JOIN USHimani (name changed), a 35 year old woman, was operated twice for lumbar spine disc disease but still had severe burning pain in the right leg, despite oral medications, and three spinal injections after surgery. The MRI showed good decompression, but also showed scar formation at site of the operation.
After counselling, she was taken up for trial lead insertion through a needle. The tip of the trial lead was kept at D 10 vertebra level, and she immediately reported a more than 70% reduction in pain. She was taken up for a permanent lead and pacemaker insertion through a small incision, and today enjoys a very good quality of life, needing medications infrequently, and has been able to start physiotherapy.
Pacemaker technology
This technology is a last resort for patients suffering from chronic pain that is resistant to any other treatment. Just like a pacemaker in the heart can regulate the contraction of the muscle and maintain a normal rhythm, a pacemaker in the spine can produce electric impulses that can neutralise the pain.
The device is implanted under the skin, and when the electrode is put over the spinal cord, electrical impulses are generated that neutralise the pain impulses, thus overriding the pain. This mechanism works over the principle known as the Gate Control Theory of Pain.
Gate control theory
When a tissue is injured or damaged, pain signals from that part of the body need to reach the brain for the individual to be able to feel it. These signals have to pass through neurological gates at the spinal cord which decide whether or not to allow these signals. This theory says that non-painful impulses close the gates to prevent pain signals from travelling to the central nervous system (from spinal cord to the brain).
Peripheral nerve fibres can be classified into three categories namely – A, B, and C. The A fibres are further classified into A-alpha, A-beta, A-gamma, and A-delta. Of these, A-delta and C fibres carry pain signals to the spinal cord. In the back of the spinal cord, in the dorsal horn, a specialised area called the substantia gelatinosa, these nerves communicate and pass signals. These impulses can be reduced by other interneurons by the release of a morphine-like chemical called enkephalin.
How does this technology feel?
Based on this principle, an electronic device is implanted under the skin and electrodes are placed in the epidural space. A few milliamperes of current are generated at a high frequency to block the pain signals from travelling through the spinal cord to the brain.
The implantation doesn’t require major surgery. Usually, it is done in two steps – trial implant and permanent implant. It is important to know how well the patient reacts to the stimulation before getting it permanently implanted. A temporary implantation is done, which is connected to an external stimulator and is programmed to cover the painful areas.
This helps the patient decide whether this therapy is effective for the level, type, location and the severity of pain.
As it has various stimulation settings and programs, the effectiveness with patient body is also checked.
Depending on the type and level of relief – immediate or with time – the type of system to be implanted – conventional or rechargeable – can be decided
If this process is effective, the second step is followed, with the permanent implantation. One or more leads are inserted depending upon the pain in the exact location using a small needle or an incision. It can be implanted at a comfortable point of your choice but it is commonly and preferably embedded in the lower abdomen on one side.
Benefits
Once the surgical wound heals, it is easy to forget about the device. The sensations can vary from person to person, but are mostly recorded as a pleasant tingling. An easy and quick healing therapy that makes one get back to routine work with a few exercises prescribed by the physician, this technology helps you get your life back.
If necessary, this device can be used round the clock, and based on the feedback, people usually turn it on during the day time and give it rest when they go to sleep, as the effect is carried over to relieve pain. This is the best part, that it can be controlled, so you can lead a normal life as anyone else does, in using any gadgets or electronic devices.
(The author is director, Neurosurgery, Artemis Hospital, Gurugram)