Larynx anatomy CT and MRI
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Larynx anatomy CT and MRI
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Larynx anatomy CT and MRI
- 1. Dr. Mohit Goel Dept. of Radiology 21/06/2013
- 2. • The larynx is a 5-7 cm long structure. • Its upper boundary starts at the tip of the epiglottis, opposite the 3rd to 4th, cervical vertebra. • Its lower end is at the lower border of the cricoid cartilage. • This lies opposite the 6th cervical vertebra.
- 6. • Largest laryngeal cartilage, "shields" larynx • 2 anterior laminae meet anteriorly at acute angle • Superior thyroid notch at anterior superior aspect • Posteriorly laminae form superior & inferior cornua • Superior cornua are elongated & narrow, attach to thyrohyoid ligament • Inferior cornua are short & thick, articulating medially with sides of cricoid cartilage
- 7. Front view Side view
- 8. • Only complete ring in endolarynx, provides structural integrity • Two portions, posterior lamina & anterior arch • Lower border of cricoid cartilage is junction between larynx above & trachea below.
- 9. Posterior view Side view
- 10. • Paired pyramidal cartilages that sit at top of cricoid cartilage lamina posteriorly. • Span supraglottis & glottis, most in supraglottis • Vertical height of arytenoid spans ventricle • Vocal & muscular processes are at level of TVC. • Vocal processes: Anterior projections of arytenoid cartilages to which posterior margins of TVC attach. • Superior process is at level of FVC Arytenoid cartilage
- 11. • Corniculate cartilage: Rests on top of superior process of arytenoid cartilage, within AE folds. • Cuneiform cartilage: Lateral & superior to corniculate within free edge of AE folds
- 12. 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.
- 14. • Extends from tip of epiglottis above to laryngeal ventricle below. • Contains vestibule, epiglottis, pre-epiglottic fat, AE folds, FVC, paraglottic space, arytenoid cartilages
- 15. • Pre-epiglottic space: Fat-filled space between hyoid bone anteriorly & epiglottis posteriorly • AE folds: Projects from cephalad tip of arytenoid cartilages to inferolateral margin of epiglottis • Represents superolateral margin of supraglottis, dividing it from pyriform sinus (hypopharynx)
- 16. • False vocal cords: Mucosal surfaces of laryngeal vestibule of supraglottis. • Beneath FVC are paired paraglottic spaces • Paraglottic spaces: Paired fatty regions beneath false & true vocal cords • Superiorly they merge into pre-epiglottic space • Terminates inferiorly at under surface of TVC
- 20. • TVC & anterior & posterior commissures • Comprised of thyroarytenoid muscle (medial fibers are "vocalis muscle") • Anterior commissure: Midline, anterior meeting point of TVC
- 23. • Subglottis extends from under surface of TVC to inferior surface of cricoid cartilage • Mucosal surface of subglottic area is closely applied to cricoid cartilage • Conus elasticus: Fibroelastic membrane extends from medial margin of TVC above to cricoid below
- 42. • Post-contrast: a) No enhancement of mucosal surface of larynx b) Hypopharyngeal mucosa enhances Collapsed piriform sinus may mimic tumor on CT – confirmation is with a modified valsalva maneuver which distends the region
- 43. • False vocal cords, aryepiglottic folds, pre and para- epiglottic spaces are fat contatining – hence appear hypoattenuating • Membranes such as thyrohyoid and cricothyroid are not well visualized • Ossified cartilages appear hyperdense in outer and inner cortex with a hypodense central area (medullary fat)
- 44. • Cortical bone, fatty marrow and non-ossified hyaline cartilage do not show post-contrast enhancement.
- 45. • Compared with CT, MR imaging has an increased ability to separate various soft tissues such as tumor and muscle. • Coronal and Axial T1 and Sagittal T2 sequences are used • Fast spin-echo (FSE) imaging gives excellent images with valuable T2 information. Fat suppression may be used, as the fat signal can be high on FSE images. This allows better appreciation of the higher signal intensity coming from abnormal soft tissues that may be bordered by fat.
- 46. Neck surface coil is needed. Slice thickness : 3–5 mm. axial plane : parallel to the true vocal cords, coronal plane :perpendicular to the defined axial plane. T1, T2, Fat saturation (FS) MRI, and Contrast- enhanced FS T1-WI are required. Imaging techniques MRI
- 47. • Sagittal images show the epiglottis, valleculae, and base of the tongue well. • The postcricoid area is seen well, and the arytenoid cartilage often can be visualized on the cricoid cartilage. • The preepiglottic fat is clearly seen on T1-weighted images.
