Patent Description:
Implantable medical devices may be configured to deliver electrical stimulation therapy or monitor physiological signals. Electrical stimulation of nerve tissue, for example, may provide relief for a variety of disorders thereby improving the quality of life for many patients.

Some implantable medical devices (IMDs) may employ electrical leads that carry electrodes. For example, electrodes may be located at a distal portion of an elongate lead. Other examples of electrical leads may be relatively short, having one or more electrodes located along a body of the lead. Such electrical leads are provided separate from the housing or body of the IMD and coupled to the IMD during implantation to provide stimulation via the electrode at a location separated from the housing of the IMD.

Simulation of different nerve branches and clusters have been explored for treating various ailments. One avenue that has shown promising development has been the stimulation of the tibial nerve for the treatment of certain ailments such as incontinence or over-active bladder.

Document <CIT> discloses an implantable stimulator for treating urinary incontinence comprising two leadless electrodes.

The invention is defined by the device of independent claim <NUM> and by the method of independent claim <NUM>. Embodiments of the present disclosure are directed to minimally invasive, leadless neurostimulation devices. Leadless devices do not require the use of a separate lead and instead provide a unitary structured device that may be more robust and less invasive than lead-based counterpart devices.

The disclosed devices include a housing containing components therein configured for delivering neurostimulation therapy, and an attached header unit. The header unit includes one or more primary electrodes that form a portion of the exterior and side of the header unit. The one or more primary electrodes are electrically insulated from other portions of the exterior surface of the neurostimulation device. The housing of the neurostimulation device includes a secondary electrode that operates in conjunction with the one or more primary electrodes to provide electrical simulation therapy or neuro sensing capabilities. The secondary electrode is positioned on the same side of the device as the one or more primary electrodes positioned in the header unit.

In an embodiment, the disclosure describes system including a leadless neurostimulation device including a header unit having at least one primary electrode having a contact surface that defines an external surface on a side of the leadless neurostimulation device, an outer housing that forms a side of the header unit opposite of the contact surface of the primary electrode, and a dielectric mount that receives at least a portion of the at least one primary electrode and at least partially surrounds the at least one primary electrode, the dielectric mount being configured to electrically insulate the at least one primary electrode from the outer housing, the dielectric mount being received and fixed within a recessed portion of the outer housing, and a housing having a secondary electrode positioned on the same side of the leadless neurostimulation device as the at least one primary electrode, the at least one primary electrode and the secondary electrode being configured to transmit an electrical stimulation signal therebetween to provide electrical stimulation therapy to a tibial nerve of a patient.

In an embodiment, the disclosure describes a leadless neurostimulation device comprising a header unit comprising at least one primary electrode having a contact surface that defines an external surface on a side of the leadless neurostimulation device, an outer housing that forms a side of the header unit opposite of the contact surface of the primary electrode, and a dielectric mount that receives at least a portion of the at least one primary electrode and at least partially surrounds the at least one primary electrode, the dielectric mount being configured to electrically insulate the at least one primary electrode from the outer housing, the dielectric mount being received and fixed within a recessed portion of the outer housing, wherein the dielectric mount defines a channel between the outer housing and the dielectric mount, the channel configured to receive a medical adhesive therein to fix the outer housing to the dielectric mount, and wherein the primary electrode comprises an interior surface that defines an interlocking structure with the dielectric mount. The leadless neurostimulation device further includes a housing comprising a secondary electrode positioned on the same side of the leadless neurostimulation device as the at least one primary electrode, the at least one primary electrode and the secondary electrode being configured to transmit an electrical stimulation signal therebetween to provide electrical stimulation therapy to a tibial nerve of a patient, and a lead pin configured to pass through the mounting plate and connect to processing circuitry and components contained in the housing configured to transmit the electrical stimulation signal between the one or more primary electrodes or secondary electrodes to provide electrical stimulation therapy to the tibial nerve, wherein the primary electrode is electrically coupled to the lead pin. The leadless neurostimulation device further includes a mounting plate, wherein the housing is coupled to a first side of the mounting plate and the header unit is coupled to a second side of the mounting plate, and wherein the at least one primary electrode and the secondary electrode define a separation distance of about <NUM> to about <NUM>, and wherein the leadless neurostimulation device defines a total volume of about <NUM> cubic centimeters (cc) to about <NUM> cc.

