DE10033400A1 - Electrical stimulation system for medical therapy selectively connects near, central and far electrodes to provide anode reference terminal for cathode pulses - Google Patents

Abstract

The system has two electrode arrangements, each with near, central and far electrodes. Devices provide a first cathode pulse at the first central electrode, and a second cathode pulse at the second central electrode. A combination of the first central electrode, the first far electrode or the first near electrode can be selectively connected to the second central electrode, the second far electrode or the second near electrode to provide an anode reference terminal for the first cathode pulse and the second cathode pulse.

Description

Background of the Invention 1. Field of the Invention

This invention relates to devices for stimulating electrically excitable Tissue. More specifically, it relates to devices for setting the location where Nerve fibers are activated in such tissue.

2. Description of the prior art

It is generally accepted that spinal cord stimulation (spinal cord Stimulation, SCS) for pain management of the painful area completely must be covered with stimulus-induced paresthesia. This means that the stimulus-induced electrical field is the parts of the dorsal pillars (dorsal columns) that correspond to the aching dermatomes, causing paresthesia in these areas. All dermatomes through their dorsal column fibers in a regular sequence, starting from the middle where most sacred dermatomes are represented, to the left and right side, where more and more rostral dermatomes for the right or left half of the body are represented. Accordingly the electrical field applied at the correct Rostro-Caudal vortex height focus on the correct medio-lateral area of the dorsal columns. In addition to medio-lateral focusing (control of the field), the  medio-lateral extension of the excited nerve fibers to be large enough to cover all aching dermatomes, what with complex pain patterns is of particular importance.

The method currently used to focus stimulation on the correct dermatome works by implanting two under the Skin (percutaneous) electrodes aligned parallel to each other Arrangements (lines) in the dorsal epidural space and selection of the Combination of electrodes connected as anodes and cathodes, the best Coverage of pain topography with paresthesia results. There a complex pain patterns generally are not a single combination will be covered, two or more will be sequentially activated Combinations used to create a spatially complementary paresthesia received [1], [2]. Because of the large number of electrodes to be tested Combinations, this empirical process is very time consuming. About that furthermore, it does not necessarily lead to complete coverage of the painful area as there are only a small number of combinations which separate paresthesia patterns are suitable.

An improved way, an optimal coverage of the (extended) painful area is achieved by means of a two-channel Pulse generator, the simultaneous pulses of a variable voltage ratio too one anode left and center right and one anode and a conventional central cathode, fed, three-pole Transverse tripolar lead. This patented system [3] allows both an almost continuous control of the field in a transverse plane as well as suppressing stimulation of the dorsal columns (i.e. one preferred stimulation of the dorsal columns), which turns the threshold into one uncomfortable sensation raised and thus the window of therapeutic applicable amplitude is increased, resulting in an increase in the Area of the dorsal columns that can be activated [4] - [6]. This System allows corrections to paresthesia after implantation without additional surgical interventions, but requires an extensive operative Intervention (a laminotomy) for its placement.  

The therapeutically usable range for the amplitudes, and thus the coverage with paresthesia, can also be raised if instead of currently available SCS cables with an elongated arrangement of electrodes small lengths and distances on bipolar or tripolar (central cathode) Way is used [5], [7]. Taking into account that to stimulate the dorsal columns required greater current when the electrode gap is reduced, an optimal electrode length or an optimal one Electrode spacing of 1.5 or 2.0-2.5 mm suggested [8].

The invention disclosed herein allows cross-directional control of the field by means of a two-chamber pulse generator, which outputs simultaneous pulses, and by means of two parallel electrode arrangements. The invention also makes use of the preferred stimulation of the dorsal columns when tight, elongated or bipoles Tripoles are used. By this method, the principle of transverse field control can be used with the SCS (e.g. with two cables lying under the skin, which are at a distance of 2- 3 mm are arranged or with a single line with two parallel to each other arranged electrode arrangements) and also with other nerve structures (e.g. with a deep brain stimulation), with a Cortex stimulation, when stimulating peripheral nerves).

