Abstract:
A device configured for implantation beneath a patient&#39;s skin for the purpose of tissue, e.g., nerve or muscle, stimulation and/or parameter monitoring and/or data communication. Devices in accordance with the invention are comprised of a sealed housing, typically having an axial dimension of less than 60 mm and a lateral dimension of less than 6 mm, containing a power source for powering electronic circuitry within. A placement structure is shown for facilitating placement of the implantable device proximate to neural/muscular tissue.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 10/718,836, filed Nov. 21, 2003; now U.S. Pat. No. 7,450,998, issued Nov. 11, 2008, which is incorporated in its entirety by reference. 
    
    
     SUMMARY OF THE INVENTION 
     In a preferred embodiment of the present invention, a placement structure is shown for facilitating placement of an implantable device having at least two electrodes proximate to neural/muscular tissue, wherein the placement structure comprises (1) a holder having a hollow cavity formed within for holding and retaining the implantable device within; (2) at least one set of elastic wings for capturing neural/muscular tissue; and wherein the placement structure is primarily formed from a biocompatible plastic. 
     The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a side view of a battery-powered implanted device, e.g., a microstimulator, made in accordance with the present invention. 
         FIG. 2  shows a side cutaway views of an implantable ceramic tube suitable for housing the system control unit and/or microstimulators and/or microsensors and/or microtransponders. 
         FIG. 3  is a perspective view of an exemplary placement structure of the present invention which is formed for holding one of the implantable devices in close proximity to a nerve, muscle tissue, or the like. 
         FIG. 4  is a perspective view of the placement structure of  FIG. 3  having one of the placement devices held within a hollow cavity within its holder portion. 
         FIG. 5  is a perspective view of the placement structure of  FIGS. 3 and 4  showing its wings capturing neural/muscular tissue. 
         FIG. 6  is an end view of the placement structure of  FIGS. 3 and 4 . 
         FIG. 7  is an end view of the placement structure of  FIGS. 3 and 4  having hooks at the ends of its wings for providing additional means for retaining the placement structure in close proximity to the neural/muscular tissue. 
         FIG. 8  is an exemplary laparoscopic device suitable for implanting the placement structure of the present invention which in turn is holding one of the aforementioned implantable devices in close proximity to neural/muscular tissue. 
         FIG. 9  is a cross sectional view of that shown in  FIG. 8  along the line  31 - 31  where the wings of the placement structure have been folded inward toward the implantable device before insertion, e.g., via its tip, into the hollow portion of the laparoscopic device. 
         FIG. 10  is a cross sectional view of that shown in  FIG. 5  along the line  32 - 32  showing the wings of the placement structure holding neural/muscular tissue and the resulting stimulation/sensing vectors. 
         FIG. 11  is an alternative embodiment of the placement structure of  FIG. 3  wherein inner portions of the wings and the cavity include conductive layers (preferably a plurality of conductive paths) to provide additional electrical coupling between the electrodes of the implantable device axially along the neural/muscular tissue. 
         FIG. 12  is a next alternative embodiment of the placement structure of  FIG. 3  wherein inner portions of the wings and the cavity include conductive layers (preferably a plurality of conductive paths) to provide additional electrical coupling between the electrodes of the implantable device transversely across the neural/muscular tissue using a pair of wings. 
         FIG. 13  is an alternative embodiment of the placement structure of  FIG. 3  and the implantable medical device of  FIGS. 1-2  where the implantable medical device additionally includes a plurality of stimulator/sensor circuitry portions that are coupled via a plurality of electrode connectors and a plurality of conductive paths to inner portions of the wings and the cavity of the placement structure to provide stimulation to or sensing from displaced portions of the neural/muscular tissue. 
         FIG. 14  shows an alternative implementation of that which is functionally described in relation to  FIG. 13 . However, in this implementation a single, essentially U-shaped, structure having elastic wings is integrally formed which encompasses the functionality of the implantable medical device of  FIGS. 1-2  contained within the placement structure. 
         FIG. 15  shows a next alternative implementation of that which is functionally described in relation to  FIGS. 13 and 14  to the extent that it too is an integral device but it has its elastic wings  504  formed from a silicone rubber impregnated cloth that is permanently attached to the functional equivalent of the implantable medical device which was described in reference to  FIGS. 1-2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a side view of a microstimulator  100  which includes battery  104  for powering the circuitry within. The battery  104  conveniently fits within a sealed elongate housing  206  (preferably hermetically sealed) which encases the microstimulator  100 . In a preferred device  100 , the axial dimension  208  is less than 60 mm and the lateral dimension  207  is less than 6 mm. 
