Spinal Cord Stimulator (SCS) is an instrument similar to cardiac pace maker. Like cardiac pace maker it is implanted permanently under the skin. From the instrument very fine wire come out and go to the spinal cord.
The machine which is implanted under the skin is called the Implantable power generator (IPG) and the wire with electrodes are called leads.
There are different kinds of IPG, depending on battery type in IPG. In the conventional type battery lasts for about 6-8 years. In rechargeable one it lasts for 12-14 years.
The lead also are different types depending on number of electrode. Octopolar lead with 8 contact points are most frequently used nowadays.
What is the mechanism of action of Spinal Cord Stimulation?
It acts by several mechanisms:
1. Gate control theory- stimulation of larger diameter nerve fibers inhibits pain carrying small diameter fibers.
2. Secretion of putative neurotransmitters that inhibits pain signals.
3. It produces supraspinal inhibition of pain either by inhibiting pain transmission or modulation of pain impulses.
4. Sympathetic inhibition by some mechanisms.
Who are the candidates?
Neuropathic pain responds best with spinal cord stimulation. When most of the other options of has failed neuro-stimulation should be tried.
1. Failed back surgery syndrome (FBSS) / Post laminectomy syndrome / Failed back syndrome
2. Radiculopathy involving single or multiple roots,
3. Complex Regional Pain Syndrome
4. Diabetic Neuropathy
5. Atypical recurrent angina
6. Post-scar or post-traumatic neuralgia,
7. Post-herpetic neuralgia
8. Phantom limb pain
What is the success rate for these procedures?
Overall success rate (more than 50% pain relief) is around 80%. Before implanting the Power generator it is advisable to give a trial stimulation to assess the efficacy of this procedure. Failure after successful trial is possible but very rare.
What is trial stimulation?
It is like temporary pacemaker. The stimulating electrodes / leads are implanted and stimulated with external power source. Then the patient is asked to assess pain relief over next few days. If pain relief is more than 50% then permanent implantation is done.
What are the preliminary steps before SCS?
1. Evaluation of pain.
2. Psychiatric evaluation.
3. Patient education: about pre- and post-procedure plan and long-term management, cost effectiveness.
4. Planning of procedure.
Is it cost-effective?
If we weigh between sufferings, total cost of other form of treatment SCS is cheaper if patient can afford.
How long it is effective?
1. It depends on type of IPG.
2. It depends on type of stimulation parameter.
3. With conventional type it is effective for 5-8 years. IPG should be replaced after that.
Can the patient lead a normal life?
1. In most patients SCS can be kept in “OFF” mode for sometimes without return of pain. Otherwise patients can lead near normal life style.
2. There are some situation when it is kept in “OFF” mode by a remote or magnet by the patients themselves.
3. Normal household equipment, such as cell or portable phones, computers, TVs, microwaves, and other appliances are safe to use with the stimulator.
What are the conditions when SCS are kept in “OFF” mode?
1. Driving cars or using heavy equipment.
2. Passing through metal detectors.
3. Passing through anti-theft devices.
4. When flying, during take off and landing.
Dr. Palak Modi(Mehta) and group of doctors during spinal cord stimulation procedure
How SCS is implanted?
It is done in two stages.
1st stage is trial stimulation. When lead is placed over spinal cord at desired position but the IPG is kept outside the body. During trial stimulation feedback is taken from patient whether and how much pain is relieved. If pain reduction is more than 50% then decision of permanent implantation is taken.
2nd stage is the permanent implantation. The IPG is implanted inside the body and connected with the leads placed at spinal cord.
This therapy aims at pain relief in patients who are refractory to all other treatment modalities. There are many advantages of using this therapy like: