[1] Mayo Clin, Dept Anesthesiol, Coll Med, Rochester, MN 55905 USA
[2] Mayo Clin, Mayo Sch Grad Med Educ, Coll Med, Rochester, MN 55905 USA
[3] Mayo Clin, Dept Neurol, Coll Med, Rochester, MN 55905 USA
[4] Mayo Clin, Dept Orthoped Surg, Coll Med, Rochester, MN 55905 USA