Optimal electrode contact polarity configurations for implantable stimulation systems

Abstract

Systems for treating a patient with a medical condition include a lead having an array of electrode contacts each being programmable to have either a first polarity or a second polarity and a programming device configured to test a multiplicity of different electrode contact polarity configurations in which a programmed polarity of one or more of the electrode contacts is varied. Methods of using an implantable stimulator system include implanting a lead having an array of programmable electrode contacts disposed thereon in communication with a stimulation site, testing a multiplicity of different electrode contact polarity configurations in which a programmed polarity of one or more of the electrode contacts is varied, selecting an optimal electrode contact polarity configuration out of the multiplicity of different electrode contact polarity configurations, and applying the stimulation current via the optimal electrode contact polarity configuration to the stimulation site in accordance with one or more stimulation parameters.

Description

RELATED APPLICATIONS

[0001] The present application claims the priority under 35 U.S.C. .sctn. 119 (e) of previous U.S. Provisional Patent Application No. 60/661,700, filed Mar. 14, 2005 for "Headache Treatment." This provisional application is hereby incorporated by reference in its entirety.

BACKGROUND

[0002] A wide variety of medical conditions and disorders have been successfully treated using an implantable stimulator. Implantable stimulators typically stimulate internal tissue, such as a nerve, by emitting an electrical stimulation current according to programmed stimulation parameters.

[0003] One type of implantable stimulator is known as a microstimulator. Microstimulators are typically formed with a small, cylindrical housing containing electronic circuitry that produces the desired electric stimulation current between spaced electrodes. These stimulators are implanted proximate to the target tissue so that the stimulation current produced by the electrodes stimulates the target tissue to reduce symptoms or otherwise provide therapy for a wide variety of conditions and disorders. Exemplary microstimulators are described in U.S. Pat. Nos. 5,312,439; 5,193,539; 5,193,540; and 5,405,367; 6,185,452; and 6,214,032. All of these listed patents are incorporated by reference in their respective entireties.

[0004] Another type of implantable stimulator is known as an implantable pulse generator (IPG). A typical IPG includes a multi-channel pulse generator housed in a rounded titanium case. The IPG is generally coupled to a lead with a number of electrodes disposed thereon. Stimulation current is generated by the IPG and delivered to target tissue via the electrodes on the lead. Exemplary IPGs are described in U.S. Pat. Nos. 6,381,496; 6,553,263; and 6,760,626. All of these listed patents are incorporated by reference in their respective entireties.

[0005] As will be readily appreciated, a key part of patient treatment using an implanted stimulator is the proper placement of the stimulator such that the stimulation electrodes are proximate to the stimulation site to be stimulated. If the stimulation electrodes are optimally placed near the stimulation site, stimulation can be affected over a wide range of parameters and power consumption can be minimized. However, optimal placement of a stimulator within a patient is often difficult to accomplish.

SUMMARY

[0006] Systems for treating a patient with a medical condition include a lead having an array of electrode contacts each being programmable to have either a first polarity or a second polarity and a programming device configured to test a multiplicity of different electrode contact polarity configurations in which a programmed polarity of one or more of the electrode contacts is varied.

[0007] Methods of using an implantable stimulator system include implanting a lead having an array of programmable electrode contacts disposed thereon in communication with a stimulation site, testing a multiplicity of different electrode contact polarity configurations in which a programmed polarity of one or more of the electrode contacts is varied, selecting an optimal electrode contact polarity configuration out of the multiplicity of different electrode contact polarity configurations, and applying the stimulation current via the optimal electrode contact polarity configuration to the stimulation site in accordance with one or more stimulation parameters.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying drawings illustrate various embodiments of the present invention and are a part of the specification. The illustrated embodiments are merely examples of the present invention and do not limit the scope of the invention.

[0009] FIG. 1A depicts the upper cervical spine area of a patient and shows a number of nerves originating in the upper cervical spine area.

[0010] FIG. 1B shows various nerves in the back of the head and neck.

[0011] FIG. 1C illustrates a view of the major nerves and arteries in the human head as viewed from above looking down on the top or superior part of the head.

[0012] FIGS. 1D and 1E depict the trigeminal nerve and its branches.

[0013] FIG. 2 illustrates an exemplary stimulator that may be used to apply a stimulus to a target nerve to treat a particular medical condition according to principles described herein.

[0014] FIG. 3 illustrates an exemplary microstimulator that may be used as the stimulator according to principles described herein.

[0015] FIG. 4 depicts a number of stimulators configured to communicate with each other and/or with one or more external devices according to principles described herein.

[0016] FIGS. 5A-5H illustrate a number of exemplary electrode contact arrangements that may be a part of a stimulating lead that is used to apply a stimulation at one or more stimulation sites within a patient according to principles described herein.

[0017] FIG. 6 is a graph illustrating the relative current threshold values of monopolar, bipolar, and tripolar electrode configurations as a function of distance from the stimulation site according to principles described herein.

[0018] FIG. 7 is a flow chart illustrating an exemplary method of current steering that may be used to determine the optimal stimulation parameters for a patient according to principles described herein.

[0019] FIGS. 8A-8C illustrate an exemplary method of current steering according to principles described herein.

[0020] Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.

DETAILED DESCRIPTION

[0021] Systems and methods for treating a patient with a medical condition are described herein. A lead with an array of electrode contacts is implanted in communication with a stimulation site. The lead is coupled at a proximal end to an implantable stimulator that is configured to generate a stimulus, such as an electrical stimulation current. Each of the electrode contacts of the array may be selectively programmed to function as an anode or cathode. Thus, many different electrode contact polarity configurations can be realized depending on which electrodes function as anodes and which as cathodes. Current steering methods are then used to test a multiplicity of different electrode contact polarity configurations and select an optimal electrode contact polarity configuration for applying the stimulus to a stimulation site within the patient.

[0022] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present systems and methods. It will be apparent, however, to one skilled in the art that the present systems and methods may be practiced without these specific details. Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearance of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

[0023] FIG. 1A depicts the upper cervical spine area (C1-C4) of a patient. As shown in FIG. 1A, a number of nerves arise from the upper cervical spine area (C1-C4). Examples of such nerves include, but are not limited to, the greater occipital nerve(s)

[0024] (132), lesser occipital nerve(s) (134), greater auricular nerve(s) (136), transverse cervical nerve(s) (138), supraclavicular nerve(s) (139), and/or branches of any of these nerves.

[0025] FIG. 1B depicts the occipital nerves (130) in the back or posterior portion of the head and upper neck area of a patient. As shown in FIG. 1B, the occipital nerves (130) are divided into greater (132) and lesser (134) occipital nerves. The occipital nerves (130) lie subcutaneously in the posterior of the head and upper neck and are therefore relatively easily accessed. Thus, as will be described in more detail below, a stimulator and/or electrode lead may be implanted in the posterior of the head or in the upper neck area of a patient to provide a stimulus to the occipital nerves (130).

