[1] Johns Hopkins Univ, Sch Med, Dept Neurol, Baltimore, MD 21218 USA
[2] Johns Hopkins Univ, Sch Med, Dept Neurosurg, Baltimore, MD 21218 USA
[3] Johns Hopkins Univ, Sch Med, Dept Pediat, Baltimore, MD 21218 USA
[4] Johns Hopkins Univ, Sch Med, Wilmer Ophthalmol Inst, Baltimore, MD 21218 USA