[1] Univ Maryland, Sch Med, Dept Neurosurg, 22 S Greene St, Baltimore, MD 21201 USA
[2] Univ Maryland, Sch Med, Dept Radiol, Baltimore, MD 21201 USA
[3] Univ Maryland, Sch Med, Dept Pathol, Baltimore, MD 21201 USA
[4] Univ Maryland, Sch Med, Dept Physiol, Baltimore, MD 21201 USA