Patent Description:
A variety of medical devices are used for chronic, i.e., long-term, delivery of therapy to patients suffering from a variety of conditions, such as chronic pain, tremor, Parkinson's disease, cancer, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, spasticity, or gastroparesis. For example, pumps or other fluid delivery devices can be used for chronic delivery of therapeutic medicaments, such as drugs or other agents. Typically, such devices provide therapy continuously or periodically according to programmed parameters. The programmed parameters can specify the therapeutic regimen (e.g., the rate, quantity, and timing of medicament delivery to a patient), as well as other functions of the medical device.

Implantable medical infusion pumps have important advantages over other forms of medicament administration. For example, oral administration is often not workable because the systematic dose of the substance needed to achieve the therapeutic dose at the target site may be too large for the patient to tolerate without adverse side effects. Also, some substances simply cannot be absorbed in the gut adequately for a therapeutic dose to reach the target site. Moreover, substances that are not lipid soluble may not cross the blood brain barrier adequately if needed in the brain. In addition, infusion of substances from outside the body requires a transcutaneous catheter, which results in other risks such as infection or catheter dislodgment. Further, implantable medical pumps avoid the problem of patient noncompliance, namely the patient failing to take the prescribed drug or therapy has instructed.

Implantable medical infusion pumps are typically implanted at a location within the body of a patient (typically a subcutaneous region in the lower abdomen), and are configured to deliver a fluid medicament through a catheter. The catheter is generally configured as a flexible tube with a lumen running the length of the catheter to a selected delivery site in the body, such as the spinal canal or subarachnoid space. Such implantable medical pumps typically include an expandable fluid reservoir, which is accessible for refill etc. through an access port. Medicament flows from the reservoir via the lumen in the catheter according to programmed parameters.

Drug molecules exiting the catheter lumen flow into the subarachnoid space, and begin mixing with the cerebrospinal fluid. Frequently, the drug exits the catheter slowly (e.g., a flow rate of <NUM> per hour or less), where it tends to stagnate in the slow-moving cerebrospinal fluid immediately surrounding the catheter. This slow moving fluid is known to those schooled in the science of fluid mechanics as a boundary-layer, which is a consequence of friction between a viscous fluid and a surface (i.e. the catheter). A slow or delayed mixing of the drug with the cerebrospinal fluid can decrease the efficacy of the drug and resultant therapeutic effect. Although various attempts have been made to improve drug dispersion within the cerebrospinal fluid, it is desirous to further improve the efficiency of intrathecal drug delivery. Applicants of the present disclosure have developed a system and method to address this concern.

Document <CIT> relates to methods and systems for conditioning cerebrospinal fluid.

Documents <CIT> and <CIT> relate to methods for uniformly delivering drugs locally to the vasculature of mammals.

Document <CIT> relates to methods for improving intravascular imaging.

Document <CIT> relates to a drug delivery system.

Embodiments of the present disclosure provide a system of utilizing the contours of a catheter positioned within the subarachnoid space of a patient to generate vortices within the natural flow of cerebrospinal fluid for the purpose of improving the dispersion of the infused medicament. For example, in one embodiment, the catheter can have a curve configured to orient a distal portion of the catheter substantially orthogonal to the natural flow of the cerebrospinal fluid, which can in turn promote mixing within the cerebrospinal fluid in the form of von Kármán vortex street. Improved mixing in the vicinity of the catheter can improve the dispersion of the otherwise relatively slow-moving medicament dispensed from the catheter.

One embodiment of the present disclosure provides an intrathecal drug delivery system according to claim <NUM>. The at least one feature configured to generate vortices within the cerebrospinal fluid can be described as a dispersion feature. Specifically, the dispersion feature is located at or adjacent a distal portion of the catheter. The medicament exit can be located at or adjacent the dispersion feature. The medicament exit itself should not be considered as the dispersion feature. In one embodiment, the curve can be configured to orient the distal portion substantially orthogonal to a natural flow of cerebrospinal fluid within the subarachnoid space. In some embodiments, the angle with respect to a proximal portion of the catheter is at least <NUM>°, especially between <NUM>° and <NUM>° and specifically between <NUM>° and <NUM>°. In one embodiment, the distal portion can induce a von Kármán vortex street within the cerebrospinal fluid. In one embodiment, the distal portion can induce turbulence within the cerebrospinal fluid. In one embodiment, the medicament exit can be positioned to expel medicament in axial alignment with a natural flow of the cerebrospinal fluid within the subarachnoid space. In one embodiment, the catheter can be manipulated between an insertion position and an infusion position. In one embodiment the catheter can be configured to assume a sinusoidal shape. In one embodiment, multiple portions of the catheter can be positioned at a substantially orthogonal angle relative to a natural flow of cerebrospinal fluid within the subarachnoid space.

