Enrico Giordan1, Waleed Brinjikji2, Giuseppe Lanzino3. 1. Department of Neurosurgery, Mayo Clinic, Rochester, MN, USA. 2. Department of Neurosurgery, Mayo Clinic, Rochester, MN, USA; Department of Radiology, Mayo Clinic, Rochester, MN, USA. 3. Department of Neurosurgery, Mayo Clinic, Rochester, MN, USA; Department of Radiology, Mayo Clinic, Rochester, MN, USA. Electronic address: Lanzino.giuspeppe@mayo.edu.