The larynx is located in the anterior part of the neck,
near the inferior portion of the pharynx and superior to the trachea.
Its primary function is to protect the lower airway by closing upon mechanical stimulation,
halting respiration and preventing the entry of liquids or solids into the airway.
Other functions of the larynx include coughing,
the Valsalva maneuver,
control of ventilation and last but not least the production of sound (phonation),
which is particularly evolved in the human being.
The larynx is composed of 3 larger unpaired cartilages (cricoid,
thyroid,
epiglottis),
3 pairs of smaller cartilages (arytenoids,
corniculate,
cuneiform) and a set of intrinsic muscles.
The hyoid bone,
even if not part of the larynx,
provides important muscular attachments from above that aid in laryngeal motion.
The larynx is divided into three parts: supraglottis,
glottis and subglottis,
(Fig. 1).
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/811928?maxheight=300&maxwidth=300)
Fig. 1: Partition of the larynx
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
The supraglottis extends from the tip of the epiglottis to the laryngeal ventricles which are located between the false and the true vocal cords.
It contains structures such as the vestibule,
epiglottis,
pre-epiglottic fat,
hyoepiglottic ligament,
aryepiglottic folds,
paraglottic space,
false vocal cords,
arytenoids cartilages and ventricles (Fig. 2,
Fig. 3,
Fig. 4,
Fig. 5).
Critical adipose space:
-pre-epiglottic space: inverted pyramid shaped space,
bounded superiorly by the hyoepiglottic ligament,
anteriorly by the thyrohyoid membrane and posteroinferiorly by the epiglottis and thyroepiglottic legaments;
-paraglottic space (Fig. 6): bounded laterally by the thyroid cartilage,
inferomedially by the conus elasticus,
medially by the ventricle and quadrangolar membrane.
Larynx and especially paraglottic space can be divided in an anterior and a posterior compartment thanks to a vertical plane tangential to the arytenoid vocal process and perpendicular to the ipsilateral thyroid lamina.
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/811950?maxheight=300&maxwidth=300)
Fig. 2: Structures of the Supraglottis
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/811960?maxheight=300&maxwidth=300)
Fig. 3: Structures of the Supraglottis
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/811967?maxheight=300&maxwidth=300)
Fig. 4: Structures of the Supraglottis
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/812004?maxheight=300&maxwidth=300)
Fig. 5: Structures of the Supraglottis and Glottis
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/812021?maxheight=300&maxwidth=300)
Fig. 6: Anterior and posterior Paraglottic Space
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
The glottis includes exclusively the true vocal cords,
paraglotic space and anterior and posterior commissures.
The true vocal cords are formed by the thyroarytenoid muscles,
whose medial fibers are named "vocalis muscle" and are located slightly lateral to the vocal ligament (Fig. 7,
Fig. 8).
Anteriorly both vocal cords meet close to the medial part of the posterior surface of the thyroid cartilage forming the anterior commissure (Fig. 9).
The posterior commisure is a name given to the posterior portion of glottis,
interarytenoid muscles are a useful landmark.
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/812057?maxheight=300&maxwidth=300)
Fig. 7: Thyroarytenoid and Vocalis muscle
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/812068?maxheight=300&maxwidth=300)
Fig. 8: Thyroarytenoid and Vocalis muscle
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/812076?maxheight=300&maxwidth=300)
Fig. 9: The Glottis
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
The subglottis extends from the inferior surface of the true vocal cords to inferior surfaces of cricoid cartilage where the trachea begins (Fig. 10).
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/812139?maxheight=300&maxwidth=300)
Fig. 10: The Subglottis
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
Position of the patient and of the US probe
To perform a correct US examination of the larynx the patient has to lay down supine with the head and neck slightly tilted back.
Many are the scanning plans useful to visualize all structures and examine them in detail,
the most used being the anterior axial approach trough the thyroid cartilage showing both true vocal cords and most other structures by fanning the probe in cranial and caudal direction (Fig. 11).
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/812188?maxheight=300&maxwidth=300)
Fig. 11: Open and closed Glottis
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
While this approach has the advantage of exploring both sides simultaneously,
fundamental for comparative assessment of true vocal cords for example (Fig. 13),
it often is impaired by calcifications of the thyroid cartilage,
which occur quite early in men and later in women,
and the rather irregular cutaneous surface.
To best assess the true vocal cords,
false vocal cords,
arytenoids cartilages and the thyroarytenoid muscles individually on each side,
the best approach is the lateral one with a light inclination to adapt to the natural angle of the glottis.
Since US and MRI have their own well-known peculiar strengths and weaknesses which are particularly stressed out in the assessment of the larynx,
we suggest lesser experienced operators to train the recognition of anatomic landmarks by using US-MRI fusion imaging techniques (Fig. 12) thus combining respective advantages and steepen their learning curves.
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/812319?maxheight=300&maxwidth=300)
Fig. 12: US-MRI fusion imaging, caudocranial direction
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/812472?maxheight=300&maxwidth=300)
Fig. 13: True vocal cords movement in a healthy patient
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019
The dynamic evaluation with US allows an immediate observation of most of the larynx movements expecially those on an axial plane,
and in particular those of the true vocal cords (Fig. 13).
In case of impaired movement,
whatever the cause,
the recognition is straightforward (Fig. 14).
![](https://epos.myesr.org/posterimage/esr/ecr2019/148168/media/812785?maxheight=300&maxwidth=300)
Fig. 14: Impaired movement of the right vocal cord
References: Department of Radiology, IRCCS San Martino, Medical University of Genoa/ Italy 2019