Apparatus and methods for stimulating tissue

A neurostimulation system, comprising:

• an implantable lead, having a plurality of lead electrodes, disposed in a vicinity of a target tissue;
• a remote electrode disposed outside the vicinity of the target tissue;
• and
• an implanted pulse generator (IPG) operably connected to the plurality of lead electrodes, the IPG comprising:
• circuitry configured to source current at a first lead electrode of the plurality of lead electrodes;
• circuitry configured to sink a first cathodic portion of the current at a second lead electrode of the plurality of lead electrodes, wherein sinking the first cathodic portion of the current creates a local current imbalance in the vicinity of the target tissue;
• and
• circuitry configured to sink a second cathodic portion of the current at the remote electrode, wherein an overall current balance is maintained among the first lead electrode, the second lead electrode, and the remote electrode.

A neurostimulation system, comprising:

• an implantable lead, having a plurality of lead electrodes, disposed in a vicinity of a target tissue, the target tissue having a first neural fiber bundle and a second neural fiber bundle;
• a remote electrode disposed outside the vicinity of the target tissue;
• an implanted pulse generator (IPG) operably connected to the plurality of lead electrodes, the IPG comprising:
• circuitry configured to source current at a first lead electrode of the plurality of lead electrodes;
• circuitry configured to sink a first cathodic portion of the current at a second lead electrode of the plurality of lead electrodes, wherein the first cathodic portion of the current has a magnitude sufficient to generate action potentials in neural fibers in the first and second neural fiber bundles, the first neural fiber bundle being a first distance from the implantable lead and the second neural fiber bundle being a second distance, that is different than the first distance, from the implantable lead, and wherein sinking the first portion of the current creates a local current imbalance in the vicinity of the target tissue;
• and
• circuitry configured to sink a second cathodic portion of the current at the remote electrode, wherein an overall current balance is maintained among the first lead electrode, the second lead electrode, and the remote electrode.

A method of using an implantable pulse generator (IPG) for neurostimulation, comprising:

• selecting a first electrode in a vicinity of a target tissue, the first electrode configured for sourcing stimulation current, the target tissue comprising a first neural fiber bundle and a second neural fiber bundle;
• selecting a second electrode in the vicinity of the target tissue, the second electrode configured for sinking stimulation current, the second electrode being a first distance from the first neural fiber bundle and a second distance, different than the first distance, from the second neural fiber bundle;
• selecting a remote electrode outside the vicinity of the target tissue, the remote electrode configured for sinking stimulation current to reduce the amount of current sunk at the second electrode;
• sourcing current at the first electrode;
• sinking a first portion of the current at the second electrode, wherein sinking the first portion of the current creates a local current imbalance in the vicinity of the target tissue;
• and
• sinking a second portion of the current at the remote electrode to reduce the amount of current sunk at the second electrode and maintain an overall current balance among the first electrode, the second electrode, and the remote electrode.