     For the embodiment shown in  FIG. 1 , the battery  104  is preferably housed within its own battery case  209 , with the battery terminals comprising an integral part of its case  209  (much like a conventional AA battery). Thus, the sides and left end of the battery  104  (as oriented in  FIG. 1 ) may comprise one battery terminal  210 , e.g., the negative battery terminal, and the right end of the battery  104  may comprise the other battery terminal, e.g., the positive battery terminal used as the output terminal  128 . Advantageously, because such a battery case  209  is conductive, it may serve as an electrical conductor for connecting an appropriate circuit node for the circuitry within the microstimulator  100  from one side of the battery to the other. More particularly, for the configuration shown in  FIG. 1 , the battery terminal  210  may serve as a ground point or node for all of the circuitry housed within the device housing  206 . Hence, stem  212  from the electrode  112   a  on the left end of the microstimulator  100 , which from an electrical circuit point of view is simply connected to circuit ground, may simply contact the left end of the battery  104 . Then, this same circuit ground connection is made available near or on the rim of the battery  104  on its right side, near one or more IC chips  216  (preferably implementing the device&#39;s power consuming circuitry, e.g., the controller  106  and stimulation circuitry  110 ) on the right side of battery  104  within the right end of the housing  206 . By using the conductive case  209  of the battery  104  in this manner, there is no need to try to pass or fit a separate wire or other conductor around the battery  104  to electrically connect the circuitry on the right of the device  100  with the electrode  112   a  on the left side of the device  100 . 
     The electrodes  112   a  and  112   b  for the microstimulator  100  shown in  FIG. 1  are made from iridium (electrode  112   b ) and tantalum (electrode  112   a ), and such materials inherently provide a substantial capacitance between them, thereby preventing DC current flow. See, e.g., col. 11, lines 26-33, of U.S. Pat. No. 5,324,316. 
       FIG. 2  shows a side cutaway view of the sealed housing  206 , the battery  104  and the circuitry (implemented on one or more IC chips  216  to implement electronic portions of the SCU  302 ) contained within. In this presently preferred construction, the housing  206  is comprised of an insulating ceramic tube  260  brazed onto a first end cap forming electrode  112   a  via a braze  262 . At the other end of the ceramic tube  260  is a metal ring  264  that is also brazed onto the ceramic tube  260 . The circuitry within, i.e., a capacitor  183  (used when in a microstimulator mode), battery  104 , IC chips  216 , and a spring  266  is attached to an opposing second end cap forming electrode  112   b . A drop of conductive epoxy is used to glue the capacitor  183  to the end cap  112   a  and is held in position by spring  266  as the glue takes hold. Preferably, the IC chips  216  are mounted on a circuit board  268  over which half circular longitudinal ferrite plates  270  are attached. The coil  116  is wrapped around the ferrite plates  270  and attached to IC chips  216 . A getter  272 , mounted surrounding the spring  266 , is preferably used to increase the hermeticity of the SCU  302  by absorbing water introduced therein. An exemplary getter  272  absorbs 70 times its volume in water. While holding the circuitry and the end cap  112   b  together, one can laser weld the end cap  112   b  to the ring  264 . Additionally, a platinum, iridium, or platinum-iridium disk or plate  274  is preferably welded to the end caps of the SCU  302  to minimize the impedance of the connection to the body tissue. 
       FIGS. 3-13  are directed to a placement structure  500  that is useful for placing and retaining one of the aforementioned implantable devices  100  in close proximity to a nerve, muscle tissue, or the like, i.e., neural/muscular tissue. For the purposes of this application neural/muscular tissue is understood to signify tissue that passes or responds to neural signals which includes nerve fibers or muscle tissue or any combination thereof. This structure  500  may present additional benefits, e.g., higher sensing sensitivity or lower stimulation power and thus longer battery life between chargings. The placement structure  500  is preferably comprised of two main portions: (1) a holder  502  for holding and retaining the implantable device  100  within and (2) one or more sets (e.g., pairs) of wings  504  for capturing neural/muscular tissue. Preferably, the placement structure  500  is primarily formed from of a biocompatible plastic silicone elastomer, e.g., SILASTIC®, a registered trademark of Dow Corning, that is elastic and is also an electrical insulator. In an exemplary embodiment, the holder  502  is essentially semi-circular in cross section and has a hollow cavity  506  having end plates  508  and  510  that essentially conforms to the size and shape of implantable device  100  such that the implantable device  100  may be snapped into the cavity  506  and is held by the elasticity of the holder  502  (see  FIGS. 3 and 4 ) which show the insertion of the implantable device  100  into the cavity  506  of the holder  502  of the placement structure  500 . It should be noted that while the exemplary capture device  500  is shown for holding an implantable device  100  having a circular cross section, it should be readily apparent to one of ordinary skill in the art that this exemplary structure is readily alterable to accommodate devices having non-circular cross sections as well. 
