[1] Univ Texas Med Branch, Dept Neuroradiol, Galveston, TX 77555 USA
[2] St Josephs Hosp, Barrow Neurol Inst, Dept Neurosurg, Phoenix, AZ USA
[3] Univ Texas Med Branch, Dept Neurol, Galveston, TX 77555 USA
[4] Univ Texas Med Branch, Dept Neurosurg, Galveston, TX 77555 USA