[0026] FIG. 1C illustrates a view of the major nerves and arteries in the human head as viewed from above looking down on the top or superior part of the head. As shown in FIG. 1C, the greater occipital nerves (132) extend to and across some of the top or superior portion of the head. The lesser occipital nerves (134) may also extend to or near the top or superior portion of the head. Consequently, an implanted stimulator or an electrode lead may be positioned along the posterior part of the head or on the superior portion of the head and still provide a stimulus to the occipital nerves (130).

[0027] FIGS. 1D and 1E depict the trigeminal nerve (100) and its branches. The trigeminal nerve (100) and its branches are responsible, in part, for the perception of head pain, including headaches and facial pain. The trigeminal nerve (100) on each side of the head arises from a trigeminal ganglion (102), which lies within the skull in an area known as Meckel's cave (110). Access to either trigeminal ganglion (102) may be achieved via the foramen ovale (112) or the foramen rotundum (114).

[0028] Procedures that ablate the trigeminal ganglia (102) do not disable the muscles of mastication, since the cell bodies of the sensory portion of the nerve are within the trigeminal ganglia (102), whereas the motor portion simply projects axons through the ganglia (the motor neuron cell bodies are in the pons). This may provide a mechanism for selective stimulation of the sensory cells via appropriate placement of a stimulator for stimulation of one or both trigeminal ganglia (102).

[0029] FIGS. 1D and 1E also show a number of braches of the trigeminal nerve (100) including, but not limited to, the ophthalmic nerve (120), the maxillary nerve (122), and the mandibular nerve (124). The supraorbital nerve (not shown) is also a branch of the trigeminal nerve (100). The ophthalmic nerve (120) and the maxillary nerve (122) are entirely sensory, and sufficiently separate to allow independent and selective stimulation via appropriate placement of a stimulator.

[0030] The mandibular nerve (124) is both sensory and motor. The mandibular nerve (124) innervates several facial muscles, including the muscles of mastication and the tensor tympani, which reflexively damps down the vibrations of the malleus by increasing the tension in the tympanic membrane. However, just distal to the foramen ovale (112), the mandibular nerve (124) splits into a purely sensory branch that innervates the superior part of the lower jaw. And, slightly more distally, another branch splits into a purely sensory branch that innervates the inferior part of the lower jaw. These branches may be sufficiently separate to allow independent and selective stimulation via appropriate placement of a stimulator.

[0031] It has been discovered that stimulating one or more of the nerves in the head with an electrical stimulation current can alleviate or eliminate headache pain. This is especially useful for patients who do not respond to other forms of treatment or who do not prefer any of the other forms of treatment. Consequently, a stimulator may be implanted in a patient to deliver an electrical stimulation current to one or more of the nerves in the head, particularly the occipital nerves (130). This stimulation may be effective to treat headache pain (including, but not limited to chronic migraine headaches) and other types of pain or medical conditions, such as occipital neuralgia, facial pain, Bells palsy, etc. It will be recognized that the stimulator may additionally or alternatively be implanted in any site within the body and configured to treat any other medical condition such as, but not limited to, incontinence, peripheral nerve damage, sexual dysfunction, etc.

[0032] As used herein, and in the appended claims, the term "stimulator" will be used broadly to refer any device that delivers a stimulus, such as an electrical stimulation current, one or more drugs or other chemical stimulation, thermal stimulation, electromagnetic stimulation, mechanical stimulation, and/or any other suitable stimulation at a stimulation site. Thus, the term "stimulator" includes, but is not limited to, a stimulator, microstimulator, implantable pulse generator (IPG), system control unit (stimulator) or similar device.

[0033] The stimulation site referred to herein may include any nerve, tissue, blood vessel, or other area within the patient. For example, the stimulation site may include one or more of the following nerves: any cranial nerve; the greater, lesser or third occipital nerves; the trigeminal nerve; the infraorbital nerve; the facial nerve; the maxillary nerve, the mandibular nerve and divisions of those nerves such as the two branches of the ophthalmic division of the trigeminal nerve, i.e., the supratrochlear and supraorbital nerves; the zygomaticotemporal nerve branching from the maxillary division of the trigeminal nerve; the auriculotemporal nerve branching from the mandibular division of the trigeminal nerve; the pudendal nerve; and the cavernous nerve. The stimulation site may additionally or alternatively include the cortex, spinal cord, or any other area of the central nervous system. In some examples, the stimulation site may include two or more stimulation sites, e.g., the occipital and trigeminal nerves.

[0034] To facilitate an understanding of the methods of optimally placing a stimulator within a patient to treat a medical condition, a more detailed description of the stimulator and its operation will now be given with reference to the figures. FIG. 2 illustrates an exemplary stimulator (140) that may be implanted within a patient (150) and used to apply a stimulus to a stimulation site, e.g., an electrical stimulation of the stimulation site, an infusion of one or more drugs at the stimulation site, or both. The electrical stimulation function of the stimulator (140) will be described first, followed by an explanation of the possible drug delivery function of the stimulator (140). It will be understood, however, that the stimulator (140) may be configured to provide only electrical stimulation, only a drug stimulation, both types of stimulation or any other type of stimulation as best suits a particular patient.

[0035] The exemplary stimulator (140) shown in FIG. 2 is configured to provide electrical stimulation at a stimulation site within a patient and includes a lead (141) having a proximal end coupled to the body of the stimulator (140). In some examples, as will be described in more detail below, a distal end of the lead (141) may be formed as a flat enlarged surface (162), referred to herein as a paddle, and implanted such that it is in communication with a stimulation site. As used herein and in the appended claims, the term "in communication with" refers to the lead (141) or other device being adjacent, in the general vicinity, in close proximity, directly next to, or directly on the stimulation site such that a desired stimulation can be effectively delivered.

[0036] A number of electrodes (142) may be disposed on the paddle (162), as illustrated in FIG. 2. The electrodes (142) may be arranged on the paddle (162) in a variety of different possible configurations. As will be described in more detail below, the electrodes (142) are configured to apply an electrical stimulation current to the stimulation site as best suits a particular application.

[0037] As illustrated in FIG. 2, the stimulator (140) includes a number of components. It will be recognized that the stimulator (140) may include additional and/or alternative components as best serves a particular application. A power source (145) is configured to output voltage used to supply the various components within the stimulator (140) with power and/or to generate the power used for electrical stimulation. The power source (145) may be a primary battery, a rechargeable battery, super capacitor, a nuclear battery, a mechanical resonator, an infrared collector (receiving, e.g., infrared energy through the skin), a thermally-powered energy source (where, e.g., memory-shaped alloys exposed to a minimal temperature difference generate power), a flexural powered energy source (where a flexible section subject to flexural forces is part of the stimulator), a bioenergy power source (where a chemical reaction provides an energy source), a fuel cell, a bioelectrical cell (where two or more electrodes use tissue-generated potentials and currents to capture energy and convert it to useable power), an osmotic pressure pump (where mechanical energy is generated due to fluid ingress), or the like. Alternatively, the stimulator (140) may include one or more components configured to receive power from another medical device that is implanted within the patient.

