Disclosed methods and devices treat chronic lower back pain from degenerated or injured intervertebral discs. Electrodes connected to a pulse generator deliver electrical impulses to nerves located within the posterior longitudinal ligament and annulus fibrosus of lumbar intervertebral discs. The stimulation reduces back pain reversibly, adjustably, and with almost complete coverage of the pain-generating region. A temporary percutaneous lead and a permanent paddle lead are used. The percutaneous lead, designed to prevent inappropriate stimulation of the thecal sac, is inserted using a specially-designed introducer cannula and lead blank. The paddle lead is configured individually for implantation in the anterior epidural space of each patient. Electrical stimulation parameters may also be selected so as to ablate the nerves, using non-thermal irreversible electroporation, or using joule heating wherein a thermal insulator covers substantially all of the thecal sac, thereby shielding the thecal sac from potential heat damage.