An example of the present disclosure and not covered by the present invention, provides a method of intrathecal drug delivery configured to improve dispersion of medicament with cerebrospinal fluid in a subarachnoid space of the patient. The method can comprise dispensing medicament from an implantable medical infusion device into the subarachnoid space the patient; and utilizing at least one feature defined by catheter of the implantable medical infusion device to promote mixing within the cerebrospinal fluid for the purpose of improving intrathecal drug dispersion.

In one embodiment, the one or more feature is a curve defined by catheter wall configured to orient a distal portion of the catheter at an angle with respect to a proximal portion of the catheter. In one embodiment, the curve is configured to orient the distal portion substantially orthogonal to a natural flow of the cerebrospinal fluid within the subarachnoid space. In one embodiment, the distal portion can generate vortices within the cerebrospinal fluid. In one embodiment, the distal portion can induce turbulence within the cerebrospinal fluid.

The summary above is not intended to describe each illustrated embodiment or every implementation of the present disclosure. The figures and the detailed description that follow more particularly exemplify these embodiments.

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 embodiments of the disclosure are amenable to various modifications and alternative forms, specifics thereof shown by way of example in the drawings will be described in detail. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the subject matter as defined by the claims.

Referring to <FIG>, an intrathecal drug delivery system <NUM> is depicted in accordance with an embodiment of the disclosure. The intrathecal drug delivery system <NUM> can include an implantable medical pump <NUM> and a catheter <NUM>. As depicted, the implantable medical pump <NUM> can be implanted within the body B of a patient. The implantable medical pump <NUM> can be in fluid communication with the catheter <NUM> having a distal tip <NUM> positioned within the subarachnoid space of the patient's spinal column S, thereby enabling intrathecal delivery of medicament through a lumen of the catheter <NUM>.

Referring to <FIG>, an exploded perspective view of an implantable medical pump <NUM> is depicted in accordance with an embodiment of the disclosure. Referring to <FIG>, a block diagram of an implantable medical pump <NUM> is depicted in accordance with an embodiment of the disclosure. The implantable medical pump <NUM> can generally include a housing <NUM>, power source <NUM>, medicament reservoir <NUM>, medicament pump <NUM>, and electronics <NUM>. The housing <NUM> can be constructed of a material that is biocompatible and hermetically sealed, such as titanium, tantalum, stainless steel, plastic, ceramic, or the like. The power source <NUM> can be a battery, such as a lithium-ion battery. The power source <NUM> can be carried in the housing <NUM>, and can be selected to operate the medicament pump <NUM> and electronics <NUM>.

The medicament reservoir <NUM> can be carried by the housing <NUM> and can be configured to contain medicament. In one embodiment, medicament within the medicament reservoir <NUM> can be accessed via an access port <NUM>. Accordingly, the access port <NUM> can be utilized to refill, empty, or exchange the fluid within the medicament reservoir <NUM>.

The medicament pump <NUM> can be carried by the housing <NUM>. The medicament pump <NUM> can be in fluid communication with the medicament reservoir <NUM> and can be in electrical communication with the electronics <NUM>. The medicament pump <NUM> can be any pump sufficient for infusing medicament to the patient, such as a piston pump, a peristaltic pump, a pump powered by a stepper motor, a pump powered by an AC motor, a pump powered by a DC motor, an electrostatic diaphragm, a piezioelectric motor, a solenoid, a shape memory alloy, or the like.

The electronics <NUM> are carried in the housing <NUM>, and can be in electrical communication with the power source <NUM> and medicament pump <NUM>. In one embodiment, the electronics <NUM> can include a processor <NUM>, memory <NUM> and <NUM>, and transceiver circuitry <NUM>. In one embodiment, the processor <NUM> can be in Application-Specific Integrated Circuit (ASIC) state machine, gate array, controller, or the like. The electronics <NUM> can be generally configured to control infusion of medicament according to programmed parameters or a specified treatment protocol. The programmed parameters or specified treatment protocol can be stored in the memory <NUM>, <NUM>. The transceiver circuitry <NUM> can be configured to receive information from an external programmer (not depicted). In one embodiment, the electronics <NUM> can be further be configured to operate a number of other features, such a patient alarm <NUM>.