[0038] When the power source (145) is a battery, it may be a lithium-ion battery or other suitable type of battery. When the power source (145) is a rechargeable battery, it may be recharged from an external system through a power link such as a radio frequency (RF) power link. One type of rechargeable battery that may be used is described in International Publication WO 01/82398 A1, published Nov. 1, 2001, and/or WO 03/005465 A1, published Jan. 16, 2003, both of which are incorporated herein by reference in their respective entireties. Other battery construction techniques that may be used to make a power source (145) include those shown, e.g., in U.S. Pat. Nos. 6,280,873; 6,458,171, and U.S. Publications 2001/0046625 A1 and 2001/0053476 A1, all of which are incorporated herein by reference in their respective entireties. Recharging can be performed using an external charger.

[0039] The stimulator (140) may also include a coil (148) configured to receive and/or emit a magnetic field (also referred to as a radio frequency (RF) field) that is used to communicate with, or receive power from, one or more external devices (151, 153, 155). Such communication and/or power transfer may include, but is not limited to, transcutaneously receiving data from the external device, transmitting data to the external device, and/or receiving power used to recharge the power source (145).

[0040] For example, an external battery charging system (EBCS) (151) may provide power used to recharge the power source (145) via an RF link (152). External devices including, but not limited to, a hand held programmer (HHP) (155), clinician programming system (CPS) (157), and/or a manufacturing and diagnostic system (MDS)

[0041] (153) may be configured to activate, deactivate, program, and test the stimulator (140) via one or more RF links (154, 156). It will be recognized that the links, which are RF links (152, 154, 156) in the illustrated example, may be any type of link used to transmit data or energy, such as an optical link, a thermal link, or any other energy-coupling link. One or more of these external devices (153, 155, 157) may also be used to control the infusion of one or more drugs into the stimulation site.

[0042] Additionally, if multiple external devices are used in the treatment of a patient, there may be some communication among those external devices, as well as with the implanted stimulator (140). Again, any type of link for transmitting data or energy may be used among the various devices illustrated. For example, the CPS (157) may communicate with the HHP (155) via an infrared (IR) link (158), with the MDS (153) via an IR link (161), and/or directly with the stimulator (140) via an RF link (160). As indicated, these communication links (158, 161, 160) are not necessarily limited to IR and RF links and may include any other type of communication link. Likewise, the MDS (153) may communicate with the HHP (155) via an IR link (159) or via any other suitable communication link.

[0043] The HHP (155), MDS (153), CPS (157), and EBCS (151) are merely illustrative of the many different external devices that may be used in connection with the stimulator (140). Furthermore, it will be recognized that the functions performed by any two or more of the HHP (155), MDS (153), CPS (157), and EBCS (151) may be performed by a single external device. One or more of the external devices (153, 155, 157) may be embedded in a seat cushion, mattress cover, pillow, garment, belt, strap, pouch, or the like so as to be positioned near the implanted stimulator (140) when in use.

[0044] The stimulator (140) may also include electrical circuitry (144) configured to produce electrical stimulation pulses that are delivered to the stimulation site via the electrodes (142). In some embodiments, as will be described in more detail below, the stimulator (140) may be configured to produce monopolar stimulation. The stimulator (140) may alternatively or additionally be configured to produce multipolar stimulation including, but not limited to, bipolar or tripolar stimulation.

[0045] The electrical circuitry (144) may include one or more processors configured to decode stimulation parameters and generate the stimulation pulses. In some embodiments, the stimulator (140) has at least four channels and drives up to sixteen electrodes or more. The electrical circuitry (144) may include additional circuitry such as capacitors, integrated circuits, resistors, coils, and the like configured to perform a variety of functions as best serves a particular application.

[0046] The stimulator (140) may also include a programmable memory unit (146) for storing one or more sets of data and/or stimulation parameters. The stimulation parameters may include, but are not limited to, electrical stimulation parameters, drug stimulation parameters, and other types of stimulation parameters. The programmable memory (146) allows a patient, clinician, or other user of the stimulator (140) to adjust the stimulation parameters such that the stimulation applied by the stimulator (140) is safe and efficacious for treatment of a particular patient. The different types of stimulation parameters (e.g., electrical stimulation parameters and drug stimulation parameters) may be controlled independently. However, in some instances, the different types of stimulation parameters are coupled. For example, electrical stimulation may be programmed to occur only during drug stimulation or vice versa. Alternatively, the different types of stimulation may be applied at different times or with only some overlap. The programmable memory (146) may be any type of memory unit such as, but not limited to, random access memory (RAM), static RAM (SRAM), a hard drive, or the like.

[0047] The electrical stimulation parameters may control various parameters of the stimulation current applied to a stimulation site including, but not limited to, the frequency, pulse width, amplitude, electrode configuration (i.e., anode-cathode assignment), burst pattern (e.g., burst on time and burst off time), duty cycle or burst repeat interval, ramp on time, and ramp off time of the stimulation current that is applied to the stimulation site. The drug stimulation parameters may control various parameters including, but not limited to, the amount of drugs infused at the stimulation site, the rate of drug infusion, and the frequency of drug infusion. For example, the drug stimulation parameters may cause the drug infusion rate to be intermittent, constant, or bolus. Other stimulation parameters that characterize other classes of stimuli are possible. For example, when tissue is stimulated using electromagnetic radiation, the stimulation parameters may characterize the intensity, wavelength, and timing of the electromagnetic radiation stimuli. When tissue is stimulated using mechanical stimuli, the stimulation parameters may characterize the pressure, displacement, frequency, and timing of the mechanical stimuli.

[0048] Specific stimulation parameters may have different effects on different types of medical conditions. Thus, in some embodiments, the stimulation parameters may be adjusted by the patient, a clinician, or other user of the stimulator (140) as best serves a particular medical condition. The stimulation parameters may also be automatically adjusted by the stimulator (140), as will be described below. For example, the amplitude of the stimulus current applied to a stimulation site may be adjusted to have a relatively low value so as to target relatively large diameter fibers of the stimulation site. The stimulator (140) may also, or alternatively, increase excitement of a stimulation site by applying a stimulation current having a relatively low frequency (e.g., less than 100 Hz) to the stimulation site. The stimulator (140) may also decrease excitement of a stimulation site by applying a relatively high frequency (e.g., greater than 100 Hz) to the stimulation site. The stimulator (140) may also, or alternatively, be programmed to apply the stimulation current to a stimulation site intermittently or continuously.

[0049] Additionally, the exemplary stimulator (140) shown in FIG. 2 is configured to provide drug stimulation to a patient, for example, a headache patient, by applying one or more drugs to a stimulation site. For this purpose, a pump (147) may also be included within the stimulator (140). The pump (147) is configured to store and dispense one or more drugs, for example, through a catheter (143). The catheter (143) is coupled at a proximal end to the stimulator (140) and may have an infusion outlet (149) for infusing dosages of the one or more drugs at the stimulation site. In some embodiments, the stimulator (140) may include multiple catheters (143) and/or pumps (147) for storing and infusing dosages of the one or more drugs at the stimulation site.

