Dorsal column stimulation in the treatment of chronic pain

Abstract

In spite of the relatively high number of implanted devices to alleviate the pain, exists scarce evidence on its exact mechanism of action. The position of electrodes in the epidural space and over structures of the spinal cord generates an electric field that is diffused in circularly form around the cathode, that creates a not desire stimulation of the fibers of the posterior root, altering the pain perception. The stimulus is monopolar if the distance among the contacts is larger than the distance between the cathode and the white matter. On the other hand in the bipolar or multipolar stimulus the smaller distance among the electrodes, favors the activation of neuronal fibers parallel to the axis of the device of stimulation. Based on the Ohm’s law, the systems of constant current have more options to discharge the appropriate stimulus to the neural tissue that the constant voltage systems.

An important consideration in the stimulation of the spinal cord is the distance between the epidural space and the layer of the spinal cord (distance of cerebrospinal fluid d-CSF), that varies according to the spinal levels. In the same way the threshold for the fibers of the dorsal root is smaller that for the fibers of the column.

Another advantage of this neuromodulatory divices is the opportunity of carry out a test which a transitorily device and produces a 50% reduction of the pain and better quality of life; otherwise the device is not implanted, avoiding an unnecessary surgery to the patient. The permanent implantation permits that the system (electrodes and generator) be internalized and they will be control by an external device for continuous utilization of the DCS. The DCS is an invaluable therapeutic option in the management of patients in pain that do not respond to other conservative forms of processing.