Abstract:
An electrical stimulation apparatus for providing a unipolar electrical field over a targeted area, which includes an elongated flexible lead body having opposed proximal and distal end portions, the proximal end portion of the lead body including a connector for operative connection with a pulse generator, and an electrode assembly connected with the distal end portion of the lead body and electrically connected to the connector. The electrode assembly includes a paddle member having defining a plurality of corner sections. Suture sites located on the paddle member for anchoring the paddle member at an implantation site adjacent a targeted area, and a plurality of electrodes supported on the paddle member and connected to the lead body, wherein each corner section of the paddle member supports a respective one of the plurality of electrodes so as to define an electrode array for generating a unipolar electrical field at the targeted area.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of priority to U.S. Provisional Patent Application No. 60/674,874, filed Apr. 26, 2005, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The subject technology pertains to an electrical stimulation device that includes a stimulation apparatus used to generate an even electrical field on a targeted area, and more particularly, to a stimulation apparatus that is adpated and condigured to be implanted in the brain area to provide long-term stimulation without migration.  
         [0004]     2. Background of the Related Art  
         [0005]     The effect of electrical stimulation on the central nervous system (CNS) has been investigated for many years. Early on, electrical stimulation was used to map specific functional areas of the brain, such as motor and language. However, electrical stimulation is currently achieving more success for therapeutic purposes. For example, electrical stimulation is known to improve neural connectivity and help restore function from movement disorders, epilepsy, intractable psychiatric disorders, stroke and coma. Electrical activation or inhibition for CNS disorders is applicable to virtually any brain or spinal cord dysfunction. Accordingly, many devices have been developed to meet the necessity of these types of treatment. However, when stimulation assemblies, and particularly paddle shaped electrodes, are implanted in the brain area, the connecting lead associated therwith typically extends posteriorly from the cranial opening, behind the ear to the anterior chest. Consequently, the connecting lead can become undesirably kinked or distorted.  
         [0006]     Recently, the generation of an electrical field near a targeted area of the brain has been suggested to beneficially treat CNS disorders by other mechanisms. Electrical stimulation can inhibit the “neurogenic inflammation” which develops in the early period of cerebral infarction. Inhibition of the macrophage infiltration may diminish the zone of apoptosis due to cerebral infarction, thus reducing the post-infarction sequelae and improving the quality of life. Unipolar stimulation is known to be better than bipolar stimulation in this situation, since cerebral infarction usually affects a deeper portion of the brain. It would be benficial therefore, to provide a unipolar electical stimulation device having a paddle shaped electrode adpated to be implanted in such a manner so as to provide an evenly distributed unipolar elecrical field to a targeted area located deep within the brain of a patient, which that will overcome the deficiencies of the prior art.  
       SUMMARY OF THE INVENTION  
       [0007]     In view of the above, there is a need for an electrode that can be easily implanted and provide an even, unipolar field deep into a targeted area.  
         [0008]     It is an object to implant an electrode that provides an even electrical field over a wider area of the brain with a unipolar electrical field. It is another object to provide an electrode that does not migrate from the targeted area during long-term stimulation.  
         [0009]     It is an object of the subject technology to generate a unipolar electrical field deep inside of the brain for attracting oppositely charged implanted cells. It is still another object to provide an electrode that is easily implanted.  
         [0010]     The present invention is directed to an electrical stimulation apparatus for providing a unipolar electrical field over a targeted area. The electrical stimulation apparatus includes an elongated flexible lead body having opposed proximal and distal end portions, the proximal end portion of the lead body including a connector for operative connection with a pulse generator and an electrode assembly operatively associated with the distal end portion of the lead body and electrically connected to the connector. The electrode assembly includes a generally planar paddle member having defining a plurality of corner sections, at least one suture site located on the paddle member for anchoring the paddle member at an implantation site adjacent a targeted area and a plurality of electrodes supported on the paddle member and operatively connected to the lead body, wherein each corner section of the paddle member supports a respective one of the plurality of electrodes so as to define an electrode array for generating a unipolar electrical field over the targeted area.  
