CHICAGO—Parkinson’s sufferers who had electrodes implanted in their brains improved substantially more than those who took only medicine, according to the biggest test yet of deep brain stimulation. The study, which followed patients for six months, offers the most hopeful news to date for Parkinson’s sufferers. The new technique reduced tremors, rigidity and flailing of the limbs and allowed people to move freely for nearly five extra hours a day. But the research also revealed higher-than-expected risks. About 40 percent of the patients who received these “brain pacemakers” suffered serious side effects, including a surprising number of falls with injuries. “We had one patient who felt so good he went up to repair his roof, fell down and broke both his legs,” said lead author Fran Weaver of Hines Veterans Affairs Hospital, outside Chicago. “Patients are feeling so much better, they forget they still have Parkinson’s.”