Department of Anaesthesia, Royal Free Hospital, London, UK
It is the use of electric energy in the vicinity of the spinal cord. The leads are placed in the epidural space to stimulate the spinal cord.
52.1 Mechanism of Action
The stimulation works on the gate theory of pain control. Noxious stimuli are inhibited once they enter the second-order neurons of the substantia gelatinosa by spinal cord stimulation, causing blockage of the spinothalamic tract. This inhibition at the entry zone of the dorsal ganglia can result in paraesthesia and analgesia. The greater is the distance between stimulation electrode and spinal cord, the greater is the energy required to stimulate. Multiple electrodes placed together give better results than a single electrode. Spinal cord stimulation also causes downregulation of the wind-up.
Two types of leads are used – paddle type or percutaneous. Percutaneous leads are less efficient in energy usage as they provide 360° stimulation. Power source is attached to the electrodes which provide power either intermittently or continuously (implantable pulse generator units).