Patent Publication Number: US-9884190-B2

Title: Surgical method for implantable head mounted neurostimulation system for head pain

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 14/717,912, filed May 20, 2015, entitled IMPLANTABLE HEAD MOUNTED NEUROSTIMULATION SYSTEM FOR HEAD PAIN, which is a continuation of U.S. patent application Ser. No. 14/460,139, filed Aug. 14, 2014, published on Apr. 23, 2015 as U.S. Patent Application Publication No. 2015-0112406, now U.S. Pat. No. 9,042,991, issued on May 26, 2015, which claims benefit of U.S. Provisional Application No. 61/894,795, filed Oct. 23, 2013, entitled IMPLANTABLE HEAD MOUNTED NEUROSTIMULATION SYSTEM FOR HEAD PAIN. U.S. application Ser. Nos. 14/717,912, 14/460,139 and 61/894,795, U.S. Patent Application Publication No. 2015-0112406, and U.S. Pat. No. 9,042,991 are incorporated by reference herein in their entirety. 
     This application is related to U.S. patent application Ser. No. 14/460,111, filed Aug. 14, 2014, published on Feb. 19, 2015 as U.S. Patent Application Publication No. 2015-0051678, entitled IMPLANTABLE NEUROSTIMULATION LEAD FOR HEAD PAIN, which claims benefit of U.S. Provisional Application No. 61/865,893, filed Aug. 14, 2013. U.S. application Ser. No. 14/460,111 and 61/865,893 and U.S. Patent Application Publication No. 2015-0051678 are incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to a head located implantable neurostimulation system and, specifically, to methods of implanting a fully head located cranial and peripheral neurostimulator system that is utilized for the purpose of treating chronic head pain. 
     BACKGROUND 
     Neurostimulation systems comprising implantable neurostimulation leads are used to treat chronic pain. Conventional implantable peripheral neurostimulation leads are designed for placement in the spinal canal as part of a spinal cord stimulation system, and for the therapeutic purpose of treating various forms of chronic back and extremity pain. 
     Until the present invention, implantable neurostimulator systems for head pain essentially involved deep brain stimulators, where leads were positioned in the substance of the brain itself; traditional spinal cord stimulator systems that were adopted and adapted for the treatment of head pain; or implantable systems for neurostimulation of the vagus nerve or sphenopalatine ganglion. 
     Historically, the most common case involves the adaption of spinal cord stimulators for the purpose of peripheral nerve stimulation, such that all publically available implantable neurostimulation systems utilized for the treatment of chronic head pain have been originally designed specifically as spinal cord stimulator systems for the therapeutic purpose of treating chronic back and extremity pain. As these systems were developed for implantation in the back, their design did not contemplate the anatomic and physiologic features unique to the head and chronic head pain, which are so significantly different from the anatomy of the spinal canal, and pathophysiology of chronic back pain, that when spinal cord stimulators were utilized for cranial implants, the clinical problems associated with these differences ultimately manifested themselves. 
     These well-documented and clinically significant problems relate to issues of patient safety and satisfaction, including the risk of an inadequate, or suboptimal, therapeutic response; issues with patient comfort and cosmetics; and an increased risk of surgical complications and technical problems. Several specific inherent deficiencies in device design and method of implant underlie these deficiencies and problems. Likely the most common methodological deficiency is the fact that the implantable pulse generator (IPG) must necessarily be implanted at a considerable anatomic distance for the cranial lead implants. Indeed, the leads must pass from their distal cranial implant positions across the cervical region and upper back to the IPG implant location, which are most commonly in the lower back, lower abdomen, or gluteal region. The related problems are due the fact that the leads must cross multiple anatomic motion segments (neck and back). Here, the simple motions of normal daily life produce adverse tension and torque forces on the leads across these motion segments, which in turn increase the risk of technical problems, including lead migration and/or lead fracture. A second problem relates to the relatively large size of the IPG, which contributes to local discomfort, cosmetic concerns, and the fact that should the IPG pocket become infected, the related clinical problem parallels the relatively large size of the IPG; that is, the larger the IPG, the larger the pocket, and the larger and more problematic any complicating infection. Additional inherent problems include the added risks, especially infection, wound dehiscence, discomfort, and cosmetic problems associated with the multiple additional incisions that are necessary to pass the leads from the IPG to their terminal positions in the head. 
     SUMMARY 
     In various implementations, an implantable head-located, unibody peripheral nerve stimulation system may be configured for implantation of substantially all electronics, including an on-site battery, at or near the implanted electrodes on the skull. The system may include an implantable pulse generator (IPG) from which two neurostimulating leads may extend to a length sufficient to provide therapeutic neurostimulation unilaterally over the frontal, parietal and occipital regions of the hemicranium. The system may be operable to provide medically acceptable therapeutic neurostimulation to multiple regions of the head, including the frontal, parietal and occipital regions of the hemicranium, substantially simultaneously. 
     Each of the leads may include an extended lead body; a plurality of surface metal electrodes disposed along the lead body, which may be divided into two or more electrode arrays; and a plurality of internal electrically conducting metal wires running along at least a portion of the length of the lead body and individually connecting an internal circuit of the IPG to individual surface metal electrodes. The extended lead body may comprise a medical grade plastic. The IPG may include a rechargeable battery, an antenna coil, and an application specific integrated circuit (ASIC). The IPG may be configured for functionally connecting with an external radiofrequency unit. The external radiofrequency unit may be operable to perform various functions including recharging the rechargeable battery, diagnostically evaluating the IPG, and programming the IPG. 
     Implementations may include one or more of the following features. The IPG may be of proper aspect ratio with respect to the specific site of intended implantation in the head, such as an area posterior to and/or superior to the ear. There may be an external portable programming unit that is capable of achieving a radiofrequency couple to the implanted IPG. The IPG may have a rechargeable battery as a power source. The rechargeable battery may be inductively recharged through the skin. 
     Implementations may include one or more of the following features. A neurostimulating lead may not include a central channel for a stylet. A neurostimulating lead may have a smaller diameter than conventional leads. 
     Implementations may include one or more of the following features. The system may include the disposition of a sufficient plurality of surface electrodes over a sufficient linear distance along the neurostimulating leads to enable medically adequate therapeutic stimulation across multiple regions of the head, including the frontal, parietal, and occipital region of the hemicranium substantially simultaneously. The extended array of surface electrodes may be divided into two or more discrete terminal surface electrode arrays. The linear layout of the multiple surface electrode arrays may include at least one array positioned over the frontal region, at least one array positioned over the parietal region, and at least one array positioned over the occipital region. 
     Specific intra-array design features may include variations in the specific number of electrodes allotted to each group; the shape of the electrodes, e.g., whether the electrodes are cylindrical or flattened; the width of each electrode within each array, and the linear distance intervals of separation of the electrodes within each array. 
     Various implementations may include a plurality of connection ports that can be connected with a plurality of leads and thus allow for attaching additional leads. 
     In various implementations, methods of treating chronic pain may include methods of treating chronic head and/or face pain of multiple etiologies, including migraine headaches; and other primary headaches, including cluster headaches, hemicrania continua headaches, tension type headaches, chronic daily headaches; further including secondary headaches, such as cervicogenic headaches and other secondary musculoskeletal headaches. 
     In various implementations, methods of treating chronic pain may include methods of treating head and/or face pain of multiple etiologies, including neuropathic head and/or face pain, nociceptive head and/or face pain, and/or sympathetic related head and/or face pain. 
     In various implementations, methods of treating chronic pain may include methods of treating head and/or face pain of multiple etiologies, including greater occipital neuralgia, as well as the other various occipital neuralgias, supraorbital neuralgia, auriculo-temporal neuralgia, infraorbital neuralgia, and other trigeminal neuralgias, and other head and face neuralgias. 