     With the implantable device  100  within the cavity  506 , the placement structure  500  may be placed in contact, e.g., snapped around, with neural/muscular  512  tissue using the elasticity of the wings  504  to capture/grab the neural/muscular tissue  512  (see  FIG. 5 , also see the cross sectional view of  FIG. 10 ). As noted in  FIGS. 6 and 7 , preferred embodiments include structures that rely upon the elasticity of the wings  504  to capture/grab the neural/muscular tissue (see  FIG. 6 ) as well as structures that include hook elements  514  that further supplement the elasticity of the wings  504  for capturing/grabbing the neural/muscular tissue  512 . 
     While a cut-down procedure may be used, it is preferred that implantable device  100  within the placement structure  500  be inserted with a hypodermic type insertion tool, e.g., an adapted laparoscopic device  516  (see  FIG. 8  and U.S. Pat. No. 6,582,441 which is incorporated herein by reference). In preparation for implantation, the wings  504  of the placement structure  500  are preferably folded inward in proximity to the implantable device  100  within holder  502  and the combination is inserted within the laparoscopic device  516  (see  FIG. 9 ). The laparoscopic device  516  is then inserted as is known in the art into the patient until the tip  518  of laparoscopic device  516  approaches the desired insertion point of the neural/muscular tissue. Upon reaching its desired insertion point, the placement structure  500  is ejected from the laparoscopic device  516  (or conversely and equivalently, the laparoscopic device  516  is withdrawn while the placement structure  500  is held at the desired insertion point) and the wings  504  elastically extend to their nominal position (see  FIG. 6 ) where they are suitable for capturing the neural/muscular tissue  512 . 
     In a first preferred embodiment  500 ′ (see  FIG. 5 ), the electrodes  112  of the implantable device  100  directly make contact with the neural/muscular tissue  512  at electrode/tissue contact points  520  and  522  (for the exemplary two electrode implantable device  100 ). Accordingly, the initial depolarization (or sensing) associated with the implantable device  100  extends axially along the neural/muscular tissue  512 . 
     In a second preferred embodiment  500 ″ (see  FIG. 11 ), the wings  504  and a portion of the cavity  506  include conductive layers  524 ,  526  (preferably comprised of a plurality of discrete conductive paths, e.g., comb shaped, slotted, or formed of serpentine paths, to reduce eddy currents and heat build up associated with the receipt of RF fields during charging). Accordingly (again referring to  FIG. 10 ), the conductive layer  524  now additionally makes contact with contact surfaces  528  and  530  (in addition to contact point  520 ) and thus there are now three contact point areas associated with each electrode  112  and thus current flow within the neural/muscular tissue  512  may be increased without increasing the compliance voltage since there will now be a lower resistance between the electrodes  112  and the neural/muscular tissue  512 . 
     In a third preferred embodiment  500 ′″ (see  FIG. 13 ), the initial depolarization (or sensing) is applied transversely to the neural/muscular tissue  512  through a single pair of wings  504 . In this embodiment, the distal end  532  of the capture device  500 ′″ is a boot type structure  534  that is suitable for capturing distal electrode  112   b  of the implantable device  100 . Within the boot type structure  534 , a conductive layer  536  (preferably a plurality of paths, e.g., slotted, to reduce eddy circuits, as previously described) electrically connect the distal electrode  112   b  of the implantable device  100  along pathway  538  to first proximal wing  504 ′ at the proximal end  540  of the capture device  500 ′″. Preferably, wing  504 ′ is longer/wider than the proximal electrode  112   a  so that electrical pathway  538  and its associated conductive layers  536  and  542  do not make contact with the proximal electrode  112   a . Conductive layer  546  extends from within the cavity  506  at the proximal end  540  to the inner surface of second proximal wing  504 ″. Accordingly, once inserted, the distal electrode  112   b  is electrically coupled to first proximal wing  504 ′ and the proximal electrode  112   a  is electrically coupled to the second proximal wing  504 ″. Once the placement structure  500 ′″ is used to capture the neural/muscular tissue  512 , stimulation vectors  548  and  550  are applied transversely to the tissue  512  (see  FIG. 10 ). Alternatively, the electrical pathways associated with second proximal wing  504 ″ may be omitted, in which case only stimulation vector  550  is present. (Note, the polarity of the stimulation vector is only shown for exemplary purposes and may be reversed as needed. Furthermore, the use of the term stimulation vector is equally applicable to describe the vector for sensing a neural/muscular signal, i.e., a sensor or stimulation/sensor vector.) 