References

• 1. [1] Alo K.M. et al. "Computer assisted and patient interactive programming of dual electrode spinal cord stimulation in the treatment of chronic pain ", Neuromodulation, 1: 30-45, 1998.
• 2. [2] Devulder J., De Laat M., Rolly G. "Dual channel electrostimulation in pain", Acta neurol beig, 98: 195-198, 1998.
• 3. [3] Holsheimer J., Struijk J. J. "Multichannel apparatus for epidural spinal cord stimulation ", U.S. Patent 5,501,703, March 26, 1996.
• 4. [4] Struijk, J.J., Holsheimer J. "Transverse tripolar spinal cord stimulation: theortical performance of a dual channel system ", Med & Biol Eng & Comput, 34: 273-279, 1996.
• 5. [5] Holsheimer J. "Effectiveness of spinal cord stimulation in the management of chronic pain: analysis of technical drawbacks and solutions ", neurosurgery, 40: 990-996, 1997.  
• 6. [6] Holsheimer J. et al. "Clinical evaluation of paresthesia steering with a new system for spinal cord stimulation ", Neurosurgery, 42: 541-547, 1998.
• 7. [7] Holsheimer J. et al. "Effects of electrode geometry and combination an nerve fiber selectivity in spinal cord stimulation ", Med & Biol Eng & Comput, 33: 676-682, 1995.
• 8. [8] Holsheimer J., Wesselink W. A. "Optimal electrode geometry for spinal cord stimulation: the narrow bipole and tripole ", Med & Biol Eng & Comput, 35: 493-497, 1997.

Summary of the invention

The present invention can be used to advantage to locate the location in to switch to an electrically excitable tissue that activates nerve cells become. According to the preferred embodiment, a first and a second electrode arrangement, each of a first, a second and a have a third electrode, arranged parallel to one another, so that their first, the second and third electrodes lie next to each other. A first negative (Cathode) pulse is applied to the central electrode of the first arrangement and a second negative (cathode) pulse is sent to the one in the middle located electrode of the second arrangement. They are facilities provided to the first and second pulses simultaneously and with a variable To deliver current ratio. The first and third electrodes of both the first as well as the second arrangement or a selection from these four electrodes with the common (anode) reference potential of the two Pulse generators connected.

By using the system described above, the degree the operative required for the implantation of the electrode arrangements Precision degraded because after the operation is complete, the place is on the nerve cells are stimulated by simply changing the Current ratio of the pulses delivered to the electrodes can be. In addition, the preferred embodiment allows one large window for the therapeutically usable amplitude, which is a prerequisite is to cover an extensive pain topography in SCS.  

Brief description of the drawings

Fig. 1 shows a schematic view of a patient with an implanted neurological stimulation system employing the present invention.

Figure 2 is a schematic cross-sectional view of the spine showing the positions of the electrode assembly used for the present invention.

Fig. 3 shows the two parallel electrode arrangements and indicates that the electrodes are respectively connected as an anode (+) and cathode (-) in the different configurations used in the present invention.

FIG. 4 shows a schematic illustration of six electrodes in two arrangements and their connections to the two pulse generators, as are used in the present invention.

FIG. 5a shows the area of the dorsal columns in which nerve fibers are reached by the circuit from FIG. 4 if two pulses of the same amplitude are emitted at the same time.

Fig. 5b shows the area of the dorsal columns in which the nerve fibers are reached by the circuit of Fig. 4 when the amplitude of the pulses delivered to the left arrangement has a value greater than zero and the amplitude of the delivered to the right arrangement Pulse is zero.

FIG. 5c shows the area of the dorsal columns in which the nerve fibers are reached by the circuit of FIG. 4 when the amplitude of the pulses delivered to the arrangement on the right has a value greater than zero and the amplitude of the delivery to the arrangement on the left Pulse is zero.

