12.1 Neck CT — Larynx/Airway & Soft Tissue

Why This Topic Is Tested

ARRT's Neck and Chest procedures category opens with Neck, and the outline names exactly two leaf items under it: larynx/airway and soft tissue neck. That brevity is deceptive — this is one of the more technique-sensitive corners of the CT blueprint because the single biggest failure mode in a neck study is not a contrast-timing error, it is a breathing-instruction error. A perfectly timed, perfectly reconstructed neck CT can still miss a small laryngeal cancer if the patient breathes quietly through the scan instead of performing the maneuver the protocol calls for. The "Focus of Questions" cross-cutting themes ARRT lists for every procedures category — anatomy/physiology, factors (including protocol considerations), contrast media, and additional procedures — apply here just as much as to the higher-question-count categories, so expect scenario-based items that test whether you can pick the right maneuver and timing for a stated clinical indication.

Larynx and Airway Anatomy

The larynx is divided into three anatomic regions relevant to CT interpretation and protocoling: the supraglottis (epiglottis, aryepiglottic folds, false vocal cords, laryngeal ventricle), the glottis (true vocal cords and anterior/posterior commissures), and the subglottis (extends from the undersurface of the true cords to the inferior cricoid cartilage). Surrounding these mucosal structures are two fat-filled spaces the exam expects you to recognize on cross-section: the pre-epiglottic space (anterior to the epiglottis) and the paraglottic space (lateral to the laryngeal ventricle, deep to the thyroid cartilage) — tumor spread into either space upstages a laryngeal cancer and changes surgical planning, which is exactly the kind of pathology-recognition detail ARRT's Anatomy and Physiology focus area tests. The cartilaginous framework includes the thyroid cartilage (the largest, forms the anterior/lateral laryngeal wall), the cricoid cartilage (the only complete cartilaginous ring in the airway, at the C6 level), and the paired arytenoid cartilages that anchor the vocal cords posteriorly. The airway itself continues inferiorly from the subglottis into the trachea, which is covered together with the central airway in Chapter 12.3's discussion of the chest's separate 'airway' leaf item — the neck-level larynx/airway item and the chest-level airway item are two distinct ARRT leaf items describing two different anatomic segments, a distinction worth keeping straight.

The Breathing-Maneuver Decision

Because the larynx is a mobile, muscular structure, how the patient breathes during acquisition directly determines whether small mucosal detail is visible:

A common exam trap presents a patient scanned with quiet breathing for suspected laryngeal carcinoma and asks why a subtle glottic lesion was missed — the answer is that apposed mucosal folds during quiet breathing can completely hide a small lesion that phonation would have revealed by separating the cords. Another trap swaps phonation and modified Valsalva in a distractor option; remember the maneuver name maps to the mechanism (phonation = vocal sound = cords; Valsalva = strain = expands the wider hypopharyngeal spaces around the cords, not the cords themselves).

Soft Tissue Neck: Anatomy and Timing

Soft tissue neck CT surveys structures outside the larynx: the oral cavity and floor of mouth, oropharynx, hypopharynx, thyroid and parathyroid glands, major salivary glands (parotid, submandibular, sublingual), the carotid space (carotid artery, jugular vein, cranial nerves IX-XII), the retropharyngeal space, and cervical lymph nodes. Contrast timing differs meaningfully from a larynx-focused acquisition: soft tissue neck is typically scanned in a venous/delayed phase around 60-70 seconds post-injection to maximize enhancement of mucosa, lymph nodes, and thyroid tissue, which is when pathologic tissue best differentiates from normal structures. This is distinctly later than a neck CTA, which uses an early arterial phase (roughly 20-25 seconds) with bolus tracking on the carotid artery to evaluate for dissection, stenosis, or vascular malformation — confusing the two timing windows is a frequent test trap, since a soft-tissue-timed scan will underopacify the arterial tree and an arterial-timed scan will underenhance nodal and mucosal disease.

Cervical Lymph Node Levels

CT reports and surgical planning for head and neck cancer use a standardized nodal level system (I-VII) rather than free-text anatomic descriptions:

• Level I — submental (Ia) and submandibular (Ib) nodes
• Level II — upper jugular nodes, from skull base to the hyoid bone
• Level III — mid jugular nodes, hyoid to the cricoid cartilage
• Level IV — lower jugular nodes, cricoid to the clavicle
• Level V — posterior triangle nodes
• Level VI — central compartment (pretracheal, paratracheal, prelaryngeal)
• Level VII — superior mediastinal nodes

Recognizing which level a pathologic node occupies matters because different primary cancers preferentially drain to different levels, and the level number directly communicates staging and surgical-planning information between the technologist's report, the radiologist, and the surgical team.

Exam Scenario

A patient with three months of progressive hoarseness is referred for a dedicated larynx CT. The requisition specifies evaluation for a possible glottic mass. The correct breathing instruction is phonation (sustained vowel sound) during image acquisition, not quiet breathing and not modified Valsalva — phonation is the maneuver that opens the space between the true vocal cords, which is precisely where a glottic tumor would otherwise be obscured by cord apposition.