Reversing recruitment order by anode intensification

A system for delivering a therapy to a patient having a spinal cord region targeted for the therapy where the spinal cord region includes relatively large diameter nerve fibers and relatively small diameter nerve fibers, and where a normal nerve fiber recruitment order activates the relatively large diameter nerve fibers prior to the relatively small diameter nerve fibers, the system comprising:

• a tripolar rostro-caudal arrangement of electrodes configured to be positioned local to the spinal cord tissue region, the tripolar rostro-caudal arrangement of electrodes including a local cathode and a two guarding local anodes on opposite sides of the local cathode;
• at least one remote cathode;
• a neural stimulator configured use the tripolar rostro-caudal arrangement of electrodes deliver therapeutic electrical stimulation wherein the therapeutic electrical stimulation includes local anodic current sourced from the local anodes and local cathodic current sunk into the local cathode, the neural stimulator being configured to deliver the therapeutic electrical stimulation to preferentially stimulate relatively small diameter nerve fibers over relatively large diameter nerve fibers by reversing an expected nerve fiber recruitment order in which the relatively large diameter nerve fibers would be activated prior to the relatively small diameter nerve fibers, wherein the neural stimulator is configured to:
• source the local anodic current from the local anodes in the tripolar rostro-caudal arrangement of electrodes to hyperpolarize nodes in the large diameter nerve fibers;
• sink a local cathodic current into the local cathode in the tripolar rostro-caudal arrangement of electrodes to depolarize both the relatively large diameter nerve fibers and the relatively small diameter nerve fibers, wherein the local cathodic current corresponds to a portion of the local anodic current, and wherein the local anodic current is sufficient to prevent the local cathodic current from generating action potentials in the relatively large diameter nerve fibers and is not sufficient to prevent the local cathodic current from generating action potentials in the small diameter nerve fibers;
• and
• sink a remote cathodic current into at least one remote cathode, the remote cathode current corresponding to a remaining portion of the local anodic current.

A non-transitory machine-readable medium including instructions, which when executed by a machine, cause the machine to deliver a therapy to a patient using a tripolar rostro-caudal arrangement of electrodes positioned local to a spinal cord tissue region targeted for therapy, where the tripolar rostro-caudal arrangement of electrodes includes a local cathode and a two guarding local anodes on opposite sides of the local cathode,

• wherein deliver the therapy includes deliver therapeutic electrical stimulation using the tripolar rostro-caudal arrangement of electrodes to preferentially stimulate relatively small diameter nerve fibers over relatively large diameter nerve fibers, the therapeutic electrical stimulation including local anodic current sourced from the local anodes and local cathodic current sunk into the local cathode, wherein deliver therapeutic electrical stimulation includes reverse an expected nerve fiber recruitment order in which the relatively large diameter nerve fibers would be activated prior to the relatively small diameter nerve fibers,
• wherein reverse the normal nerve fiber recruitment order includes:
• hyperpolarize nodes in the large diameter nerve fibers to prevent action potentials in the relatively large diameter nerve fibers, wherein hyperpolarize nodes in the relatively large diameter nerve fibers includes source the local anodic current from the local anodes in the tripolar rostro-caudal arrangement of electrodes;
• depolarize both the relatively large diameter nerve fibers and the relatively small diameter nerve fibers by sinking the local cathodic current into the local cathode in the tripolar rostro-caudal arrangement of electrodes, wherein the local cathodic current corresponds to a portion of the local anodic current, and wherein the local anodic current is sufficient to prevent the local cathodic current from generating action potentials in the relatively large diameter nerve fibers and is not sufficient to prevent the local cathodic current from generating action potentials in the small diameter nerve fibers;
• and
• sink a remote cathodic current into at least one remote cathode, the remote cathode current corresponding to a remaining portion of the local anodic current.