In an embodiment, the disclosure describes a method of manufacturing a leadless neurostimulation device, the method comprising forming a header unit, including a primary electrode having a contact surface that defines an external surface on a side of the leadless neurostimulation device, forming the header unit comprising forming an outer housing as a side of the header unit opposite of the contact surface of the primary electrode, forming a dielectric mount to receive at least a portion of the primary electrode and at least partially surround the at least one primary electrode, the dielectric mount being configured to electrically insulate the at least one primary electrode from the outer housing, and fixing the dielectric mount within a recessed portion of the outer housing. The method of manufacturing further comprising forming a housing, including a secondary electrode positioned on the same side of the leadless neurostimulation device as the primary electrode.

The disclosure can be more completely understood in consideration of the following detailed description of various embodiments of the disclosure, in connection with the accompanying drawings, in which:.

While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the claims.

Embodiments of leadless neurostimulation devices described herein may be useful for numerous types of neurostimulation therapies, such as for pain control, autonomic nervous system modulation, functional electrical stimulation, tremors, and more. In preferred embodiments, the leadless neurostimulation devices described herein may be useful for stimulating one or more nerves to control symptoms of overactive bladder, urgency frequency, nocturia, painful bladder syndrome, chronic pelvic pain, incontinence, or other pelvic health conditions. These embodiments may also be useful for stimulating one or more peripheral nerves to control pain in one or more areas of the body, such as a foot, ankle, leg, groin, shoulder, arm, wrist, or the back, for example. In one example, embodiments of the disclosed leadless neurostimulation devices may be used to stimulate a tibial nerve of a patient.

<FIG> is schematic view showing an example leadless neurostimulation device <NUM>. Leadless neurostimulation device <NUM> includes a housing <NUM> containing components therein configured for delivering neurostimulation therapy, a header unit <NUM> that includes one or more primary electrodes <NUM>, and a mounting plate <NUM> that couples housing <NUM> to header unit <NUM>. Header unit <NUM> includes at least one primary electrode <NUM> that forms part of an exterior surface of header unit <NUM>. Housing <NUM> includes a secondary electrode <NUM> that forms part of an exterior surface of housing <NUM> and is positioned on the same side of device <NUM> as primary electrode <NUM>. In an alternate embodiment not depicted, primary electrode <NUM> and secondary electrode <NUM> may be arranged on opposite sides of device <NUM>.

Primary electrode <NUM> and secondary electrode <NUM> operate in conjunction with one another to provide stimulation therapy to a target treatment site (e.g., a tibial nerve). Secondary electrode <NUM> may also be referred to as a case electrode, can electrode or reference electrode. In an embodiment, primary electrode <NUM> may comprise a cathode and secondary electrode <NUM> may comprise an anode. In some embodiments, primary and secondary electrodes <NUM> and <NUM> may be characterized as a bipolar pair or system.

The terms "primary" and "secondary" are used to differentiate two or more electrodes that are configured to transmit an electrical signal therebetween. The terms are not used to imply a hierarchy among the electrodes, positive and negative terminal, a total number of electrodes, or a directionality by which a signal is transmitted between the electrodes.

<FIG> provide various schematic views of mounting plate <NUM> and header unit <NUM> and the components contained therein. In particular, <FIG> is a schematic view of a partially assembled header unit <NUM> coupled to mounting plate <NUM>. <FIG> is an exploded view that illustrates how the components of header unit <NUM> and mounting plate <NUM> are assembled. <FIG> is a cross sectional view of <FIG> along line A-A that illustrates portions of header unit <NUM>.

Header unit <NUM> includes outer housing <NUM>, primary electrode <NUM>, and dielectric mount <NUM>. Outer housing <NUM> is coupled to mounting plate <NUM> and may define a partially recessed cavity that receives dielectric mount <NUM> and primary electrode <NUM>. Outer housing <NUM> and mounting plate <NUM> may be made of metal or metal alloy (e.g., titanium or titanium alloy) to allow for easy coupling there between (e.g., laser welding) as well as allow for the coupling of mounting plate <NUM> to housing <NUM>. Additionally, or alternatively, outer housing <NUM> or mounting plate <NUM> may be composed of a ceramic material, or non-conductive plastic material (e.g., polypropylene) including appropriate mechanisms (e.g., metal inserts) for coupling outer housing <NUM> to mounting plate <NUM>.

