[1] Yale Univ, Sch Med, Dept Neurol, New Haven, CT 06510 USA
[2] Univ W Indies, Dept Med, Kingston 7, Jamaica
[3] Yale Univ, Sch Med, Dept Neurosurg, New Haven, CT USA
[4] Yale Univ, Sch Med, Dept Diagnost Radiol, New Haven, CT 06510 USA
[5] Yale Univ, Sch Med, Dept Biomed Engn, New Haven, CT USA