         [0011]     In another embodiment, the subject technology is directed to an electrical stimulation apparatus for providing a unipolar electrical field over a targeted area of the brain, including an elongated flexible lead body having opposed proximal and distal end portions, a connector operatively associated with the proximal end portion of the lead body for operative connection with an implanted pulse generator and an electrode assembly operatively associated with the distal end portion of the lead body and electrically connected to the connector. The electrode assembly includes a generally polygonal paddle member defining a plurality of corner sections, a suture site located at each corner section for securing the paddle member at an implantation site adjacent a targeted area of the brain and an electrode disposed at each corner section of the paddle member so as to define an electrode array for generating a unipolar electrical field over the targeted area. The electrical stimulation apparatus also includes conductor means extending through the lead body for electrically connecting the electrodes of the electrode assembly to the connector.  
         [0012]     In another embodiment, the subject technology is directed to and electrical stimulation apparatus for providing a unipolar electrical field over a targeted area of the brain, including an elongated flexible lead body having opposed proximal and distal end portions, a connector operatively associated with the proximal end portion of the lead body for operative connection with an implanted pulse generator, and an electrode assembly operatively associated with the distal end portion of the lead body and electrically connected to the connector. The electrode assembly includes a generally square paddle member defining four corner sections, a suture aperture located at each corner section for securing the paddle member at an implantation site adjacent a targeted area of the brain and an electrode disposed at each corner section of the paddle member so as to define an electrode array for generating a unipolar electrical field over the targeted area. The electrical stimulation apparatus also includes a conductor means extending through the lead body for electrically connecting the electrodes of the electrode assembly to the connector.  
         [0013]     It should be appreciated that the present invention can be implemented and utilized in numerous ways, including without limitation as a process, an apparatus, a system, a device, a method for applications now known and later developed. These and other unique features of the system disclosed herein will become more readily apparent from the following description and the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     So that those having ordinary skill in the art to which the disclosed system appertains will more readily understand how to make and use the same, reference may be had to the drawings as follows.  
         [0015]      FIG. 1  shows a partial cross-sectional side view of a patient with a stimulation apparatus implanted in the cranial openings, connected to a pulse generator in accordance with the subject technology.  
         [0016]      FIG. 2  shows a top view of polygonal shaped stimulation apparatus of  FIG. 1  including a 5-electrode array, apertures in three corners, and a connecting lead.  
         [0017]      FIG. 3  shows a side view of stimulation apparatus shown in  FIG. 1 .  
         [0018]      FIG. 4  shows a magnified view of  FIG. 3 , highlighting the stimulation apparatus fixed with dura.  
         [0019]      FIG. 5  shows the generation of electrical field from the surface to a deeper portion of the target brain in accordance with the subject technology. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0020]     The present invention overcomes many of the prior art problems associated with stimulating brain tissue. The advantages, and other features of the systems and methods disclosed herein, will become more readily apparent to those having ordinary skill in the art from the following detailed description of certain preferred embodiments taken in conjunction with the drawings which set forth representative embodiments of the present invention and wherein like reference numerals identify similar structural elements.  
         [0021]     In breif overview, a stimulation apparatus is provided for treating CNS disorders, for which generation of an electrical field can be applied. Generation of an electrical field can be an important mechanism to restore the lost function of CNS. Some examplary situations for beneficial use of this electrical field generation include, but are not limited to, the acute destructive disorders where inhibition of “neurogenic inflammation” is required; chronic destructive disorders where implantation of stem cell is required; and some disorders where neuromodulation is required. Further, an electrical field may be applied to CNS damage from origins as varied as congenital, traumatic, degenerative, coma, psychiatric disorders such as depression and epilepsy, central pain syndromes, stroke and the like.  