[0050] The pump (147) or controlled drug release device described herein may include any of a variety of different drug delivery systems. Controlled drug release devices based upon a mechanical or electromechanical infusion pump may be used. In other examples, the controlled drug release device can include a diffusion-based delivery system, e.g., erosion-based delivery systems (e.g., polymer-impregnated with drug placed within a drug-impermeable reservoir in communication with the drug delivery conduit of a catheter), electrodiffusion systems, and the like. Another example is a convective drug delivery system, e.g., systems based upon electroosmosis, vapor pressure pumps, electrolytic pumps, effervescent pumps, piezoelectric pumps and osmotic pumps. Another example is a micro-drug pump.

[0051] Exemplary pumps (147) or controlled drug release devices suitable for use as described herein include, but are not necessarily limited to, those disclosed in U.S. Pat. Nos. 3,760,984; 3,845,770; 3,916,899; 3,923,426; 3,987,790; 3,995,631; 3,916,899; 4,016,880; 4,036,228; 4,111,202; 4,111,203; 4,203,440; 4,203,442; 4,210,139; 4,327,725; 4,360,019; 4,487,603; 4,627,850; 4,692,147; 4,725,852; 4,865,845; 5,057,318; 5,059,423; 5,112,614; 5,137,727; 5,234,692; 5,234,693; 5,728,396; 6,368,315 and the like. Additional exemplary drug pumps suitable for use as described herein include, but are not necessarily limited to, those disclosed in U.S. Pat. Nos. 4,562,751; 4,678,408; 4,685,903; 5,080,653; 5,097,122; 6,740,072; and 6,770,067. Exemplary micro-drug pumps suitable for use as described herein include, but are not necessarily limited to, those disclosed in U.S. Pat. Nos. 5,234,692; 5,234,693; 5,728,396; 6,368,315; 6,666,845; and 6,620,151. All of these listed patents are incorporated herein by reference in their respective entireties.

[0052] The stimulator (140) of FIG. 2 is illustrative of many types of stimulators that may be used to apply a stimulus to a stimulation site to treat headaches and other medical conditions. For example, the stimulator (140) may include an implantable pulse generator (EPG) coupled to one or more leads having a number of electrodes, a spinal cord stimulator (SCS), a cochlear implant, a deep brain stimulator, a drug pump (mentioned previously), a micro-drug pump (mentioned previously), or any other type of implantable stimulator configured to deliver a stimulus at a stimulation site within a patient. Exemplary IPGs suitable for use as described herein include, but are not limited to, those disclosed in U.S. Pat. Nos. 6,381,496; 6,553,263; and 6,760,626. Exemplary spinal cord stimulators suitable for use as described herein include, but are not limited to, those disclosed in U.S. Pat. Nos. 5,501,703; 6,487,446; and 6,516,227. Exemplary cochlear implants suitable for use as described herein include, but are not limited to, those disclosed in U.S. Pat. Nos. 6,219,580; 6,272,382; and 6,308,101. Exemplary deep brain stimulators suitable for use as described herein include, but are not limited to, those disclosed in U.S. Pat. Nos. 5,938,688; 6,016,449; and 6,539,263. All of these listed patents are incorporated herein by reference in their respective entireties.

[0053] Alternatively, the stimulator (140) may include an implantable microstimulator, such as a BION.RTM. microstimulator (Advanced Bionics.RTM. Corporation, Valencia, Calif.). Various details associated with the manufacture, operation, and use of implantable microstimulators are disclosed in U.S. Pat. Nos. 5,193,539; 5,193,540; 5,312,439; 6,185,452; 6,164,284; 6,208,894; and 6,051,017. All of these listed patents are incorporated herein by reference in their respective entireties.

[0054] FIG. 3 illustrates an exemplary microstimulator (200) that may be used as the stimulator (140; FIG. 2) described herein. Other configurations of the microstimulator (200) are possible, as shown in the above-referenced patents and as described further below.

[0055] As shown in FIG. 3, the microstimulator (200) may include the power source (145), the programmable memory (146), the electrical circuitry (144), and the pump (147) described in connection with FIG. 2. These components are housed within a capsule (202). The capsule (202) may be a thin, elongated cylinder or any other shape as best serves a particular application. The shape of the capsule (202) may be determined by the structure of the desired target nerve, the surrounding area, and the method of implantation. In some embodiments, the volume of the capsule (202) is substantially equal to or less than three cubic centimeters. In some embodiments, the microstimulator (200) may include two or more leadless electrodes (142) disposed on the outer surface of the microstimulator (200).

[0056] The external surfaces of the microstimulator (200) may advantageously be composed of biocompatible materials. For example, the capsule (202) may be made of glass, ceramic, metal, or any other material that provides a hermetic package that will exclude water vapor but permit passage of electromagnetic fields used to transmit data and/or power. The electrodes (142) may be made of a noble or refractory metal or compound, such as platinum, iridium, tantalum, titanium, titanium nitride, niobium or alloys of any of these, in order to avoid corrosion or electrolysis which could damage the surrounding tissues and the device.

[0057] The microstimulator (200) may also include one or more infusion outlets (201). The infusion outlets (201) facilitate the infusion of one or more drugs at a treatment site to treat a particular medical condition. The infusion outlets (201) may dispense one or more drugs directly to the treatment site. Alternatively, catheters may be coupled to the infusion outlets (201) to deliver the drug therapy to a treatment site some distance from the body of the microstimulator (200). The stimulator (200) of FIG. 3 also includes electrodes (142-1 and 142-2) at either end of the capsule (202). One of the electrodes (142) may be designated as a stimulating electrode to be placed close to the treatment site and one of the electrodes (142) may be designated as an indifferent electrode used to complete a stimulation circuit.

[0058] The microstimulator (200) may be implanted within a patient with a surgical tool such as a hypodermic needle, bore needle, or any other tool specially designed for the purpose. Alternatively, the microstimulator (200) may be implanted using endoscopic or laparoscopic techniques.

[0059] A stimulator may be configured to operate independently. Alternatively, as shown in FIG. 4 and described in more detail below, the stimulator (140) may be configured to operate in a coordinated manner with one or more additional stimulators, other implanted devices, or other devices external to the patient's body. For instance, a first stimulator may control, or operate under the control of, a second stimulator, other implanted device, or other device external to the patient's body. The stimulator (140) may be configured to communicate with other implanted stimulators, other implanted devices, or other devices external to the patient's body via an RF link, an untrasonic link, an optical link, or any other type of communication link. For example, the stimulator (140) may be configured to communicate with an external remote control unit that is capable of sending commands and/or data to the stimulator (140) and that is configured to receive commands and/or data from the stimulator (140).

