[1] Ctr Hosp Valais Romand, Hop Sion, Serv Diagnost & Intervent Imaging, Neuroradiol Unit, Ave Grand Champsec 80, CH-1950 Sion, Valais, Switzerland
[2] CIC Valais, Saxon, Switzerland
[3] Ctr Hosp Valais Romand, Hop Sion, ENT Serv, Sion, Valais, Switzerland
[4] Klin Hirslanden, Zentrum Neuroradiol, Zurich, Switzerland
[5] Univ Klinikum Essen, Inst Diagnost & Intervent Radiol & Neuroradiol, Essen, Germany
[6] Johns Hopkins Univ Hosp, Div Intervent Neuroradiol, Baltimore, MD 21287 USA