1. Department of Clinical Neurological Sciences, London Health Sciences Centre, Western University, London, Ontario, Canada
2. Department of Neurosurgery, Oakland University William Beaumont School of Medicine, Rochester, Michigan, USA
3. Michigan Head and Spine Institute, Southfield, Michigan, USA
4. Department of Neurosurgery, Albany Medical College, Albany, New York, USA
5. Department of Anesthesiology & Perioperative Medicine, Oregon Health and Science University, Portland, Oregon, USA
6. Department of Anesthesiology, Albany Medical College, Albany, New York, USA
7. Department of Neurology, Albany Medical College, Albany, New York