History and present state of targeted intrathecal drug delivery.

Nearly 50 years ago, the seminal experiments of Melzack and Wall, culminating in the gate control theory, coupled with the discovery of endogenous opioid receptors, helped shape modern understandings of pain and provided interventionalists a potent therapeutic gateway to neuraxial analgesia. This paper emphasizes the historical antecedents, present state, and emerging future of the neuromodulatory technique of targeted intrathecal drug delivery (TIDD) for chronic pain. The strengths of TIDD are its customizability, reversibility, programmability, and low risk profile. Its benefits are evidenced by improved pain relief and quality of life and reduced demand for health-care resources.