In some embodiments, the seam between mounting plate <NUM> and outer housing <NUM> may form at least a partial hermetic seal. As discussed further below, while portions of mounting plate <NUM> and outer housing <NUM> define the exterior shape and body of leadless neurostimulation device <NUM>, the exterior surface of these components may be coated with a dielectric material to prevent the body of such components from interfering with the electrical pathway of primary electrode <NUM> and secondary electrode <NUM> as well as contribute to the hermetic seal of device <NUM>. In an alternate embodiment not depicted, header unit <NUM> may be configured so as to be coupleable directly to housing <NUM>, without the need for a separate mounting plate element.

Primary electrode <NUM> defines exterior contact surface <NUM> configured to be brought into direct contact with tissue of the patient. Contact surface <NUM> may also form a portion of a side of header unit <NUM>, which is preferably on the same side of device <NUM> as secondary electrode <NUM>. The exterior perimeter of contact surface <NUM> is bordered by dielectric mount <NUM>, which also forms a portion of the exterior surface of header unit <NUM> and electrically insulates and physically separates primary electrode <NUM> from outer housing <NUM> and mounting plate <NUM>.

Primary electrode <NUM> may be of any suitable size and shape to provide electrical stimulation to the tibial nerve through the fascia layer of a patient. In some embodiments, primary electrode <NUM> may define a contact surface area of about <NUM><NUM> to about <NUM><NUM>. In preferred embodiments that include only a single primary electrode <NUM>, the contact surface area may be greater than about <NUM><NUM>, greater than about <NUM><NUM>, greater than about <NUM><NUM>, less than <NUM><NUM>, less than <NUM><NUM>, and less than <NUM><NUM>. As discussed further in the provisional application serial nos. <CIT>, and <CIT>, both entitled "MINIMALLY INVASIVE LEADLESS NEUROSTIMULATION DEVICE, the surface area of primary and secondary electrodes <NUM> and <NUM>, and separation distance there between may be optimized to provide sufficient penetration and stimulation of the tibial nerve through the fascia layer in a patient's leg.

In some embodiments, the size, shape, and physical separation distance between primary electrode <NUM> and secondary electrode <NUM> may be configured to produce an impedance of less than <NUM>,<NUM> ohms (e.g., between about <NUM> ohms and <NUM>,<NUM> ohms). Additionally, or alternatively, primary and secondary electrodes <NUM> and <NUM> may be arranged in a nonconcentric arrangement such that one electrode does not substantially encircle the other.

In some embodiments, contact surface <NUM> of primary electrode may be substantially flat (e.g., flat or nearly flat) as shown in <FIG>. Alternatively, primary electrode <NUM> may define a curved surface (e.g., a semi-cylindrical shape or other 2D or 3D curved plane) that helps primary electrode <NUM> follow the curvatures of the fascia layer of a patient when implanted to provide better contact and focusing of the electrical signal directed to the tibial nerve. The curved surface may extend over the entirety of contact surface <NUM>, or only over a portion of the surface. Additionally, or alternatively, the curved curvature may be confined to only contact surface <NUM> of primary electrode <NUM>, or may extend over other portions of device <NUM> such as other parts of header <NUM>, mounting plate <NUM>, or housing <NUM>. By including the curvature over other portions of device <NUM>, the device may provide a more ergonomic fit when implanted while also helping to direct the stimulation signal to the tibial nerve.

In some embodiments, contact surface <NUM> of primary electrode <NUM> may also protrude from the plane defined by housing <NUM>. Such a protrusion may help apply additional pressure to the fascia of the patient and help guide the electrical stimulation signal deeper into the tissue of the patient. Primary electrode <NUM> may also define one or more interlocking features, carveouts, recesses, or other structures below contact surface <NUM> that reduce the overall volume of primary electrode <NUM> without interfering with contact surface <NUM>. The reduced volume and interlocking features may also help reduce manufacturing costs as well as help fix primary electrode <NUM> relative to dielectric mount <NUM>. In some embodiments, contact surface <NUM> may possess a textured finish such as a laser textured finish. The textured finish may be added to the general shapes described above. For example, contact surface <NUM> may be flat or curved with a laser texturing added to contact surface <NUM>. In some examples, contact surface <NUM> may include a titanium, titanium alloy, or platinum iridium textured surface.