     In various implementations the unibody neurostimulation system with two leads, including one with multiple arrays, is fully implanted with all components positioned within the subcutaneous layer of the skin and without the requirement of sutures, anchors, or other fixation devices to fix the systems, or portions thereof in position. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the implementations will be apparent from the description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of this disclosure and its features, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  depicts a side view of a head-located, unibody neurostimulator system for migraine and other head pain. The system features an implantable pulse generator (IPG) from which two neurostimulating leads extend—a Fronto-Parietal Lead (FPL) and an Occipital Lead (OL). Each lead includes a plurality of electrodes in a distribution and over a length to allow full unilateral coverage of the frontal, parietal, and occipital portions of the head; 
         FIG. 2  depicts a side view of a Frontal Electrode Array (FEA) with Internal Wires. The FEA is disposed over the distal portion (such as 8-10 cm) of the FPL, which anatomically places it over the frontal region, and specifically over the supraorbital nerve and other adjacent nerves of the region. In general the layout, disposition and connections of the Internal Wires and Surface Electrodes disposed over the Parietal Electrode Array (PEA) and the Occipital Electrode Array (OEA) are the same as that depicted for the FEA; 
         FIG. 3  depicts a side view of the Internal Wires exiting from the IPG&#39;s Internal Circuit enroute to the Surface Electrodes disposed over the FPL and the OL; 
         FIG. 4  depicts a cross-sectional view of a Lead Central Body comprising a Cylindrical Lead Body (with Internal Wires) between the IPG Internal Circuit and the Lead Surface Electrodes; 
         FIG. 5  depicts a rear view of a Head with a full Head-Mounted Neurostimulator System In-Situ. Prominent here is the OL depicted passing from the IPG caudally and medially across the occipital region, whereby the OEA is disposed in a fashion to cross over and cover the major associated nerves—primarily the greater occipital nerve, but typically including the lessor and/or third occipital nerve as well. Also depicted are the PEA and the FEA of the FPL as they cross and cover the primary nerves of the Parietal Region, including the auriculo-temporal nerve, and the Frontal Region, including the supraorbital nerve; 
         FIG. 6  depicts a side view of a Head with a full Head-Located Neurostimulator System In-Situ. Prominent here is the PEA, as it covers a portion of the Parietal Region and the major associated nerves, including the auriculo-temporal nerve, as well as adjacent cutaneous nerves. Also depicted are the courses of the distal portion of the FPL and the OL, as they pass over and cover the associated nerves of the Frontal (Supraorbital) and Occipital Regions; 
         FIG. 7  depicts a front view of a Head with a full Head-Located Neurostimualtor System In-Situ. Prominent here is the FEA, as it covers a portion of the Frontal (Supraorbital) Region and the major associated nerves—primarily the supraorbital nerve, but also commonly the greater trochlear nerve, as well as adjacent nerves. Also depicted is the course of the parietal portion of the FL; 
         FIGS. 8A and 8B  depicts a front view and a side view of a Portable Programmer for a Head-Mounted Neurostimulator System; 
         FIG. 9  depicts a side view of a head and initial interventional step in the procedure; 
         FIG. 10  depicts a side view of the head and the next step of the procedure following that depicted in  FIG. 9 ; 
         FIG. 11  depicts a side view of the head and the next step of the procedure following that depicted in  FIG. 10 ; 
         FIG. 12  depicts a frontal view of the FL as having been positioned subcutaneously as discussed in  FIG. 11 ; 
         FIGS. 13A and 13B  depict a side view of the next step in the procedure after the step depicted in  FIGS. 11 and 12 ; 
         FIG. 14  depicts a cross section view of the skin at the Supra-auricular Incision at the stage of the procedure depicted in  FIG. 13 . Prominent here is the IPG in its Subcutaneous Pocket, as well as the initial proximal segments of the FL and the OL as they pass per the Subcutaneous Layer. The Peel-Away Introducer noted in  FIG. 13  is also prominent; 
         FIG. 15  depicts a cross section view of the skin at the point where the Active Electrode Array of the OL has been positioned over (superficial to) the Subcutaneous Layer; 
         FIG. 16  depicts a view of the head from the top after the full neurostimulator system has been implanted; 
         FIG. 17  depicts two implanted IPGs with leads to cover both sides of the head; and 
         FIG. 18  depicts one implanted IPG with leads to cover both sides of the head; 
         FIG. 19  illustrates the embodiment of  FIG. 17  with a charging/communication headset disposed about the cranium; 
         FIG. 20  illustrates a diagrammatic view of the headset interfaced with the implants; 
         FIG. 21  illustrates a schematic view of the implants and headset; 
         FIGS. 22A-B  illustrate block diagrams of the headset/charger system; and 
         FIG. 23  is a flowchart for the activation process to test the implant(s) after implantation. 
     
    
    
     INDEX OF ELEMENTS 
     
         
           10 : Implantable Pulse Generator 
           10   a : Implantable Pulse Generator Passed Subcutaneously 
           11 : Antenna 
           12 : Battery 
           13 : Application Specific Integrated Circuit 
           14 : Medical Plastic Cover 
           20 : Fronto-Parietal Lead 
           20   a : Plastic Body Member 
           20   b : Fronto-Parietal Lead Passed Subcutaneously 
           21  Distal End 
           22 : Proximal End 
           22   a : Proximal Lead Segment 
           22   b : Proximal Lead Segment Passed Subcutaneously 
           23 : Distal Non-Stimulating Tip 
           24 : Surface Metal Electrode 
           25 : Frontal Electrode Array 
           26 : Parietal Electrode Array 
           27 : Inter-Array Interval 
           28  Point of Cross Section  FIG. 4   
           28   a : Distal Lead Segment Passed Subcutaneously 
           29  Lead Internal Wire 
           30  Occipital Lead 
           30   b : Occipital Lead Passed Subcutaneously 
           31  Distal End 
           32  Proximal End 
           32   a  Proximal Lead Segment 
           33  Distal Non-Stimulating Tip 
           34  Surface Metal Electrode 
           35  Occipital Electrode Array 
           36  Interelectrode Distance 
           37  Surface Electrode Width 
           38  Lead Internal Wire 
           39  Plastic Body Member 
           40 : Portable Programmer 
           41 : Liquid Crystal Display 
           42 : Remote Charge Status 
           43 : IPG Charge Status 
           44 : Program Running Icon 
           44   a : LCD Head Graphic 
           45 : Right &amp; left Toggle Buttons 
           46 : Increase &amp; Decrease Buttons 
           47 : Confirm/Enter Button 
           48 : On/Off Button 
           49 : Top View with Lock Button 
           50  Occipital Region of Head 
           51   a : Cross Section of Greater Occipital Nerve 
           51  Greater Occipital Nerve 
           52  Lesser Occipital Nerve 
           53  Third Occipital Nerve 
           60  Parietal Region of Head 
           61  Auriculotemporal Nerve 
           62 : Zygomaticotemporal Nerve 
           63 : Apex of Pinna 
           64 : Vertical Pre-Pinna Line 
           65 : Vertical Mid-Pinna Line 
           66 : Vertical Post-Pinna Line 
           67 : Horizontal Supra-Pinna Line 
           68 : Supra-auricular Subcutaneous Incision 
           68   a : Lower Point of Supra-auricular Subcutaneous Incision 
           68   b : Blowup of Supra-auricular Subcutaneous Incision 
           69 : Temple Subcutaneous Incision 
           69   a : Lower point of Temple Subcutaneous Incision 
           70  Frontal Region of Head 
           71  Supraorbital Nerve 
           72 : Supratrochlear Nerve 
           80 : Cross Section of Scalp 
           81 : Dermis 
           82 ; Subcutaneous Tissue Layer 
           83 : Fascia 
           84 : Muscle Layer 
           85 : Aponeurosis 
           86 : Boney Skull 
           87 : Arrow Indicating Direction of Fronto-Parietal Lead 
           88 : Skin Incision Depth to Subcutaneous Layer 
           90 : Tubular Metal Introducer 
           91 : Scalpel 
           92 : Local Anesthetic Infiltrated in Skin 
           93 : Syringe 
           94 : Step Dilator 
           95 : Peel-Away Introducer 
           96 : Flex Elevator 
           96   a ; Flex Elevator Handle 
           96   b : Flex Elevator Tissue Spatula 
       
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, wherein like reference numbers are used herein to designate like elements throughout, the various views and embodiments of implantable head located neurostimulation system for head pain are illustrated and described, and other possible embodiments are described. The figures are not necessarily drawn to scale, and in some instances the drawings have been exaggerated and/or simplified in places for illustrative purposes only. One of ordinary skill in the art will appreciate the many possible applications and variations based on the following examples of possible embodiments. 
     A. INTRODUCTION 
     The present disclosure provides a fully head located implantable peripheral neurostimulation system designed for the treatment of chronic head pain. It incorporates multiple elements and features that take into account the unique anatomic, physiologic, and other related challenges of treating head pain with implantable neurostimulation, thereby greatly improving on therapeutic response, patient safety, medical risk, and medical costs, which combine to improve overall patient satisfaction. 
     Prior implantable peripheral neurostimulation systems and components, including leads and pulse generators, have been designed and developed specifically as spinal cord stimulator systems and for the specific therapeutic purpose of treating chronic back and extremity pain. Over the years, these spinal cord stimulators were ultimately adopted and adapted for use as implantable peripheral nerve stimulators for the treatment of migraine headaches, and other forms of chronic head pain; however, they were so utilized with full recognition of the inherent risks and limitations given that they were developed only to address, and accommodate to, the unique anatomic and physiologic features of the back and chronic back pain. 
     U.S. Provisional Patent Application Ser. No. 61/865,893 describes the manifold problems associated with the application of spinal cord stimulators for head pain as fundamentally due to design flaws associated with, and inherent to, the use of an implantable therapeutic device in an area of the body that it was not designed for. 
     Indeed, the anatomy of the head, and the pathophysiology of headaches, and other forms of head pain, are so significantly different from the anatomy of the spinal canal, and pathophysiology of chronic back pain, that when spinal cord stimulators are utilized for cranial implants, the clinical problems associated with these differences manifest themselves. Importantly, these well-documented problems are clinically very significant and include issues of patient safety and satisfaction, the risk of an inadequate, or suboptimal, therapeutic response; and issues with patient comfort and cosmetics; as well as a recognized increased risk of surgical complications and technical problems. 
