1. Neurosurgical Service, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA;
2. Neurosurgical Research Network (NRN), Universal Scientific Education and Research Network (USERN), Tehran, Iran;
3. Department of Neurosurgery, Tehran University of Medical Sciences, Tehran, Iran;
4. Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA