FIGURE 112.20 Effects of inspiration and positioning on prevertebral (retropharyngeal) soft tissues A: Increased prevertebral space (asterisk ) with expiration B: Repeat radiograph in the same patient during inspiration reveals normal prevertebral space with no suggestion of cervical spine abnormality C: Increased soft tissue space (arrow ) with expiratory phase of respiration D: Normal soft tissue space (arrow ) with inspiration in patient C (A , B : Reprinted with permission from Harris J, Edeiken-Monroe B The Radiology of Acute Cervical Spine Trauma 2nd ed Baltimore, MD: Williams & Wilkins; 1987:6.)