1 Department of Neurological Surgery, Thomas Jefferson University and Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA.
2 Department of Neurological Surgery, Thomas Jefferson University and Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA; Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
3 Department of Orthopedic Surgery, Rothman Orthopedic Institute, Philadelphia, Pennsylvania, USA.
4 Department of Internal Medicine, Clinical Excellence Research Center (CERC), Stanford University School of Medicine, Stanford, California, USA.