         [0022]     The stimulation apparatus can be implanted epidurally and subdurally. For example, a craniotomy may be required to subdurally implant the stimulation apparatus. Location is dependent on the nature of the disease and the treatment desired. For instance in alleviating central pain, the stimulation apparatus is implanted over the motor cortex. For neocortical epilepsy, the stimulation apparatus is implanted over the presumed epeileptogenic area. For damaged brain, the stimulation apparatus is implanted over the surrounding compensatory area.  
       The Stimulation Apparatus  
       [0023]     Referring now to  FIG. 1 , a stimulation apparatus is designed for generating an electrical field in a targeted area of the brain and referred to generally by the reference numeral  10 . The stimulation apparatus  10  includes an electrode assembly  12  for implantation in the target area. A connecting lead  14  passes from a corner of the electrode assembly  12  and provides power and passes necessary electrical signals from a pulse generator  16  to the electrode assembly  12 . As such, the pulse generator  16  can be implanted in a plurality of locations, preferably the chest area.  
         [0024]     The electrode assembly  12  has a polygonal configuration as to be easily adjusted along the curve from a cranial opening to the location of the pulse generator  16 , usually the anterior chest. The generally planar, polygonal shape (square as shown) is designed such that the electrode assembly  12  is easily inserted inside a cranial opening. The connecting lead  14  is blended into a corner to prevent kinking. Further, the polygonal shape yields improved coverage of the functional compartment of the brain, as most functional compartments are divided by gyrus and sulcus running horizontally or vertically. By trailing the lead  14  to a corner of the electrode assembly  12 , the surgeon has flexibility with the lead  14  to move to a desired direction with less strain while the electrode assembly  12  is adjusted to the shape of each functional compartment.  
         [0025]     Referring now to  FIGS. 2 and 3 , top and side detailed views, respectively, of the stimulation apparatus  10  are shown. The connecting lead  14  has a distal end  18  adapted for connection to the electrode assembly  12  and a proximal end  20  having a standard connector  36  adapted for connection to the pulse generator  16 . The electrode assembly  12  has a first corner  22  connected to the distal end  18  of the lead. The electrode assembly  12  is blended into the connecting lead  14  with consideration of the durable resistance against an unexpected force. The electrode assembly  12  has three additional corners  24  for anchoring the electrode assembly  12  in place. Each corner  24  has a suture site such as a hook or fabric that can be pierced. Preferably, each corner  24  defines an aperture  26  sized and configured for epidural fixation. Thus, after implanting the electrode assembly  12 , migration is prevented during long-term stimulation.  
         [0026]     Five electrodes  28  mount on the electrode assembly  12  and operatively connect to the lead  14 . Four electrodes  28  of the five electrodes  28  are mounted near the corners  22 ,  24 , respectively, and the fifth electrode  28  is substantially centrally mounted on the electrode assembly  12 . The fifth, cental electrode  28  is positioned to supplement a “blank” area of the electrical field in order that an even electrical field is acheived. Each electrode  28  is connected to the other with wires (not shown). Thus, when the electrodes  28  receive an electrical signal from the pulse generator  16 , the electrodes  28  generate a positive or a negative electric field. In one embodiment, each electrode  28  is an annular ring electrode.  
         [0027]     It is envisioned that various polygons may form a plurality of corners and central locations that may receive electrodes and suture sites. More or fewer electrodes  28  could be utilized in a variety of arrangements. For example, the number of electrodes  28  may be increased and/or electrodes  28  may be utilized intermediate the corners and centrally to achieve a stronger or more even electrical field. Additionally, the size of the electrode assembly  12  may be increased or decreased to suit a particular application. For example, if the size of the electrode assembly  12  is increased, a concomitant increase of electrodes  28  can be considered with a similar configuration. The electrode assembly may be a polygon of three or more sides, which may be regular or irregular in configuration. The polygon may also include one or more portions that are not linear. As a result, the various polygons can be used to facilitate implantation and tailor the shape of the field generated thereby. In one embodiment configured as shown in the figures, the width of the paddle is about 2 cm and a thickness  30  of the paddle is about 1.15 cm. The diameter of the fixing apertures  26  is about 0.25 cm. Preferably, but without limitation, the diameter of the electrode varies between 2 mm to 8 mm, the width of the paddle varies from 2 cm to 4 cm, the thickness varies from about 0.75 mm to 1.5 cm and the diameter of the fixing apertures varies from 0.25 mm to 1.5 mm although any desirable configuration could be a achieved by one of ordinary skill in the pertinent art.  