Detailed description of the preferred embodiments

Fig. 1 shows a schematic view of a patient 10 having an implant of a neurological stimulation system which employs a preferred embodiment of the present invention, in order to stimulate the spinal cord 12 of the patient. The preferred system employs an implantable pulse generator 14 for generating a number of independent stimulation pulses which located by insulated conductor wires 16 and 18 in the vicinity of the spinal cord 12 electrode assemblies 16 A and 18 A (Fig. 2) is connected.

The implantable pulse generator 14 is preferably a modified, implantable pulse generator ITREL III, available from Medtronic, Inc., wherein several outputs are provided which output pulses of independently adjustable amplitudes and durations, which are selected either simultaneously or with a time delay relative to one another can be. This preferred system uses a programming device 20 which is connected to a radio frequency antenna 24 via a cable 22 . This system allows healthcare professionals to choose the various post-implant pulse output options using radio frequency transmission. While the preferred system uses fully implanted pulse generators, systems using both implanted and external components that communicate with one another via radio frequency transmission can also practice the present invention (e.g., a modified Mattrix pulse generator) from Medtronic, Inc.).

Fig. 2 shows a schematic cross-sectional view of the spine 26, wherein electrode assemblies 16 A and 18 A (connected to the pulse generator 14 by means of insulated conductive wires 16 and 18) in the dorsal epidural space 28 are shown. The electrode assemblies can be under-skin (percutaneous) leads with a small contact pitch (e.g., Pisces Compact, available from Medtronic, Inc.). The two electrode arrangements can also be arranged parallel to one another on the same insulating carrier material. Also shown are the dura mater 29, which is the part of the epidural space 28 and the subdural space 30 filled with cerebrospinal fluid, and the vertebral bone 32 . The nerve structures are the spinal roots 34 and the spinal cord, embedded in the cerebrospinal fluid. The spinal cord consists of gray substance 36 in the middle and surrounding white substance, for example the dorsal columns 38 .

The representation in Fig. 3 shows the stimulation circuit. The cathode outputs 47 B and 48 B of the pulse generators 47 and 48 are connected to electrodes 41 and 44 of the electrode arrangements 16 A and 18 A, respectively. The anode outputs 47 A and 48 A of the pulse generators are connected to each other and form the common (anode) reference pole for the cathode pulses. This common reference pole is connected to the electrodes 40 , 42 , 43 and 45 or to at least two of these electrodes.

FIG. 4A shows the two electrode arrangements 16 A and 18 A, which each consist of at least three electrodes: 40, 41, 42 and 43, 44, 45. The electrodes 40 and 43 lie next to one another as do the electrodes 41 and 44 and electrodes 42 and 45 . Figures 4B-F show various anode (+) - cathode (-) configurations as used in the present invention. All configurations have in common that the electrodes 41 and 44 are connected to the cathode outputs 47 B and 48 B of the pulse generators 47 and 48 ( FIG. 3). At least two of the electrodes 40 , 42 , 43 and 45 are connected to the anode outputs 47 A and 48 A of the pulse generators 47 and 48 , respectively. In Fig. 4B, all of the electrodes 40, 42, 43 and 45 connected as anodes, and thus form a double tripole. In Fig. 4C, the electrode is not connected 43rd In FIGS. 4D-F, only two electrodes are connected as anodes, with which they form a single tripole ( FIG. 4D), a double dipole ( FIG. 4E) or an obliquely connected dipole ( FIG. 4F). The configurations shown in FIGS. 4C-F can also include a different selection of electrodes 40 , 42 , 43 and 45 .

Although the subject of the present invention is to control the electrical field in a nerve substrate by changing the ratio of the currents of the cathode pulses delivered to electrodes 41 and 44 , respectively, the configurations shown in Figures 4B-F control an additional means of control the field that may be useful, e.g. B. if the electrode arrangements assume asymmetrical positions with respect to the center line of the spinal cord or if the impedances of the electrodes 40 , 42 , 43 and 45 differ significantly from one another. In addition, a large overlap with paresthesia, as is necessary in the treatment of complex pain, is strongly preferred by the tripolar and bipolar configurations shown in FIGS . 4B-F.

