I'm glad you asked this question because it is a very important point. The prevertebral fascia is an excellent barrier to infection. Thus, infections that start in the retropharyngeal space do not reach the prevertebral space, and vice versa (unless the fascia has been disrupted by tumor or surgery).
@@ENT_Imaging Thank you Dr. Branstetter. Based on my eyes, I thought some white spots (I guess it is contrast enhanced area ) are located in left pre-vertebral muscles. Actually they are not. Analyzing the radiological features of lesions need long time training. Thank you for sharing your precious experiences, now I know infection will not usually break fascia between prevertebral and retropharyngeal space. This is important clinical experiences I leaned.