Implantable technologies for pain management

Chronic pain occurs in up to half the adult population at some point in their lives, with 10% of this group disabled by pain. Unrelieved chronic pain is a major socioeconomic and healthcare problem and successful management of affected individuals requires a full range of treatment options. Since Melzack and Wall's Gate Theory of Pain was first proposed, an improved understanding of neuroscience has lead to development of implantable ‘neuromodulatory’ technologies for refractory pain. Simply put, such technologies involve drug delivery to, or electrical stimulation of neural pathways. In the context of pain management, neuromodulation aims to reduce afferent activity within pain pathways by targeted electrical neurostimulation or drug delivery into cerebrospinal fluid. Targets for implanted neurostimulators include the spinal cord, peripheral nerves or brain, while implantable pumps deliver analgesic drugs to intrathecal or intracerebroventricular sites. Implantable neuromodulation therapies are expensive, invasive and prone to side effects and complications. Clinicians and health professionals involved with implantation and aftercare of such devices require a high level of expertise. In spite of these challenges the uptake of these therapies continues to rise worldwide as does the evidence for cost-effectiveness. To optimize outcomes, patients being considered for neuromodulatory therapies must undergo comprehensive biopsychosocial assessment, be fully informed regarding risks and have realistic expectations. This article will focus on spinal cord stimulation and intrathecal drug delivery (ITDD) for the non-expert.