Fig. 5A shows the area 50 in the dorsal columns 38, are achieved in the nervous fibers when the pulse generators 47 and 48 at the same time leave pulses of the same current intensity and duration through the respective cathode outputs 47 B and 48 B, and the electrode configuration as shown in Fig. 3 is used. The area 50 reached is also symmetrical both because of the symmetrical position of the electrode arrangements 16 A and 18 A with respect to the center line of the spinal cord and because of the symmetrical electrode configuration.

FIG. 5B shows the achieved in the dorsal columns 38 region 50, when the amperage of 48 18 A delivered to the electrode 44 of the arrangement of cathode pulses being reduced to zero via the outlet 48 B of the pulse generator, which means that the cathode-Pulse are only emitted from the pulse generator 47 to the electrode 41 of the arrangement 16 A. Under these conditions, the area 50 reached is maximally shifted to the side of the dorsal columns that corresponds to the active cathode 41 and is centered around this electrode.

FIG. 5C shows the achieved in the dorsal columns 38 region 50, when the amperage of are reduced 47 16 A delivered to the electrode 41 of the arrangement of cathode pulses to zero via the output 47 B of the pulse generator, which means that the cathode-Pulse are only emitted from the pulse generator 48 to the electrode 44 of the arrangement 18 A. Under these conditions, the area 50 reached is maximally shifted to the side of the dorsal columns that corresponds to the active cathode 44 and is centered around this electrode.

The Fig. 5B-C show the medio-lateral margin within which the range reached by the pulse generators 47 and 48 respectively output pulses cathode 50 can be controlled by changing the ratio of the current intensities. This span covers the full lateral extent of the dorsal columns 38 when the electrode assemblies 16 A and 18 A are centered on the left and right portions of the dorsal columns.

If quadrupolar or octopolar, percutaneous (percutaneous) leads are used as 16 A and 18 A electrode assemblies, the configurations shown in Fig. 4 can be shifted up or down along these assemblies to cover the best longitudinal position of the painful area with paresthesia, along with the possibility of medio-lateral control of the present invention.

While this invention with reference to an illustrative Embodiment has been described, this description should not be in one restrictive sense. Different modifications of the illustrative embodiment as well as others Embodiments of the invention, the various substrates electrically excitable tissue as previously enumerated will become apparent to one skilled in the art upon reference to this description. It is believed, therefore, that the appended claims are any cover such modifications or exemplary embodiments as long as they are under fall within the true scope of the invention.

Claims (6)

1. System for providing medical, electrical stimulation with:
a first electrode arrangement with a first central electrode, a first far electrode and a first near electrode;
a second electrode arrangement with a second central electrode, a second far electrode and a second near electrode;
means for providing a first cathode pulse to the first central electrode;
means for providing a second cathode pulse to the second central electrode;
means for selectively connecting any combination of the first central electrode, the first far electrode and the first near electrode and the second central electrode, the second far electrode and the second near electrode as an anode reference pole for the first cathode pulse and the second Cathode pulse. 2. System according to claim 1, characterized in that the device for selected connecting any combination from the first central Electrode, the first far electrode and the first near electrode as well the second central electrode, the second distal electrode and the second near electrode as an anode reference pole for the first cathode Pulse and the second cathode pulse continue to be a device for selected connection of any two electrodes from the first central electrode, the first far electrode, the first near electrode, the second central electrode, the second distal electrode and the second near electrode as an anode reference pole for the first cathode Pulse and the second cathode pulse. 3. System according to claim 1, characterized in that there is also a Device for simultaneous delivery of the first and the second cathode Has pulse.   4. System according to claim 1, characterized in that it is also a Device for delivering the first and the second cathode pulse with has the same current ratios. 5. System according to claim 1, characterized in that it is also a Device for delivering the first and the second cathode pulse with has unequal current ratios. 6. System according to claim 1, characterized in that there is also a Device for delivering the first and the second cathode pulse with has an adjustable current ratio.