[1] Univ Texas Med Branch, Dept Neurosurg, Galveston, TX 77555 USA
[2] Univ Texas SouthWestern Med Ctr, Dept Neurosurg, Dallas, TX USA
[3] Meharry Med Coll, Dept Biochem & Canc Biol, Nashville, TN USA
[4] NYU, Grossman Sch Med, Dept Neurol Surg, New York, NY USA
[5] Univ Texas Med Branch, 301 Univ Blvd, Galveston, TX 77555 USA