A few points to note:
- Epiglottis can be seen behind hyoid bone.
- Vallecula is the space between the root of tongue and the epiglottis.
- Aryepiglottic fold can be traced sloping backwards and downwards from epiglottis.
- Larynx is seen as poorly defined soft density because it is surrounded by muscles, ligaments covered in mucous membrane.
- There is a step off from hypopharynx to larynx. This is because esophagus has soft tissue density and is located behind the air-filled trachea.
Before interpretation, consdier the adequacy !
- A good neck X ray is taken when patient’s neck is in neutral position and in end inspiration.
- An x ray taken during flexion or end expiration can produce false tissue swelling simulating a retropharyngeal infection !
My approach: from back to front
a. Cervical vertebrae
b. Pre-vertebral soft tissue shadow:
- Prevertebral swelling if > 3/4 of the corresponding vertebral body width
- Presence of any air/air fluid level
d. Air column in subglottic space (larynx compartment just above trachea) and trachea
- Cavity of larynx is divided into 3 parts: vestibule, ventricle and subglottic (infraglottic space).
e. Hyoid bone and laryngeal cartilage ossifications
- Better view to assess for any mass effect on subglottic space/trachea
What can be detected via these X rays:
- Consider in kids presenting with 3S (sound hoarseness, seal barking cough and stridor).
- Steeple sign can be seen in AP view due to subglottic swelling, but may be seen in lateral view too.
- Suspect in toxic looking child with high fever, severe sore throat and trismus. Patient often is reluctant to talk (patient in croup often appears well unless the kid is in stridor).
- Thumb sign due to epiglottic swelling, but aryepiglottic fold swelling and obliteration of the vallecula space can be seen.
The vallecula space is obliterated due to soft tissue swelling.
From Imaging of an Acute Adult Epiglottitis with Vallecula Sign. J Emerg Crit Care Med 2013:24(3);112-114
c) Retropharyngeal infection, Ludwig angina (soft tissue cellulitis of the floor of mouth)
- Massive prevertebral swelling can be seen.
d) Foreign objects
- In esophagus will present in coronal plane
- In trachea will present in sagittal plane (best seen in lateral)
- Normally a linear opacity with prevertebral soft tissue swelling can be seen.
- If it causes esophageal penetration air can be seen in esophagus.
- If it causes infection and abscess formation, air fluid level maybe seen.