1. Department of Neurosurgery, Stanford University , Palo Alto, California , USA
2. Department of Neurological Surgery, University of Louisville School of Medicine , Louisville, Kentucky , USA
3. Department of Extended Care and Palliative Medicine Service, VA Palo Alto Health Care System , Palo Alto, California , USA
4. Section of Neurosurgery, VA Palo Alto Health Care System , Palo Alto, California , USA