A study designed to evaluate a new Burst mode in some St. Jude Medical Inc. (St. Paul, Minn.) spinal cord stimulation (SCS) devices compared to traditional tonic stimulation has shown a strong patient preference for the intermittent "burst" pulses for chronic pain. St. Jude said the SUNBURST study, which it launched about two years ago, demonstrated that Burst stimulation is superior to traditional tonic stimulation when used to relieve chronic pain.