1. Department of Neurosurgery, University of Virginia, Charlottesville, VA 22908, USA
2. Department of Neurosurgery, Tulane University, New Orleans, LA 70112, USA
3. Department of Molecular Physiology and Biophysics, Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA
4. Department of Neurosurgery, University of Iowa, Iowa City, IA 52242, USA
5. Department of Neurological Surgery, Thomas Jefferson University, Philadelphia, PA 19106, USA
6. Department of Neurosurgery, Kaohsiung Medical University Hospital, No. 100, Tzyou 1st Road, Kaohsiung, Taiwan
7. Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan