The Eon Mini is world's smallest rechargeable spinal cord stimulator, approved by the FDA to treat chronic pain of the trunk and limbs and pain from failed back surgery. The device is typically implanted in the buttock area and sends mild electrical pulses to leads located near the spinal cord. These pulses interrupt the pain signals as they travel to the brain. Battery needs surgical replacement after about 10 years. Credit: St. Jude Medical Inc.