larynx and hypopharynx radiology anatomy

he laryngopharynx, also referred to as the hypopharynx, is the most caudal portion of the pharynx and is a crucial connection point through which food, water, and air pass. Specifically, it refers to the point at which the pharynx divides anteriorly into the larynx and posteriorly into the esophagus. The act of swallowing, or deglutination, is a complex multistep process performed by several essential structures in the oral cavity, pharynx, and larynx. Swallowing ensures proper transport of food and water posteriorly into the esophagus at the level of the laryngopharynx. Although the laryngopharynx’s primary physiologic function is as a cavity through which air, water, and food pass from the oral cavity to their respective destinations, it also contains structures that play an important role in speech.

The laryngopharynx is a clinically important anatomical location because of the high proportion of pharyngeal cancers that originate there. The pyriform sinus is the most frequent site of laryngopharyngeal cancer, with squamous cell carcinoma accounting for 95% of cases. The laryngopharynx is also clinically relevant due to a disorder related to the retrograde flow of digestive stomach contents to the laryngopharynx, known as laryngopharyngeal reflux (LPR).

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Structure and Function
STRUCTURE:

The pharynx is located posteriorly to the nasal and oral cavities and functions as a cavity through which food and air pass to the esophagus and larynx, respectively. The pharynx is made up of three separate regions: the nasopharynx, oropharynx, and laryngopharynx.

Nasopharynx:

The nasopharynx is the most rostral portion of the pharynx and refers to the region between the base of the cranium and the soft palate. It contains the opening of the Eustachian tubes that connect the pharynx to the middle ear. It also includes the adenoids and tubal tonsils, which are lymphoid tissues that play an essential role in the immune system.

Oropharynx:

The oropharynx is posterior to the oral cavity, between the soft palate and the pharyngoepiglottic fold. Important structures within the oropharynx include the soft palate, tonsils, base of the tongue, and pharyngeal bands, which are nodules of lymphoid tissue. The laryngopharynx is the final pharyngeal cavity and is located inferiorly to the oropharynx.[1]

Laryngopharynx (Hypopharynx):

The laryngopharynx;s position is inferior to the epiglottis and is bordered by the pharyngoepiglottic fold superiorly and the upper esophageal sphincter inferiorly. It refers to the portion of the pharynx where the cavity diverges anteriorly into the larynx and posteriorly into the esophagus. It contains three main structures: the posterior pharyngeal wall, pyriform sinuses, and the post-cricoid area. The pyriform sinuses, which play an essential role in speech, are two pear-shaped recesses located on either side of the laryngeal orifice. Medially to the pyriform sinuses lie the aryepiglottic folds. Thyroid cartilage lies latera

1. LARYNX AND HYPOPHARYNX DR. SHIVANGI LAHOTY

2. The hypopharynx and larynx both begin at the lower margin of the oropharynx and end at the lower margin of the cricoid cartilage. The hypopharynx is part of the digestive tract, carrying food and liquids to the esophagus. The larynx is part of the respiratory tract, connecting to the trachea, creating speech, and preventing aspiration.

3. LEVELS OF THE LARYNX AND THEIR BOUNDARIES The supraglottic division: From the superior-most tip of the epiglottis -to a transverse plane through the laryngeal ventricle. The glottis : From this transverse plane to 1 cm inferiorly and includes the true vocal cords. The subglottic region From the inferior-most plane of the true cords -to the inferior portion of the cricoid cartilage.

4. Supraglottis Extends from tip of epiglottis above to laryngeal ventricle below. Contains vestibule, epiglottis, pre-epiglottic fat, AE folds, FVC, paraglottic space, arytenoid cartilages

5. Axial graphic at the level of hyoid bone

6. Axial graphic at the mid supraglottic level

7. Glottis Comprises of: TVC Anterior commissure Posterior commissure

8. Subglottis Subglottis extends from under surface of TVC to inferior surface of cricoid cartilage

9. Coronal graphic view of larynx

10. Sagittal graphic of midline larynx

11. Imaging Protocol Contrast-enhanced CT or MRI is used for pre-treatment evaluation of the laryngeal carcinoma. Thin section CT images are normally obtained from the level of skull base to thoracic inlet in a plane parallel to ventricle of the larynx . During scanning, quiet breathing is ensured to keep vocal cords away. Breath hold, swallowing or phonation is to be avoided by the patient as it opposes the medial margins of the cord. MRI is performed using dedicated neck coil, short duration sequences and phase encoding gradients in AP direction in order to avoid pulsation artefacts arising from great vessels of the neck.

