1. Department of Neurosurgery, Beth Israel Deaconess Medical Center, Boston, MA 02215; Department of Neurosurgery, Harvard Medical School, Boston, MA 02115; and Department of Neurosurgery, Mt. Auburn Hospital, Cambridge, MA 02138, U.S.A.
2. Molecular Pathology Department, Massachusetts General Hospital, Charlestown, MA 02114, U.S.A.
3. Department of Anesthesiology, Rush Medical Center, Chicago, IL 60612, U.S.A.
4. Department of Neurosurgery, Beth Israel Deaconess Medical Center, Boston, MA 02215, U.S.A.