Primary electrode <NUM> may be formed using any suitable material capable of delivering electrical stimulation therapy to the patient once implanted and having desirable long-term biological compatibility with the surrounding tissue. Such materials may include, but are not limited to titanium, titanium alloy, platinum iridium, or the like. In preferred embodiments, at least contact surface <NUM> is formed of platinum iridium, titanium, titanium alloy, while the body of primary electrode <NUM> may be made of the same or different material. For example, the body of primary electrode <NUM> may be formed of titanium or titanium alloy with contact surface <NUM> formed of platinum iridium. Using platinum iridium may be beneficial in reducing or eliminating the potential for charge buildup on the external surface of device <NUM> during operation. Platinum iridium also provides low impedance with the surrounding bodily tissue, has great biological compatibility, and works well as a contact surface for implantable electrodes. However, platinum iridium can be costly or can have diminished compatibility (e.g., metallurgical bonding) with other metals or alloys.

In some embodiments, primary electrode <NUM> can be made entirely out of platinum iridium, titanium, or titanium alloy. Titanium or titanium alloy offers significant cost advantages over platinum iridium or other specialty metals. However, titanium-based electrodes have been generally discouraged in implantable devices that administer chronic or long-term stimulation therapy. It is believed that such titanium-based electrodes can develop an oxide surface layer with time. This oxide layer along the surface of the electrode can increase the impedance between the electrode and bodily tissue and lead to charge buildup along the outer surface. As a result, the efficacy of the stimulation therapy can diminish with time when using titanium-based electrodes requiring increased voltage or current to deliver therapeutic stimulation levels.

Due to the relatively large surface area of primary electrode <NUM> (e.g., approximately <NUM><NUM>), the phenomenon of diminished efficacy while using a titanium-based electrode has been observed to be negligible or avoided altogether. Thus, titanium-based electrodes may be used for primary electrode <NUM> (including contact surface <NUM>) without experiencing reduced efficacy in the stimulation therapy over the useful life of device <NUM>. In some embodiments, primary electrode <NUM> can be made out of commercially pure titanium (e.g., metal comprised of > <NUM>% Ti, or Grade <NUM> titanium). Commercially pure titanium, particularly Grade <NUM> titanium, offers certain manufacturing advantages including, for example, the ability for primary electrode <NUM> to be produced through machine stamping rather than a casting or other costly fabrication process. Titanium and select titanium alloys also have general acceptance as being biologically compatible and suitable for construction of implantable medical devices.

Titanium and titanium alloys also offer good compatibility (e.g., metallurgical bonding) compared to platinum iridium with other metals and alloys. For example, lead pin <NUM>, which is discussed further below, is used to couple primary electrode <NUM> to the device circuitry contained in housing <NUM>. Lead pin <NUM> may be constructed of niobium or niobium alloy. Soldering or welding between niobium and platinum iridium has been found to have reduced metallurgical compatibility causing the introduction micro fractures and other indications of poor bonding through the well joint between the niobium and platinum iridium metals. These micro fractures can diminish the reliability and impedance of the device. In contrast, titanium has great compatibility with niobium and can be coupled to lead pin <NUM> efficiently through laser welding.

In some embodiments, improved bonding between niobium and platinum iridium through the use of an intermediary or constructing the body of primary electrode <NUM> using a different material than platinum iridium. For example, the body of primary electrode <NUM> can be made of titanium and surface <NUM> can be coated with platinum iridium (e.g. through sputtering or other deposition method) thereby offering the advantages of having contact surface <NUM> formed of platinum iridium while also obtaining good bonding capabilities through the use of titanium. Additionally, or alternatively, a titanium sleeve can be introduced between the niobium based lead pin <NUM> and platinum iridium body of primary electrode <NUM> to obtain a similar effect. The titanium improves the electrical coupling between lead pin <NUM> and primary electrode <NUM> because titanium can be efficiently welded or friction bonded to both niobium and platinum iridium. The titanium body or sleeve acts as an intermediary between the niobium and platinum iridium to eliminate the presence of micro fractures and other indications of poor bonding thereby improving the conductive transfer and reliability of device <NUM> over its lifespan.

