Fractionalized stimulation pulses in an implantable stimulator device

#The present invention relates to therapeutic electrical stimulation systems and methods and, more specifically, relates to adjusting electrodes of an implantable stimulator device.

#Implantable stimulation devices are devices that generate and deliver electrical stimuli to body nerves and tissues for the therapy of various biological disorders, such as pacemakers to treat cardiac arrhythmia, defibrillators to treat cardiac fibrillation, cochlear stimulators to treat deafness, retinal stimulators to treat blindness, muscle stimulators to produce coordinated limb movement, spinal cord stimulators to treat chronic pain, cortical and deep brain stimulators to treat motor and psychological disorders, and other neural stimulators to treat urinary incontinence, sleep apnea, shoulder sublaxation, etc. The present invention may find applicability in all such applications, although the description that follows will generally focus on the use of the invention within a spinal cord stimulation system, such as that disclosed in U.S. Pat. No. 6,516,227, which is incorporated herein by reference in its entirety.

#Spinal cord stimulation is a well-accepted clinical method for reducing pain in certain populations of patients. As shown in FIGS. 1A, 1B, 2A, and 2B, a Spinal Cord Stimulation (SCS) system typically includes an Implantable Pulse Generator (IPG) or Radio-Frequency (RF) transmitter and receiver 100 (collectively, “IPGs”), at least one electrode lead 102 and/or 104 having a plurality of electrodes 106, and, optionally, at least one electrode lead extension 120. The electrodes 106 are arranged in a desired pattern and spacing on the lead(s) 102, 104 to create an electrode array 110. Wires 112, 114 within one or more leads(s) 102, 104 connect each electrode 106 in the array 110 with appropriate current source/sink circuitry in the IPG 100.

#FIGS. 1A and 1B show an electrode array and the manner in which it is coupled to the implantable stimulator device in a SCS.

#FIGS. 2A and 2B show a placement of the percutaneous lead for spinal cord stimulation with an in-line electrode array inserted alongside the spinal cord in the epidural space, in close proximity to the dura mater.

#FIG. 3A and 3B show placement of two in-line electrode arrays on the left and right sides of the physiological midline of the spinal cord, respectively, in a perspective view and in cross-section.

#The description that follows relates to use of the invention within a spinal cord stimulation (SCS) system. However, the invention is not so limited. Rather, the invention may be used with any type of implantable medical device system. For example, the present invention may be used as part of a system employing an implantable sensor, an implantable pump, a pacemaker, a defibrillator, a cochlear stimulator, a retinal stimulator, a stimulator configured to produce coordinated limb movement, a cortical and deep brain stimulator, or in any other neural stimulator configured to treat any of a variety of conditions.

#A method for configuring stimulation pulses in an implantable stimulator device having a plurality of electrodes is disclosed, which method is particularly useful in adjusting the electrodes by current steering during initialization of the device. In one aspect, a set of ideal pulses for patient therapy is determined, in which at least two of the ideal pulses are of the same polarity and are intended to be simultaneously applied to corresponding electrodes on the implantable stimulator device during an initial duration. These pulses are reconstructed into fractionalized pulses, each comprised of pulse portions. The fractionalized pulses are applied to the corresponding electrodes on the device during a final duration, but the pulse portions of the fractionalized pulses are not simultaneously applied during the final duration.

#An improved current steering technique for an implantable stimulator device is illustrated in FIGS. 8A and 8B. However, before discussion of that technique, a more fundamental understanding of the technological and biological aspects of the technique are illustrated in FIGS. 7A and 7B.