1Department of Parasitology, College of Medicine, Chung-Ang University, Seoul 151, Korea.
2Department of Neurosurgery, College of Medicine, Chung-Ang University, Seoul 140, Korea.
3Department of Neurosurgery, College of Medicine, Seoul National University, Seoul 110, Korea.
4Department of Neurosurgery, St. Mary's Hospital, Catholic Medical College, Seoul 150, Korea.
5Department of Neurology, College of Medicine, Seoul National University, Seoul 110, Korea.