[1] Univ Michigan, Dept Pediat, Ann Arbor, MI 48109 USA
[2] Univ Michigan, Dept Neurol, Ann Arbor, MI 48109 USA
[3] Univ Calif San Francisco, Dept Neurol, San Francisco, CA 94143 USA
[4] Univ Calif San Francisco, Dept Pediat, San Francisco, CA 94143 USA