We are going to recognize normal/benign air locations and pathologic gas and its clinical settings on: trauma ,
abscess (retropharyngeal space abscess and oral cavity abscess),
postradiation effects (chondronecrosis),
laryngocele,
diverticulum (Zenker and lateral cervical esophageal) and spontaneous cervical emphysema.
Normal/benign air locations
Remember to check always this anatomic normal gas landmarks ( Fig. 1,
Fig. 2 ).
Pharyngeal recess (fossa of Rosenmuller) ( Fig. 3 ) is located posterior and superior to the ostium of the Eustachian tube.
Key point: Check this recess in search of a Nasopharyngeal carcinoma.
Vallecula ( Fig. 1 ,
Fig. 4 ,
Fig. 5 ) is a recess behind the root of the tongue between the medial and lateral glosso-epiglottic folds.
Pyriform sinus ( Fig. 5 ,
Fig. 6 ) is a recess circumscribed medially by the aryepiglottic fold,
laterally by the thyroid cartilage and hyothyroid membrane.
Esophagic air in low quantity is normal but a dilated esophagus with significative air inside is pathologic and is important to investigate the cause of obstruction ( Fig. 7 ,
Fig. 8 ,
Fig. 9 ).
Ventricle of the Larynx ( Fig. 1 ,
Fig. 10 ) is a fusiform fossa situated between the true and false vocal folds and extending nearly their entire length.
Pathologic gas and its clinical settings
Trauma ( Fig. 11 ,
Fig. 12 ): History of esophageal,
pharyngeal,
laryngeal,
superficial trauma.
Key points: Know the mechanism of trauma is very important to determinate the path and the structures involved.
CT Findings: Extraluminal air in neck and laryngeal,
hyoid,
or facial fractures.
Retropharyngeal Space Abscess ( Fig. 13 ,
Fig. 14 ): The retropharyngeal space lies between the alar fascia posteriorly and the posterior aspect of the pretracheal fascia anteriorly,
posterior to the retropharyngeal space is the danger space,
which is bound by the alar fascia anteriorly and the prevertebral fascia posteriorly descending freely to the posterior mediastinum until the diaphragm for this reason the danger space provides a anatomic route for contiguous spread between the neck and the chest.
The retropharyngeal space (RPS) contains lymph nodes (prominent in the young child and atrophic in adults).
These lymph nodes drain the nasopharynx,
adenoids,
posterior paranasal sinuses,
middle ear,
and eustachian tube.
Infections in these areas may lead to suppurative adenitis of the retropharyngeal lymph nodes.
The rupture of suppurative RPS node derivate in RPS abscess.
Other less common causes are ventral spread of discitis and prevertebral infection,
pharyngeal penetrating foreign body and mediastinal abscess spreading cranially.
Complications include: airway compromise and stridor ,
mediastinitis ,
jugular vein thrombosis or thrombophlebitis,
aspiration pneumonia ,
ICA pseudoaneurysm and epidural abscess.
These life-threatening complications requires early diagnosis and aggressive management to had a good prognosis.
CT Findings: CECT shows rim-enhancing,
focal fluid collection in RPS.
Oral Cavity Soft Tissue abscess ( Fig. 15 ,
Fig. 16 ) : Focal collection of pus within oral cavity soft tissue space.
Most common cause is dental infection with periapical dental abscess leading to mandibular osteomyelitis.
Ludwig's angina is a bilateral infection of the submandibular space.
It is an aggressive,
rapidly spreading cellulitis without lymphadenopathy.
Airway compromise is a potential complication,
and requires a rapid intervention for prevention of asphyxia and aspiration pneumonia.
Other causes of oral cavity soft tissue abscess are sialolithiasis/sialadenitis ,
pharyngitis + suppurative nodes and penetrating trauma.
CT Findings: CECT shows rim-enhancing,
focal fluid collection in oral cavity space(s).
Chondronecrosis ( Fig. 17 ,
Fig. 18 ) : Postradiation larynx is the spectrum of soft tissue and cartilage changes following radiation therapy (XRT).
Changes may be XRT effects or complications.
XRT effects seen in all patients.
Complications are chondronecrosis and osteoradionecrosis (hyoid).
This is a difficult diagnosis and sometimes needs a biopsy to differentiate from a progression or infection.
CT Findings: Laryngeal cartilage fragmentation/collapse and adjacent gas.
Cartilage sclerosis concerning for necrosis if not present pre XRT.Osteoradionecrosis of hyoid has similar findings.
Laryngocele ( Fig. 19 ,
Fig. 20 ) : Internal laryngocele: Dilated,
air- or fluid-filled laryngeal saccule located in paraglottic region of supraglottis.
Mixed laryngocele: Extends laterally through thyrohyoid membrane to low submandibular space.
The clinical settings usually are hoarseness or stridor in the internal laryngocele and anterior neck mass in mixed laryngocele.
Always ask for a endoscopic exam to exclude an underlying lesion of true or false cords.
CT Findings: Internal laryngocele: Thin-walled,
air or fluid-filled cystic lesion communicating with laryngeal ventricle.
Mixed laryngocele: Internal + extralaryngeal extension through thyrohyoid membrane.
Diverticulum,
Esophago-Pharyngeal (Zenker) ( Fig. 21 ,
Fig. 22 ):Mucosal herniation through area of anatomic weakness just above cricopharyngeal muscle (Killian triangle).
The classic clinical settings are a transient oropharyngeal dysphagia ,
foul breath,
regurgitation,
chronic cough,
aspiration,
and weight loss.
CT Findings: Well-defined mass posterior and to left of esophagus with air,
fluid,
± food debris.
Diverticulum,
Lateral Cervical Esophageal:Lateral outpouching from proximal cervical esophagus below cricopharyngeus muscle.
CT Findings: Well-defined round or oval mass lateral to proximal esophagus.
Can move anteriorly,
left thyroid lobe and common carotid artery.
Density may be air,
fluid,
food debris,
or mixed.
Cervical Emphysema,
Spontaneous ( Fig. 23 ,
Fig. 24 ): Spontaneous cervical emphysema is closely related to spontaneous pneumomediastinum and is described as free air or gas located within the mediastinum that is not associated with any noticeable cause such as chest trauma.
Usually had benign course and resolves in 7 days.
CT Findings: Pneumomediastinum and cervical emphysema.