Abstract:
The present invention discloses techniques for operation of neurostimulation or drug delivery devices to stop treatment therapy during times when the patient does not need to be treated. Advantageously, the present invention reduces battery usage and/or drug dosage during periods when treatment therapy need not be provided. Further, the present invention slows or reduces the tolerance the patient may develop from the electrical stimulation or treatment therapy. In one embodiment, the present invention includes a timer or a real time clock for shutting off the device during periods when the patient is sleeping in accordance with a preset schedule. The present invention preferably turns off after the patient has fallen asleep and right before the patient has awakened. Alternatively, the invention may include a sensor for sensing conditions indicative of whether the patient is awake or asleep. This sensed information may also be used to determine whether the treatment therapy should be delivered or stopped.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to neurostimulation or drug infusion devices, and more particularly relates to techniques for activating or deactivating a neurostimulator or drug delivery system based on time-of-day or biological rhythmic patterns.  
           [0003]    2. Description of Related Art  
           [0004]    Neurostimulation devices and drug delivery devices are now capable of treating any number of disorders as well as symptoms of disorders. In the context of neurostimulators, an electrical lead having one or more electrodes is typically implanted near a specific site in the brain or spinal cord of a patient. The lead is coupled to a signal generator which delivers electrical energy through the electrodes to nearby neurons and neural tissue. The electrical energy delivered through the electrodes creates an electrical field causing excitation of the nearby neurons to directly or indirectly treat the neurological disorder or a symptom of the disorder. In the context of a drug delivery system, a catheter coupled to a pump is implanted near a treatment site in the brain or spinal cord. These systems are commonly implanted within the body and are operated by a power source such as a battery.  
           [0005]    Recent advances have allowed these neurostimulation devices and drug delivery systems to adjust treatment in accordance with the patient&#39;s needs. Generally, these systems incorporate a sensor for sensing a physical or chemical characteristic of the body and generating a sensor signal in response. The sensor signal may then be used to adjust the treatment therapy. U.S. Pat. No. 5,716,377, for example, discloses a method of treating movement disorders by closed loop brain stimulation.  
           [0006]    These systems, however, provide electrical stimulation or drug delivery regardless of the time of day or the patient&#39;s needs. These system are capable of adjusting the treatment but are incapable of recognizing periods when a patient does not require any therapy. For example, patients often will not require any stimulation or drug therapy during periods when he/she is resting or sleeping. During such time periods, the manifestation of the movement disorder may be minimal or even non-existent. This is often the case for patients suffering from movement disorders and certain types of pain.  
           [0007]    Stimulation or drug delivery at times when it is not required by the patient unnecessarily depletes the battery or the drug reserve which is often implanted within the body. This requires more frequent surgical procedures to replace the spent battery or more frequent drug injections. An even greater concern with continuous therapy systems is that the patient may develop a higher tolerance to the treatment, thereby requiring higher dosage or stronger stimulation to achieve the desired result.  
           [0008]    Often, physicians will request the patient to turn off his/her neurostimulator at night. This requires the patient or care giver to manually turn the device off at night before falling asleep and turn on the device after waking up the next day. However, after the neurostimulator is turned off but before the patient has fallen asleep, symptoms of movement disorders, illnesses or other maladies (such as tremor) or pain often return, thereby rendering sleep difficult. Accordingly, there remains a need in the art for automatically shutting off the electrical stimulation or drug delivery during periods when the patient does not require treatment therapy.  
         SUMMARY OF THE INVENTION  
         [0009]    As explained in more detail below, the present invention overcomes the above-noted and other shortcomings of the prior art neurostimulation devices. The present invention provides a technique for shutting off the electrical stimulation or drug delivery during periods when the treatment therapy is not desired. In one embodiment, the neurostimulator has a timer or a clock capable of turning on or off the treatment therapy at predetermined times. Accordingly, the system may be automatically turned off at a time when the patient is usually fast asleep and turned on at a time prior to the patient awakening. In the context of a neurostimulation device, the present invention includes an implantable signal generator, a timer coupled to the signal generator for providing timing information to the signal generator, and circuitry (a microprocessor) within the signal generator for determining whether the signal generator is turned off or on in response to the timer information. Timer may alternatively be a real time clock.  
           [0010]    In an another embodiment, the present invention includes a sensor coupled to the signal generator for generating a signal indicative of whether a patient is asleep or awake. The microprocessor receives time of day information from the timer and information as to whether the patient is awake or asleep from the sensor. Based on these signals, the microprocessor may automatically initiate or stop the treatment therapy to the patient.  