Dielectric mount <NUM> is configured to conform to at least some of the internal surfaces of primary electrode <NUM> to help physically retain and electrically insulate primary electrode <NUM> from other portions of header unit <NUM> and mounting plate <NUM>. In some embodiments, primary electrode <NUM> and dielectric mount <NUM> define interlocking interior surfaces <NUM> that allow primary electrode <NUM> to sit within dielectric mount <NUM> and help prevent physical separation (e.g., movement of primary electrode <NUM> out of device <NUM>). For example, primary electrode <NUM> may define a retention channel, protuberance, or some other physical structure that forms at least a portion of a perimeter of the interior surface(s) of primary electrode and provides interlocking surface <NUM>. Additionally, including the presence of a structure that provides interlocking surface <NUM> may help reduce the overall quantity of material used to form primary electrode <NUM> which may reduce manufacturing costs as well as help fix primary electrode <NUM> relative to dielectric mount <NUM> and header <NUM>.

Dielectric mount <NUM> may be formed of any suitable material that electrically insulates primary electrode <NUM> from other portions of header unit <NUM> and mounting plate <NUM>. In some embodiments, dielectric mount <NUM> may be formed of liquid silicone rubber (LSR), silicone, or similar material. For example, LSR, silicone, or other suitable dielectric material may be cast or molded around primary electrode <NUM> to produce a secure fit with primary electrode <NUM>, prevent physical separation there between, and provide the desired physical and electrical separation from outer housing <NUM> and portions of mounting plate <NUM>. In some embodiments, dielectric mount <NUM> may be formed integrally with outer housing <NUM> provided the components are formed of a non-conductive material.

In some embodiments, dielectric mount <NUM> may also include one or more recesses or strategically placed gaps, that may receive a medical adhesive to help aid with assembly of header unit <NUM>. For example, as shown in <FIG>, dielectric mount <NUM> may be generally shaped to be received within the recessed area <NUM> defined by outer housing <NUM>. Along a portion of the adjacent surfaces between dielectric mount <NUM> and outer housing <NUM>, dielectric mount <NUM> may define a channel <NUM> configured to receive, after assembly, a suitable adhesive (e.g., non-conductive medical adhesive, epoxy volcanized silicone, or the like) that fixes dielectric mount <NUM> and outer housing <NUM> together. As best seen in <FIG> and <FIG>, outer housing may define a filling port <NUM> that is in fluid communication with channel <NUM> and allows for injection of the adhesive after assembly.

Dielectric mount <NUM> may also be shaped to provide a gap <NUM> between mounting plate <NUM> and primary electrode <NUM>. Upon assembly, gap <NUM> provides access for coupling the one or more primary electrodes <NUM> to the respective lead pins <NUM> which are used to electrically connect primary electrode <NUM> to the device circuitry contained in housing <NUM>. After coupling primary electrode <NUM> to lead pin <NUM> (e.g., soldering), gap <NUM> may be filled with a dielectric material <NUM> such as the medical adhesive injected through fill port <NUM>, LSR, silicone, or other suitable material.

Outer housing <NUM> may form the majority of the body of header unit <NUM>. In particular, outer housing <NUM> forms the side of header unit <NUM> opposite of contact surface <NUM>, the perimeter edges (apart from the contact surface provided with mounting plate <NUM>), and a portion of the same side of header unit <NUM> as contact surface <NUM> of primary electrode <NUM>. In some embodiments, outer housing <NUM> may have a rounded, semi-circular, or D-shaped perimeter edge that provides a relatively smooth surface without any abrupt or sharp edges or lines than may present an irritation to the patient after implantation. In some embodiments, outer housing <NUM> is configured to receive and form a partial shell around dielectric mount <NUM>. As such, outer housing <NUM> may define a concave interior surface (not shown) that receives a portion of dielectric mount <NUM>. Dielectric mount <NUM> may be secured to outer housing <NUM> using a suitable medical adhesive.

Header unit <NUM> is coupled to mounting plate <NUM> and likewise mounting plate <NUM> is coupled to housing <NUM>. Housing <NUM> includes secondary electrode <NUM>. In some embodiments, secondary electrode <NUM> may be defined by an area of the body of housing <NUM>. For example, housing <NUM> may be formed of a metallic material (e.g., titanium) and electrically coupled to the processing circuitry of leadless neurostimulation device <NUM>. The outer surface of housing <NUM>, including portions of mounting plate <NUM> and header unit <NUM>, may be coated with a dielectric material apart from the surface area that defines secondary electrode <NUM> and primary electrode <NUM>. The dielectric material may at least partially encapsulate device <NUM> such that the boundary created by the dielectric material defines the area of secondary electrode <NUM>, contact surface <NUM>, or both.

