Larynx

Technique

Computed tomography using short exposure times and 2-3 mm slices is recommended to successfully demonstrate the details of the glottic and supraglottic larynx. Magnetic resonance imaging has still certain limitations but has the possibility to depict the larynx in the coronal projection which may better demonstrates tumor extension, relative to the laryngeal ventricle.

Anatomy

The ring-shaped cricoid cartilage is the foundation of the laryngeal skeleton supporting the thyroid and the arytenoid cartilages. The paired lamina of the thyroid cartilage protect the laryngeal airway. The vocal cords take their origin from the vocal processes of the arytenoids which articulate with the cricoid lamina posteriorly. The vocal cords converge and insert in the midline on the inside of the thyroid cartilage above the thyroid notch. The racket shaped epiglottis, which folds back to protects the airway during swallowing, is connected to the inside of the thyroid cartilage just above the anterior commissure of the true vocal cords. The preepiglottic space is filled in by fatty areolar tissue in between the thyroid lamina and the epiglottis. Above the true vocal cords the laryngeal ventricles are formed by the overlying folds of the false vocal cords. The laryngeal skeleton is interconnected and connected to the surrounding structures by several ligaments and muscles. The hypopharynx runs down behind the larynx and the pyriform sinuses forms lateral gutters medial to the posterior thyroid lamina (Fig. 25 a-c).

Pathology

Benign lesions

Laryngoceles are sac like out pouching originating from the saccule in the roof of the laryngeal ventricle. Saccular cysts and laryngoceles can be both congenital and acquired, the latter sometimes being found in trumpet players. If the air filled sac stays on the inside of the thyroid lamina it forms an internal laryngocele which will expand the false vocal cord obscuring the glottis. If the laryngocele penetrates the thyrohyoid membrane it becomes an external laryngocele which can be seen intermittently as a soft neck mass. Laryngoceles have a characteristic appearance and since they are often air filled they can easily be demonstrated by computed tomography.

Malignant tumors

Squamous cell carcinoma accounts for more than 95 % of all malignant laryngeal tumors, most commonly originating out of the true vocal cords. Hoarseness is therefore often a presenting symptom in laryngeal cancer. Hypopharyngeal carcinoma occurring in the pyriform sinuses will because of the close relationship to the larynx have similar symptoms from

Figure 26. Ca of the larynx - computed tomography Transverse section at the level of the vocal cords. An infiltrating tumor is seen along the right vocal cord filling in the posterior commissure and destroying parts of the cricoid cartilage (arrow).

the upper airway along with complaints of dysphagia. Computed tomography and magnetic resonance imaging can be used as an adjunct to the clinical inspection since a better demonstration of the deep extension into the paralaryngeal, the preepiglottic and subglottic spaces is possible (Fig. 26). The irregular calcification of the laryngeal skeleton still makes assessment for cartilage invasion difficult even by these methods.

Other soft tissue tumors can also originate from the supporting soft tissue structures of the larynx. Chondroma and chondrosarcoma can arise from the laryngeal skeleton and then most commonly the cricoid cartilage.

Sven G. Larsson and Anthony A. Mancuso