           [0011]    The present invention may also be implemented within an implantable drug delivery system in accordance with the principles of the above-described embodiments.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    These and other advantages and features of the invention will become apparent upon reading the following detailed description and referring to the accompanying drawings in which like numbers refer to like parts throughout and in which:  
         [0013]    [0013]FIG. 1 depicts a neurostimulation device in accordance with an embodiment of the present invention;  
         [0014]    [0014]FIG. 2 is a schematic block diagram of the circuitry of device or signal generator in accordance with a preferred embodiment of the present invention;  
         [0015]    [0015]FIG. 3 illustrates a schematic block diagram of another embodiment of signal generator wherein timer is coupled to a power source such as battery of signal generator;  
         [0016]    [0016]FIG. 4 discloses another embodiment of the present invention wherein a sensor provides feedback as to whether the patient is awake or asleep to determine whether signal generator should be turned on or off;  
         [0017]    [0017]FIG. 5 illustrates a schematic block diagram of the signal generator of FIG. 2 including a sensor signal input from sensor; and  
         [0018]    [0018]FIG. 6 depicts a drug infusion system in accordance with an embodiment of the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    [0019]FIG. 1 depicts a neurostimulation device  10  in accordance with an embodiment of the present invention. Device  10  made in accordance with the preferred embodiment is preferably implanted below the skin of a patient or, alternatively, may be an external device. Device  10  may be implanted as shown in FIG. 1, in the abdomen or any other portion of the body. A lead  22 A is positioned to stimulate a specific site in a brain (B). Device  10  may take the form of a modified signal generator Model 7424 manufactured by Medtronic, Inc. under the trademark Itrel II. Lead  22 A may take the form of any of the leads sold with the Model 7424, for stimulating the brain, and is coupled to device  10  by a conventional conductor  22 . Alternatively, lead  22 A may be any lead suitable for stimulation of a spinal cord. Lead  22 A may include a paddle lead, a lead having recording and stimulation electrodes, or a combination catheter/lead capable of providing electrical stimulation and drug delivery.  
         [0020]    As shown in FIG. 1, the distal end of lead  22 A terminates in one or more stimulation electrodes generally implanted into a portion of the brain by conventional stereotactic surgical techniques. Any number of electrodes may be used for various applications. Each of the electrodes is individually connected to device  10  through lead  22 A and conductor  22 . Lead  22 A is surgically implanted through a hole in the skull and conductor  22  is implanted between the skull and the scalp. Conductor  22  is joined to implanted device  10  in the manner shown.  
         [0021]    Conductor  22  may be divided into twin leads  22 A and  22 B that are implanted into the brain bilaterally as shown. Alternatively, lead  22 B may be supplied with stimulating pulses from a separate conductor and signal generator. Leads  22 A and  22 B could be two electrodes in 1) two separate nuclei that potentiate each other&#39;s effects or 2) nuclei with opposite effects with the stimulation being used to fine tune the response through the application of one stimulation pattern to one cite and the application of another stimulation pattern to the other cite.  
         [0022]    [0022]FIG. 2 is a schematic block diagram of the circuitry of device or signal generator  10  in accordance with a preferred embodiment of the present invention. As preferred, signal generator includes a timer  201  coupled to a microprocessor or a controller  200 . Timer  201  establishes when the system is “on” or “off.” When implanted, timer  201  is calibrated to turn the stimulation device “on” or “off” in accordance with predetermined counts of timer  201 . The operator or patient may calibrate timer  201  such that signal generator  10  is “on” at a specific time in the morning right before the patient usually wakes up and is “off” at a specific time in the evening after the patient has fallen asleep. This calibration may be accomplished during the implantation of signal generator  10 . As preferred, timer  201  may be remotely calibrated to adjust for changing time conditions or preferences of the patient (such as changing sleep habits). The additional components of signal generator  10  are discussed in further detail herein.  
         [0023]    [0023]FIG. 3 illustrates a schematic block diagram of another embodiment of signal generator  10  wherein timer  201  is coupled to a power source  203  such as battery of signal generator  10 . During “off” periods, timer  201  disconnects power source  203  from providing any electrical energy to signal generator  10 . During the “on” stage, timer  201  reconnects power source  203  to provide electrical energy to signal generator  10 . Operation of signal generator  10  during the “on” stage may be handled under techniques known in the art.  
         [0024]    In yet another embodiment of the present invention, timer  201  may be a real time clock. Clock may be adjusted manually such as, for example, by a switch  230  (FIG. 2) that the patient may access via telemetry or, alternatively, clock may be responsive to an external source, such as a wristwatch or a central satellite, to ensure that the clock is timed properly. Advantageously under the latter embodiment, clock may be periodically adjusted to reflect the accurate time-of-day. As such, changes due to daylight savings time changes as well as changes in time zones (if the patient is traveling outside of his/her time zone) may be automatically accounted.  
         [0025]    [0025]FIG. 4 discloses another embodiment of the present invention wherein a sensor  130  provides feedback as to whether the patient is awake or asleep to determine whether signal generator  10  should be turned on or off. In one embodiment, sensor  130  may sense a condition of a patient indicating whether the patient is asleep such as whether the eyes are closed, the breathing patterns, or the heart rate. Advantageously, device  10  shuts on or off in response to any number of physical, biological and/or chemical rhythms of the body indicative of whether the patient is sleeping. For example, the system may sense whether the patient&#39;s eyes shut for an extended period of time signifying that the patient is napping, sleeping or resting. Alternatively, the system may monitor activity or motion, heart rate, or respiration. Other chemical characteristics may also be monitored to determine whether the treatment therapy should be stopped such as oxygen partial pressure, carbon dioxide concentration, or glucose and insulin concentrations. These characteristics may be measured, for example, in the blood stream or other bodily fluid. Any type of sensor may be used to sense the above characteristics of the body. More detailed description of sensor  130  and other examples of sensors are disclosed in U.S. Pat. No. 5,716,377 entitled “Method of Treating Movement Disorders By Brain Infusion,” issued on Feb. 10, 1998 and assigned to Medtronic, Inc., which is incorporated herein by reference in its entirety. Other such sensors are also disclosed in U.S. Pat. Nos. 5,683,422; 5,702,429; 5,713,923; 5,716,316; 5,792,186; 5,814,014; and 5,824,021, all of which are incorporated herein by reference in their entireties.  
