

(33) In the lower, region of the casing 52 a coil 58 is arranged spirally, as can be seen more clearly in FIG. 9. The coil 58 is a sending and receiving coil and is connected to a transducer 60. The transducer 60 has several functions which will be explained hereinafter.

(34) At the casing, an aperture for introducing the guide wire is closed before implanting the casing.

(35) The electrical leads 22 and the wires 23, 24 are connected to the transducer 60. The transducer is adapted to measure currents and/or voltages. For example, the transducer 60 can measure a thermovoltage on the wires 23 and 24 of the thermocouple, thereby monitoring the temperature at the distal end of the catheter 10. The transducer 60 can also measure potentials between the electrical contacts 12 and 14, for example. Such potentials can provide information about the excitation condition of nerve roots or the spinal cord, for example.

(36) The transducer 60 is addressed by an external device 70 comprising an antenna 72 cooperating with the sending and receiving coil 58 of the transducer 60. The pulse generator 39 and indication devices 76 are connectable to the external device 70.

(37) The pulse generator 39 produces a pulsed high frequency current. The high frequency pulses are inductively transmitted by the antenna 72 to the coil 58 and are relayed by the transducer 60 to the leads 22 of the electrical contacts 12 and 14. The contacts 12 and 14, the leads 22, and the transducer 60 and the coil 58 are adapted both for application of pulses for a test stimulation of nerves or of a spinal cord having, for example, a voltage in the range of 0 to 12 V, a frequency in the range of 50 to 150 Hz, and a pulse width in the range of 150 to 400 microseconds, as well as for applying pulsed high frequency, for example, within a voltage ranging from 20 to 30 V and a pulsed frequency of 500 kHz and a pulse width of 20 ms. The numerical values given are only examples to illustrate the range of application of the catheter.

(38) During pauses in-between the pulses and at times where no stimulation takes place, the transducer 60 can send signals via the coil 58 to the external device 70, which receives the signals by means of its antenna 72. Information can be transmitted concerning the temperature measured by the temperature sensor as well as information concerning electrical signals the transducer 60 receives from the electrical contacts 12 and 14. Furthermore, further signals can be transmitted from the transducer 60 to the external device 70 or in the opposite direction for control purposes, for example. The indication devices 76 can display measured voltages, currents or temperatures.

(39) In case the transducer 60 detects that an allowable maximum temperature of the temperature sensor 21 is exceeded, the transducer 60 can effect an automatic switching off or changing of parameters of pulse generation of the pulse generator 39 by means of control signals, for example. Thus, an adaptive or stepwise control of pulse generation can be provided that reduces the power and/or frequency of the pulses when an Intended upper temperature limit is approached. Alternatively or, if the temperature is too high, additionally the pulse generation can be temporarily stopped until a sufficiently low temperature is reached again.

(40) FIG. 9 shows the casing 52 of the catheter 10 of FIG. 8 as viewed from the bottom of FIG. 8. The spiral configuration of the coil 58 is visible.

(41) FIG. 10 shows an endoscopic probe 80 with a light conductor 82 that contains optical fibers for light delivery and visualization, as is known in the art. However, the endoscopic probe 80 also comprises a stimulation lead 84 having a distal electrical contact 12 in the distal region of the probe 80. The light conductor 82 ends at the distal end of the probe 80.

(42) The endoscopic probe 80 and the stimulation lead 84 are configured similar to the catheter 10 of FIG. 1, the major difference being that the hose line 18 is replaced by the light conductor 82. Therefore, similar parts are numbered with the same numbers as in FIG. 1, and the respective parts of the description of the catheter of FIG. 1 are included herein by reference. Another difference to the catheter 10 of FIG. 1 is that the stimulation lead 84 has only one contact 12 in its distal region. This contact 12 is connected to the connector 36. A second, external contact 86 is connected via a wire 88 to the connector 38.

(43) Contact 12 forms an annular strip encircling the probe 80. A thermocouple is thermally connected to the contact 12. At the connecting member 26, the light conductor 82 continues within a light cable 90 that is compatible to standard light cables for endoscopy and ends at a connector 92.

(44) FIG. 11 shows a sectional view of a spinal cord 100 and a spinal column at a level of a vertebra 102. Dorsal roots 104 and ventral roots 106 as well as spinal ganglia 108 of spinal nerves 110 are indicated. Within the spinal canal, an epidural space 112 is shown into which the catheter 10 is to be inserted.

(45) FIG. 12 schematically shows insertion of the partially shown catheter 10 into the spine. For example, the catheter 10 can be placed at the medullary conus 114 and cauda equina 116. The 12th thoracic vertebra 118, the 5th lumbar vertebra 120 and the 1st sacral vertebra 122 are indicated.

(46) The catheter 10 can be inserted in a similar manner as conventional spinal cord stimulation (SCS) electrodes. A guide wire (mandrel) is used to steer the catheter in place and can be bent. The procedure is as easy as the placement of an SCS.