[0060] In order to determine the strength and/or duration of electrical stimulation and/or amount and/or type(s) of stimulating drug(s) required to most effectively treat a medical condition, various indicators of the medical condition and/or a patient's response to treatment may be sensed or measured. These indicators include, but are not limited to, electrical activity of the brain (e.g., EEG); neurotransmitter levels; hormone levels; metabolic activity in the brain; blood flow rate in the head, neck or other areas of the body; medication levels within the patient; patient input, e.g. when prodromal symptoms are sensed the patient can push a button on a remote control or other external unit; temperature of tissue in the stimulation target region, including the occipital nerve; physical activity level, e.g. based on accelerometer recordings; brain hyperexcitability, e.g. increased response of given tissue to the same input; indicators of collateral tissue stimulation might be used to adjust stimulation parameters; and/or detection of muscle tone in neck (mechanical strain, pressure sensor, EMG). In some embodiments, the stimulator (140) may be configured to change the stimulation parameters in a closed loop manner in response to these measurements. The stimulator (140) may be configured to perform the measurements. Alternatively, other sensing devices may be configured to perform the measurements and transmit the measured values to the stimulator (140). Exemplary sensing devices include, but are not limited to, chemical sensors, electrodes, optical sensors, mechanical (e.g., motion, pressure) sensors, and temperature sensors.

[0061] Thus, one or more external devices may be provided to interact with the stimulator (140), and may be used to accomplish at least one or more of the following functions:

[0062] Function 1: If necessary, transmit electrical power to the stimulator (140) in order to power the stimulator (140) and/or recharge the power source (145).

[0063] Function 2: Transmit data to the stimulator (140) in order to change the stimulation parameters used by the stimulator (140).

[0064] Function 3: Receive data indicating the state of the stimulator (140) (e.g., battery level, drug level, stimulation parameters, etc.).

[0065] Additional functions may include adjusting the stimulation parameters based on information sensed by the stimulator (140) or by other sensing devices.

[0066] By way of example, an exemplary method of treating a patient with a medical condition may be carried out according to the following sequence of procedures. The steps listed below may be modified, reordered, and/or added to as best serves a particular application.

[0067] 1. A stimulator (140) is implanted so that its electrodes (142) and/or infusion outlet (149) are coupled to or located near a stimulation site (e.g., the occipital nerves or other nerves in the patient's head). If the stimulator (140) is a microstimulator, such as the microstimulator (200) described in FIG. 3, the microstimulator itself may be coupled to the stimulation site.

[0068] 2. The stimulator (140) is programmed to apply at least one stimulus to the stimulation site. The stimulus may include electrical stimulation, drug stimulation, chemical stimulation, thermal stimulation, electromagnetic stimulation, mechanical stimulation, and/or any other suitable stimulation.

[0069] 3. When the patient desires to invoke stimulation, the patient sends a command to the stimulator (140) (e.g., via a remote control) such that the stimulator (140) delivers the prescribed stimulation. The stimulator (140) may be alternatively or additionally configured to automatically apply the stimulation in response to sensed indicators of the medical condition.

[0070] 4. To cease stimulation, the patient may turn off the stimulator (140) (e.g., via a remote control).

[0071] 5. Periodically, the power source (145) of the stimulator (140) is recharged, if necessary, in accordance with Function 1 described above. As will be described below, this recharging function can be made much more efficient using the principles disclosed herein.

[0072] In other examples, the treatment administered by the stimulator (140), i.e., drug therapy and/or electrical stimulation, may be automatic and not controlled or invoked by the patient.

[0073] For the treatment of different patients, it may be desirable to modify or adjust the algorithmic functions performed by the implanted and/or external components, as well as the surgical approaches. For example, in some situations, it may be desirable to employ more than one stimulator (140), each of which could be separately controlled by means of a digital address. Multiple channels and/or multiple patterns of stimulation may thereby be used to deal with the multiple medical conditions, such as, for example, the combination of migraine with another form or forms of headache or the combination of headache with facial or other pain.

[0074] As shown in the example of FIG. 4, a first stimulator (140) implanted beneath the skin of the patient (208) provides a stimulus to a first location; a second stimulator (140') provides a stimulus to a second location; and a third stimulator (140'') provides a stimulus to a third location. As mentioned earlier, the implanted devices may operate independently or may operate in a coordinated manner with other implanted devices or other devices external to the patient's body. That is, an external controller (250) may be configured to control the operation of each of the implanted devices (140, 140', and 140''). In some embodiments, an implanted device, e.g. stimulator (140), may control, or operate under the control of, another implanted device(s), e.g. stimulator (140') and/or stimulator (140''). Control lines (262-267) have been drawn in FIG. 4 to illustrate that the external controller (250) may communicate or provide power to any of the implanted devices (140, 140', and 140'') and that each of the various implanted devices (140, 140', and 140'') may communicate with and, in some instances, control any of the other implanted devices.

[0075] As a further example of multiple stimulators (140) operating in a coordinated manner, the first and second stimulators (140, 140') of FIG. 4 may be configured to sense various indicators of a particular medical condition and transmit the measured information to the third stimulator (140''). The third stimulator (140'') may then use the measured information to adjust its stimulation parameters and apply stimulation to a stimulation site accordingly (e.g., to the occipital nerves). The various implanted stimulators may, in any combination, sense indicators of the medical condition, communicate or receive data on such indicators, and adjust stimulation parameters accordingly.

[0076] Alternatively, the external device (250) or other external devices communicating with the external device may be configured to sense various indicators of a patient's condition. The sensed indicators can then be collected by the external device (250) for relay to one or more of the implanted stimulators or may be transmitted directly to one or more of the implanted stimulators by any of an array of external sensing devices. In either case, the stimulator, upon receiving the sensed indicator(s), may adjust stimulation parameters accordingly. In other examples, the external controller (250) may determine whether any change to stimulation parameters is needed based on the sensed indicators. The external device (250) may then signal a command to one or more of the stimulators to adjust stimulation parameters accordingly.

[0077] One of the difficulties that arises in using a stimulator and a lead within a patient is determining the optimal stimulation parameters for that patient, both initially and over time. In particular, it is difficult to account for lead migration. Implanted stimulators are implanted, generally, on a long-term or permanent basis. However, with time and the natural movement of the patient, a lead from an implanted stimulator tends to move away from the location where it was first implanted. For example, a simple nod of the head may cause the position of a lead that is implanted in the neck to shift positions. This tendency is known as lead migration, or simply, migration.

[0078] Unfortunately, as the lead moves or migrates, the stimulator may continue to operate under the same stimulation parameters and output the same stimulus. However, because the position of the stimulator and/or its lead(s) has changed due to migration, the resulting stimulation experienced by the patient will be different. This may result due to a change in tissue impedance or distance or orientation of the electrodes caused by migration relative to the stimulation site. Consequently, lead migration may render the lead unable to provide the optimal treatment with minimal power consumption that was realized when the lead was more properly positioned.

[0079] While efforts are made to avoid migration, adjustment in the stimulation parameters as migration occurs may compensate for the change in position and allow the stimulator to continue to provide effective treatment. Hence, a number of methods and systems will be described herein that may be used to determine the optimal stimulation parameters for a particular patient at various points in time.

[0080] The optimal stimulation parameters, including the optimal electrode contact configuration, may vary depending on the particular medical condition being treated, the time of day that the stimulation is to be applied, and/or the requirements of the stimulator itself. For example, the stimulation parameters may be different during the day as opposed to during the night for a particular patient. The stimulation parameters may also be configured to optimize power consumption of the stimulator. Hence, the methods and systems described herein may be used to continuously identify and select optimal stimulation parameters as best serves a particular application.

[0081] In some examples, as will be described in more detail below, a technique known as "current steering" may be used to determine the optimal stimulation parameters and compensate for lead migration. Current steering is also know as neuronavigation or e-trolling. As used herein and in the appended claims, the term "current steering" will be used to describe a process used to determine the optimal stimulation parameters for a particular patient.

[0082] To facilitate an understanding of current steering, as described herein, a number of exemplary electrode arrangements that may be used in current steering will now be described in connection with FIGS. 5A-5H. FIGS. 5A-5H illustrate a number of exemplary electrode arrangements that may be a part of a stimulating lead (141; FIG. 2) that is used to apply a stimulus at one or more stimulation sites within a patient. Each of the electrode configurations in FIGS. 5A-5H is disposed on a paddle portion (162) of the lead (141; FIG. 2). The electrodes will also be referred to herein and in the appended claims, unless otherwise specifically denoted, as "electrode contacts" or simply "contacts."

[0083] The size and shape of the paddle (162), as opposed to a thin, cylindrical lead, makes it less likely that the paddle (162) will migrate or move away from the desired stimulation site once implanted. Moreover, with time, tissue naturally begins to grow around the implanted paddle (162), further securing the paddle (162) in place. The paddle (162) may be coated with drugs that encourage such tissue growth over and around the paddle (162) to hold the paddle (162) in place. As will be appreciated, the size and shape of the paddle (162) can be adjusted as best suits a particular application or implantation environment.

[0084] The electrode contacts (142) on the paddle (162) may be oriented on one or both side of the paddle (162) so as to direct the stimulating current to the target stimulation site. Typically, however, the contacts (142) will be arranged on one side of the paddle (162) which is then implanted in an orientation with the contacts (142) facing the tissue to be stimulated. As shown in FIGS. 5A-5H, and as will be described in more detail below, the electrode contacts (142) may be arranged in an array with a variety of configurations to facilitate different types of stimulation or provide different current steering effects.

[0085] For example, the stimulator (140; FIG. 2) may be configured to provide monopolar and/or multipolar electrical stimulation at a stimulation site via the electrode contacts (142). To this end, each electrode contact (142) may be selectively programmed or configured to act as an anode or as a cathode. Each electrode contact (142) may also be programmed to be "off," i.e., not part of the circuit deliver the stimulation current. Monopolar stimulation is achieved by placing an electrode contact acting as a cathode (or anode) adjacent to or near a stimulation site, and placing an electrode of opposite polarity relatively "far away" from the stimulation site. Bipolar stimulation is achieved by placing an anode-cathode pair adjacent to or near a stimulation site. Tripolar stimulation is achieved by placing a cathode surrounded by two anodes or an anode surrounded by two cathodes adjacent to or near a stimulation site.

[0086] Monopolar and multipolar electrode configurations have different stimulation properties. For example, as illustrated in FIG. 6, relative current threshold values vary as a function of distance from the stimulation site for each of these electrode configurations. As used herein and in the appended claims, the term "current threshold value" will be used to refer to the minimum amount of current required to stimulate, e.g., evoke a tissue response from, a stimulation site. FIG. 6 is a graph illustrating the relative current threshold values of monopolar, bipolar, and tripolar electrode configurations as a function of distance from the stimulation site. The graph is based on a theoretical mathematical model of neural stimulation. The current threshold values are normalized by the current threshold of the monopolar configuration.

[0087] As shown in FIG. 6, when the stimulation site is relatively near the stimulating lead (141; FIG. 2), lower stimulation thresholds may be achieved with a properly spaced bipole or tripole electrode configuration than with a monopole electrode configuration. However, as the distance between the stimulation site and the stimulating lead (141; FIG. 2) increases, the thresholds for the bipolar and tripolar electrode configurations begin to exceed that of the monopolar electrode configuration. Thus, monopolar stimulation is often used when the stimulation site is relatively "far" from the stimulating lead (141; FIG. 2) and multipolar stimulation is often used when the stimulation site is relatively "close" to the stimulating lead (141; FIG. 2).

[0088] Monopolar and multipolar electrode configurations often have different stimulation localization properties. For example, a monopolar electrode configuration emits a multidirectional electrical field that may be used to stimulate a relatively general stimulation site. A multipolar electrode configuration, on the other hand, emits a more localized electrical field that is often used to stimulate a relatively specific stimulation site, and may be used to stimulate stimulation sites that have a particular orientation (e.g., a nerve).

[0089] Returning to FIGS. 5A-5H, the electrode contacts (142) may be made of any conducting material that will withstand and operate effectively in an implanted environment. Such materials include, for example, a conducting ceramic, conducting polymer, copper, and/or a noble or refractory metal, such as gold, silver, platinum, iridium, tantalum, titanium, titanium nitride, niobium, and/or an alloy thereof. The use of one or more of these materials in constructing the electrode contacts (142) may serve to minimize corrosion, electrolysis, and/or damage to surrounding tissues.

[0090] The surfaces of the electrode contacts (142) may have any of a number of properties. For example, the surfaces may be smooth or rough. A rough surface increases the actual surface area of an electrode contact and may, with some materials (e.g., platinum or iridium), increase the pseudo-capacitance of the electrode contact. An increased pseudo-capacitance may serve to minimize the risk of adverse electrical affects to a patient being treated. A rough surface may also serve to minimize lead migration.

[0091] Moreover, the electrode contacts (142) may have any suitable size or shape. Differently shaped electrode contacts (142) provide different current densities. For example, a round or oval electrode contact, as shown in FIGS. 5A-5H, may provide a more uniform current density than an electrode contact that is rectangular. However, the shape of the electrode contacts (142) may vary as best serves a particular application.

[0092] As mentioned, the electrode contacts (142) may be arranged in a variety of array configurations to facilitate different types of stimulation. FIGS. 5A-5H illustrate a number of exemplary electrode contact arrangements that may be used to provide monopolar and/or multipolar stimulation at a stimulation site. However, it will be recognized that the electrode contact arrangements shown in FIGS. 5A-5H are merely illustrative of the many different electrode contact arrangements that may be used to provide monopolar and/or multipolar stimulation at a stimulation site.