The distal tip <NUM> of the catheter <NUM> can extend into the subarachnoid space of a patient's spine, thereby enabling delivery of medicament into the cerebrospinal fluid of the patient. The cerebrospinal fluid resides within the brain ventricles and the cranial and spinal subarachnoid spaces. Cerebrospinal fluid circulation is a dynamic phenomenon closely correlated with the patient's arterial pulse wave; although other factors, such as respiratory waves, the patient's posture, jugular venous pressure, and physical effort may also affect cerebrospinal fluid flow dynamics and pressure. The cerebrospinal fluid volume is estimated to be about <NUM> in adults, with approximately <NUM> located in the cranial and spinal subarachnoid spaces and the remaining <NUM> located in the brain ventricles. Through normal pulsatile flow, the cerebrospinal fluid is renewed about four times every <NUM> hours.

Referring to <FIG>, a catheter <NUM> according to the prior art is depicted as being positioned within the subarachnoid space of a patient. The catheter <NUM>, which can have a substantially cylindrical cross section, can extend between a proximal end and a distal tip <NUM>. The catheter <NUM> generally includes a wall <NUM> defining a lumen <NUM> extending between the proximal end and a medicament exit <NUM>. The medicament exit <NUM> can be positioned on the distal tip <NUM> of the catheter. Alternatively, as depicted, the medicament exit <NUM> can be positioned proximately from the distal tip <NUM> along the wall <NUM> of the catheter <NUM>.

The proximal end of the catheter <NUM> can be operably coupled to the implantable medical pump, such that the lumen <NUM> of the catheter <NUM> is in fluid communication with the medical pump <NUM> and reservoir <NUM>. The catheter <NUM> enters the subarachnoid space at an insertion site, and extends substantially parallel to a longitudinal axis A of the patient's spinal column S, thereby enabling intrathecal delivery of medicament through the lumen of the catheter <NUM>.

<FIG> depict the catheter <NUM> as the medicament <NUM> exits the medicament exit <NUM> and flows into the subarachnoid space. Specifically, <FIG> depicts the dispersion of medicament <NUM> after approximately <NUM> seconds of initiating infusion, and <FIG> depicts the dispersion of medicament <NUM> after approximately <NUM> seconds of initiating infusion. As the medicament <NUM> exits the medicament exit <NUM> and flows into the subarachnoid space, the medicament <NUM> begins mixing with the cerebrospinal fluid. However, because the medicament <NUM> is expelled from the medicament exit <NUM> at a relatively slow rate (e.g., a flow rate of <NUM> per hour), the medicament <NUM> commonly stagnates in the slow-moving cerebrospinal fluid immediately surrounding the catheter <NUM>. Although the pulsatile flow of the cerebrospinal fluid eventually causes the medicament <NUM> to drift away from the catheter <NUM> and into faster moving cerebrospinal fluid, proper mixing of the medicament <NUM> into the cerebrospinal fluid can take several minutes. A slow or delayed mixing of medicament with cerebrospinal fluid can decrease the efficacy of the medicament, as well as the resultant therapeutic effect.

Referring to <FIG>, a catheter <NUM> configured for increased intrathecal drug dispersion is depicted in accordance with an embodiment of the disclosure. In one embodiment, the catheter <NUM> can generally include cylindrical cross-section, and can extend between a proximal end and a distal tip <NUM>. Similar to conventional catheter designs, catheter <NUM> can generally include a wall <NUM> defining a lumen <NUM> extending between the proximal end and a medicament exit <NUM>. However, unlike conventional catheter designs, catheter <NUM> can include one or more features <NUM> configured to generate vortices within the cerebrospinal fluid for the purpose of improving intrathecal drug dispersion.

