1. Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
2. Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
3. Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
4. Comprehensive Headache Center, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
5. Clinic for Anesthesiology and Intensive Care, Essen University Hospital, Essen, Germany