- 49. The coronal view represents the ideal orientation for evaluation of the upper margin of the true cord. On T1-weighted images true cord can be seen contrasted against the high signal intensity fat of the false cord immediately above.
- 50. • The axial images represent slices perpendicular to the inner surface of the thyroid and cricoid cartilage, allowing assessment of cartilaginous erosion. • Ossified cartilage with fat in the medullary space has a high signal intensity on T1-weighted sequences. By comparison, the non-ossified cartilage tends to be dark on both T1-weighted and T2-weighted sequences.
- 53. • Hypopharyngeal and laryngeal mucosa show low to intermediate SI on T1WI, higher SI on T2WI and significant post-contrast enhancement • Muscular tissue eg pharyngeal constrictors and vocal cords show intermediate SI on T1 and T2WI, with no post-contrast enhancement • Therefore, with a T2WI and a post-contrast T1WI, we can easily differentiate mucosa (which enhances) from muscle (which doesn’t enhance).
- 55. Enhancing mucosa with underlying non- enhancing muscle
- 56. • Previously described fat containing structures as expected show high SI on T1 and intermediate SI on T2 SE. • On T1 and T2 FSE – fatty tissue shows high SI. • Despite MRI’s excellent tissue depiction, thin connective tissue and membranes cannot be visualized.
Editor's Notes
- Anterior view of laryngeal cartilage which provides structural framework for soft tissues of larynx to drape over. Note two large anterior laminae of thyroid cartilage "shield" the larynx. Thyrohyoid membrane contains an aperture through which internal branch of superior laryngeal nerve & associated vessels course. Mixed (external) laryngoceles herniate through thyrohyoid membrane to extend into submandibular space.
- Posterior view shows arytenoid cartilage sitting on top of posterior cricoid cartilage. True vocal cord attaches to vocal process of arytenoid cartilage & forms glottis. Epiglottis is a leaf-shaped cartilage which forms lid of larynx & contains fixed & free margins. Cricoid cartilage is only complete ring in endolarynx & provides structural integrity. Lower border of cricoid represents junction between larynx above & trachea below.
- Free edge of epiglottis is attached to hyoid bone via hyoepiglottic ligament which is covered by glossoepiglottic fold, a ridge of mucous membrane.
- Graphic at mid-supraglottic level shows hyoepiglottic ligament dividing lower pre-epiglottic space. No fascia separates pre-epiglottic space from paraglottic space. These two endolaryngeal spaces are submucosal locations where tumors hide from clinical detection. Aryepiglottic fold represents junction between larynx & hypopharynx.
- Graphic at low supraglottic level shows false vocal cords (FVC) formed by mucosal surfaces of laryngeal vestibule. Paraglottic space is beneath FVC, a common location for submucosal tumor spread.
- (Top) Graphic at glottic, true vocal cord level shows thyroarytenoid. Medial fibers of thyroarytenoid muscle are known as vocalis muscle. Pyriform sinus apex is seen at glottic level. Thyroarytenoid gap is location where tumors may spread between larynx & hypopharynx.
- Graphic at level of undersurface of true vocal cord shows posterior lamina of cricoid cartilage. Post-cricoid hypopharynx represents anterior wall of lower hypopharynx & extends from cricoarytenoid joints to lower edge of cricoid cartilage at cricopharyngeus muscle. Posterior wall of hypopharynx represents inferior continuation of posterior oropharyngeal wall & extends to cervical esophagus.
- Graphic at subglottic level shows cricothyroid joint immediately adjacent to recurrent laryngeal nerve, located in tracheoesophageal groove.
- Coronal graphic posterior view shows false & true vocal cords separated by laryngeal ventricle. Quadrangular membrane is a fibrous membrane which extends from upper arytenoid & corniculate cartilages to lateral epiglottis. Conus elasticus is a fibroelastic membrane which extends from vocal ligament of true vocal cord to cricoid. There membranes represent a relative barrier to tumor spread but are not seen on conventional imaging.
- Sagittal graphic of midline larynx shows laryngeal ventricle, air-space which separates false vocal cords above with true vocal cords below. Aryepiglottic folds project from tip of arytenoid cartilage to inferolateral margin of epiglottis. Aryepiglottic folds represent junction between supraglottis & hypopharynx. Medial wall of aryepiglottic fold is endolaryngeal while posterolateral wall is anteromedial margin of pyriform sinus.
- (Top) First of nine axial CECT images presented from superior to inferior of larynx & hypopharynx with patient in quiet respiration. Hyoid bone represents the level of the roof of larynx & hypopharynx Glossoepiglottic & pharyngoepiglottic folds represent transition from oropharynx above to larynx & hypopharynx below.