     These medical issues stem from the design of conventional leads and the IPG. Conventional lead designs include a relatively large diameter, a cylindrical shape, (often) inadequate length and the necessity of implanting the IPG in the torso and distant from the distal leads, and a number and disposition of the surface electrodes and active lead arrays that do not match the requirements. A cylindrical lead of relatively large diameter results in increased pressure on, and manifest tenting of, the overlying skin, particularly of the forehead. Because conventional leads are of inadequate length to extend from the head to the IPG implant site, commonly in the lower back, abdomen, or gluteal region, lead extensions are often employed, and there are attendant risks of infection, local discomfort, and cosmetic concerns. 
     With respect to prior leads: 1) There is only a single array of electrodes, with common lead options including 4, 8, or 16 electrodes disposed over that single array; 2) The array is relatively short with most leads having an array of from 5-12 cm in length; 3) Within this single array, the individual electrodes are disposed uniformly with constant, equal inter-electrode distances. This results in the need to implant multiple (often four or more) of the conventional leads to adequately cover the painful regions of the head. 
     There are several practical clinical outcomes that result from the use of prior leads for the treatment of chronic head pain. First, since they comprise a single, relatively short active array, the currently available leads provide therapeutic stimulation to only a single region of the head; that is, they can provide stimulation to only the frontal region, or a portion of the parietal region, or a portion of the occipital region. Therefore, if a patient has pain that extends over multiple regions, then multiple separate lead implants are required—basically one lead implant is required for each unilateral region. A great majority of patients with chronic headaches experience holocephalic pain; that is they experience pain over the frontal and parietal and occipital regions bilaterally. Therefore, commonly these patients will need 4 to 7 leads implanted to achieve adequate therapeutic results (2 or 3 leads on each side). 
     Second, the need for multiple leads includes considerable added expense, and more importantly, added medical risk associated with adverse events attendant to the multiple surgical procedures. Such adverse events include an increased risk of infection, bleeding, and technical issues with the leads, e.g., lead fracture, lead migration, and local irritation. 
     Third, as the clinical database discloses, the inter-electrode spacing may be of central therapeutic significance. That is, for example, whereas commonly pain over the occipital region is consistently effectively treated by quadripolar leads (leads with four evenly spaced electrodes) that have the electrodes relatively widely spaced apart (approximately a cm or more apart), clinically it is often found that electrodes configurations that are more narrowly spaced may be more effective over the supraorbital nerve and regions. Thus, a quadripolar lead that has the electrodes only 1-2 mm apart may be more effective in this region, as it allows for more precise control of the delivered electrical pulse wave delivery. 
     Inter-electrode spacing is also of therapeutic significance. For example, whereas pain over the occipital region is commonly treated effectively by systems incorporating relatively widely-spaced quadripolar leads (four electrodes at approximately 1 cm or more intervals), more narrowly spaced contacts are often more effective over the supraorbital region. 
     When an IPG implant designed for spinal cord stimulation systems is employed as a peripheral nerve stimulator for head pain, several outcomes result. First, the IPG is implanted at a considerable anatomic distance for the cranial lead implants. Indeed, the leads must pass from their distal cranial implant positions across the cervical region and upper back to the IPG implant location, which are most commonly in the lower back, lower abdomen, or gluteal region. The leads must cross multiple anatomic motion segments, including the neck and upper back and/or chest at a minimum, and commonly include the mid back, lower back and waist segments, as well. The simple motions of normal daily life produce adverse tension and torque forces on the leads across these motion segments, which in turn increases the risk of various outcomes, including lead migration and/or lead fracture. In addition, the relatively large size of a spinal cord stimulator IPG contributes to local discomfort, cosmetic concerns, and increased risk of infection that may become larger and harder to treat in proportion to the size of the IPG pocket. 
     The present disclosure is directed to an implantable head-located unibody peripheral neurostimulation system that includes an IPG from which two neurostimulating leads extend to a length sufficient to allow for therapeutic neurostimulation unilaterally over the frontal, parietal and occipital regions of the head. 
     The present disclosure addresses and effectively solves problems attendant to publically available leads. The most important of these is the fact that current leads can only adequately stimulate a single region of the head due to design element flaws associated with terminal surface electrode number and disposition. The disclosure additionally addresses and solves other problems inherent with the currently available leads, including problems with cosmetics and patient comfort, particularly over the frontal regions, due the uncomfortable pressure placed on the skin of the forehead, due the cylindrical shape and relatively large diameter of the distal portion of the lead. Finally, the lead of the present disclosure solves the currently available leads&#39; problem of inadequate lead length to reach a gluteal location of the implantable pulse generator, which therefore necessitates the additional risk and expense of further surgery to implant lead extensions. 
     In one aspect, the implantable, head-located, neurostimulation system for head pain is operable for subcutaenous implantation in the head, and to provide neurostimulation therapy for chronic head pain, including chronic head pain caused by migraine and other headaches, as well as chronic head pain due other etiologies. The peripheral neurostimulator system disclosed herein takes into account unique anatomic features of the human head, as well as the unique, or singular, features of the various pathologies that give rise to head pain, including migraine and other headaches, as well as other forms of chronic head pain. This lead design for implantation in the head for chronic head pain recognizes that thus far all commercially available systems that have been clinically utilized for implantation as a peripheral neurostimulator system were actually originally designed specifically for placement in the epidural space, as part of a spinal cord stimulation system, for the therapeutic purpose of treating chronic back and/or extremity pain. Thus, there are currently no commercially available leads or a complete system that have designs in the public domain, that have been designed and developed for use in the head and for head pain. 
     In another aspect, the implantable, head-located, neurostimulation system for head pain comprises multiple design features, including disposition of a sufficient plurality of surface electrodes over a sufficient linear distance along the distal lead, such as will result in a lead that, as a single lead, is capable of providing medically adequate therapeutic stimulation over the entire hemicranium; that is, over the frontal, parietal, and occipital region substantially simultaneously. Currently available systems, which were designed specifically for epidural placement for chronic back pain, are capable of only providing stimulation over a single region; that is over either the frontal region alone, or the parietal region alone, or the occipital region alone. 
     Currently available leads, which were designed specifically for epidural placement for chronic back pain, are capable of only providing stimulation over a single region; that is over either the frontal region alone, or the parietal region alone, or the occipital region alone. 
     In yet another aspect, the implantable, head-located, neurostimulation system for head pain comprises multiple design features, including the physical grouping of the extended array of surface electrodes into three or more discrete terminal surface electrode arrays. The linear layout of these two or more (preferably three or more) surface electrodes arrays is designed such that following implantation there would be at least one array positioned over the frontal region, at least one array positioned over the parietal region, and at least one array positioned over the occipital region. This feature further improves upon therapeutic effectiveness of the extended terminal surface electrode array sufficient for hemicranial stimulation by allowing for more precise control of the therapeutic neurostimulation parameters. 
     In still another aspect, the implantable, head-located, neurostimulation system for head pain comprises multiple design features, including incorporating individual design features within each of the three or more individual surface electrode arrays; examples of such intra-array design features would include the specific number of electrodes allotted to each group; whether the electrodes are cylindrical or flattened; the width of each electrode within each array, and the linear distance intervals of separation of the electrodes within each array. This feature further improves upon therapeutic effectiveness of the extended terminal surface electrode array sufficient for hemicranial stimulation, and the grouping of these electrodes into three or more separate surface electrode arrays, by providing each specific array location with a unique intra-array design that takes into account, and thereby seeks to optimize, design elements that are known to be possibly or likely beneficial to the therapeutic end result, given the anticipated post-implant anatomic location of that array. 
     In yet another aspect, the implantable, head-located, neurostimulation system for head pain comprises multiple design features, including incorporating individual design features into a single lead design and thereby achieving additive benefits. 
     In still another aspect, an implantable, head-located, neurostimulation system for head pain results in a marked decrease in the number of separate lead implants required to adequately treat a single patient. A single implant will provide the same therapeutic anatomic coverage that it would take the implantation of three or four of the currently available leads; that is, instead of the current implant, which often calls for three or more leads to be implanted to provide adequate hemicranial coverage, the same anatomic region may be covered with a single stimulator lead implant. The lead can provide extended coverage over the full hemicranium; that is achieving medically acceptable neurostimulation unilaterally over the frontal, parietal, and occipital regions simultaneously. In contrast, publically known leads are able to consistently provide medically acceptable neurostimulation therapy only over a single region; meaning that it would require three separate surgically placed lead implants to achieve the same therapeutic coverage of a single implant of a lead of the present disclosure. This will decrease the total number of surgeries required, as well as the extent of each individual surgery, for many patients. 