       Implantation and Use of the Stimulation Apparatus  
       [0028]     Referring now to  FIGS. 4 and 5 , the stimulation apparatus  10  is shown implanted and in use, respectively. The stimulation apparatus  10  may be used with any kind of implantable pulse generator and the pulse generator  16  is preferably located in the anterior chest. To implant the electrode assembly  12 , a target site of the brain is determined according to the extent of the damage in the target area of the brain, the purpose of the treatment, and the mechanism by which a lost brain function may be restored. Exemplary situations are: for chronic central damage, when the electrode assembly  12  is usually located in the motor cortex; for chronic intractable neocortical epilepsy, where the epileptogenic area must be figured out by other methods such as magnetic resonance imaging and/or invasive recording; for damaged brain to be treated with stem cells when the electrode assembly  12  is located over the center of damage where stem cells are collected; and for neurogenic inflammation when the electrode assembly  12  is placed in the periphery of the lesion.  
         [0029]     Once the target is determined, a patient is anesthetized, locally or generally. A surgeon cuts about a 6×6 cm portion of scalp and reflects the cut portion down. One burr hole is made in the postero-inferior point of the presumed craniotomy. Bone flap is made in a square fashion using a bone saw. The electrode assembly  12  is place epidurally or subdurally over the target sites of the brain. The electrode assembly  12  is fixed to dura with silk using the fixing apertures  26 . Bone flap is replaced and fixed with the connecting lead  14  passing through the burr hole without any strain. The connecting lead  14  is passed subcutaneously to the anterior chest and connected to the pulse generator  16 . As shown in  FIG. 5 , upon subsequent pulses being sent from the pulse generator  16  to the electrode assembly  12 , an electrical field  32  is generated within the brain  34 .  
         [0030]     Stem cell therapy is increasingly gaining attention for the treatment of CNS disorders. Stem cells are implanted locally in the lesioned area or introduced in the veins. However, one of the challenges to delivering stem cells is that a number of cells are not easily settled in a target lesion area. To facilitate the settlement, the subject electrode  10  can be used to generate a positively-charged electrical field over the targeted area. The positively-charged electrical field helps to collect and stabilize electrically charged stem cells thereto resulting in improved settlement.  
         [0031]     The aforedescribed electrode can be of two types, unipolar or bipolar as would be known to those of ordinary skill in the pertinent art. As is known in the bipolar type, two electrodes are present and a pulse is applied between them. In the unipolar type, each electrode and the body saline solution and/or body tissue, which are electrically conductive, provide the return electric path between the electrode and an outer plate, which is electrically connected to the associated circuitry. One example of a prior art unipolar electrode is described in U.S. Pat. No. 3,735,766, which is incorporated herein by reference.  
         [0032]     Unless otherwise specified, the illustrated embodiments can be understood as providing exemplary features of varying detail of certain embodiments, and therefore, unless otherwise specified, features, components, modules, elements, and/or aspects of the illustrations can be otherwise combined, interconnected, sequenced, separated, interchanged, positioned, and/or rearranged without materially departing from the disclosed systems or methods. Additionally, the shapes and sizes of components are also exemplary and unless otherwise specified, can be altered without materially affecting or limiting the disclosed technology.  
         [0033]     While the invention has been described with respect to preferred embodiments, those skilled in the art will readily appreciate that various changes and/or modifications can be made to the invention without departing from the spirit or scope of the invention as defined by the appended claims.