Abstract:
A neuromodulation system, comprises an implantable electrode which is implanted within a body adjacent to a target nerve structure to which electric energy is to be applied via the electrode and a connection port which is implanted in the body with a proximal surface thereof substantially flush with an outer surface of a skin of the body, the connection port including a device interface for electrically connecting to an external device which remains external to the body in combination with an electric line extending from the device interface to the electrode for carrying electric energy from the external device to the electrode and a cover selectively closing an opening of the external surface of the implanted connection port.

Description:
BACKGROUND INFORMATION 
   Many debilitating medical conditions may be alleviated by stimulating targeted nerves and muscles. For example, electric current may be applied to a nerve or bundle of nerves to disrupt signals carried by, or to affect muscles controlled by, those nerves. Common examples of neural stimulation devices include cardiac pacemakers, devices to control epilepsy and chronic pain, etc. 
   In conventional applications, the ability of neuromodulation systems to operate over extended periods of time is limited by the endurance of their power supplies (e.g., batteries). This approach works well for devices used for short time periods, but can be problematic for devices which must operate beyond the life span of the batteries. For such devices, additional surgery may be necessary to replace the worn batteries. Alternatively, an external power supply carried by the patient may be connected to the implanted device by wires or other connections to provide a long lasting, constant power supply. However, the wires penetrating the skin increase the likelihood of infection and other negative reactions at the location where the connections penetrate the skin. 
   The size of components of conventional implanted neuromodulation systems often causes discomfort and may reduce a patient&#39;s ability to carry out routine tasks. In addition, the cost of such implanted devices (e.g., implanted pulse generators) may be significant. Implanted pulse generators also have a limited life span, usually around 5 to 10 years, after which they must be replaced. As with batteries, this may involve additional surgery with the associated discomfort and costs. It may also be extremely difficult to perform upgrades or repairs to conventional, implanted pulse generators due to the same concerns described above. 
   SUMMARY OF THE INVENTION 
   In one aspect, the present invention is directed to a neuromodulation system, comprising an implantable electrode which is implanted within a body adjacent to a target nerve structure to which electric energy is to be applied via the electrode and a connection port which is implanted in the body with a proximal surface thereof substantially flush with an outer surface of a skin of the body, the connection port including a device interface for electrically connecting to an external device which remains external to the body in combination with an electric line extending from the device interface to the electrode for carrying electric energy from the external device to the electrode and a cover selectively closing an opening of the external surface of the implanted connection port. 
   In a further aspect, the present invention is directed to a method for neuromodulation therapy, comprising surgically implanting an electrode adjacent to a target nerve structure and implanting a connection port including a housing which, when implanted, lies beneath a surface of the skin, the housing defining an opening to a surgically created opening in the skin, the connection port including a device interface for electrically coupling to an external device and a cover selectively sealing the opening in combination with forming a tunnel between the incision site and the implanted connection port and passing an electric line though the tunnel to connect the device interface and the electrode. A connector of an external medical device is inserted through the opening and coupled to the device interface electric current is applied from the external device to the electrode via the device interface and the electric line. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  shows a diagram of a neuromodulation system with external pulse generator according to an embodiment of the present invention; 
       FIG. 2  shows a diagram of a passive valve used in a connector for a neuromodulation system according to the present invention; and 
       FIG. 3  shows a diagram of another passive valve used in a connector for a neuromodulation system according to the present invention. 
   

   DETAILED DESCRIPTION 
   The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates to devices used to block nerve signals and to stimulate selected nerves. In particular, the present invention relates to nerve stimulation devices comprising a first implanted portion and a second external portion connected to the implanted portion through an implanted connection port. 
   As described above, a variety of medical disorders are now treated via neuromodulation (i.e., the application of electrical stimuli to a targeted nerve or bundle of nerves). The stimulation may be designed to interfere with the electrical activity of the target nerves by blocking it, or by applying different electrical signals to the nerve(s). As would be understood by those skilled in the art, such procedures may be employed to treat a variety of ailments including, for example, movement disorders such as Parkinson&#39;s disease and Multiple Sclerosis, epilepsy, chronic pain, stroke, Alzheimer&#39;s disease, head injuries, spinal chord injuries, Hydrocephalus, obesity, urinary urge incontinence, fecal incontinence, interstitial cystitis, chronic pelvic pain and psychological disorders such as depression. Depending on the condition being treated, different stimuli may be applied to the target nerve(s). However, in general, the hardware components used are substantially similar. 
   The treatment of urinary urge incontinence, for example, often involves the implantation of a bulky and expensive Pulse Generator (IPG). The IPG generates electrical pulses the intensity and duration of which are tailored to supply desired signals to the nerves connected to specific muscles. IPG&#39;s have a finite life of about 5 to 10 years after which they must be replaced through invasive surgery. One example of an IPG for treating urinary urge incontinence is the Interstim device, available from the Medtronic Corporation. 
