Persistent Fixed Torticollis due to Atlanto-Axial Rotatory Fixation: Report of 4 Pediatric Cases - Chiapparini, L; Zorzi, G; De Simone, T; Maccagnano, C; Seaman, B; Savoiardo, M; Corona, C; Nardocci, N (Neuropediatrics, 2005)