Spinal Cord Stimulation
Spinal cord stimulation (SCS) is a surgical procedure used to stimulate the spinal cord and help relieve chronic back pain. The procedure is reserved for patients who have exhausted all other forms of treatment both nonoperative and operative (if indicated) to help ease the chronic back pain.
The spinal cord travels inside the conduit formed by the vertebral column starting from the base of the brain. The spinal cord travels down the body giving numerous branches known as spinal nerves and ends near the L1-L2 vertebrae. The spinal cord is responsible for sending the neural signals from the brain to all four limbs. The spinal cord also transports signals from the peripheral limbs and thorax to the brain. Together these signals help the brain to coordinate the movements of the limbs and sense the different external inputs.
Pain is the body’s natural defense mechanism to help prevent further injury and usually lasts only till the inciting factor is present. The pain gradually gets better once the inciting event has subsided. The inciting event may be an infection, a tumor, a traumatic injury, or a degenerative condition. Chronic pain is usually defined as the pain that continues to affect the patient even after the inciting event is not present.
Mechanism of Spinal Cord Stimulation
The spinal cord stimulation consists of electrodes implanted under the skin that reach the space (epidural space) between the vertebrae and the covering of the spinal cord. The electrodes carry a small amount of electric current from a current generator (small device) which is also implanted in the skin. The patient has the ability to start and change the level of electrical stimulation when he experiences pain.
The stimulator does not remove the source of pain but simply alters the pain signal traveling from the spine to the brain. The altered signal does not relay the signal responsible for triggering the pain center in the brain.
Besides the basic electric impulse from the electrical generator, there are different modes depending upon the patient’s pain level and activity. The physician usually selects the mode which is best suited according to the needs of the patient.
The battery of the SCS may be non-rechargeable or rechargeable. The batteries of non-rechargeable systems may need to be changed every 2-4 years depending upon the manufacturer.
The patients with chronic pain report a significant reduction in the intensity of the pain experienced after implantation of a spinal cord stimulator. The reduction of pain may vary among different patients but the goal is to achieve a reduction of 50% or more in the intensity of pain. With a reduction in pain, the majority of the patients report significant improvement in their quality of sleep and during their day to day activities.
Candidates for Spinal Cord Stimulation
Patients with chronic pain in whom all other forms of conservative management have failed may benefit from spinal cord stimulation. The procedure may also help patients suffering from a failed back syndrome who may not benefit from revision surgery. The patients are typically screened for any underlying psychiatric illness and drug addiction. Besides the chronic back pain caused by degenerative arthritis or trauma, patients with conditions such as complex regional pain syndrome and arachnoiditis may also benefit from SCS.
The procedure of implanting a spinal cord stimulator first involves the implantation of a trial stimulator under local anesthesia. The trial stimulator involves the placement of an electrode through the skin to the epidural space that is connected to an external generator. The patient returns after a week or so to determine if he would get relief from a stimulator. The time period of the trial stimulator also allows the patient to report any side effects of the stimulation that may warrant not going ahead with the procedure.
The placement of a spinal cord stimulation device involves light anesthesia and the creation of holes in the vertebral structures (laminotomy) to insert the electrodes. The electrodes never touch the spinal cord directly and are placed in the epidural space (space between the vertebrae and the spinal cord lining). The wires go under the skin to attach to the generator which is implanted in the buttock.
Commonly patients may report an unusual feeling of paraesthesia upon activating the device for pain. Usually changing the frequency and intensity of transmission may alleviate the symptoms of paraesthesia. As with any surgical procedure, there may be complications of bleeding or infection. Additionally, there may be a complication of leakage of cerebrospinal fluid during the procedure causing frequent headaches.
There may be complications during the procedure such as inadvertent damage to the spinal nerves or the spinal cord from the electrodes which may cause paralysis or numbness of the extremities. There may be battery failure or skin complications from implantation of the generator and electrodes.
Spinal cord stimulation provides excellent pain relief in patients with chronic pain in whom all other treatment options have been tried. The device may be inserted with minimal incisions and is reversible, i.e the stimulator along with the electrodes may be taken out.