     In another aspect, the present disclosure is directed to a system that is fully localized to the head, which obviates the requirement of currently available systems of having long leads and extensions extending across the neck and back to IPG locations commonly in the low back and gluteal region, and thereby decreases the risk of problems attendant to such long leads and extensions, including discomfort, infection, technical extension issues such as fracture, and other morbidities. This ultimately results in a decreased number of surgeries required by a patient. 
     In other aspects the system may include one or more of the following features. A neurostimulating lead may not require a central channel for a stylet, which would be necessary to secure the lead against migration. A neurostimulating lead may have a smaller diameter than currently available leads. 
     In other aspects the system may include one or more of the following features. The system may include the disposition of a sufficient plurality of surface electrodes over a sufficient linear distance along the system&#39;s leads to enable medically adequate therapeutic stimulation across multiple regions of the head, and preferably the entire hemicranium; that is, over the frontal, parietal, and occipital region simultaneously. The extended array of surface electrodes may be divided into two or more discrete terminal surface electrode arrays, each capable of being designed for the particular associated region to be stimulated. The preferred linear layout of these multiple surface electrode arrays includes at least one array positioned over the frontal region, at least one array positioned over the parietal region, and at least one array positioned over the occipital region. 
     In other aspects, intra-array design features may include variations in the specific number of electrodes allotted to each group; the shape of the electrodes, e.g., whether the electrodes are cylindrical or flattened; the width of each electrode within each array, and the linear distance intervals of separation of the electrodes within each array. 
     In other aspects, the system may include a plurality of connection ports that can be connected with a plurality of leads and thus allow for attaching additional leads should they later be required. 
     In another aspect, an implantable, head-located, neurostimulation system for head pain comprises multiple design features; including features aimed at improving patient safety by improving the incidence of adverse events, including the risk of infection, as well as the risk and incidence of known technical problems associated with implanted leads, including lead migration and lead fracture, amongst others. The lead may comprise two or more (i.e. three or more) surface electrode arrays, each uniquely designed, that are disposed over a sufficient lead length to allow for medically acceptable therapeutic neurostimulator coverage of at least regions within the supraorbital, parietal, and occipital cranial regions. To achieve the same clinical coverage from a prior art implant, it would require three or more separately surgically implanted leads that are first implanted, followed by waking the patient up and activating the electrodes to determine if they are properly placed, and once the surgeon is satisfied, the leads are connected to an IPG and the IPG disposed in a pocket somewhere in the body, typically in the lower torso. Therefore, by reducing the number of surgical incisions, as well as the number of surgically implanted leads, the associated risks of adverse events are proportionally diminished. 
     In yet another aspect, an implantable, head-located, neurostimulation system for head pain may treat chronic head and/or face pain of multiple etiologies, including migraine headaches; and other primary headaches, including cluster headaches, hemicrania continua headaches, tension type headaches, chronic daily headaches, transformed migraine headaches; further including secondary headaches, such as cervicogenic headaches and other secondary musculoskeletal headaches; including neuropathic head and/or face pain, nociceptive head and/or face pain, and/or sympathetic related head and/or face pain; including greater occipital neuralgia, as well as the other various occipital neuralgias, supraorbital neuralgia, auriculotemporal neuralgia, infraorbital neuralgia, and other trigeminal neuralgias, and other head and face neuralgias. 
     In other aspects, an implantable, head-located, neurostimulation system for head pain may not require a central channel for stylet placement over its distal (frontal) portions. The lead may improve patient comfort and cosmetics by virtue of its relatively small diameter over the distal portions of the lead, partially due the lack of a central stylet channel, as well as due to a progressive decrease in the number of internal wires continuing after each terminal electrode. The lead may further improve cosmetic appearance and patient comfort by incorporating a flattened lead design for that portion of the lead expected to be over the frontal portion of the head. The lead may be compatible with currently available implantable pulse generators. The lead may incorporate an electrode array design that is capable as a single lead of providing medically acceptable neurostimulation coverage over the supraorbital, auriculotemporal, and occipital nerves unilaterally. The lead may be of sufficient length to adequately reach all common pulse generator locations, thereby potentially obviating the need for lead extensions and in turn decreasing the risk of problems attendant to such extensions, including discomfort, infection, technical extension issues such as fracture, and other morbidities. The single lead may be operable to provide medically acceptable neurostimulation coverage that treats head pain over the frontal, lateral, and posterior regions. The single lead may be operable to provide medically acceptable therapeutic neurostimulation coverage that would otherwise often require unilateral leads (six total leads if, as is common, the pain is global/holocephalic), thereby resulting in a decrease in the number of patients that require more than one associated Implantable Pulse Generator (IPG). Currently available IPGs are capable of accepting a maximum of four leads, each having the ability to cover only one anatomic region, as each lead only has one active array. The lead may include a progressively tapering diameter over the lead segment containing t three active arrays, a feature serving clinical improvements in patient comfort and cosmetics. The lead may further comprise a distal array disposed over a thin, flattened terminal portion of the lead, which is the portion intended to be positioned over the supraorbital (frontal) region, a feature serving clinical improvements in patient comfort and cosmetics. 
     Thus the present disclosure provides for a peripheral neurostimulation lead that is uniquely designed for subcutaneous implantation in the head as a therapy for chronic head pain, and is designed to solve the known design issues associated with current leads, as the lead of the present disclosure seeks to optimize the therapeutic response, improve patient comfort, improve cosmetics, reduce the number of surgical leads required, reduce medical risk, and reduce medical costs. 
     B. OVERVIEW 
     Turning now to the drawings, which depict the system and several of its components in various aspects and views, and in which similar reference numerals denote similar elements. The drawings illustrate an IPG from which two neurostimulating leads may extend to a length sufficient to allow for therapeutic neurostimulation unilaterally over the frontal, parietal and occipital regions. The leads include an extended plastic lead body; a plurality of surface metal electrodes disposed along the lead, which may be divided into two or more electrode arrays; a plurality of internal electrically conducting metal wires running along at least a portion of its length and individually connecting the IPG&#39;s internal circuit to individual surface metal electrodes. The implantable pulse generator includes a rechargeable battery, an antenna coil, and ASIC. The system may be operable to provide medically acceptable therapeutic neurostimulation to multiple regions of the head, including the frontal, parietal and occipital regions simultaneously, and three figures demonstrate various views of this feature as the lead is depicted in-situ. 
     C. FULL HEAD-LOCATED NEUROSTIMULATOR SYSTEM 
       FIG. 1  depicts a side view of a full neurostimulator system, which consists of an implantable pulse generator (IPG)  10  along with two unibody plastic lead extensions—a Fronto-Parietal Lead (FPL)  20  and an Occipital Lead (OL)  30  of adequate length to extend to roughly the midline of the forehead and to the midline at the cervico-cranial junction, respectively. Arrows  28  indicate the point of cross section of  FIG. 4 . 
       FIGS. 5, 6 and 7  depict posterior, lateral and frontal views of the system in-situ. The unit is demonstrated in an implant position where the IPG  10  is posterior and cephalad to the pinna of the ear. The drawings demonstrate the complete neurostimulator system implant subcutaneously with the FPL  20  passing over the parietal  60  and frontal  70  regions of the head, including auriculotemporal nerve  61  and supraorbital nerve  71 , in a manner that places the FEA over the supraorbital nerve  71  and the PEA over the auriculotemporal nerve  61 . The OL  30  is shown passing caudally and medially over the occipital region of the head  50  such that the OEA  35  cross over the greater occipital nerve  51  and the lesser occipital nerve  52 , and the third occipital nerve. 
     D. FRONTO-PARIETAL LEAD 
     Continuing with  FIG. 1 , the FPL  20  as part of the unibody construction, is connected to and extends from the IPG. The FPL  20  comprises a plastic body member  20   a  and a set of internal conducting wires  29 . 
     The plastic body member  20   a  is an elongated, cylindrical, flexible member, which may be formed of a medical grade plastic polymer. It has a proximal end  22 , a distal end  21 , and may be conceptually divided into five segments along its linear dimension. Progressing from the proximal end  22 , these segments sequentially include a proximal lead segment (PLS)  22   a , a parietal electrode array (PEA)  26 , an inter-array interval  27 , a frontal electrode array (FEA)  25 , and a distal non-stimulating tip  23 . 
     The lead internal wires  29  pass along the interior of the plastic body member as depicted in  FIG. 4 . 
     E. FRONTAL ELECTRODE ARRAY 
     Continuing with  FIG. 1 , the FEA  25  is disposed at the distal end of the FPL  20  and consists of a plurality of surface metal electrodes (SMEs)  24  uniformly disposed over a portion of the distal aspect of the FPL  20 . Lead internal wires  29  connect to the SME  24  as depicted in  FIG. 2 , which represents the distal four SMEs  24  of the lead. The distal four SMEs  24  associated with the array  25  have an interelectrode spacing and design that is specific to stimulating the frontal region. Also, the number of electrodes required for the array will be a function of the particular region, the frontal region, that is being treated. As will be described hereinbelow, each of these electrodes can be designated as an anode or a cathode and any combination can be designated to be energized in a set up procedure performed by a clinician. This provides a configuration that can be adapted to a particular patient at a particular placement of the FEA  25 . 
