Outcome after surgical anastomosis (bypass surgery) The purpose of surgical anastomosis, either direct or indirect method, is essentially to prevent recurrent stroke. This means that the neurological deficits that are already present will not disappear. In the case of ischemic onset, the purpose is to prevent recurrent ischemic events. Although not proved scientifically, many Japanese neurosurgeons believe that it will work. Actually, many patients with ischemic events experience reduction of or no such events thanks to the anastomotic surgery. When the patients are young, such anastomotic surgery is usually recommended in Japan. It is not emphasized, however, some of such patients have a fairly good outcome even without anastomosis (probably due to refusal to surgery). In the case of hemorrhagic onsets, the purpose of anastomosis is to prevent recurrent bleeding. The surgical benefits are not proved and to prove real benefits of bypass surgery, clinical trial is under way in Japan. Many case reports in such situations are not conclusive because some say beneficial, but some believe not beneficial. The clinical outcome of moyamoya disease has a wide spectrum, i.e., many patients with transient ischemic attack or minor stroke have fairly good outcome, but patients with hemorrhage have generally grave prognosis due to recurrent, occasionally fatal hemorrhage. 2004.2.6.