1. Department of Radiology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul 110-744, Korea.
2. Department of Neurosurgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul 110-744, Korea.
3. Department of Neurosurgery, Hallym University Sacred Heart Hospital, Hallym University College of Medicine, Anyang 431-796, Korea.
4. Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 138-736, Korea.
5. Department of Neurology, Stroke Center, Myongji Hospital, Goyang 412-270, Korea.
6. Department of Neurosurgery, Sun Hospital, Daejeon 301-725, Korea.