[0093] For example, FIG. 5A shows a first electrode contact arrangement that may be used to provide monopolar and/or multipolar stimulation at a stimulation site. The electrode contact arrangement of FIG. 5A includes a center electrode contact (142-1) surrounded by three electrode contacts (142-2,3,4) in an equilateral triangle or trigonal planar configuration. As mentioned, each of the electrode contacts (142) may be selectively configured to act as an anode or cathode. Hence, monopolar stimulation may be achieved by using, for example, the top electrode contact (142-2) and one of the bottom electrode contacts (e.g., 142-3) as an anode-cathode pair. Bipolar stimulation may be achieved by using, for example, the center electrode contact (142-1) with one of the other electrode contacts (e.g., 142-2) as an anode-cathode pair. Tripolar stimulation may be achieved by using, for example, the center electrode contacts (142-1) with two of the other electrode contacts (e.g., 142-3 and 142-4) in an anode-cathode-anode or cathode-anode-cathode configuration.

[0094] As illustrated in FIGS. 5A-5H, there are many possible configurations for the electrode contact array. The illustrated examples are merely exemplary and other configurations are within the scope of the principles described herein. FIG. 5B illustrates a configuration with a central electrode contact (142) and four additional electrode contacts (142) arranged in a square around the central electrode contact (142). The four additional electrode contacts (142) may be located at the corners of a square paddle lead as shown in FIG. 5B. FIG. 5C illustrated a line of four electrode contacts (142) with a line of two electrode contacts (142) both above and below the line of four, with the lines of two electrode contacts (142) each being centered with respect to the larger line of four. FIG. 5D illustrates a similar configuration only with two lines of four electrode contacts (142) arranged between the upper and lower lines of two.

[0095] FIG. 5E illustrates a configuration in which the electrode contacts (142) are arranged in a two-by-four rectangular array. FIG. 5F illustrates a configuration in which a line of four electrodes is disposed adjacent a line of three electrodes, both lines being centered with respect to a rectangular paddle. FIG. 5G illustrated a configuration with six electrode contacts (142) in three columns of two electrode contacts (142) each. The center column is offset vertically with respect to the two side columns. FIG. 5H illustrates a configuration in which the electrode contacts (142) are arranged in a circle or ring pattern. Each configuration illustrated and other possible configurations for the electrode contacts (142) will provide different current steering options and may be particularly well suited to treating a particular condition or patient.

[0096] As mentioned, current steering may be used to determine the optimal stimulation parameters for a particular patient. FIG. 7 is a flow chart illustrating an exemplary method of current steering that may be used to determine the optimal stimulation parameters for a particular patient. The steps shown in FIG. 7 are merely illustrative and may be modified, reordered, or removed as best serves a particular application. Moreover, the steps shown in FIG. 7 may be performed by a processor or the like via a set of computer readable instructions. These computer readable instructions may be constructed in any programming language, such as Java or C, for example, and stored on any medium configured to store computer readable instructions such as a flash drive, memory chip, compact disk (CD), digital versatile disc (DVD), floppy disk, or hard drive, for example.

[0097] As shown in FIG. 7, one or more of the electrode contacts (142; FIGS. 5A-5H) are programmed to act as anodes (step 700). One or more of the electrode contacts (142; FIGS. 5A-5H) are also programmed to act as cathodes (step 701). It is also possible that one or more of the electrode contacts are programmed to be "off."

[0098] Any of the other stimulation parameters may also be adjusted (step 702). For example, the frequency, pulse width, amplitude, burst pattern (e.g., burst on time and burst off time), duty cycle or burst repeat interval, ramp on time, and/or ramp off time of the stimulation current applied by each of the electrode contacts (142; FIGS. 5A-5H) may be adjusted.

[0099] Once all of the electrode contacts (142; FIGS. 5A-5H) have been programmed and the other stimulation parameters adjusted, a stimulation current is generated by the stimulator (140; FIG. 2) and applied via the electrode contacts (142; FIGS. 5A-5H) (step 703). The process is repeated until it is determined that the stimulation is optimal (Yes; step 704). Exemplary methods for determining when the stimulation is optimized will be described below. In some examples, the process is repeated until all possible combinations of anode and cathode assignments are tested.

[0100] A number of techniques may be used to determine whether the stimulation applied by the electrode contacts (142; FIGS. 5A-5H) is optimal (step 704). In some examples, patient feedback may be used to determine the optimal stimulation parameters. For example, if the stimulation is being applied to a nerve (e.g., the greater or lesser occipital nerves) to treat chronic headache pain, the stimulation parameters may be adjusted until the patient indicates that the greatest amount of relief from the headache pain has been achieved. Alternatively, a neural response to a particular set of stimulation parameters may be measured by a recording electrode or other device. The stimulation parameters may be adjusted until an optimal neural response is measured. Any other method may be used as best serves a particular application to determine the optimal stimulation parameters.

[0101] The current steering method described in connection with FIG. 7 may be performed automatically with a computerized programming station or another suitable programming device. The programming device may include a self-contained hardware/software system, or it may include software running on a standard personal computer (PC). Exemplary programming devices include, but are not limited to, the clinician programming system (157; FIG. 2) and the hand held programmer (155; FIG. 2) described above. The programming device may include a transmitting coil attachment configured to communicate with the implanted stimulator (140; FIG. 2). Alternatively, the programming device may be included within the stimulator (140; FIG. 2) itself.

[0102] Alternatively, the current steering method may be performed manually. For example, a physician or patient may manually steer the current with the aid of a computer, hand-held programmer, joystick, or other device.

[0103] A simplified example of current steering will now be given in connection with FIGS. 8A-8C. FIGS. 8A-8C include the exemplary electrode arrangement of FIG. 5A. As will be described in connection with these figures, the current may be steered in a clockwise path to find the best cathode-anode combination for a particular patient.

[0104] A simplified example of current steering will now be given in connection with FIGS. 8A-8C. FIGS. 8A-8C include the exemplary electrode arrangement of FIG. 5A. As will be described in connection with these figures, the current may be steered in a clockwise path to find the best cathode-anode combination for a particular patient.

[0105] As shown in FIG. 8A, the center electrode contact (142-1) is initially programmed as an anode (+) and the top electrode contact (142-2) is initially programmed as a cathode (-). The bottom electrode contacts (142-3,4) are programmed to be off. Hence, the stimulation current flows from the center electrode contact (142-1) to the top electrode contact (142-2) and creates an electric field E.sub.1, as shown in FIG. 8A.

[0106] The top electrode contact (142-2) is then turned off and the bottom right electrode contact (142-4) is programmed to act as a cathode (-), as shown in FIG. 8B. The current now flows from the center electrode contact (142-1) to the bottom right electrode contact (142-4), as indicated by the arrow labeled E.sub.2.

[0107] The bottom right electrode contact (142-4) is then turned off and the bottom left electrode contact (142-3) is programmed to act as a cathode (-), as shown in FIG. 8C. The resulting current flow, E.sub.3, is now between the center electrode contact (142-1) and the bottom left electrode contact (142-3).

