About the size of a matchbox, the battery-operated Medtronic Restore uses electrical impulses to reduce chronic nerve pains such as those related to spinal injury and diabetes.

Introduced in the United States in 2005, it was brought to Singapore a year later.

Its latest version, RestoreUltra, will be out soon. RestoreUltra is smaller and has better software features that are tailored to counter the patient's pain more effectively.

The device is surgically implanted and can be turned on through a hand-held programmer.

In Mr Mercado's case, electrical leads inserted in his spine were tunnelled under the skin and attached to a battery that was implanted in his abdomen.

The electrical impulses produced prevent pain signals from reaching his brain.

The battery is recharged by an external charger, which needs only to be in contact with the skin above the abdomen.

The frequency of recharging will depend on the duration of use.

Mr Mercado recharges the battery of his device once every three weeks as he turns it off when he is asleep.

This device is used at SGH's Pain Management Centre, the National Neuroscience Institute, The Pain Specialist and the Singapore PainCare Center.

US medical technology company Medtronic, which has headquarters in Minneapolis, opened a Singapore plant this month in Changi.

This article was first published in Mind Your Body, The Straits Times.