DBS on one side of the brain usually affects only symptoms on the opposite side of the body. Most patients have symptoms on both sides of the body and thus require both sides of the brain to be implanted for maximal benefit. Some surgical centers only perform "staged” surgeries, that is each side done in a separate surgery separated by several months. As this surgery has become more rapid and routine, many centers now offer "simultaneous bilateral" procedures, or implantation of both leads in a single surgery, to many patients. The brain side opposite the most affected body side is implanted first. Then, if the patient and anesthesiologist agree to proceed, the second side is then implanted. For elderly patients, or patients concerned about a longer operation, it may be best to stage the procedures several months apart.