(47) The inventor found out that it is plausible to place the catheter at the conus 114 and cauda equina 116. Here the nerve roots converge and can be treated by the passing catheter 10 one by one. Thus, the catheter is, for example, inserted at the contralateral or ipsilateral side into the mid-line of epidural space 112 or laterally and pushed obliquely upwards, passing the dorsal roots 104 of the spinal nerves 110. The catheter 10 is usually inserted under local or general anesthesia percutaneously through a Tuhoy needle by the loss of resistance technique into the epidural space 112. The catheter 10 is then pushed forward in an oblique way to lie at the dorso-lateral wall of the spinal canal.

(48) The point of insertion of course depends on the nerves intended to treat. If, for example, it is intended to treat the lumbar nerves the catheter is introduced at the L2/3 space, as indicated in FIG. 12, pushing it up to the Th. 12 level, thus enabling to stimulate the nerves Th 12 up to L5. Or if it is intended to stimulate the sacral nerves the catheter has to be inserted at a deeper level L3/4, as indicated with a dashed line, pushing it up to the level L1. Then it is possible to treat the entire lumbar roots in addition to all sacral roots.

(49) To be sure which nerves are affected they can be identified by stimulation with a frequency of 80 Hz, for example. The response of the patient is an accurate indication for the distances of the tip to the desired nerve.

(50) After inserting and pushing upwards the catheter 10, at first the most cranial nerve root is stimulated and there, the PRF application is performed. Then, while stimulating, the catheter 10 is slowly retrieved. The sensations diminish and then when reaching the next nerve root rise again. There, the next PRF application is started. This procedure is repeated until all nerve roots positioned in the course of the catheter have been treated. The temperature sensor at the tip allows to be continuously informed about the temperatures at the tip.

(51) The catheter 10 can be left in place up to 30 days. The procedures can be repeated at the same or any other level. It is also possible to add the catheter to an implantable device to repeat the PRF application at any time, as described herein before.

(52) The catheter 10 is cannulated and allows to inject fluids, like steroids and other substances used in adhesiolysis, if desired. Medicaments can be injected as in any other catheter. Thus, it is possible to stimulate the dorsal nerve roots and ganglia proximal to the spinal ganglia and to apply PRF.

(53) Especially when dealing with several segments and in difficult anatomical structures this flexible catheter is easier and safer to use. There are at least one or more contacts at the tip of the catheter. The distal contact applies PRF and stimulation with all possible frequencies. This enables a very accurate positioning of the tip. Adapters can be provided for to connect the catheter to any radio frequency generator.

(54) If intended for research, nerve conduction can be measured.

(55) The catheter allows direct application of pulsed radio frequency to neural structures in the skull, the epidural space and in the spinal canal. This was until today impossible. It largely extends the use of radio frequency which was limited by using thermo-lesion needles outside of the epidural space, the spinal cord or canal. It is safer than heat and can be applied directly to the spinal cord. A permanent temperature control at the top of the catheter makes the procedure safe.

(56) Adhesiolysis and the injection of steroids are possible. Exact placement by stimulation is another benefit of the catheter. The new oblique application technique could be of great therapeutic value.

(57) With the catheter or lead of the invention, pulsed radio frequency may be applied for treatment of a medical condition that is related to and influenced by the central or peripheral nervous system. The indications and targets for application of pulsed radio frequency which have been mentioned above are confirmed by the following example of the treatment of a patient that suffered from a neurogenic bladder.

(58) The female patient, born 1934, had a disk herniation at the L4/5 position in 1979. She suffered from a severe urinary retention due to a neurogenic bladder. The residual urine capacity was about 1000 ml. The patient could only void 50 ml spontaneously. In spite of several medications her problem could not be solved. A complete urological examination came to the conclusion that there was no possible cure except a conventional operation.

(59) Then, in May 2004, the catheter was introduced via the sacral hiatus, and the S 2 to S 4 roots were stimulated by pulsed radio frequency.

(60) Since that date slowly the conditions got better. The spontaneous urine was once 720 ml (3 Nov. 2004) and once 580 ml (4 Nov. 2004).

(61) In addition to a nearly normalization of the conditions the patient was able to feel her urge to void from the first day on after the stimulation, which was a feeling she had missed for many years. At least this was described as a great improvement by the patient.

(62) Furthermore, by the application of pulsed radio frequency according to the invention, a dilatation of peripheral blood vessels or hyperemia may be effected. This has been confirmed by the treatment of patients with pulsed radio frequency applied through the catheter of the invention. The patients felt a hyperemia in their feet, and a dilatation of their peripheral blood vessels was recognized.

(63) The given examples also confirm that an organ being associated with or innervated by a part of a central or peripheral nervous system may be treated according to the invention.

(64) The invention being thus described, it will be obvious that the same may be varied in many ways. Furthermore, all the disclosed elements and features of each disclosed embodiment of the catheter, stimulation system, lead, endoscopic probe or method can be combined with, or substituted for, the disclosed elements and features of every other disclosed embodiment of the catheter or method, respectively, except where such elements or features are mutually exclusive. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.