For example, in one embodiment, the wall <NUM> of the catheter <NUM> can define a curved portion <NUM>, such that a distal portion <NUM> of the catheter <NUM> is oriented substantially orthogonally to a proximal portion <NUM> of the catheter <NUM>. Other angular orientations between the distal portion <NUM> and proximal portion <NUM> are also contemplated. Accordingly, a medicament exit <NUM>, which can be positioned proximately from the distal tip <NUM> along the wall <NUM> of the catheter <NUM>, can be positioned to expel medicament in-line with or parallel to the longitudinal axis A of the patient's spinal column S. In other words, the distal portion <NUM> (which can include the medicament exit <NUM>) can be positioned substantially perpendicular to the flow of cerebrospinal fluid within the subarachnoid space, thereby generating vortices, inducing turbulence, or otherwise generally promoting mixing in the cerebrospinal fluid immediately surrounding the distal portion <NUM>.

To promote ease in inserting the catheter <NUM> into the subarachnoid space of a patient, the catheter <NUM> can be manipulated between an insertion position and an infusion position. For example, in one embodiment, the catheter <NUM> can be constructed of a heat-setting polyurethane or similar material, which can be naturally biased to orient the distal portion <NUM> relative to the proximal portion <NUM> in the desired infusion position. During insertion of the catheter <NUM> into the subarachnoid space, a needle or stylet can be positioned within the lumen <NUM> to straighten the catheter <NUM>, or otherwise inhibit the catheter <NUM> from assuming the infusion position.

The dispersion of medicament delivered via catheter <NUM> into the subarachnoid space can be simulated using computational fluid dynamics (CFD) modeling methods such as the well-known finite-volume, finite-element, or finite-difference techniques for finding approximate solutions to systems of partial differential equations. In the case of intrathecal delivery, the system of partial differential equations that model conservation of mass and momentum, also known as the Navier-Stokes equations, can simulate cerebrospinal fluid flow. To be more precise, the equations for laminar, oscillating flow of an incompressible fluid with properties similar to water at body temperature can be used to simulate medicament deliver scenarios. Medicament dispersion can further be modeled using various techniques including the Eulerian passive scalar approach or the Lagrangian particle approach.

<FIG> and <FIG> represent predictions of the respective volumes of dispersed clouds of medicament in an idealized intrathecal space geometry with cerebrospinal fluid that oscillates according to a sine function with a <NUM> frequency and <NUM>/s amplitude. With a nominal straight catheter <NUM> (such as that depicted in <FIG>), at a time of <NUM> seconds after the start of a bolus infusion at <NUM>/hr, the infused medicament can occupy a volume of approximately <NUM><NUM>. By contrast, for a design where the tip of the catheter <NUM> is curved (such as that depicted in <FIG>), with all other model parameters kept constant, the infused medicament can occupy a volume of approximately <NUM><NUM>. Thus, it can be seen that the one or more features <NUM> described above can have the effect of increasing the volume of dispersed medicament approximately <NUM> times that of prior art designs after <NUM> seconds of infusion. In some embodiments, bolus deliveries may be longer than a period longer than <NUM> seconds, and the presence of the medicament in the cerebrospinal fluid can last for several hours after infusion.

Referring to <FIG>, a cylindrical object positioned within a fluid flow can result in a repeating pattern of swirling vortices, caused by a process known as vortex shedding, which is responsible for the unsteady separation of flow of a fluid around blunt bodies. Such a fluid flow is commonly referred to in the field of fluid dynamics as a von Karman vortex street, and is responsible for such phenomena as the "singing" of suspended telephone power lines and the vibration of a car antenna at certain speeds.

Referring to <FIG>, in intrathecal drug delivery, positioning of the distal portion <NUM> perpendicular to the pulsatile flow of cerebrospinal fluid, can be used to generate a series of counter-rotating vortices to promote local mixing of the medicament with the cerebrospinal fluid along the flow direction, thereby carrying the medicament away from the relatively slow-moving fluid in the boundary layer of the catheter <NUM>. Further, in some embodiments, the medicament exit <NUM> can be positioned within the subarachnoid space, such that the pulsatile flow of cerebrospinal fluid can act to push slow-moving or stagnant medicament out of the medicament exit <NUM> to further improve mixing.