- (Middle) Image of high supraglottic level of larynx shows C-shaped pre-epiglottic space, a common location for tumors to hide. If supraglottic tumor extends to pre-epiglottic space, it becomes a T3 tumor
- (Bottom) Image of high supraglottic level shows pre-epiglottic & paraglottic spaces are continuous, with no intervening fascia. This allows tumors to spread submucosally in these locations. Posterolateralwall of aryepiglottic fold is anteromedial margin of pyriform sinus.
- (Top) Image of mid-supraglottic level shows thyroepiglottic ligament dividing the pre-epiglottic space. Aryepiglottic folds are at margin of pyriform sinus & larynx & a tumor primary to aryepiglottic fold is considered a "marginal supraglottic" tumor..II
- (Middle) Image of low supraglottic level shows false vocal cord level. Paraglottic space represents deep fatty space beneath false vocal cords. Tumors that cross laryngeal ventricle & involve false & true vocal cords are considered transglottic
- . (Bottom) Image at glottic level shows true vocal cords in abduction in quiet respiration. True vocal cord level is identified on CT when arytenoid and cricoid cartilages are seen and muscle fills inferior paraglottic space. Anterior and posterior commissures of true vocal cords should be less than 1 mm in normal patients. Post-cricoid hypopharynx is typically collapsed.
- In this image through the undersurface of true cord level the cricothyroid space is seen. Lack of arytenoid cartilage identifies undersurface of true cord level.
- (Middle) Image more inferior shows subglottic level with cricoid ring nearly complete. Cricoid is only complete cartilage ring in larynx & provides structural integrity. Dislocations of cricothyroid joint may result in vocal cord paralysis secondary to recurrent laryngeal nerve injury. There may be associated atrophy of posterior cricoarytenoid muscle on involved side of vocal cord paralysis
- (Bottom) At the level of the inferior cricoid cartilage the inferior margin of larynx & hypopharynx are transitioning to the trachea & cervical esophagus.
- First of three axial CECT images from superior to inferior in patient with breath holding shows adduction of false & true vocal cords as well as aryepiglottic folds.
- (Middle) Image at low supraglottic level shows level of false vocal cords in adduction. Note mucosa of aryepiglottic folds contacts posterior hypopharyngeal wall
- (Bottom) Image at glottic level shows adduction of true vocal cords. With breath holding, true vocal cords oppose in midline. A cord that remains paramedian is either paralyzed or mechanically fixed. Vocal cord paralysis typically results in a paramedian true vocal cords with associated abnormal location of arytenoid cartilage which is fixed in an anterior-medial position. With breath holding, paralyzed cord remains fixed while opposite normal cord crosses midline in attempt to close glottis. There may be an associated patulous pyriform sinus.
- In this image the laryngeal ventricle is visible as an air space between false vocal cords above & true vocal cords below. When a tumor crosses laryngeal ventricle to involve true & false cords it is transglottic, which has important treatment implications. Coronal imaging is particularly useful for evaluation of transglottic disease.
- This image reveals pre-epiglottic fat to be continuous with paraglottic fat. These are the most important spaces of endolarynx as they allow submucosal spread of tumors which is undetectable by clinical exam.
- Pre-epiglottic fat is seen at midline posterior & inferior to hyoid bone. Diseases of posterior hypopharyngealwall are well seen on sagittal imaging. Sagittal imaging also helps define cranial to caudal extent of lesions.
- A, MR T1-weighted sagittal image, just off the midline, shows the true cord and false cord separated by the dark air-filled ventricle (arrow). Arrowhead, Preepiglottic fat; E, epiglottis. B, More lateral scan shows the cricoid (C) and arytenoid (A).
- MR T1WI seen from front to back. A, Anterior scan shows the muscle intensity (white arrow) of the Thyro-aryetnoid muscle at the level of the cord. The paraglottic space at the level of the false cord shows bright fat intensity (black arrow). V, Ventricle; S, saccule of the ventricle; F, preepiglottic fat. B, Slightly more posterior scan. C, More posterior to B. Arrow, Posterior TAM; P, pyriform sinus; E, epiglottis; C, cricoid; G, submandibular gland. D, Posterior to C. C, Cricoid lamina; M, interarytenoid muscle; AE, AE fold; P, pyriform sinus. E, Posterior larynx shows the posterior cricoid (C). The muscle intensity to either side (arrow) represents the posterior cricoarytenoid muscle.
- Normal coronal MR image. Coronal image through the larynx shows the triangular TAM (arrow) forming the bulk of the true cord. The ventricle (arrowhead ), preepiglottic space (PS).