     F. PARIETAL ELECTRODE ARRAY 
     Returning to  FIG. 1 , the PEA  26  consists of a plurality of SMEs  24  uniformly disposed along a linear portion of the FPL. The PEA  26  is separated along the FPL from the FEA by an inter-array interval  27 . It is separated on the lead from the IPG by the PLS  22   a . The lead internal wires  29  connect to the individual SME  24  of the PEA in the same fashion as they do with respect to the SME of the FEA as shown in  FIG. 2 . As was the case with respect to the FEA  25 , the SMEs  24  of the PEA  26  have an interelectrode spacing and design that is specific for stimulating the nerves in the parietal region. Also, the number of electrodes required for the array will be a function of the particular region, the parietal region, that is being treated. As will be described hereinbelow, each of these electrodes can be designated as an anode or a cathode and any combination can be designated to be energized in a set up procedure performed by a clinician. This provides a configuration that can be adapted to a particular patient at a particular placement of the array  25 . 
     Typically, the FPL  20  is a single lead having the two arrays,  25  and  26 , disposed along the length thereof. The diameter and the shape of this lead can be uniform or it can be of any shape that facilitates surgical placement of the lead. However, with a single lead, two distinct regions of the cranium can be therapeutically treated, each independently controlled by the IPG  10  via the leads  29  and each having a design via the interelectrode spacing and even the electrode configuration to facilitate the requirements of such therapeutic treatment of a particular region associated with a particular set of nerves. This, thus, requires only a single incision to feed the FPL  20  from the incision point to a particular region. 
     G. OCCIPITAL LEAD 
     Continuing with  FIG. 1 , the occipital lead (OL)  30  is an integral part of the unibody construction, and extends from the IPG  10 . It comprises a plastic body member  39  and a set of lead internal wires  38  that pass through the central cylinder of the lead to connect to a series of SME  34 , each of surface electrode width  37 , that are uniformly disposed at an interelectrode distance  36  from each other along a portion of the length of the lead. These lead internal wires  38  pass and connect in the same manner as described above for the SMEs  24  of the FEA  25  and the PEA  26  as depicted in  FIG. 2  and  FIG. 4 . 
     The plastic body member  39  is an elongated, cylindrical, flexible member, which may be formed of a medical grade plastic polymer. It has a proximal end  32  and a distal end  31 . Progressing along the lead from the proximal end  32 , these segments sequentially include a proximal lead segment (PLS)  32   a , an occipital electrode array (OEA)  35 , and a distal non-stimulating tip  33 . 
     H. OCCIPITAL LEAD ARRAY 
     As depicted in  FIG. 1 , the OEA  35  consists of a plurality of surface metal electrodes (SME)  34  uniformly disposed over a portion OL  30 . Lead internal wires  38  connect to the SME  24  in the same fashion as depicted for the FEA as shown in  FIG. 2 . As was the case with respect to the FEA  25  and the PEA  26 , the SMEs  34  of the OL  30  have an interelectrode spacing and design that is specific for stimulating the occipital region. Also, the number of electrodes required for the array will be a function of the particular region, the occipital region, that is being treated. As will be described hereinbelow, each of these electrodes can be designated as an anode or a cathode and any combination can be designated to be energized in a set up procedure performed by a clinician. This provides a configuration that can be adapted to a particular patient at a particular placement of the OL  30 . 
     I. IMPLANTABLE PULSE GENERATOR 
     Referring to  FIG. 1  and  FIG. 3 , the three primary physical and functional components of the IPG  10  include a rechargeable battery  12 , an antenna  11 , and an application specific integrated circuit (ASIC)  13 , along with the necessary internal wire connections amongst these related components, as well as to the incoming lead internal wires  29 ,  39 . These individual components may be encased in common interior  15  that may include a can made of a medical grade metal and plastic cover  14 , which itself transitions over the exiting FPL  20  and OL  30 . 
     Battery  12  is connected to the ASIC  13  via a connection that is flexible. The overall enclosure for the battery  12 , antenna  11  and ASIC  13  has a very low flat profile (seen in a top view in  FIG. 1 ) with two lobes, one low for housing the ASIC  13  and one low for housing the battery  12 . The antenna  11  can be housed in either of the lobes or in both lobes, this being a function of the coupling to an outside communication/charging source. By utilizing the two lobes and the flexible connection between the ASIC  13  and the battery  12 , this allows the IPG  10  to conform to the shape of the human cranium when subcutaneously implanted without securing such to any underlying structure with an external fixator. 
     The ASIC  13  is operable to interface with the lines  29  in the FPL  20  and the lines  39  in the OL  34  driving the respective SMEs  24 ,  34 . The ASIC  13  is a state machine that is configured to provide stimulation signals in the form of pulses, variable frequencies, etc., to the respective electrodes in accordance with a predetermined program. Once the program is loaded and initiated, the state machine will execute the particular programs to provide the necessary therapeutic stimulation. The ASIC  13  has memory associated there with and a communication capability, in addition to charge control to charge battery  12 . Each of the set of wires  29  and  39  interface with the ASIC  13  such that the ASIC  13  individually controls each of the wires in the particular bundle of wires. Thus, each electrode in each of the arrays,  25 ,  26  and  35 , can be individually controlled. As noted hereinabove, each electrode can be designated as an anode or a cathode, or it can even be turned off. 
     During a charging operation, the IPG  10  is interfaced with an external charging unit via the antenna  11  which is coupled to a similar antenna or coil in the external charging unit (not shown). The charging operation is controlled by the ASIC  13 , as the battery  12 , in one embodiment, can include the use of a lithium ion battery. It is important for power management to control the amount of charge delivered to the battery, the charging rate thereof and to protect the battery  12  from being overcharged. 
     Additionally, the ASIC  13  is capable of communicating with an external unit, typically part of the external charging unit, to transfer information thereto and receive information there from. In this manner, configuration information can be downloaded to the ASIC  13  and status information can be retrieved therefrom. Although not illustrated herein, a headset or such is provided for such external charging/communication operation. 
     K. CONNECTIONS OF MAIN ELEMENTS AND SUB-ELEMENTS 
     The system may include a unibody construction to provide physical and functional continuity of the related components and sub-components. This unibody construction is basically an enclosure that encloses the entire IPG and the interface with the FPL  20  and the OL  30 . The FPL  20  and the OL  30  are separate assemblies that are attached to the ASIC  13  via either a connector or via a hardwired connection. The FPL  20  and the OL  30  are totally enclosed and sealed with only the distal end of leads  29 ,  39  extending therefrom. Once attached to the ASIC  13 , or the PC board associated there with, a material is disposed about the entire IPG  10  to provide a seal therefore which extends over the IPG  10  and the proximal ends  22  and  32  of the FPL  20  and OL  30 , respectively. With such a unibody construction, a surgeon need only make one incision to subcutaneously insert the entire assembly including both the IPG  10  and associated leads in a desired region in the cranium, typically just behind the parietal bone and slightly above the mastoid bone and the pinna. This allows the FPL  20  to be fed around toward the frontal bone and the OL  30  to be fed backwards toward the occipital bone. Thus, the entire neurostimulator system will be disposed subcutaneously about the cranium and will require no anchor. Without the requirement for an anchor, there is no protuberance required in the IPG  10 , allowing the IPG  10  to be completely sealed. This is facilitated by the fact that very little movement will occur with respect to the tissue surrounding the IPG  10  after implantation thereof. Due to this minimal amount of movement, no stylet will be required (but such can be incorporated if desired) to secure either the FPL  20  or the OL  30  in place to underlying fascia. 
     The overall mechanistic purpose of an implantable neurostimulation system is to generate and conduct a prescribed electrical pulse wave from an IPG  10  down a set of lead internal wires  29 ,  38  running a portion of the length of the lead to specified programmed set of SME  24 ,  34 , whereby the current is then conducted by tissue and/or fluid to an adjacent, or nearby, set of one or more SME  24 ,  34 , which in turn passes the signal proximally down the lead wire  29 ,  38  back to the IPG  10  and its ASIC  13 , thus completing the circuit. 
     L. FIRST EMBODIMENT 
     The first embodiment provides for the implantation of the neurostimulator system that incorporates one or more of the features outlined above and includes a head-located, unibody neurostimulating system comprising an IPG  10  and at least two neurostimulating leads (FPL  20  and OL  30 ). The system may be implanted in a manner such that the IPG  10  and two leads  20 ,  30  are subcutaneously disposed as illustrated in  FIG. 5 ,  FIG. 6  and  FIG. 7 . The IPG  10  is capable of functionally connecting to and communicating with a portable programmer  40  and an external power source for battery recharging. 