<FIG> depict the catheter <NUM> as the medicament <NUM> exits the medicament exit <NUM> and flows into the subarachnoid space. Specifically, <FIG> depicts the dispersion of medicament <NUM> after approximately <NUM> seconds of initiating infusion, and <FIG> depicts the dispersion of medicament <NUM> after approximately <NUM> seconds of initiating infusion. As the medicament <NUM> exits the medicament exit <NUM> and flows into the subarachnoid space, the medicament <NUM> begins mixing with the cerebrospinal fluid. Despite the medicament <NUM> being expelled from the medicament exit <NUM> at the same relatively slow rate (e.g., a flow rate of <NUM> per hour) mixing of the medicament <NUM> with the cerebrospinal fluid is enhanced by the vortices generated by the catheter <NUM>. In particular, the counter-rotating vortices of the von Karman vortex street promote faster distribution of the medicament <NUM> throughout the cerebrospinal fluid by quickly transporting the medicament <NUM> away from the catheter <NUM> and into faster moving cerebrospinal fluid. Accordingly, intrathecal infusion via catheter <NUM> enables dispersion of the medicament <NUM> to occur more rapidly than infusion via conventional methods (particularly in comparison to the infusion method depicted in <FIG>), thereby increasing the efficacy of the medicament.

Referring to <FIG>, a catheter <NUM> configured for increased intrathecal drug dispersion is depicted in accordance with a second embodiment of the disclosure. Catheter <NUM> can generally include a cylindrical cross-section, and can extend between a proximal end and a distal tip <NUM>. Catheter <NUM> can generally include a wall <NUM> defining a lumen <NUM> extending between the proximal end and a medicament exit <NUM>. Catheter <NUM> can include multiple features 410A, 410B, and 410C configured to generate vortices within the cerebrospinal fluid for the purpose of improving intrathecal drug dispersion. For example, catheter <NUM> can be configured to assume a sinusoidal shape, such that multiple portions 412A, 412B, 412C, 412D of the catheter <NUM> can be positioned and an acute, obtuse, or substantially orthogonal angle relative to the flow of cerebrospinal fluid within the subarachnoid space. Accordingly, the medicament exit <NUM>, which can be positioned proximately from the distal tip <NUM> along the wall <NUM> of the catheter <NUM> can be positioned to expel medicament substantially in-line with the longitudinal axis A of the patient's spinal column S. In one embodiment, the catheter <NUM> can include multiple medicament exits oriented in different directions or extending along the length of the catheter <NUM>.

<FIG> depict the catheter <NUM> as the medicament <NUM> exits the medicament exit <NUM> and flows into the subarachnoid space. Specifically, <FIG> depicts the dispersion of medicament <NUM> after approximately <NUM> seconds of initiating infusion, and <FIG> depicts the dispersion of medicament <NUM> after approximately <NUM> seconds of initiating infusion. As the medicament <NUM> exits the medicament exit <NUM> and flows into the subarachnoid space, the medicament <NUM> begins mixing with the cerebrospinal fluid. Upon infusion, mixing of the medicament <NUM> with the cerebrospinal fluid is initially promoted by the vortices associated with portion 412A and feature 410A. Mixing up the medicament with the cerebrospinal fluid is subsequently promoted by portions 412B, 412C and 412D and features 410B and 410C, which serve to further promote a mixing effect within the cerebrospinal fluid. Accordingly, intrathecal infusion via catheter <NUM> enables dispersion of the medicament <NUM> to occur more rapidly than infusion via conventional methods.

<FIG> depict alternative embodiments of catheters <NUM>, <NUM>, <NUM>, <NUM> including one or more features <NUM>, <NUM>, <NUM>, <NUM> configured to generate vortices within the cerebrospinal fluid of a patient for the purpose of improving the dispersion of intrathecally administered medicament. In embodiments, the one or more features <NUM>, <NUM>, <NUM>, <NUM> can be positioned between a distal tip <NUM>, <NUM>, <NUM>, <NUM> and a medicament exit <NUM>, <NUM>, <NUM>, <NUM> defined by the catheter wall <NUM>, <NUM>, <NUM>, <NUM>. Other configurations are also contemplated.

