1 School of Medicine, University of Utah, Salt Lake City, UT, USA.
2 Reno School of Medicine, University of Nevada, Reno, NV, USA.
3 Department of Neurosurgery, Clinical Neurosciences Center, University of Utah, Salt Lake City, UT, USA.
4 Department of Surgery, University of Missouri Kansas City, Marion Bloch Neuroscience Institute, Saint Luke's Hospital of Kansas City, Kansas, MO, USA.