While nobody's exactly sure how it works, it's been clinically proven over the past 30-40 years that low levels of electrical energy, delivered straight to the nerve fibers in the spinal cord, can disrupt the signals that certain chronic pain conditions send to the brain, and replace them with a much more pleasant tingling sensation. Now, St Jude Medical has received FDA and CE mark approvals for the world's smallest and longest-lasting rechargeable neurostimulator. The Eon Mini is the size of a silver dollar, about 1cm thick (1/2 inch), and weighs only 29g (1oz). It sits under the skin of the buttock or abdomen, and its rechargeable battery should last nearly 10 years. It can be programmed by remote control to treat as many as eight different chronic pain areas and, in doing so, it can get many patients with chronic pain off morphine and back into a semblance of normal life.

Chronic pain is a broad condition that simply refers to pain that continues to be present long after an injury is expected to be healed. For many sufferers, it's a crippling and ever-present fact of life that affects work, relationships, sleep and many other areas. Often, the side effects of pain relief strategies can be as crippling as the pain itself.

The first use of small electrical currents as a human analgesic was reported in 1971 - a Japanese team found that by sending small electrical currents through wires running along the epidural space - the outermost part of the spinal canal - they could disrupt the crippling pain signals being sent back to the brain, and replace them with a much more pleasant buzzing sensation.

Spinal Cord Stimulation (SCS) is not a cure for chronic pain conditions - it's just a pain relief strategy. But it can be extremely effective, reducing the pain by 50 percent or more without the side effects associated with opioid analgesics like morphine. It's viewed as somewhat of a last resort for cases in which patients are unable to achieve a satisfactory quality of life using other pain relief methods.

The Eon Mini represents a step forward in the delivery of SCS pain relief. Its small size allows the main unit to be implanted more deeply and less obtrusively under the skin than larger alternatives, and the 10-year life of its rechargeable battery means that patients need replacement operations far less frequently.

The patient first takes a short trial to see if the system is likely to deliver effective pain relief. This involves the implantation of the electrodes, but not the SCS device. If the doctor deems the results satisfactory and the patient suitable, the Eon Mini is buried under the skin.

The doctor is able to treat up to eight pain areas through 16 different header contacts, allowing the treatment of complex pain patterns throughout the lower body. It's programmed on the operating table with the patient awake and reporting back to the doctor on which areas of pain need the most attention. It's usually an outpatient treatment, and the results are immediate and last as long as the battery.

It's not precisely known how the SCS technique confuses the body's pain receptors - it could be one of a handful of different ways. But it's effective in many cases, and shows very few side effects. More information at www.poweroveryourpain.com.