The dielectric coating may be applied using any suitable technique. In some such examples, the areas defining contact surface <NUM> and secondary electrode <NUM> may be masked with a suitable material such as tape. Leadless neurostimulation device <NUM> may be then coated using vapor deposition, dip coating, spray coating of similar technique with an adherent dielectric material followed by subsequent removal of the mask material to expose the surfaces of contact surface <NUM> and secondary electrode <NUM>.

Suitable dielectric materials for coating leadless neurostimulation device <NUM> may include, but are not limited to, parylene, LSR, or silicone. Additionally, or alternatively, the outer surface of neurostimulation device <NUM> or portions thereof, may include a surface treatment such as an anodization treatment to modify portions of the surface to make the surface non-conductive. For example, portions of housing <NUM>, outer housing <NUM>, or both, if made of metal (e.g., titanium) may be treated through anodization to make select surfaces non-electrically conductive. In such examples, for purposes of this disclosure the exterior surface of the components may still be characterized as being metal (e.g., titanium) although the component has received such surface treatment.

In preferred examples, the outer surface of leadless neurostimulation device <NUM> may be formed primarily of parylene. Formation of the desired electrode profiles may utilize dielectric blocking methods (e.g., use of a masking material during manufacture) or dielectric removal methods (e.g., removal via laser or soda blast) without damaging the dielectric coating.

In some embodiments, the dielectric coating may also contribute to creating a hermetic seal around leadless neurostimulation device <NUM>. The general configuration of attaching header <NUM> and housing <NUM> respectively to mounting plate <NUM> may also produce a hermetic seal within device <NUM>. Coating device <NUM> with a dielectric material possessing sealing properties such as parylene, LSR, or silicone may either provide additional robustness to the hermetic seal of device <NUM>. Providing leadless neurostimulation device <NUM> in a hermetically sealed form may contribute to the device's long-term functionality thereby providing advantages over other non-hermetically sealed devices.

Secondary electrode <NUM> may define a contact surface area of about <NUM><NUM> to about <NUM><NUM>. However, devices having larger sized secondary electrodes may increase the minimal current needed to create a therapeutic response. The separation distance between primary electrode <NUM> and secondary electrode <NUM> may be about <NUM> to about <NUM>.

The processing circuitry and components of neurostimulation device <NUM> are contained within housing <NUM>. Examples of such processing components may include one or more electronic circuits for delivering electrical stimulation therapy, telemetry hardware, power supply, memory, processor(s). Housing <NUM> can also include communication circuitry disposed therein for receiving programming communication from an external programmer, or providing feedback to a programmer or other external device.

In one example, housing <NUM> can include an energy source enclosed therein, e.g., a rechargeable or non-rechargeable battery. In another example, leadless neurostimulator <NUM> can also be configured to receive energy signals from an external device and transduce the received energy signals into electrical power that is used to recharge a battery of the device, an energy source e.g., a battery, processing circuitry, and other necessary components enclosed therein. In some embodiments, device <NUM> can be configured to receive energy signals from an external device and transduce the received energy signals into electrical power that is used to recharge a battery of device <NUM>. Additionally, or alternatively device <NUM> may include a non-rechargeable primary cell battery.

In some embodiments, housing <NUM> of leadless neurostimulation device <NUM>, and its various processing components may be substantially similar to the housing portion of the InterStim Micro Neurostimulator available from Medtronic. The InterStim Micro Neurostimulator may be modified to receive header unit <NUM> described herein along with modifications to provide secondary electrode <NUM>. The total volume of neurostimulation device <NUM> may be relatively small as well. In some embodiments device <NUM> may have a total volume of about <NUM> cubic centimeters (cc) to about <NUM> cc, about <NUM> cc to about <NUM> cc, or about <NUM> cc to about <NUM> cc.

