When Spinal Cord Stimulation is used for management of pain?

• For persisting back pain following spinal surgery. (Failed back surgery syndrome/ perineural fibrosis)
• Adhesive arachnoiditis
• CRPS type I & CRPS type II
• Post herpetic neuralgia
• Peripheral neuropathy
• Phantom limb pain/stump pain
• Peripheral vascular insufficiency
• Angina
• Cerebral palsy
• Multiple sclerosis

How Spinal Cord Stimulation relieves the pain?

Spinal cord stimulator act in by several ways.

• Gate control theory of pain The pain impulses from periphery are transmitted through smaller diameter nonmyelinated C fibres and lightly myelinated A-delta fibres. They terminate at the substantial gelatinosa of dorsal horn of spinal cord (the gate). Other sensory impulses like touch and vibration are carried by larger diameter myelinated A-beta fibres that also terminate at the dorsal horn (gate) of spinal cord. The reception of large fibre information (touch and vibration) would switch off the gate to reception of small fibre information. The end result of this closure of gate is analgesia. Shealy and colleagues use same principle; stimulation of A-beta fibres of dorsal column by electricity closes the gate and antidromically inhibits the pain impulses from small fibres.
• It produces supraspinal inhibition of pain either by inhibiting pain transmission or modulation of pain impulses.
• Blocking transmission in the spinothalamic tract
• It activates the central inhibitory mechanisms for influencing sympathetic efferent neurons. This leads to vasodilatation. In fact this effect is used in improving perfusion in peripheral vascular disease and also to take care of pain.
• It has been observed that even after cessation of spinal cord stimulation, the analgesia lasts for longer time. This is being attributed to activation of putative neurotransmitters or neuromodulators.

What are the advantages of spinal cord stimulation?

This therapy aims at pain relief in patients who are refractory to all other treatment modalities. They are very tough group to get good results.
There are many advantages of using this therapy like:

1. It’s a simple Percutaneous/ surgical procedure.
2. It’s a nondestructive procedure. No permanent surgical or chemical interruption of nerve pathway is done.
3. A trial therapy checks whether patient is going to get pain relief or not.
4. The procedure is reversible; if patient is not relieved of his symptoms, the stimulator can be removed. There will not be any side effects.
5. From patient’s point of view:
1. Significant reduction in pain intensity
2. Reduction in opioids or other drug intake
3. Improvement of quality of life.

How to select a patient for spinal cord stimulation?

Selection criteria for spinal cord stimolation are -

1. The pain syndrome should be established & patient should have radiating pain.
2. The conservative treatments have failed.
3. Drug addiction/alcohol abuse should be ruled out.
4. There should be no major.
5. Trial stimulation should be successful.

 Is it cost-effective?

If we weigh between sufferings, total cost of other form of treatment SCS is cheaper if patient can afford.

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. 

Procedure - 

The procedure involves percutaneous insertion of lead, typically a ‘longitudinal’ lead with a linear array of electrodes through an epidural needle into the epidural space and oriented parallel to spinal column. First step is the introduction of a trial electrode for temporary purpose. The lead is connected to an external battery source that transmits radiofrequency signals to the lead. The external transmitters help in adjusting the amplitude, pulse width and rate of stimulation. The low voltage electrical stimulation is applied to the spinal cord to create a current field that activates neurons in the dorsal column. This stimulation is done by the external power supply connected to lead by either a conducting wire or extension. The stimulation produces paraesthesia that interferes with or blocks pain signals to brain. The vertebral level at which it is placed depends upon the location of pain. If patient gets 50% or more pain relief after trial stimulation, then patient is considered for permanent implant. Replacing the temporary lead with permanent lead usually does this. Implanted pulse generator provides the power supply.

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.





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.

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.