LOS EMPRESARIOS Y LOS CONSUMIDORES

The parapharyngeal space is a triangular fat-fi lled space that extends from the skull base superiorly to the level of the hyoid bone, and is subdivided into the prestyloid (par-apharyngeal [PPS]) space and the post-styloid ( carotid space [CS]). In addition to fat, the major contents of in-terest in the PPS are minor salivary glands. Medially is the pharynx, posteromedially the retropharyngeal space, posterolaterally the CS, and laterally the masticator space.

Fig. 2.92 Simple ranula. A well-defi ned, thin-walled, unilocular, nonenhancing, cystic low-attenuation lesion is seen, within the sub-lingual space. A pertinent negative is the lack of adjacent soft tissue swelling or abnormal enhancement.

Fig. 2.93 Benign mixed tumor (pleomorphic adenoma). There is a small, smoothly marginated, round mass lesion (arrow) in the deep lobe of the left parotid gland. The mass displays characteristic low signal intensity on T1- and high signal intensity on T2-weighted images, and demon-strates prominent enhancement (image not shown). The diagnosis was confi rmed by fi ne needle aspiration and at subsequent resection.

is a lesion with low signal intensity on T1, intermediate to high signal intensity on T2, with moderate contrast enhancement. Warthin tumors are the second most com-mon type of benign parotid lesions. These lesions arise from intraparotid lymph nodes and are isolated to the parotid gland as other salivary glands do not contain lymph nodes ( Fig. 2.94 ). A classic presentation is that of

Fig. 2.94 Warthin tumor. On axial and coronal reformatted CT im-ages obtained during bolus intravenous contrast administration, a mass lesion (*) is seen continuous with and medial to the right parotid gland, with slightly higher density. A portion of the lesion is lower in density, raising the question of a cystic component (com-mon with this diagnosis). As with most Warthin tumors, the lesion is located more posteriorly near the parotid tail. The lesion is ovoid and smoothly marginated. Tissue diagnosis was confi rmed by fi ne needle aspiration.

or posterior displacement of the sternocleidomastoid muscle and anterior displacement of the submandibular gland. One must be careful making this diagnosis in an adult as a level II necrotic node may mimic a branchial cleft cyst.

■ Larynx

The mucosal surface of the larynx is well evaluated by la-ryngoscopy, with the role of imaging to determine deep tumor extent and tumor margins. The epiglottis has an PPS displacement medially occurs by masses in the

mas-ticator space, the PPS may be displaced anteriorly by deep lobe parotid masses or masses in the CS and lateral dis-placement is caused by pharyngeal mucosal space lesions, particularly tonsil pathology.

Salivary gland tumors (arising from the minor salivary glands) are the most common primary lesions in the PPS, with most being benign mixed tumors. Neurogenic tu-mors (usually vagal schwannomas) ( Fig. 2.97 ) and glo-mus vagale paragangliomas are the most common lesions to arise in the CS. Second branchial cleft cysts typically produce medial displacement of the CS, as well as lateral

Fig. 2.95 Epithelial carcinoma. A large mass lesion is identifi ed involving the right parotid gland. The mass is homogeneous, well de-fi ned, and slightly lobulated. Although ma-lignant lesions can have irregular borders and heterogeneity suggesting their diag-nosis, benign and malignant salivary gland tumors cannot be diff erentiated on imaging alone, with malignant lesions often having what otherwise might be considered benign features, as in this case. Malignant epithelial tumors represent up to 20% of all salivary gland tumors, and include adenoid cystic and mucoepidermoid carcinomas.

Fig. 2.96 Perineural tumor spread. This patient is status post resection of a mu-coepidermoid carcinoma in the parotid.

The fi rst image depicts tumor recurrence (black arrow) in the lateral pterygoid muscle. The subsequent axial and coronal images depict enhancing tumor extending along the third division (CN V3) of the tri-geminal nerve through the foramen ovale (white arrows), which is enlarged, with ex-tension to the Meckel cave.

The valleculae are the small bilateral recesses between the tongue base and free margin of the epiglottis. The ary-epiglottic folds lie above the false vocal cords, and form the lateral margins of the vestibule (the supraglottic airspace), extending from the arytenoid cartilages to the free mar-gin of the epiglottis. The pyriform sinuses are lateral to the aryepiglottic folds, being mucosal recesses between the thyroid cartilage and the aryepiglottic folds. The ventricles are the lateral recesses between the true and false cords.

The anterior commissure lies in the midline between the true vocal cords anteriorly, and, on thin section CT at this level, air should directly abut the thyroid cartilage. In a Valsalva maneuver, the patient attempts to exhale against a closed glottis, with the true cords adducted. In quiet res-piration, the true cords will be slightly abducted but not completely eff aced.

Innervation of the larynx is by the recurrent laryngeal nerve (RLN). These paired nerves emerge from the vagus nerve with diff erent courses. The right RLN arises at the level of, and loops under, the subclavian artery while the left arises at the level of the aortopulmonary window and loops under the aorta. The nerves then ascend in the tra-cheoesophageal grooves. Supraglottic lymphatics drain to upper jugular nodes and subglottic lymphatics drain to paratracheal and pretracheal nodes and then, eventually, to lower jugular nodes.

A Zenker diverticulum is a posterior outpouching of the pharyngeal wall just above the cricopharyngeus muscle (thus just above the esophagus). The cricopharyngeus mus-cle is often prominent, with the diagnosis of a Zenker diver-ticulum typically made on the basis of a barium swallow.

A laryngocele is a dilatation of the laryngeal ventricle.

They are typically air-fi lled but may be fl uid-fi lled in which case they are termed saccular cysts. The classic acquired laryngocele was seen in glassblowers and trumpet play-ers, due to constant increased pressure in the larynx with forced expiration. They may also be caused by an obstruct-ing tumor. A laryngocele may be internal (confi ned within the larynx) ( Fig. 2.98 ) or external (extending through the thyrohyoid membrane).

Foreign bodies can result from ingestion or aspiration.

A foreign body may initially lodge in the pyriform sinus, from which point it can migrate into the larynx ( Fig. 2.99 ).

Ninety-fi ve percent of all malignancies of the larynx are squamous cell carcinoma. These tumors arise on the mu-cosal surface, with deep lesion extent relative to precise landmarks not possible to be assessed by endoscopy, thus the role of imaging. Smoking and heavy consumption of alcohol are important risk factors. Treatment options in-clude several voice sparing operations, typically coupled with radiation therapy ( Fig. 2.100 ). The supraglottic re-gion includes the false vocal cords, aryepiglottic folds, preepiglottic and paraglottic spaces, and epiglottis. In a supraglottic laryngectomy (which is voice sparing), the larynx above the ventricle is removed, with the resection line made through the ventricle. The key to feasibility is upper free margin and is attached inferiorly to the thyroid

cartilage. The hyoid bone is the ceiling from which the lar-ynx is suspended. The largest of the laryngeal cartilages is the thyroid cartilage consisting of an anterior body, two small superior horns (cornua), and two large posterior horns. The thyrohyoid membrane extends from the hyoid bone superiorly to the superior cornua inferiorly. Inferior to the thyroid cartilage is the cricoid cartilage, which re-sembles a “signet” ring that faces posteriorly. The inferior margin of the cricoid cartilage is the junction between the larynx and trachea. The cricothyroid membrane closes the gap between the cricoid and the thyroid cartilages. The arytenoid cartilages articulate superolaterally with the cri-coid posteriorly. The thyroarytenoid (vocalis) muscles at-taches to the lower anterior surface of the arytenoid, form-ing the bulk of the true vocal cord. The true cord is inferior to the false cord, with the glottis defi ned as the horizontal space between the true and false vocal cords.

Fig. 2.97 Vagal schwannoma. Neurogenic lesions account for up to 25% of tumors of the retrostyloid parapharyngeal (carotid) space, with most being schwannomas of the vagus nerve. As the nerve lies behind the internal carotid artery (ICA), most tumors displace the ICA (white arrow) anteriorly and medially, and the internal jugular vein (black arrow) posteriorly and laterally, as do glomus vagale para-gangliomas. Most schwannomas are fairly homogeneous in com-position; however, there can be areas of hemorrhage or necrosis, leading to a heterogeneous appearance. Schwannomas are typically well-defi ned, ovoid masses, with hyperintensity on T2-weighted scans and prominent enhancement. However, as opposed to glo-mus vagale paragangliomas, schwannomas do not exhibit fl ow voids or a “salt and pepper” appearance.

Fig. 2.98 Laryngocele. (Part 1) On an axial MR image, a thin walled air-fi lled lesion is visualized lateral to the false vocal cord on the right, consistent with an internal (simple) laryngocele. There is mild airway compression. (Part 2) In a second patient (a 56-year-old trumpet player), huge bilateral laryngoceles are seen on axial and coronal CT images.

There is extension bilaterally through the thyrohyoid membrane, with these lesions thus representing mixed (internal/external) laryngoceles.

Fig. 2.99 Foreign body. There is a linear radiopaque density (a wire, arrow), approximately 2 cm in length, which lies in the vicinity of the left false vocal cord parallel to the thyroid cartilage. The anterior extent of the foreign body appears to lie within the left false cord an-teriorly. The posterior tip of the foreign body abuts the left pyriform sinus. There is mild surrounding soft tissue swelling likely related to infl ammatory changes.

inferior tumor extension ( Fig. 2.101 ) and tumor must be clearly separated from the anterior commissure. Part of one arytenoid can be removed, but the thyroid cartilage cannot be involved by tumor. Lymph node involvement with supraglottic tumor is common. Tumors of the true vocal cord (glottic carcinomas) present early, due to a change in voice (early vocal cord paralysis), with lymph node involvement uncommon. Contraindications to sur-gery, specifi cally hemilaryngectomy (unilateral removal of the true and false cords, and thyroid ala—an operation which is also voice sparing), include extension across the anterior commissure, subglottic extension, involvement of the cricoarytenoid joint, and thyroid cartilage invasion.

Cartilage involvement is best identifi ed on MR by the dem-onstration of cartilage enhancement. Tumors of the sub-glottic larynx (inferior surface of true vocal cords to cricoid cartilage) are least common, often presenting as T4 lesions (defi ned by invasion of the thyroid cartilage and/or exten-sion beyond the larynx). Cricoid invaexten-sion is common. Large lesions require total laryngectomy and radiation therapy.

In unilateral vocal cord paralysis the aff ected vocal cord rests in a paramedian position. Etiologies outside of the larynx include malignancy involving the vagus or recur-rent laryngeal nerves, and iatrogenic injury (prior surgery, especially thyroid).

Fig. 2.100 Extensive supraglottic squamous cell carcinoma. A bulky soft tissue mass involves the epiglottis, aryepiglottic folds, pre- epiglottic space, and supraglottic region. The lesion did not, how-ever, extend to the level of the false vocal cords (image not shown).

Fig. 2.101 Supraglottic squamous cell carcinoma. A mass lesion (arrow) involves the laryngeal surface of the epiglottis, with some in-volvement of the pre-epiglottic fat. On the lower axial image, there is no evidence of extension to the level of the true cord.