12. Supraglottic carcinoma These may arise from any mucosal surface of the supraglottic larynx but epiglottis is the most common site of origin . Early tumors of epiglottis are often seen on imaging as midline, well-defined enhancing nodules. With further spread, epiglottic tumors may spread superiorly to vallecula and base of tongue and laterally to aryepiglottic folds, false vocal cords .Anterior extension of epiglottic tumors involves fat in pre-epiglottic space. Pre-epiglottic space has rich and bilateral lymphatic drainage and tumors involving this space have high probability of bilateral neck node metastases.

13. CT shows epiglottic tumor involving aryepiglottic fold (arrow), para laryngeal space (black arrowheads) and pre-epiglottic space (white arrowhead). CT shows right aryepiglottic tumor (white arrow) with extension to the pyriform sinus (black arrow).

14. Glottic Carcinoma True vocal cords are the most common site of laryngeal carcinoma. Most glottis carcinoma arise along the anterior free margin of the true vocal cords. With anterior spread, glottis carcinoma readily involves anterior commissure. From here, it may spread to contralateral vocal cord or extend along tendon of the anterior commissure to thyroid cartilage where this tendon is attached. This results in early thyroid cartilage invasion . Posterior extension of the glottis carcinoma involves interarytenoid region (posterior commissure) and cricoarytenoid joint. Glottic carcinoma superiorly spread to ventricle and false vocal cords. It may also extend inferiorly to subglottic region.

15. CT shows tumor in left true vocal cord with extension to anterior commissure. There is invasion of left paraglottic space with sclerosis and focal lysis of the thyroid cartilage. Bone window image of a different patient shows frank erosion of the right lamina of thyroid cartilage (arrow).

16. Subglottic Carcinoma Carcinoma primarily arising at subglottic larynx is rare and most are extensions of glottic or supraglottic carcinomas . Primary subglottic carcinoma is seen as circumferential mucosal thickening of the subglottis. Because of the close proximity, cricoid cartilage invasion occurs early. It may also spread superiorly to involve glottis.

17. Post radiotherapy neck Radiotherapy results in edema and fibrosis and it affects all areas of pharynx, larynx and superficial soft tissues of the neck included in radiation field. On imaging, thickening of the skin and platysma muscle, enhancement of the mucosa and salivary glands as well as increase density and trabecular thickening of subcutaneous fat is seen in most patients 3 to 4 months after completion of radiotherapy. In larynx, radiotherapy also causes symmetric thickening of epiglottis, aryepiglottic folds, and false vocal cords. Such thickening is uncommon in glottis and subglottis.

18. Post-radiotherapy neck: CT shows diffuse increased density and trabeculations of subcutaneous fat, thickening of skin and platysma muscles (large arrow), atrophy of submandibular salivary glands (small arrows) and symmetric thickening of the pharyngeal wall.

19. A baseline post-treatment scan is obtained 3–4 months after completion of radiotherapy. The post-treatment changes and edema have attenuations less than that of muscles and the appearance remain stable on serial imaging. Any high density or enhancing mass or progressively enlarging mass is suspicious for residual or recurrent tumor. Differentiation of recurrence form fibrosis may sometimes be difficult on CT. MRI is useful in such situations but only if the scar is mature, as both tumor and the immature scar tissue are T2 hyperintense and show contrast enhancement on MRI. Diffusion-weighted MRI, perfusion CT and PET-CT may help in differentiating residual/ recurrent tumor from post therapy changes.

20. HYPOPHARYNX Hypopharynx extends from the level of hyoid bone superiorly to the level of inferior margin of the cricoid cartilage. Hypopharynx continues below as the cervical esophagus. Parts of hypopharynx are Posterior pharyngeal wall Bilateral pyriform sinuses Post-cricoid region

21. Pyriform sinuses are lateral air distended recess created by aryepiglottic folds. At the level of cricoid cartilage, posterior parts of two pyriform sinuses merge to form the post cricoid region of the hypopharynx. Most SCC of hypopharynx arise at the pyriform sinus . CT or MRI is required for assessment of submucosal extent of the tumor. Adequate distension of the pyriform sinus is essential during imaging. CT shows right pyriform tumor (black arrow) involving aryepiglottic fold and extension to paralaryngeal space (white arrow). Thyroid cartilage invasion is seen as sclerosis of the right thyroid lamina and focal lysis (arrowhead)

22. Carcinoma of the postcricoid cause concentric wall thickening and narrowing of the hypopharyngeal lumen. Because of the close anatomical proximity, these usually spread to posterior part of the larynx and involve arytenoids and cricoid cartilages .Inferior extension of the carcinoma of postcricoid involves cervical esophagus. CT shows postcricoid tumor (white arrow) with anterior extension to glottis with invasion and sclerosis of cricoid and arytenoids cartilages (black arrows).