From the Department of Medicine, Divisions of Neurology (Drs. Brey, Navarrete, and Hermosillo–Romo, and A. Saklad, C. Stallworth, C. Valdez, C. Rhine, and P. Padilla) and Clinical Immunology (Drs. Escalante and del Rincón); Audie L. Murphy Veterans Association Hospital (Dr. Holliday), San Antonio, TX; Willford Hall United States Air Force Medical Center (Dr. Gronseth and D. McGlasson), Lackland Air Force Base, TX. (At 2002-04-23)