[1] Univ Iowa Hosp & Clin, Dept Neurosurg, 1616 JCP,200 Hawkins Dr, Iowa City, IA 52246 USA
[2] Univ Iowa Hosp & Clin, Dept Neurol, Iowa City, IA 52242 USA
[3] Univ Iowa Hosp & Clin, Dept Radiol, Iowa City, IA 52242 USA
[4] Univ Penn, Dept Neurosurg, Philadelphia, PA 19104 USA
[5] Thomas Jefferson Univ Hosp, Dept Neurosurg, Philadelphia, PA 19107 USA