     In this embodiment, the leads are constructed as described above and as depicted in the drawings. The FPL  20  is approximately 26 cm in length from its proximal end  22  to its distal end  21 . The FPL  20  has a distal non-stimulating tip of approximately 3 mm in length that abuts the FEA, which may have ten SME  24  uniformly disposed over approximately 8 cm. This is followed by an inter-array interval  27  of approximately 4 cm, then the PEA, which may include eight SME  24  uniformly disposed over approximately 6 cm, and finally a proximal lead segment  22   a  that ends at the proximal end  22 , where the lead transitions to the IPG  10  and the lead internal wires  29 ,  38  connect to the ASIC  13 . 
     In this embodiment, the occipital lead may comprise a plastic body member  39  over which six SME  34  may be disposed uniformly over approximately a 10 cm length of the lead, and the lead terminates in approximately a 3 mm distal non-stimulating tip  33 . 
     In this embodiment, the IPG  10  comprises the elements described above and depicted in the drawings, including an ASIC  13 , a rechargeable battery  12 , and an antenna  11 , which all may be housed in a medical grade metal can with plastic cover  14 . In this embodiment the dimensions of the IPG  10  measured along the outer surface of the plastic cover  14  may be approximately 5 cm by 3 cm by 0.5 mm. 
     The system includes a portable programmer  40  and a portable recharging unit, both of which functionally couple to the IPG through a radiofrequency mechanism. 
     In this embodiment, the system is capable of handling a program from the portable programmer  40  that includes such parameters as pulse amplitude, frequency and pulse width. 
     The procedure itself involves the permanent subcutaneous implantation of an IPG with multi-lead, multi-array neurostimulator system. The patient may have had a period of trial neurostimulation, which is standard in traditional neurostimulator evaluations but is optional here. The actual permanent implant takes place in a standard operating suite with appropriate sterile precautions and is typically performed under general anesthesia with the patient positioned prone with the hair and body prepped and draped. 
     While the IPG may be positioned subcutaneously anywhere over the head or upper cervical region, in this embodiment it is positioned above and behind the ear. Thus, at a position approximately 1-2 cm above the ear and a couple of cm posterior to the ear, a Supraorbital Incision of sufficient length (approximately 4-6 cm) is made to a depth sufficient to reach the subcutaneous layer. At the posterior aspect of this incision a pocket to accept the IPG is fashioned by standard dissection techniques. The pocket should be 10-20% larger than the IPG itself to allow for a comfortable fit and no undue tension on the overlying skin and/or incision. A second approximately 1-2 cm incision is made to the subcutaneous layer at a point above and anterior to the pinna of the ear in the temple region. 
     In this embodiment, in the supra-auricular incision, a tubular introducer with a plastic-peel away shell (Peel-Away Introducer) is advanced subcutaneously from the supra-auricular incision to the temple incision. The FL is then passed per the introducer, whereby the peel-away shell is removed leaving the proximal segment of the FL in position in the subcutaneous layer. A new Peel-Away Introducer is then advanced subcutaneously from the Temple Incision medially and commonly 1-2 cm above the eyebrow to its final position where the distal tip of the lead approximates the midline; a position that results in the frontal electrode array (FEA) over the superficial nerves of the frontal region. 
     In this embodiment, and prior to activation thereof, the IPG is next positioned in the previously fashioned subcutaneous pocket posterior to the supra-auricular incision. Then, from the inferior aspect of the supra-auricular incision a new peel-away introducer is advanced subcutaneously medially, and inferiorly to cross the nerve region of the occipital region such that the distal tip of the introducer approximates the midline. Per the introducer the OL is passed, whereby the Peel-Away Introducer is then removed, leaving the lead in position with its active array over the superficial nerves of the occipital region. 
     Following the entire placement of the complete system, including the IPG and both leads and suturing, the neurostimulator unit is then powered-up and its circuits checked. Upon recovery from anesthesia the system is turned on for the patient with a portable programmer and the multiple parameters for the system programmed to an optimal therapeutic endpoint for the patient. 
     In this embodiment, the implantable unit contains a multi-year battery that is capable of being recharged from an external source. 
     In this embodiment, the system is capable of handling a program from the portable programmer  40  that includes such parameters as pulse amplitude, frequency and pulse width. The system is charge balanced, current controlled and rechargeable at preferably intervals that exceed one week. The preferred stimulation paradigm may be current controlled, voltage controlled, or a combination of both. The pulsing may be charge balanced or charge imbalanced. The preferred work cycle is between 10 and 100%. 
       FIGS. 8A and 8B  depicts a front view and a top view, respectively, of a Portable Programmer  40  for a Head-Mounted Neurostimulator System. The Programmer  40  is specifically designed for application to the Head-Mounted System and specifically for use with patients with migraine and other head pain. The figure is labelled independently. On the front of the Programmer  40  is disposed a liquid crystal display  41  for displaying one side of the head of individual. In the upper left-hand corner of the display  41 , there is illustrated an orientation for the left side of the head. As noted herein, there can be provided two implanted Neurostimulator Systems, one for the right and one for the left side of the head. Thus, the user can select between both sides for display. 
     The illustrated image includes an image of the left side of the head that is divided into three sections. There is a first frontal section including the supraorbital nerve region, a medial section including the parietal nerve region and a distal section that includes the occipital nerves. As noted herein, the programmer  40  is operable to interfaced through a headset or external charging/communication circuit (not shown) with one or more implanted neurostimulator systems. Thus, there is provided a display area  43  in the LCD display for depicting the recharge level of the Programmer  40  and a display area  42  for depicting the charge level of each neurostimulator system, one for the left and one for the right, if two neurostimulator systems are implanted and being monitored. For each section of the displayed head image, the frontal, the medial and the distal, there is illustrated a percentage of value illustrating the percentage level of stimulation that is being applied. There are provided left and right toggle buttons  45  that allow a particular section to be selected and increase/decreased buttons  46  to increase and decrease the level of stimulation. A confirm button  47  is provided for actually entering information after selection thereof. A lot button is disposed on the upper side, as illustrated in  FIG. 8B . 
       FIG. 9  depicts a side view of a head and the initial interventional step in the procedure for implanting the Neurostimulator system. Prominent here are depictions of the two incisions required for placement of the neurostimulator: 1) a supraauricular incision where the IPG will be implanted and from which the FPL and OL are tunneled subcutaneously to their final subcutaneous positions over the Fronto-Parietal and Occipital regions respectively, and 2) a Temple Subcutaneous Incision per which the FPL is initially passed from the IPG in the Supra-auricular Incision, whereupon it is again passed subcutaneously to its final subcutaneous position over the nerves of the supraorbital region. Four drawn lines are also depicted which are used as references to define relative positions for incisions and passing the leads. What is illustrated is the parietal region of head  60  wherein lines are drawn about the pinna. A horizontal supra-pinna line is disposed above the apex  63  of the pinna, a vertical pre-pinna line  64  is drawn to the frontal side of the pinna, a vertical mid-pinna line  65  is drawn down the medial section of the pinna, a vertical post-pinna line  66  is drawn at the back of the pinna and a horizontal supra-pinna line  67  is drawn above the pinna. In this embodiment, the supra-auricular subcutaneous incision  68  is disposed above the line  68  inbetween the two lines  65  and  66 . The lower point  68   a  of the incision  68  is disposed almost exactly between the two lines  65  and  66  and extends upward at an angle distal to the pinna. A Temple subcutaneous incision  69  is disposed forward of the line  64  with a lower point  69   a  of the incision being disposed at approximately the level of the line  67  forward of the line  64  and extending an angle upward and frontal to the point  69   a.    
       FIG. 10  depicts a side view of the head and the next step of the procedure following that depicted and described in  FIG. 9 . The same incisions are depicted as referenced in  FIG. 9 ; the Supra-auricular Incision  68  and Temple Incision  69 . A traditional tubular Peel-Away Introducer  95  is depicted as having been passed subcutaneously from the Supra-auricular Incision to the Temple Incision. This introducer  95  provides a lumen through which to pass in the league  20  after insertion thereof. The introducer  95  is comprised of two parts that are connected together with a serrated or breakable connection. Once the lead  20  is passed through the lumen of the introducer  95 , it can be fully pulled through such that the frontal portion  25  is pulled all the way through the incision  69 . The peel away introducer  95  can then be extracted by pulling each edge, there being two extensions for grabbing either&#39;s side of the introducer and peeling away, leaving the lead in place between incision  68  and  69 . It can be seen that the IPG  10  and the assembly  30  are still not implanted, nor is the FEA  25 . Thus, the FPL is passed through the Peel-Away Introducer, which is depicted in this drawing as beginning to separate in the act of being removed. Note that the OL and the Distal Segment of the FPL are still exterior to the skin. 
       FIG. 11  depicts a side view of the head and the next step of the procedure following that depicted and described with respect to  FIG. 10 . Prominent here is the depiction of a new Peel-Away Introducer as having been passed subcutaneously from the Temple Incision  69  to its final position proximate to the supraorbital nerve region where its distal tip approximates the midline, and the FEA is in the Subcutaneous Layer, which places it over the nerves of the Supraorbital Region. The Proximal Lead Segment of the FPL is depicted as having been positioned subcutaneously such that the PEA is positioned in the Subcutaneous Layer over the nerves of the associated Parietal Region. The IPG  10  and OL  30  are depicted as remaining exterior to the incision  68  at this point in the procedure. 