     In the third preferred embodiment  500 ′″, the implantable device  100  is inserted into the capture device  500 ′″ by first inserting the distal end, i.e., electrode  112   b , of the implantable device  100  into the boot type structure  534  of the placement structure  500 ′″ and then pressing the proximal end, i.e., electrode  112   a , of the implantable device  100  into the proximal end  540  of the placement structure  500 ′″. This differs from the other two embodiments where both ends of the implantable device  100  are preferably inserted concurrently into the placement structure. 
     Notably, in the third preferred embodiment, there is only one set of wings, i.e., first and second proximal wings  504 ′ and  504 ″. Accordingly, during implantation, only a single pair of wings needs to capture the neural/muscular tissue  512  and thus implantation is simplified. 
       FIG. 13  is an alternative embodiment  500 ′″ of the placement structure of  FIG. 3  and the implantable medical device of  FIGS. 1 and 2  wherein the implantable medical device  100 ″ additionally includes a plurality of stimulator/sensor circuitry portions  560  (e.g.,  560   a - 560   n ) that are coupled to inner portions of the wings  504  via electrode connectors  562 ,  564  on the outer surface of the implantable medical device  100 ″ and the cavity of the placement structure  500 ′″ includes a plurality of conductive paths to provide electrical coupling between the electrode connectors  562 ,  564  of the implantable device  100 ″ to electrodes  567 ,  569  within the wings  504  for coupling to displaced portions of the neural/muscular tissue. In this embodiment, the implantable medical device  100 ″ includes a plurality of stimulator/sensor circuitry portions  560 . 
     To facilitate use of these functions, the implantable medical device  100 ″ may include a plurality of electrode connectors (preferably semicircular rings)  562 ,  564  which are coupled to the stimulator/sensor circuitry portions  560 . Lower portions of these rings  562 ,  564  are respectively coupled to the placement structure  500 ′″ when the implantable medical device  100 ″ is located within the placement structure  500 ′″ to contact electrical pathways  566 ,  568 . Upper portions of these rings/electrodes  562 ,  564  may make direct contact with the neural/muscular tissue after implantation. These functions may be further facilitated by the placement of electrodes  567 ,  569  within the wings  504  that have displaced locations within the wings and, in operation, are distributed around the neural/muscular tissue. Preferably, upper portions of the electrical pathways that would otherwise contact the neural/muscular tissue are coated with an insulation layer  570  (not shown) with the exception of the portions corresponding to electrodes  567 ,  569  to allow the electrodes  567 ,  569  to perform current steering. 
       FIG. 14  shows an alternative implementation of that which was functionally described in relation to  FIG. 13 . However, in this implementation a single, essentially U-shaped, structure  600  having elastic wings  504  is integrally formed which encompasses the functionality of the implantable medical device  100 ″ contained within the placement structure  500 ′″. In this single integral structure  600 , a plurality of electrodes  602 ,  604 ,  606  (e.g.,  602   a - 602   n ,  604   a - 604   n ,  606   a - 606   n ) are distributed (and preferably individually driven by circuitry portions  560  contained within the U-shaped structure  600  along with other circuitry as described in reference to  FIG. 3A ) within the inner U-shaped cavity  608  of structure  600 . 
       FIG. 15  shows a next alternative implementation of an integral device  650  similar to that shown in  FIG. 14  to the extent that it too is an integral device but in this case it has its elastic wings  504  formed from a silicone rubber impregnated cloth that is permanently attached to the functional equivalent of the implantable medical device  100 ″ described in reference to  FIG. 13 . In most other aspects, this embodiment is functionally equivalent to that which has been previously described. 
     While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention. For example, while not expressly shown, the hook portions shown and described in reference to  FIG. 7  are equally applicable to the embodiments of  FIGS. 14 and 15 . It is therefore to be understood that within the scope of the claims, the invention may be practiced otherwise than as specifically described herein.