[1] Univ Brescia, Radiol Sci & Publ Hlth, Dept Med & Surg Specialties, Div Neurosurg, Brescia, Italy
[2] Mayo Clin, Rhoton Neurosurg & Otolaryngol Surg Anat Program, Rochester, MN USA
[3] Mayo Clin, Dept Neurol Surg, Rochester, MN USA
[4] Mayo Clin, Dept Otolaryngol Head & Neck Surg, Rochester, MN USA
[5] Mayo Clin, Dept Neurol, Div Cerebrovasc Disorders & Stroke, 200 1St St SW, Rochester, MN 55905 USA