       FIG. 12  depicts a frontal view of the FL as having been positioned subcutaneously as discussed in  FIG. 11 . The FL is depicted having its FEA in its subcutaneous position where it is crossing over and superficial to the nerves of the Frontal Region, including here the Supraorbital Nerve  71  and the Supratrochlear Nerve  72 . 
       FIGS. 13A and 13B  depict a side view of the next step in the procedure after the step depicted and described with respect to  FIGS. 11 and 12 . Prominent here are the IPG  10  and OL  30  which have been passed and positioned subcutaneously in the IPG pocket and over the nerves of the Occipital Region, respectively. The FPL  20   b  is depicted as having been passed subcutaneously as demonstrated in  FIGS. 11 and 12 . Also prominent is a blow-up view of the Supra-Auricular Incision  68  at this step in  FIG. 13B , where the IPG  10   a  is pictured in its Subcutaneous Pocket and the most proximal segments of the FPL  20   b  and OL  30   b  are depicted as they enter the subcutaneous spaces in route to their final positions as depicted in the previous figures. Of note is the Peel-Away Introducer  95  over the OL  30   b , which is depicted as just being separated as part of the procedure of removing it. The FPL  20   b  is depicted as having been passsed subcutaneously to its final position as depicted in the previous figures. The IPG  10   a  can either be inserted into the IPG subcutaneous pocket prior to insertion of the OL  30   b  into the introducer  95  or in the opposite sequence. 
       FIG. 14  depicts a cross-section view of the skin at the Supra-auricular Incision  68  at the stage of the procedure depicted in  FIG. 13 . Prominent within the subcutaneous layer  82  is the IPG  10   a  in its Subcutaneous Pocket, as well as the initial proximal segments of the FPL  20   b  and the OL  30   b  as they pass per the Subcutaneous Layer. The Peel-Away Introducer  95  noted in  FIG. 13  is also prominent. Once the peel away introducer  95  is removed, the Supra-auricular Incision  68  can be closed. At this point in time, the incision is closed prior to activating the IPG  10   a . It could, of course, be activated prior to closing of the incision but at this stage, the Neurostimulator System is completely implanted and all the leads positioned. 
       FIG. 15  depicts a cross-section view of the skin at the point where the Active Electrode Array of the OL  30   b  has been positioned over (superficial to) the Subcutaneous Layer, which lies between the superficial Dermis and the underlying Fascia. The Muscle Layer, Aponeurosis and the Boney Skull are represented as sequentially deeper layers beneath the Fascia. The regions illustrated are the Boney skull  86  over which lies a thin layer  85 , the Aponeurosis, over which lies a muscle layer  84 , over which lies the subcutaneous tissue layer  82  and finally the dermis  81 . Illustrated within the subcutaneous tissue layer  82  is a cross-section of the greater occipital nerve  51   a . The OL  30   b  is disposed within the subcutaneous tissue layer  82  above the greater occipital nerve  51   a.    
       FIG. 16  depicts a view of the head from the top after the full neurostimulator system has been implanted. Prominent here are the full system, including the IPG  10   b , FPL  20   b  and OL  30   b , which all lie within the Subcutaneous Layer. Also prominent are the FEA  25 , the PEA  26 , the OEA  35  in their final positions over (superficial to) the corresponding nerves in the Frontal Region, the Parietal Region, and the Occipital Region respectively. 
       FIG. 17  depicts two implanted IPGs with leads to cover both sides of the head. The two structures are numbered identically with respect to their compliments, and they are implanted identically, one on the left side of the head and one on the right side of the head, as described above. 
       FIG. 18  depicts one implanted IPG with leads to cover both sides of the head. In this embodiment, the FPL 20   b  extends from the IPG  10   a  on one side of the head around the parietal region on that side of the head, the two frontal regions and on the parietal region on the opposite side of the head such that there are two PEAs  26 , two FEAs  25  and two OEAs  35 . This, of course, requires an incision to be made on the temporal region on the side of the head on which the IPG  10  is implanted and a frontal incision made to allow the FPA  20  to be routed to and in a frontal incision and then to a temporal incision on the upside the head and finally to the parietal region on the upside the head. This is the same with respect to the occipital lead  30  that must be routed through possibly an additional acetylene incision of the back of the head. All that is required is the ability to route particular leads to the respective regions proximate the nerves associated therewith. This will allow a single IPG  10  to cover two frontal regions, two parietal regions and two occipital regions. 
     Thus, the procedure to implant, in summary, is to first provide a neurostimulator system that has a unibody construction comprised of an IPG integrated with the leads as opposed to a separate system wherein the leads are implanted first, positioned, activated and then connected to the IPG. Then the IPG implanted into an associated pocket. With the unibody construction of the disclosed neurostimulator system, this requires each of the multiple leads to first be positioned proximate to a desired nerve region through one or more incisions through the subcutaneous layer. This typically involves a single initial incision that is associated with the subcutaneous pocket for the IPG, wherein the leads are first inserted through the incision to the particular nerve region subcutaneously and then the IPG disposed within the pocket subcutaneously. However, the IPG is not secured to an underlying structure, such as bone or fascia. The reason for this is that the IPG is, first, very lightweight, and second, disposed in an area of the skull that is subject to very little movement, thus minimizing the possibility of any migration of the leads. 
     M. ALTERNATE EMBODIMENTS 
     There are multiple alternate embodiments that preserve the features of the neurostimulation system disclosed herein, which include an externally rechargeable and programmable IPG, sized and configured for implantation in the head, and from which fronto-parietal and occipital leads, along with their respect surface metal electrode arrays, extend to cover multiple regions of the head. In various embodiments, the spacing and dimensions of the electrode array(s) for each specific array may be constant, or the electrode arrays may be specifically designed with respect to electrode type, dimensions, and layout for improving the therapeutic effectiveness for the specific cranial region it is to be associated with. The multiple alternate embodiments also include a subcutaneously positioned unibody neurostimulator device that contains an IPG and two leads, one with a single electrode array and the other with two electrode arrays. 
     Thus, the disclosure comprises extended electrode array designs (two or more regions by a single lead), and/or multiple arrays and optimized intra-array electrode dispositions. The disclosure also comprises lead configurations, which include the capability of a modular lead design that provides for ports on either the standard FPL and OLs. In another embodiment, the IPG may receive additional separate leads, if and as necessary either at the time of initial implant or in the future. 
     Further, the lead lengths, along with the specific technical makeup and dimensions of the individual surface metal electrodes and electrode arrays, may be varied to include more or less than three unilateral regions of the head (occipital, parietal, and frontal) contemplated by the first embodiment. For example, a single IPG may energize and control multiple additional leads of varying lengths that ultimately could be disposed over virtually every region of the head and face bilaterally, to thus cover multiple and disparate regions, with each of these leads and arrays of electrodes associated therewith designed for a particular cranial region. Further, each of these leads can have one or more disparate arrays associated therewith so as to accommodate more than a single cranial region, this single multi-array lead allowing a single incision to accommodate these multiple regions. 
     At least two electrodes may be included per region (an thus per array), and while the first embodiment calls for a total of 24 electrodes disposed over three arrays covering three different regions of the head—the occipital, parietal and frontal regions—there is no absolute limit to the maxim (or minimum) number of electrodes. Similarly, while the first embodiment calls for three electrode arrays, the disclosure contemplates two, or even one array (so long as the arrays covers at least two regions). There is also no limiting maximum for the number of arrays. Also, there may be multiple variations of design within each separate array, including for example, variations in the number, dimensions, shape, and metal composition of the individual electrodes, as well as the distance and constancy of distance between electrodes, within each array. Further, each array may have the same or completely different designs. 
     While the neurostimulation system has been described for subcutaneous implantation as a peripheral neurostimulator in the head and for head pain, it is capable of being implanted and used as a peripheral nerve stimulator over other regions of the head and face than described above and also over other peripheral nerves in the body. 
     In another embodiment the IPG may be positioned subcutaneously over virtually any other point of the head that can accept the unit. 
     In another embodiment the leads may be passed such that their respective electrode arrays over positioned subcutaneously over other painful regions of the face, head and neck. 
     In another embodiment the leads may be passed by measures other than a standard Peel-Away Introducer. For example they may be passed per the previous retrograde positioning of a standard, metal tubular introducer, which is then removed over the lead once it has been positioned. 
     While a common embodiment includes the implantation of two neurostimulator systems (one on each side), other embodiments may include only system or may include more than two systems. These would depend upon the nature, location and extension of a patient&#39;s pain report. 
     While the neurostimulation system has been described for implantation as a peripheral neurostimulator in the head and for head pain, it is capable of being implanted and used as a peripheral nerve stimulator over other regions of the head and face than described above and also over other peripheral nerves in the body. 
