Neurostimulation overrides the body’s nervous system to bring relief from painful conditions, says Dr Melanie Wynne-Jones
Our brain controls what we feel, how we move and behind-the-scenes activities, such as hormone production, as well as how we think and react. Body areas are represented in the ‘sensory cortex’, which registers touch, pain, temperature, position, hearing, sight, taste and smell, and in the ‘motor cortex’, which controls voluntary and involuntary movements, such as the heartbeat.
Billions of neurones (nerve cells) form a complex web, and collect information and relay instructions from the body. Neurotransmitter chemicals, such as dopamine, acetylcholine and serotonin, enable electrical signals to jump across ‘junction boxes’ in the brain and spinal cord.
Pain, strange sensations and movement disorders can be caused by ‘wiring faults’ as well as by disease, so pain, which is supposed to alert us, can become a long-term problem in itself.
How we currently treat pain
Aspirin and other non-steroidal anti-inflammatory drugs, such as ibuprofen, target prostaglandin chemicals produced by inflammation, which can trigger pain signals in the affected part. Paracetamol targets similar chemicals.
Opiates, such as codeine and morphine, work by blocking pain receptors in the brain, spine and around the body. Amitriptyline (a tricyclic antidepressant), gabapentin and other epilepsy drugs used for neuropathic pain/neuralgia (such as sciatica, or after shingles), block nerve pain signals so they can’t reach the brain.
All these drugs can cause drowsiness, nausea and other side effects.
Nerve blocks at the dentist, for minor surgery or relief of sciatica/labour pain (epidural) use injected local anaesthetic to change nerve cell chemistry, so it can’t transmit pain signals.
What is neurostimulation?
We use this instinctively when we ‘rub it better’ or treat pain with a hot or cold compress. These sensations out-compete pain signals. TENS (transcutaneous electrical nerve stimulation) machines have been around for some time and involve placing a special pad on the affected area.
The machine then produces tiny electric impulses that relieve pain.
Newer neurostimulation (or neuromodulation) techniques work by inserting tiny microelectrodes into tissue. These trigger electrical signals that activate nearby nerve tissue. For example, unmanageable sciatica may be relieved by peripheral nerve stimulation (PNS) or spinal cord stimulation (SCS). ‘Trial’ electrodes are inserted under the skin first to see if it works.
Deep brain stimulation (DBS) is another type of neurostimulation. This ‘functional’ brain surgery changes the way the brain behaves, and has around a 50% chance of relieving chronic pain, or replacing it with a more pleasant tingling sensation. An electrode is inserted through your skull, using local anaesthetic.
This means you can tell the surgeon what you’re feeling, and where, so it can be correctly located.
If PNS or DBS appear to work, then they’ll be connected to permanent wires and an external controller, which you can programme yourself.
But as PNS or DBS may not be fully effective, or may cause problems with bleeding, infection or MRI scans, they’re often only used for pain that can’t be controlled by the usual means, and may not be available in all areas.
5 more uses for the treatment
1. DBS can relieve symptoms of Parkinson’s disease, other movement disorders and some forms of epilepsy.
2. Cochlear implants placed behind the ear can restore hearing caused by nerve deafness.
3. Advances in spinal-cord stimulation are helping people with paraplegia to walk.
4. Sacral neuromodulation (device implanted in the buttock) can improve bladder control and incontinence.
5. Researchers believe neurostimulation could be developed to treat anorexia nervosa, obesity, Tourette’s syndrome or depression.