Spinal Cord Stimulation

What is spinal cord stimulation?

Spinal cord stimulation or posterior medullary cord stimulation is a technique that has shown success in selected patients suffering from chronic pain. It is based on the principle that electrical impulses block the perception of pain, which is replaced by a tingling sensation in the painful region.

A small wire (an electrode) is implanted in the epidural space, and connected to a generator that is placed under the skin. The generator produces low-voltage electrical signals that are transmitted from the electrode to the spinal cord or specific nerves, thus preventing the painful signals from reaching the cerebral cortex. Using a remote control (a special knob) the patient can turn the electrical stimulation on and off and adjust the intensity.

Most patients describe the perceived sensations as a pleasant tingling sensation instead of pain in the affected body area.

Recently, another implantable modality has also become available: the High Frequency Spinal Neurostimulation System, which produces pain relief without paresthesia or cramping and is indicated as an adjunct in the treatment of chronic refractory pain of the trunk and extremities, including unilateral or bilateral pain.

How is it implanted?

Surgical implantation of the stimulator is performed in two phases:

• Test phase. It is used to test the stimulation system and check if it is effective in relieving pain and if it is satisfactory for the patient. It is performed under intravenous sedation and local anesthesia. With radiological image control, one or two electrodes are implanted inside the spine until they are left in the lumbar, dorsal or cervical epidural space (depending on the part of the body where the pain is located). The opposite end of the electrode is then brought to the outside and connected to an external stimulator device. For several weeks the patient will carry the external stimulator with him and will try different stimulation modalities, in order to assess whether his pain is relieved and whether the definitive implant is worthwhile.
• Definitive implant. It is performed in the same way under sedation and local anesthesia. An incision is made in the buttock, abdomen or chest area, depending on where the electrodes are located and where it is most comfortable for the patient, and a pulse generator (similar to a cardiac pacemaker) is inserted under the skin. The generator is connected to the electrodes in the vicinity of the medulla, passing them under the skin. From this moment on, the modifications to be made in the operation of the electrodes will be made by means of an external remote control, and can be carried out by the patient himself.

It is usual that during the first weeks it is necessary to make adjustments in the electrical parameters of stimulation, so that the pain relief is optimal.

Which patients can benefit?

Spinal cord stimulation has been shown to be effective in patients with the following conditions:

• Lumbar or cervical pain radiating to the extremities after failed surgery.
• Complex Regional Pain Syndrome (Reflex Sympathetic Dystrophy).
• Refractory anginal pain.
• Chronic pain due to ischemia of the lower extremities.

Despite promising results, spinal cord stimulation is not the first therapeutic option to be considered. It should be reserved for patients in whom all other pharmacological, rehabilitative and minimally invasive treatments have failed.

Lifestyle after implantation

• Do not drive or operate heavy machinery while the stimulator is running. You can ride as a passenger.
• Although the electrodes are fixed to the spine with a special system, however, they can be mobilized, which can happen, being necessary to reposition them. It is therefore necessary to take into account that the wearers of a stimulation system may not perform strenuous physical exercise or sports involving flexion and extension of the spine. It is also not recommended that they carry weights or exert themselves.
• With a spinal cord stimulator it is not recommended to perform radiofrequency procedures or magnetic resonance imaging.
• Spinal cord stimulators may set off metal detector alarms (as in airports). You will need to carry special identification at all times to certify that you have an implanted stimulation system.
• During the flight, staff may ask you to turn off the stimulator during takeoff and landing.
• Some stimulators may be sensitive to the anti-theft controls in some stores, and produce variations in stimulation while crossing. If in doubt, it is best to turn the stimulator off when passing through the controls.
• The stimulator control acts like a magnet, so it is advisable to keep it at least 5 cm away from magnetic strips such as credit cards and hard disks.

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