Department of Neurological Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California Reprint requests: James B. Elder, M.D., Department of Neurological Surgery, Keck School of Medicine, University of Southern California, 1200 N. State Street, Suite 5046, Los Angeles, CA 90033. Email: [email protected] Received, April 10, 2008. Accepted, April 18, 2008.