[1] Univ Maryland, Sch Med, Dept Neurosurg, Baltimore, MD 21201 USA
[2] Univ Maryland, Sch Med, Dept Pathol, Baltimore, MD 21201 USA
[3] Univ Maryland, Sch Med, Dept Physiol, Baltimore, MD 21201 USA
[4] Yale Univ, Sch Med, Dept Neurol, New Haven, CT 06510 USA
[5] Yale Univ, Sch Med, Dept Neurosurg, New Haven, CT USA