[1] Univ Pittsburgh, Sch Med, Dept Neurosurg, Pittsburgh, PA 15261 USA
[2] Univ Miami, Dept Neurosurg, Miami, FL 33152 USA
[3] Univ Calif Davis, Dept Neurol Surg, Davis, CA 95616 USA
[4] Penn State Univ, Dept Neurosurg, State Coll, PA 16804 USA
[5] Primary Childrens Med Ctr, Salt Lake City, UT USA
[6] Univ Pittsburgh, Sch Med, Dept Biostat, Pittsburgh, PA USA
[7] Baylor Coll Med, Dept Phys Med & Rehabil, Dallas, TX USA