A, Arrow a indicates normal occiput-C1 joint congruity. Arrow b indicates intact C2 isthmus. Bracket c indicates normal facet relationships throughout cervical spine. B, Arrow a indicates Wackenheim’s line with normal relationship between clivus and posterior dens. Arrow b indicates atlantodens interval, which is normal in width. Arrow c indicates normal soft-tissue density width less than 5 mm at C3 midbody.