Conventional radiography and fluoroscopy
Conventional plain radiography (plain radiograph) is rarely used for a detailed assessment of the larynx itself, but remains the first-line method for acute conditions accompanied by airway obstruction (e.g., stridor in children, which frequently occurs secondary to infection).
- Epiglottitis (Epiglottitis): To confirm the diagnosis, a lateral neck radiograph is performed, which clearly visualizes marked thickening of the epiglottis.
- Croup (Croup): Imaging is rarely required for this condition; however, a posteroanterior chest radiograph can demonstrate subglottic narrowing (subglottic narrowing) and overinflation of the hypopharynx. Epiglottic thickening is not observed in croup.
- Tracheomalacia (Tracheomalacia): Fluoroscopy (fluoroscopy) is used for dynamic evaluation, as the trachea characteristically collapses precisely during expiration.
- Vascular rings and slings (Vascular ring or sling): Barium swallow fluoroscopy in a strict lateral projection (with good esophageal distention) is used. Anomalous vessels indent the contrast column. Today, the method is employed for the functional assessment of intermittent obstruction (especially when tailoring non-invasive ventilation modes) to avoid high radiation exposure from repeated dynamic CT scans.
CT and ultrasound in tumor diagnostics
Head and neck anatomy is exceptionally complex. Modern diagnostic imaging methods allow for the visualization of the finest details, which is critical for accurate staging and planning targeted therapy (e.g., proton therapy, brachytherapy, or intensity-modulated radiation therapy — IMRT).
- Computed tomography (CT). Contrast-enhanced axial CT of the neck is an essential method for evaluating malignant neoplasms. For example, in a supraglottic tumour, CT allows visualization of ulceration, infiltration of the pre-epiglottic fat, crossing of the midline by the lesion, and submucosal spread involving the paraglottic fat. CT is also necessary to detect subtle erosions of the laryngeal cartilages in squamous cell carcinoma (SCC).
- Ultrasound (US). Laryngeal ultrasound is effective for soft tissue visualization. Tumor infiltration of the paraglottic space appears as hypoechoic tissue. A major limitation of the method: structures are well visualized only if the laryngeal cartilages have a minimal degree of calcification.
Differential diagnosis of obstruction
Imaging modalities play a key role in foreign body aspiration into the airways. Acute respiratory distress in a young child requires emergency bronchoscopy, but imaging is ordered in non-emergent cases.
Most foreign bodies (e.g., nuts, plastic) are radiolucent. In such cases, plain radiography will demonstrate indirect signs: lobar collapse or local/diffuse hyperlucency due to the formation of an air trapping effect via a ball-valve mechanism.
Rapid pulsed fluoroscopy helps differentiate causes of varied lung lucency. The obstructed and overinflated lung does not change volume during the respiratory cycle, while the mediastinal structures shift toward the healthy (contralateral) side upon expiration.
Relationship with the retropharyngeal space
Laryngeal tumors and adjacent structures can extend beyond the organ itself. For example, the retropharyngeal space (retropharyngeal space) is frequently involved secondarily due to lymph node metastasis (during staging of hypopharyngeal, oropharyngeal, or nasopharyngeal cancer). Less commonly, tumors invade directly from the posterior pharyngeal wall. A key task for the radiologist during staging is to determine whether the normal thin fat-density line of the retropharyngeal space is preserved on imaging.
How to avoid confusing projections in stridor: "Epiglottitis — lateral, Croup — AP". If epiglottitis is suspected, a lateral neck radiograph is obtained (looking for a thickened epiglottis), whereas for croup, an AP chest radiograph is performed (looking for narrow subglottic narrowing).
Class and exam questions
In what cases is laryngeal ultrasound uninformative?
Ultrasound loses its diagnostic value if the patient has prominent laryngeal cartilage calcification. With minimal calcification, the method clearly visualizes hypoechoic tumors and submucosal tissue infiltration.
What does contrast-enhanced neck CT show in supraglottic cancer?
CT details the tumor focus, its potential ulceration, extension across the midline of the neck, and infiltration of the pre-epiglottic fat and paraglottic space.
Why is fluoroscopy used in tracheomalacia?
Fluoroscopy allows for the dynamic assessment of airway patency. In tracheomalacia, expiration will clearly reveal tracheal collapse, which cannot be captured on a static plain radiograph.
How to identify radiolucent foreign body aspiration on a radiograph?
Plastic or nuts cannot be seen directly, but the radiograph will show indirect signs of the check-valve mechanism: air trapping (hyperlucency of a lung segment), lobar collapse, or mediastinal shift toward the healthy side on expiration.
What else to study on this topic
- Diagnostic imaging of foreign body aspiration (organic objects and button batteries)
- Ultrasound and radioisotope diagnostics of thyroid pathologies
- Computed tomography of the temporal bone and external auditory canal
- Anatomy and imaging evaluation of the masticator and carotid spaces of the neck
- CT visualization of congenital bronchopulmonary malformations
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