[1] Dallas VA Med Ctr, VA North Texas Hlth Care Syst, Neurol Sect, Dallas, TX USA
[2] Univ Texas SW Med Ctr Dallas, Dept Neurol, Dallas, TX 75390 USA
[3] Tech Univ Munich, Klinikum Rechts Isar, Dept Neurol, D-80290 Munich, Germany
[4] Univ Rostock, Dept Neurol, D-18055 Rostock, Germany