For example, in the embodiments depicted in <FIG>, the one or more features <NUM>, <NUM> can be in the form of a V-shaped ridge <NUM>, <NUM> originating in proximity to the distal tip <NUM>, <NUM> and terminating at an apex <NUM>, <NUM> in proximity to the medicament exit <NUM>, <NUM>. In some embodiments, the catheter <NUM>, <NUM> can include a pair of V-shaped ridges <NUM>, <NUM> positioned on opposing lateral sides of the catheter <NUM>, <NUM>. In operation, the V-shaped ridge <NUM>, <NUM> can interact with medicament expelled from the medicament exit <NUM>, <NUM>, so as to promote separation of the medicament from the slow moving cerebrospinal fluid immediately surrounding the catheter <NUM>, <NUM>, as well as generating vortices within the cerebrospinal fluid surrounding the catheter <NUM>, <NUM>. In some embodiments, the distal tip <NUM> can be pointed or otherwise formed as a wedge. In some embodiments, the distal tip <NUM> can be blunt or otherwise assume a frustoconical shape.

In the embodiment depicted in <FIG>, the one or more features <NUM> can be in the form of a spiral ridge <NUM> originating in proximity to the distal tip <NUM> and terminating in proximity to the medicament exit <NUM>. In operation, the spiral ridge <NUM> generate vortices within the cerebrospinal fluid surrounding the catheter <NUM>, thereby promoting faster mixing of the medicament expelled from the medicament exit <NUM> with the cerebrospinal fluid.

In the embodiment depicted in <FIG>, the one or more features <NUM> can be in the form of a shelf <NUM> at least partially surrounding the wall <NUM> of the catheter <NUM>. In operation, the shelf <NUM> can present a barrier to inhibit fluid from traversing along a boundary layer, and to generate vortices in the vicinity of the medicament exit <NUM>, thereby improving local mixing of the medicament with the cerebrospinal fluid.

Predictions of the respective volumes of dispersed clouds of medicament for catheters <NUM>, <NUM>, <NUM>, and <NUM> having one or more features <NUM>, <NUM>, <NUM>, and <NUM> (such as that depicted in <FIG>), with the same model parameters described above, can have an infused medicament volume of approximately <NUM>. Accordingly, in comparison to a nominal straight catheter <NUM> (such as that depicted in <FIG>), the one or more features <NUM>, <NUM>, <NUM>, and <NUM> can have the effect of increasing the volume of dispersed medicament approximately <NUM> times that of prior art designs after <NUM> seconds of infusion.

In some examples of the present disclosure the system can be used in combination with a method of intrathecal drug delivery configured to improve dispersion of medicament with cerebrospinal fluid in a subarachnoid space of a patient. The method comprises: dispensing medicament from an implantable medical infusion device into the subarachnoid space of the patient; and utilizing at least one feature defined by a catheter of the implantable medical infusion device to promote mixing within the cerebrospinal fluid for the purpose of improving intrathecal drug dispersion.

The at least one feature can be a curve defined by a catheter wall configured to orient a distal portion of the catheter at an angle with respect to a proximal portion of the catheter, especially the curve can be configured to orient the distal portion substantially orthogonal to a natural flow of the cerebrospinal fluid within the subarachnoid space.

The distal portion can induce a von Kármán vortex street within the cerebrospinal fluid.

Various embodiments of systems and devices 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 inventions.

It should be understood that the individual steps used in the methods of the present teachings may be performed in any order and/or simultaneously, as long as the teaching remains operable. Furthermore, it should be understood that the apparatus and methods of the present teachings can include any number, or all, of the described embodiments, as long as the teaching remains operable.

Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted.

Claim 1:
An intrathecal drug delivery system (<NUM>) configured to improve dispersion of medicament with cerebrospinal fluid in a subarachnoid space of a patient, the intrathecal drug delivery system (<NUM>) comprising:
an implantable medical pump (<NUM>); and
a catheter (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) having a wall (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) defining a lumen extending between a proximal end in fluid communication with the implantable medical pump (<NUM>) and structure defining a medicament exit (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) positionable within the subarachnoid space of the patient, the wall (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) further defining at least one feature (<NUM>, 410A, 410B, 410C, <NUM>, <NUM>, <NUM>, <NUM>) configured to generate vortices within the cerebrospinal fluid,
characterized in that the at least one feature comprises at least one of a curve (<NUM>) defined by the catheter wall (<NUM>) configured to orient a distal portion (<NUM>) of the catheter (<NUM>) at an angle with respect to a proximal portion of the catheter, a V-shaped ridge (<NUM>, <NUM>), a spiral ridge (<NUM>), a shelf (<NUM>), a groove, or combination thereof.