A Spinal Cord Stimulator (SCS) is used to exert pulsed electrical signals to the spinal cord to control chronic pain. Spinal cord stimulation, in the simplest form, consists of stimulating electrodes, implanted in the epidural space, an electrical pulse generator, implanted in the lower abdominal area or gluteal region, conducting wires connecting the electrodes to the generator, the generator remote control, and the generator charger. Spinal cord stimulation has notable analgesic properties and, at the present, is used mostly in the treatment of failed back surgery syndrome, complex regional pain syndrome and refractory pain due to ischemia.
Electrotherapy of pain by neurostimulation began shortly after Melzack and Wall proposed the gate control theory in 1965. This theory proposed that nerves carrying painful peripheral stimuli and nerves carrying touch and vibratory sensation both terminate in the dorsal horn (the gate) of spinal cord. It was hypothesized that input to the latter could be manipulated to “close the gate” to the former. As an application of the gate control theory, Shealy et al. implanted the first spinal cord stimulator device directly on the dorsal column for the treatment of chronic pain in 1971.
Spinal cord stimulation does not eliminate pain. The electrical impulses from the stimulator override the pain messages so that the patient does not feel the pain intensely. In essence, the stimulator masks the pain. The stimulation must be done on a trial basis first before the stimulator is permanently implanted. Implanting the stimulator is typically done using a local anesthetic and a sedative. The physician will first insert a trial stimulator through the skin (percutaneously) to give the treatment a trial run. (A percutaneous stimulator tends to move from its original location, so it is considered temporary.) If the trial is successful, the physician can then implant a more permanent stimulator. The stimulator itself is implanted under the skin of the abdomen, and the leads are inserted under the skin to the point where they are inserted into the spinal canal. This placement in the abdomen is a more stable, effective location. The leads, which consist of an array of electrodes, could be percutaneous type or paddle type. Percutaneous electrodes are easier to insert in comparison with paddle type, which are inserted via incision over spinal cord and laminectomy.
There are a number of the problems that exist in currently available SCS systems that limit the full benefits of dorsal column stimulation from an effectiveness and patient user friendly perspective. For example, SCS systems are limited at the moment to only 16 electrodes with a maximum of 16 independent current sources. In addition, current SCS systems have complicated trialing methods that involve multiple gadgets and hardware even in current wireless SCS systems. Patients at the moment must carry an independent remote control in order to control the IPG in their daily lives.