Referring now to implantation, <FIG> is a side view of a patient's leg <NUM> showing the leadless neurostimulation device <NUM> of <FIG> implanted and <FIG> shows a cross-sectional schematic view of leadless neurostimulation device <NUM> implanted in leg <NUM> of a patient near the ankle adjacent to the tibial nerve <NUM>. The cross section of leg <NUM> illustrates tibia <NUM>, fibula <NUM>, fibularis tertius <NUM>, flexor digitorum longus <NUM>, flexor hallucis longus <NUM>, fibularis brevis <NUM>, soleus <NUM>, posterior tibial artery <NUM>, posterior tibial vein <NUM>, skin <NUM>, cutaneous fat layer <NUM>, and fascia layer <NUM>. Device <NUM> can be implanted through skin <NUM> and cutaneous fat layer <NUM> via a small incision <NUM> (e.g., about one to three cm) above the tibial nerve on a medial aspect of the patient's ankle. Device <NUM> may be positioned adjacent to the region defined by flexor digitorum longus <NUM>, flexor hallucis longus <NUM>, and soleus <NUM> in which tibial nerve <NUM> is contained and implanted adjacent and proximal to fascia layer <NUM> with primary electrode <NUM> and secondary electrode <NUM> facing toward tibial nerve <NUM>.

In an embodiment, incision <NUM> does not cross fascia layer <NUM> thereby reducing the risk of complications with the surgical procedure. While incision <NUM> is shown approximately horizontal to the length of the tibial nerve, other incisions or implantation techniques could be used according to physician preference. In an embodiment, leadless neurostimulation device <NUM> may be implanted such that primary electrode <NUM> is oriented inferiorly relative to secondary electrode <NUM>.

Optional testing of leadless neurostimulation device <NUM> may be performed to determine if device <NUM> is been properly positioned in proximity to tibial nerve <NUM> to elicit a desired response from an applied electrical stimulation. In an example, device <NUM> has controlled by an external programmer to deliver test stimulation, and one or more indicative responses are monitored, such as toe flexion from simulation of the tibial motor neurons controlling the flexor hallucis brevis or flexor digitorum brevis, or a tingling sensation in the heel or sole of the foot excluding the medial arch. If such testing does not elicit appropriate motor or sensory responses, the practitioner may reposition device <NUM> and retest.

Once a practitioner has determined device <NUM> is properly positioned to provide an appropriate patient response to delivered stimulation therapy, housing <NUM> can be secured in place if needed. Such anchoring means may be optional as the natural shape of the region in which device <NUM> is implanted, and the shape of device <NUM> itself has shown good compatibility with the surrounding tissue thus preventing device <NUM> from shifting or rolling after implantation, in some embodiments, leadless neurostimulation device <NUM> may further include one or more suture points to help secure device <NUM> to fascia <NUM> or other parts of leg <NUM>. In some embodiments, a suture anchor <NUM> may be included at the distal end of housing <NUM>, opposite of the end attached to mounting plate <NUM>.

An advantage of the devices and methods described herein can be improved patient safety and satisfaction after implant. In contrast to other approaches, leadless neurostimulation device <NUM> does not require fascia layer <NUM> to be disturbed which may reduce risks affiliated with alternative procedures. Further, as device <NUM> is a unitary structure and can be hermetically sealed, the device is more robust than other lead-based stimulation units.

During operation, an electrical stimulation signal may be transmitted between primary electrode <NUM> and secondary electrode <NUM> through facia layer <NUM>. The electrical signal may be used to stimulate tibial nerve <NUM> which may be useful in the treatment of overactive bladder (OAB) symptoms of urinary urgency, urinary frequency and/or urge incontinence, or fecal incontinence.

Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed invention as defined by the claims.

Claim 1:
A leadless neurostimulation device comprising:
a header unit comprising:
a primary electrode having a contact surface that defines an external surface on a side of the leadless neurostimulation device;
an outer housing that forms a side of the header unit opposite of the contact surface of the primary electrode; and
a dielectric mount that receives at least a portion of the primary electrode and at least partially surrounds the primary electrode, the dielectric mount being configured to electrically insulate the primary electrode from the outer housing, the dielectric mount being received and fixed within a recessed portion of the outer housing; and
a housing comprising a secondary electrode positioned on the same side of the leadless neurostimulation device as the primary electrode, the primary electrode and the secondary electrode being configured to transmit an electrical stimulation signal therebetween to provide electrical stimulation therapy to a tibial nerve of a patient.