1. Department of Otolaryngology-Head and Neck Surgery; Mayo Clinic; 200 First Street S.W.; Rochester; Minnesota; U.S.A.
2. Department of Neurologic Surgery; Mayo Clinic; 200 First Street S.W.; Rochester; Minnesota; U.S.A.
3. Department of Radiology; Mayo Clinic; 200 First Street S.W.; Rochester; Minnesota; U.S.A.