[1] Baylor Coll Med, Dept Neurosurg, Houston, TX 77030 USA
[2] Texas Childrens Hosp, Div Pediat Neurosurg, Houston, TX 77030 USA
[3] Univ Utah, Sch Med, Dept Neurosurg, Salt Lake City, UT USA
[4] Primary Childrens Med Ctr, Div Pediat Neurosurg, Salt Lake City, UT 84113 USA