   To reduce the costs of neuromodulation treatment, a system according to the present invention utilizes external components in place of several of the implanted components of prior systems. This approach reduces patient discomfort and eliminates additional surgery for replacing or updating most of the system components. In these systems, a lead and electrodes are implanted with the electrodes in contact with, or in proximity to, the target nerve(s). A connection port is implanted at a convenient location (e.g., in proximity to the lead or a selected distance therefrom with an extension connecting the lead to the implanted connection port). The bulkier and more expensive components of these systems (e.g., the pulse generator) remain external and are connected to the implanted components via the implanted connection port. 
   The embodiments of the present invention describe a neuromodulation system utilizing an implanted connection port to facilitate neuromodulation and/or neurostimulation procedures, eliminating the need for an IPG (or other large device) by allowing connection between the electrodes and external devices via the implanted port. The port may be placed substantially even with a level of the skin and may include a housing which extends a small distance below the skin level. The port is connected to a lead with electrodes which interface with a targeted nerve structure (e.g., a nerve, nerve bundle or nerve junction) to allow external devices to be connected to the electrode leads for the application of various therapeutic signals (e.g., test stimulation signals and/or predetermined neuromodulation signals) to the target nerve structure. The external devices which can be connected to the implanted connection port include, but are not limited to, Test Stimulators, Programmers and Pulse Generators. These devices may be hand held, table top mounted, or may be wearable by the patient to enhance patient mobility. 
   Using a connection port at the skin level to couple one or more external components (e.g., a pulse generator) to electrodes greatly reduces the cost of the implant. Both the implantation and subsequent care and maintenance of the system are simplified decreasing discomfort and reducing the risks and costs associated with surgery. The system also increases flexibility in selecting treatment options, and frees the patient to select between a larger number of physical locations at which the treatment may be performed. The connection port according to the invention allows the connection of a table top pulse generator located, for example, at a physician&#39;s office, a hospital, or in the patient&#39;s home. Hand held devices or other portable devices may then be employed at any time and/or place desired by the patient or physician. In addition, a patient wearable external device may be placed on a belt, a wristband or carried in a pocket. 
     FIG. 1  shows an exemplary embodiment of a neuromodulation system  100  according to the invention, which includes an implantable connection port  102 . The system  100  is designed to stimulate a target nerve structure  122  with electrical impulses. According to embodiments of the invention, the implanted connection port  102  is used to connect one or more external components of the system  100 , for example a pulse generator or programmer  116 , to an implanted extension  112  coupled to a lead  113  extending to electrodes  114  which are coupled to a distal end thereof. In many cases, the electrodes  114  will be positioned adjacent to the target nerve structure  122  with the lead  113  extending therefrom to a proximal end connected to the implanted connection port  102  either directly or via the extension  112 . In many cases, the distance between the implanted connection port  102  and the electrodes  114  will be minimized. However, when longer distances are necessary to simplify the surgical procedure and/or to enhance patient comfort, an extension  112  with an extension connector  110  may be coupled to the proximal end of the lead  113  to span the distance between the implanted connection port  102  and the target nerve structure  122 , as shown in  FIG. 1 . 
   According to the exemplary embodiment shown in  FIG. 1 , the implanted connection port  102  comprises a housing  104  that is placed below the skin layer  120 . A connection jack  108  is mounted within the housing  104  connected to the extension cable  112  that extends out of the housing  104  to the extension connector  110  which is connected to the lead  113  and the electrodes  114 . The lead  113 , the electrodes  114 , the extension cable  112  and the connector  110  are positioned by tunneling to the electrode implant site and feeding the electrodes  114 , the lead  113 , the connector  110  and the extension cable  112  through the surgical tunnel until the electrodes  114  reach the electrode implant site while the proximal end of the extension cable  112  extends to the connection jack  108  in the implanted connection port  102 . Those skilled in the art will understand that the extension cable  112  may be provided in different lengths to accommodate different distances between the site of the port  102  and the electrode implant site and that the extension cable may be connected directly to the lead  113  without the extension connector  110 . During assembly of the implanted connection port  102 , the extension cable  112  may be passed through an opening  109  of the housing  104 , and connected to the connection jack  108  which may then be sealingly fixed to the housing  104 .  FIG. 1  shows one pair of electrodes. it is understood that multiple pairs can be employed to increase the likelihood of stimulating the correct site, or to selectively activate electrodes to maximize treatment on an ongoing basis (for example if lead migration occurs). 
