Selective dorsal column stimulation in SCS, using conditioning pulses

A system and method is described for preferentially stimulating dorsal column fibers while avoiding stimulation of dorsal root fibers. The invention applies hyperpolarizing (anodic) pre-pulses (HPP) and depolarizing (cathodic) pre-pulses (DPP) to neural tissue, such as spinal cord tissue, through a lead placed over the spinal cord having the electrodes arranged on a line approximately transverse to the axis of the spine. To increase the threshold needed to stimulate dorsal root fibers, the anodal pulse given by each lateral contact of the electrode, is preceded by a DPP. The cathodic pulse, given simultaneously by the central electrode contact is preceded by an HPP, thereby reducing the stimulation threshold for the dorsal column fibers.