     N. OPERATION 
     When functioning; that is when the internal circuit of lead internal wires is connected to an IPG; the SMEs of the various arrays are programmed to function as anodes and cathodes. The ASIC  13  then drives with a generated electrical pulse wave then passes from the ASIC of the IPG to the associated internal lead wire, and ultimately to its associated terminal surface metal electrode. The current then passes a short distance from the subcutaneous tissue, within which the neurostimulator system is implanted, to a contiguous, or nearby, electrode, whereby it passes back up the lead to its associated proximal metal contact, and then back to the IPG and the ASIC  13  to complete the circuit. The generated pulse waves pass through the subcutaneous tissue between two terminal electrodes that stimulates the sensory nerves of the area. As noted hereinabove, the configuration for the ASIC  13  can define certain of the SMEs as anodes and certain of the SMEs as cathodes. When active, the IPG may be programmed to produce continuous series of pulse waves of specified frequency, amplitude, and pulse width. It is this series of pulse waves actively stimulating a patient&#39;s locally associated nerves that underpins the therapeutic effect of the implanted unit. The electrical pulse wave then passes from a connected proximal surface metal contact, along the associated internal lead wire, and ultimately to its associated terminal surface metal contact. 
     With respect to  FIGS. 5, 6 and 7 . The neurostimulator system is subcutaneously implanted on the left side of the hemicranium over the respective nerve regions. The main body of the IPG  10  is disposed proximate to and rearward of the parietal bone just above the ear. A small incision (shown below) is made into which the FPL  20  is inserted and routed forward to the frontal bone passing over the auriculotemoral nerve  61  and the supraorbital nerve  71 . The OL  30  is routed through the incision backwards to the a occipital nerve. Then the IPG  10  is inserted through the incision and then the incision closed. Thus, with a single incision, the entire neurostimulator system can be disposed in a subcutaneous region of the cranium, the regions selected such that a minimal amount of movement will occur with everyday activity of an individual. The selection of the region in which the main body is implanted is selected based upon a region that will result in minimal migration of the IPG  10  (noting again tht it is not secured to bone), be very unobtrusive to the individual and allow easy access to the frontal and a possible regions of the cranium. There is no need to secure the main IPG  10  to the bone or to even provide any stylet securing it to the fascia. 
     It is to be understood that the implementations disclosed herein are not limited to the particular systems or processes described which might, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular implementations only, and is not intended to be limiting. As used in this specification, the singular forms “a”, “an” and “the” include plural referents unless the content clearly indicates otherwise. Thus, for example, reference to “an accumulator” includes a combination of two or more accumulators; and, reference to “a valve” includes different types and/or combinations of valves. Reference to “a compressor” may include a combination of two or more compressors. As another example, “coupling” includes direct and/or indirect coupling of members. 
     Although the present disclosure has been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. 
     Referring now to  FIG. 19 , there is illustrated a headset  1902  disposed about the cranium for interfacing with the two implants  10   a  of  FIG. 17 . The headset  1902  includes right and left coupling coil enclosures  1904  and  1906 , respectively that contain coils coupled to the respective coils in the implants  10   a . The coil enclosures  1904  and  1906  interface with a main charger/processor body  1908  which contains processor circuitry and batteries for both charging the internal battery in the implants  10   a  and also communicating with the implants  10   a . Thus, in operation, when a patient desires to charge their implants  10   a , all that is necessary is to place the headset  1902  about the cranium with the coil enclosures  1904  and  1906  in close proximity to the respective implants  10   a . This will automatically effect charging. For communication, there is provided some internal communication required for charging but also, an external interface can be provided to the user via the handheld unit described in  FIGS. 8A and 8B . 
     Referring now to  FIG. 20 , there is illustrated a diagrammatic view of the interface of the headset  1902  with the implants  10   a . Each of the implants  10   a  is interfaced with the leads  20  and  30  and includes the processor  13  and the battery  12 . Also, although not illustrated, the coil  11  is disposed therein. It should be understood that the processor  13  can be any type of instruction based processing device or state machine and even an ASIC that is capable of executing a sequence of events that results in some pattern of stimulating signals to be transmitted to the electrodes and also facilitates charging/powering and communication. 
     Referring now to  FIG. 21 , there is illustrated a schematic view of the overall headset and implants. The headset  1902  is comprised of two coupling coils  2002  and  2004 , each operable to couple with the respective coil  11  of the respective implants  10   a . There is coupling of both charging power and communication, this communication being bidirectional. The two series coils  2002  and  2004  are controlled by a charger and TX/RX circuit  2006 . This circuit  2006  is operable to generate sufficient energy at a resonant frequency of the coil to couple across the skin to the coil  11 , which is then used to charge the respective battery  12 . The processor  13  is operable to facilitate the charging and communication operations and also the driving operations for driving current to the associated leads  20  and  30 . 
     Referring now to  FIGS. 22A and 22B , there are illustrated block diagrams for the operation of the overall system. With reference specifically to  FIG. 22A , there is illustrated a block diagram for implantation  10   a , wherein a microprocessor  2204  is contained at the heart of the overall operation. This is interfaced with a memory for storing instructions programs and also with a driver  2208  for driving leads  20  and  30 . The coil  11  is interfaced with a detector  2210  that is operable to detect energy across the coil  11  and convert it to a DC value for input to a charge control circuit  2212 , which is controlled by the microprocessor  2204 , and discharges the battery  12 , the battery  12  providing power to the entire implant  10   a . Additionally, the coil  11  has an interface through a connection  2214  to a TX/RX circuit  2218  which is operable to detect received data that is interposed onto the resonant frequency of the energy transfer such that information can be received. Also, transmitted information can be the same type of signal, which is transmitted onto the coil  11 . This TX/RX signal can be transferred across the coil  11  to the respective coil  2002  or  2004  between the headset  1902  and the implants  10   a  such that the charger and TX/RX circuit  2006  in the headset  1902  can communicate with implant  10   a . It should be understood that the microprocessor  2204  can be any type of instruction based processing device or state machine and even an ASIC that is capable of executing a sequence of events that results in some charging/powering of the implant and communication therewith. 
     Referring now to  FIG. 22B , there is illustrated a block diagram of headset  1902  interfaced with the handheld device, as indicated by block  2222 . The headset includes a processor  2224  which is interfaced with a battery through a signal supply line  2226 . The processor  2224  is interfaced with a charge control circuit  2230  that drives the two coils  2002  and  2004 . The processor  2224  also controls a RX/TX circuit  2228  that is operable to communicate with the implants  10   a  by inserting a data signal onto the resonant frequency of the coils  2002  and  2004  with an AC signal that can be coupled across the skin to the coils  11  or both transmit and receive operations. The processor  2224  also interfaces with a communication interface  2234  that is operable to wirelessly communicate with the handheld device  2222 . This navigation interface can use any type of communication interface required such as Bluetooth, Bluetooth low energy, Zigbee or any type of communication protocol. This merely allows a user to interface with processor  2224  on the headset  1902  for the purpose of interfacing with the implant. This allows a surgeon, for example, after implanting the devices, to test the devices without having to actually access the leads themselves to plug into a separate controller. Thus, the implants are implanted and the incisions closed up before any attempt is made to determine the efficacy of the overall operation of the implants in any particular patient. 
     Referring now to  FIG. 23 , there is illustrated a flowchart depicting the overall operation of activating the implant after surgery. This is initiated at a Start block  2302  and then proceeds to a block  2304  wherein the headset is placed onto the patient after surgery. Thereafter, communication with the headset is effected through a handheld unit, for example, as indicated by block  2306 . The program then flows to a decision block  2308  to determine if a link with the implant can be made. Initially, the implants have batteries with a finite charge such that they are able to communicate with the headset  1902 . However, if not, the implants will charge. Once sufficient charge has been provided to the implants, a link will be made with the implant and the program will flow to a block  2310  to activate a test program. However, until the link is made, a return loop will be made back to the input of the decision block  2308  until a timeout has occurred and then an error will be indicated. Once the test program has been activated, the program flows to a decision block  2312  to determine if a confirmation has been received that the operation has occurred. This typically is feedback to the patient and in that the therapeutic relief expected by the patient has been achieved to some extent. If no confirmation has been received, the program will flow to a block  2320  in order to troubleshoot the system. In general, what might happen is that different programs would have to be implemented in order to adjust the distribution of the driving signals across the electrodes associated with the various implanted leads. 
     It will be appreciated by those skilled in the art having the benefit of this disclosure that this implantable head mounted neurostimulation system for head pain provides a unibody construction with implanted leads to cover the frontal, parietal, and occipital regions of the head. It should be understood that the drawings and detailed description herein are to be regarded in an illustrative rather than a restrictive manner, and are not intended to be limiting to the particular forms and examples disclosed. On the contrary, included are any further modifications, changes, rearrangements, substitutions, alternatives, design choices, and embodiments apparent to those of ordinary skill in the art, without departing from the spirit and scope hereof, as defined by the following claims. Thus, it is intended that the following claims be interpreted to embrace all such further modifications, changes, rearrangements, substitutions, alternatives, design choices, and embodiments.