Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2002-05-17
2003-08-19
Layno, Carl (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S059000
Reexamination Certificate
active
06609032
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for programming an implantable electrode array used with an implantable stimulator. More particularly, one embodiment of the invention relates to a device used to provide directional programming for the implantable electrode array associated with an implantable stimulator that electrically stimulates the spinal cord for the purposes of controlling and reducing pain.
Within the past several years, rapid advances have been made in medical devices and apparatus for controlling chronic intractable pain. One such apparatus involves the implantation of an electrode array within the body to electrically stimulate the area of the spinal cord that conducts electrochemical signals to and from the pain site. The stimulation creates the sensation known as paresthesia, which can be characterized as an alternative sensation that replaces the pain signals sensed by the patient. One theory of the mechanism of action of electrical stimulation of the spinal cord for pain relief is the “gate control theory”. This theory suggests that by simulating cells wherein the cell activity counters the conduction of the pain signal along the path to the brain, the pain signal can be blocked from passage.
Spinal cord stimulator and other implantable tissue stimulator systems come in two general types: “RF” controlled and fully implanted. The type commonly referred to as an “RF” system includes an external transmitter inductively coupled via an electromagnetic link to an implanted receiver that is connected to a lead with one or more electrodes for stimulating the tissue. The power source, e.g., a battery, for powering the implanted receiver-stimulator as well as the control circuitry to command the implant is maintained in the external unit, a hand-held sized device that is typically worn on the patient's belt or carried in a pocket. The data/power signals are transcutaneously coupled from a cable-connected transmission coil placed over the implanted receiver-stimulator device. The implanted receiver-stimulator device receives the signal and generates the stimulation. The external device usually has some patient control over selected stimulating parameters, and can be programmed from a physician programming system. An example of an RF system is described, e.g., in U.S. Pat. No. 4,793,353, incorporated herein by reference.
The fully implanted type of stimulating system contains the programmable stimulation information in memory, as well as a power supply, e.g., a battery, all within the implanted pulse generator, or “implant”, so that once programmed and turned on, the implant can operate independently of external hardware. The implant is turned on and off and programmed to generate the desired stimulation pulses form an external programming device using transcutaneous electromagnetic, or RF links. Such stimulation parameters include, e.g., the pulse width, pulse amplitude, repetition rate, and burst rates. An example of such a commercially-available implantable device is the Medtronic Itrel II, Model 7424. Such device is substantially described in U.S. Pat. No. 4,520,825, also incorporated herein by reference.
The '825 patent describes a circuit implementation of a cyclic gradual turn on, or ramping of the output amplitude, of a programmable tissue stimulator. The implementation contains separate memory cells for programming the output amplitude and number of pulses at each increasing output level or “step”. In devices of the type described in the referenced '825 patent, it is desirable to provide some means of control over the amplitude (intensity), the frequency, and the width of the stimulating pulses. Such control affords the patient using the device the ability to adjust the device for maximum effectiveness. For example, if the pulse amplitude is set too low, there may be insufficient pain relief for the user; yet, if the pulse amplitude is set too high, there may be an unpleasant or uncomfortable stinging or tingling sensation felt by the user. Moreover, the optimum stimulation parameters may change overtime. That is, numerous and varied factors may influence the optimum stimulation parameters, such as the length of time the stimulation has been ON, user (patient) postural changes, user activity, medicines or drugs taken by the user, or the like.
In more complex stimulation systems, one or more leads can be attached to the pulse generator, with each lead usually having multiple electrode contacts, Each electrode contact can be programmed to assume a positive (anode), negative (cathode), or OFF polarity to create a particular stimulation field when current is applied. Thus, different combinations of programmed anode and cathode electrode contacts can be used to deliver a variety of current waveforms to stimulate the tissue surrounding the electrode contacts.
Within such complex systems, once one or more electrode arrays are implanted in the spinal cord, the ability to create paresthesia over the painful site is firstly dependent upon the ability to accurately locate the stimulation site. This may more readily be accomplished by programming the selection of electrode contacts within the array(s) than by physically maneuvering the lead (and hence physically relocating the electrode contacts). Thus, the electrode arrays may be implanted in the vicinity of the target site, and then the individual electrode contacts within the array(s) are selected to identify an electrode contact combination that best addresses the painful site. In other words, electrode programming may be used to pinpoint the stimulation area correlating to the pain. Such electrode programming ability is particularly advantageous after implant should the lead contacts gradually or unexpectedly move, thereby relocating the paresthesia away from the pain site. With electrode programmability, the stimulation area can often be moved back to the effective site without having to re-operate on the patient in order to reposition the lead and its electrode array.
Electrode programming has provided different clinical results using different combinations of electrode contacts and stimulation parameters, such as pulse width, amplitude and frequency. Hence, an effective spinal cord stimulation system should provide flexible programming to allow customization of the stimulation profile for the patient, and thereby allow for easy changes to such stimulation profile over time, as needed.
The physician generally programs the implant, external controller, and/or external patient programmer through a computerized programming station or programming system. This programming system can be a self-contained hardware/software system, or can be defined predominately by software running on a standard personal computer (PC). The PC or custom hardware can have a transmitting coil attachment to allow for the programming of implants, or other attachments to program external units. Patients are generally provided hand-held programmers that are more limited in scope than are the physician-programming systems, with such hand-held programmers still providing the patient with some control over selected parameters.
Programming of the pulse generators, or implants, can be divided into two main programming categories: (1) programming of stimulation pulse variables, and (2) programming electrode configurations. Programmable stimulation pulse variables, as previously indicated, typically include pulse amplitude, pulse duration, pulse repetition rate, burst rate, and the like. Programmable electrode configuration includes the selection of electrodes for simulation from the available electrode contacts within the array as well as electrode polarity (+/−) assignments. Factors to consider when programming an electrode configuration include the number of electrode contacts to be selected, the polarity assigned to each selected electrode contact, and the location of each selected electrode contact within the array relative to the spinal cord, and the distance between selected electrodes (a
L. Peterson David K.
Loeb Gerald E.
Meadows Paul M.
Woods Carla Mann
Advanced Bionics Corporation
Gold Bryant R.
Layno Carl
LandOfFree
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