         [0026]    Signal generator  10  may be automatically turned on or off if any of the conditions sensed by sensor  130  indicates that the patient is sleeping. Sensor  130  may be used in conjunction with or as an alternative to timer  201  (or a real time clock). If used in conjunction with timer  201 , signal generator  10  may operate with a default of being “off” at night and a default of being “on” during the day. The default is determined by timer  201 . During the day, device  10  may shut off only when a certain threshold of characteristics are sensed by sensor  130  such that it is clear that the patient is asleep. At night when the patient is normally asleep, device  10  may be turned on only when sensor  130  senses characteristics that clearly indicate that the patient has awaken. Sensor  130  provides information to signal generator  10  to determine whether to deviate from the default. These threshold parameters may be adjusted by the physician or the patient. The patient may also have the capability to manually turn on or off signal generator  10  as provided in the art.  
         [0027]    Sensor  130  may also be used to provide closed-loop feedback control of the treatment therapy during periods when device  10  is in operation. Alternatively, one or more additional sensors may be implemented for feedback control. The additional sensor is attached to or implanted into a portion of a patient&#39;s body suitable for detecting symptoms of a disorder being treated, such as a movement disorder or ischemic pain. The additional sensor is adapted to sense an attribute of the symptom to be controlled or an important related symptom. For motion disorders that result in abnormal movement of an arm, such as arm  122 , sensor may be a motion detector implanted in arm  122  as shown in FIG. 4. Such feedback control techniques are disclosed in the patents described above.  
         [0028]    Referring to FIG. 4, the output of sensor  130  is coupled by cable  132  to signal generator  10 . Alternatively, the output of an external sensor would communicate with signal generator  10  via telemetry. In the embodiment of FIG. 4, sensor  130  monitors heart rate and optionally movement.  
         [0029]    [0029]FIG. 5 illustrates a schematic block diagram of the signal generator  10  of FIG. 2 including a sensor signal input from sensor  130 . Sensor  130  is coupled to an analog to digital converter  206  of signal generator  10 . The output of the analog to digital converter  206  is connected to a microprocessor  200  through a peripheral bus  202  including address, data and control lines. Depending upon the particular sensor signal used, an analog to digital converter would not be necessary. The output from sensor  130  can be filtered by an appropriate electronic filter in order to provide a control signal for signal generator  10 .  
         [0030]    Microprocessor  200  is coupled to timer  201  to receive timing information and to sensor  130  to receive patient information. Microprocessor  200  may then responsively determine whether the treatment therapy should be turned on or off. Other componentry of signal generator  10  is shown to generate the desired signal pulsing parameters and/or to provide feedback control of the treatment therapy. The present invention may be practiced without microprocessor  200 . For example, a controller or electrical circuitry having the desired functionality may be implemented in place of microprocessor  200  to receive the timer and/or sensor information and process the information to determine whether treatment therapy is to be delivered.  
         [0031]    The present invention is equally suitable for use in drug infusion systems to automatically provide or cease providing drug therapy to a patient. As shown in FIG. 6, the drug infusion system includes a pump  410  having at least one reservoir for storing at least one drug. The drug may be delivered via a catheter  422 . Catheter  422  may be coupled to a single tube  422 A or tube  422 A may be divided into twin tubes, tube  422 A and a second tube (not shown), that are implanted into the brain bilaterally. The second tube may supply drugs from a second catheter and pump or may supply drugs from catheter  422  to a second location within the brain B. Such drug infusion systems that may incorporate the present invention are disclosed in U.S. Pat. Nos. 5,711,316; 5,713,923; 5,735,814; and 5,782,798, each of which are incorporated herein by reference in their entireties. The drug pump may include similar componentry as that of the signal generators  10  discussed in FIGS. 2,3 and  5 .  
         [0032]    Advantageously, the present invention may be utilized in a number of different treatment therapies, including, but not limited to, treatment of pain, movement disorders and other neurological disorders such as epilepsy, to provide a mechanism to automatically turn off treatment therapy during periods that it is not required or necessary. As used herein, the term disorder includes any disorder, illness or maladies. Additionally, the present invention may automatically turn on the treatment therapy during or right before the patient requires the treatment therapy.  
         [0033]    Those skilled in that art will recognize that the preferred embodiments may be altered or amended without departing from the true spirit and scope of the invention, as defined in the accompanying claims.