   According to the exemplary embodiment of the invention, the housing  104  of the implanted connection port  102  comprises a passive elastomeric valve  126  covering an external portion of the housing  104 . More specifically, the housing  104  comprises a cover  106  which covers an entire outward facing opening of the housing  102 . The cover  106  preferably includes the passive elastomeric valve  126  over a portion thereof. In one embodiment, the passive elastomeric valve  126  comprises a disk made from an elastomer, such as silicon, C-Flex, latex, etc., with one or more slits cut thereinto. These slits are biased to a closed position by the elastomeric material. However, as would be understood by those skilled in the art, these slits may be easily opened by pushing an electrical connector or other component therethrough to enter the housing  102  and connect to the connection jack  108 . The cover  106  and the passive valve  126  prevent contaminants such as dirt, fluids, bacteria etc. from entering the housing  104 . At the same time, the passive valve  126  facilitates insertion of an electrical lead, such as a connector  118  of a pulse generator  116 , into the housing  104 , so that it may be mated to the connection jack  108 . The connection jack  108  may, for example, be a standard phone jack configured to receive an electrical connector such as a shrouded multi-conductor phone connector. However, those skilled in the art will understand that any of a variety of known or custom connection jacks may be used for the connection jack  108  so long as it is configured to receive the connector of the device(s) which are to be connected to the electrodes  114 . Those skilled in the art will understand that the slits may take on any of a variety of shapes extending along portions of one or more curves, tricuspid shapes, etc. 
     FIG. 2  shows an exemplary embodiment of a cover  206  with a passive elastomeric valve  208 , according to the invention. The valve  208  is formed of a thin (0.005″-0.100″) elastomeric membrane  212  with a slit  210  cut therethrough. The dimensions of the membrane  212  and of the slit  210  may be adjusted to obtain the desired closing force which retains the valve normally closed, and may vary depending on the material forming the valve  208 .  FIG. 3  shows an alternative exemplary embodiment of a cover  306  according to the invention. Here, the cover  306  has a passive elastomeric valve  308  formed of a membrane  312  with a pair of slits  310  arranged in a cruciform pattern. The slits  310  preferably have a size and shape optimized for insertion of an electrical contact therethrough with a natural shape of the membrane  308  urging the and to retain the valve  308  closed in normal operation, when the electrical contact is removed. 
   In a different embodiment according to the invention, the cover  106 ,  206  and  306  of the housing  104  may be replaced by a simple removable cap. In this manner, the additional expense of manufacturing a passive valve is eliminated. For example, the removable cap may be removed to permit insertion of the connector  118  into the housing  104 . When the connector  118  is not in use, the housing  104  is closed by replacing the cap. In a different exemplary embodiment, the connector  112  and the connector jack  108  are formed integrally with the housing  104 . In this case, the implanted connection port  102  may preferably be provided with extension cables  112  of different lengths to suit a variety of applications. In addition, the extension cables  112  and other component of the system  100  may preferably be coated with an antimicrobial compound, to prevent infection. 
   During an exemplary procedure for implanting a neurostimulation system according to the present invention, an incision is made and the electrodes  114  are placed adjacent to the target nerve structure  122 . A tunnel is then surgically formed between the site at which the electrodes  114  are implanted and the site at which the implanted connection port  102  is to be placed with the lead  113  extending into the tunnel toward the site of at which the connection port  102  is to be implanted. In some cases, these two locations are substantially the same, and tunneling is not necessary. A temporary sheath may be left behind in the tunnel site, so that the extension cable  112  can later be fed through the sheath to be joined to the proximal end of the lead  113 . As would be understood by those skilled in the art, the extension cable  112  may be made available in different lengths to accommodate different tunneling distances. After the extension cable  112  has been positioned, the sheath is removed over the cable, and the extension cable  112  is mated to the lead  113  via the extension connector  110 . The incision at the site of the implantation of the electrodes  114  may then be closed and the implanted connection port  102  is fixed to the skin using conventional methods as would be understood by those skilled in the art. 
   A test stimulation of the target nerve structure  122  may then be performed to verify the appropriate response prior to final implantation. After the surgical aspects of the procedure have been completed, the implanted connection port  102  is used to connect external components to the electrodes  114  via the lead  113 . For example, the connector  118  of a pulse generator  116  may be inserted into the housing  104  through the passive elastomeric valve  126  and connected to the connection jack  108 . As would be understood by those skilled in the art, various therapeutical stimuli may then be delivered directly to the target nerve structure  122  based on, for example, a schedule selected by medical personnel programmed into the pulse generator  116 . 
   The present invention has been described with reference to specific exemplary embodiments. Those skilled in the art will understand that changes may be made in details, particularly in matters of shape, size, material and arrangement of parts. Accordingly, various modifications and changes may be made to the embodiments. For example, the location of the implanted components of the system may be varied to reflect the location of the nerves and muscles that are to be stimulated. Additional or fewer components may be located external to the body of the patient, depending on the condition that is being treated using the neurostimulation system. The specifications and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.