[0108] This process may be repeated with some or all of the other combinations of anodes and cathodes until the optimal cathode-anode configuration is found. It will be recognized that the current may be steered in any path as best serves a particular application and that other stimulation parameters (e.g., frequency, pulse width, amplitude, burst pattern (e.g., burst on time and burst off time), duty cycle or burst repeat interval, ramp on time, and/or ramp off time) may additionally or alternatively be adjusted to determine the optimal stimulation parameters for a particular application.

[0109] A number of alternative current steering techniques may be used in connection with the present methods and systems described herein. For example, an exemplary current steering method is disclosed in U.S. Pat. No. 6,393,325, which is incorporated herein by reference in its entirety.

[0110] In some examples, the current steering methods and systems described herein are used when the lead (141; FIG. 2) and stimulator (140; FIG. 2) are initially implanted within the patient to determine the initial stimulation parameters that are best suited for the particular patient. Additionally or alternatively, the current steering methods and systems described herein may be used subsequently to account for lead migration and other changes within the patient that may occur after implantation.

[0111] The methods and systems described herein are particularly useful in stimulating nerves within the head or neck to treat headache pain and/or other medical conditions. However, it will be recognized that the methods and systems described herein may be used to stimulate any stimulation site within the patient to treat any medical condition.

[0112] As mentioned, the stimulator (140; FIG. 2) may be configured to additionally or alternatively infuse one or more drugs at the stimulation site. In some examples, the one or more drugs may have charges that are attracted to or repelled by the electrode contacts acting as anodes and cathodes. For example, a drug having a positive charge may be attracted to a cathode having a negative charge and repelled by an anode having a positive charge. Hence, in some examples, a drug may be steered to a particular stimulation site by appropriately programming the electrode contacts to have positive or negative charges.

[0113] The preceding description has been presented only to illustrate and describe embodiments of the invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. Many modifications and variations are possible in light of the above teaching.

Claims

1. A system for treating a patient with a medical condition, said system comprising: a lead having an array of electrode contacts each being programmable to have either a first polarity or a second polarity; and a programming device configured to test a multiplicity of different electrode contact polarity configurations in which a programmed polarity of one or more of said electrode contacts is varied.

2. The system of claim 1, wherein said programming device is further configured to select an optimal electrode contact polarity configuration out of said multiplicity of different electrode contact polarity configurations.

3. The system of claim 2, further comprising: a stimulator configured to apply a stimulation current to a stimulation site in accordance with one or more stimulation parameters using said optimal electrode contact polarity configuration.

4. The system of claim 3, wherein said programming device is further configured to: test a multiplicity of different sets of said stimulation parameters; select an optimal set of said stimulation parameters out of said multiplicity of different sets of stimulation parameters; and signal to said stimulator to apply said stimulation current according to said optimal set of stimulation parameters; wherein each set of said stimulation parameters comprises different values for at least one or more of a frequency, pulse width, amplitude, burst pattern, duty cycle, ramp on time, and ramp off time of said stimulation current.

5. The system of claim 3, wherein said programming device is configured to select said optimal electrode contact polarity configuration by: signaling said stimulator to apply a stimulus to said stimulation site with each of said multiplicity of different electrode contact polarity configurations; and selecting said optimal electrode contact polarity configuration based on at least one or more of an optimal response of said stimulation site to said stimulus and a maximum amount of relief from said medical condition from said stimulation current.

6. The system of claim 3, wherein said stimulation site comprises at least one or more of an occipital nerve and a trigeminal nerve.

7. The system of claim 3, wherein said stimulation current comprises at least one or more of a monopolar stimulation current and a multipolar stimulation current.

8. The system of claim 3, wherein said programming device is included within said stimulator.

9. The system of claim 1, wherein said medical condition comprises at least one or more of a headache, occipital neuralgia, facial pain, and Bells palsy.

10. The system of claim 1, wherein said programming device comprises at least one or more of a clinician programming system and a hand held programmer.

11. A method of using an implantable stimulator system, said method comprising: implanting a lead in communication with a stimulation site, said lead having an array of electrode contacts disposed thereon for applying a stimulation current to said stimulation site, each electrode contact being programmable to have either a first polarity or a second polarity; testing a multiplicity of different electrode contact polarity configurations in which a programmed polarity of one or more of said electrode contacts is varied; selecting an optimal electrode contact polarity configuration out of said multiplicity of different electrode contact polarity configurations; and applying said stimulation current via said optimal electrode contact polarity configuration to said stimulation site in accordance with one or more stimulation parameters.

12. The method of claim 11, further comprising: testing a multiplicity of different sets of said stimulation parameters; selecting an optimal set of said stimulation parameters out of said multiplicity of different sets of stimulation parameters; and applying said stimulus to said stimulation site according to said optimal set of said stimulation parameters; wherein each of said sets of said stimulation parameters comprises different values for at least one or more of a frequency, pulse width, amplitude, burst pattern, duty cycle, ramp on time, and ramp off time of said stimulus.

13. The method of claim 11, wherein said selecting said optimal electrode contact polarity configuration comprises: selecting said optimal electrode contact polarity configuration based on at least one or more of an optimal response to said stimulation current by said stimulation site and a maximum amount of relief from a medical condition resulting from said stimulation current.

14. The method of claim 11, further comprising using said stimulator system to treat at least one or more of a headache, occipital neuralgia, facial pain, and Bells palsy.

15. The method of claim 11, wherein said stimulation site comprises at least one or more of an occipital nerve and a trigeminal nerve.

16. The method of claim 11, wherein said first polarity comprises an anodic polarity and said second polarity comprises a cathodic polarity.

17. The method of claim 11, wherein said stimulation current comprises at least one or more of a monopolar stimulation current and a multipolar stimulation current.

18. The method of claim 11, further comprising automatically performing said steps of testing of said multiplicity of different electrode contact polarity configurations and selecting said optimal electrode contact polarity configuration with a processor.

19. A system for treating a patient with a medical condition, said system comprising: a lead having an array of electrode contacts disposed thereon for applying a stimulation current to a stimulation site, each electrode contact being programmable to have either a first polarity or a second polarity; means for testing a multiplicity of different electrode contact polarity configurations in which a programmed polarity of one or more of said electrode contacts is varied; means for selecting an optimal electrode contact polarity configuration out of said multiplicity of different electrode contact polarity configurations; and means for applying said stimulation current via said optimal electrode contact polarity configuration to said stimulation site in accordance with one or more stimulation parameters.

20. The system of claim 19, further comprising: means for testing a multiplicity of different sets of said stimulation parameters; means for selecting an optimal set of said stimulation parameters out of said multiplicity of different sets of stimulation parameters; and means for applying said stimulation current to said stimulation site according to said optimal set of said stimulation parameters; wherein each of said sets of said stimulation parameters comprises different values for at least one or more of a frequency, pulse width, amplitude, burst pattern, duty cycle, ramp on time, and ramp off time of said stimulation current.