In one embodiment, an introducer is provided for implanting an electrical stimulation lead to enable electrical stimulation of nerve tissue. The introducer includes an outer sheath and an inner penetrator. The outer sheath may accommodate insertion of the electrical stimulation lead and may be inserted into a human body near the nerve tissue. The inner penetrator is removably housed within the outer sheath and includes an inner channel configured to accommodate a guide wire, a tip end having a shape and size substantially conforming to that of the guide wire, a body region having a shape and size substantially conforming to that of the outer sheath, and one or more transition regions substantially connecting the tip end with the body region. At least a portion of the transition regions of the inner penetrator may flex to substantially follow flexures in the guide wire during advancement of the inner penetrator.