Laryngocele
The laryngeal ventricles of Morgagni are paired structures of the larynx residing between the vocal and vestibular folds; the saccule is an appendageal diverticulum extending vertically from the ventricle between the vestibular fold and the thyroid cartilage, and is responsible for producing mucus that lubricates the vocal cords. Cystic dilatation of the saccule is termed a laryngocele, which may be developmental due to failure of regression after birth, and can also be seen in persons who experience high throat pressures, such as wind musicians, glass blowers, and those with excessive coughing [3]. These are often asymptomatic and found incidentally, but occasionally can present with hoarseness and stridor. Symptoms may be episodic due to intermittent filling and resultant one-way valve effect, or due to infection [4].
On imaging, a laryngocele appears as a thin-walled air- or fluid-filled space lateral to and communicating with the laryngeal lumen; the wall will demonstrate absent or minimal enhancement [5] (Fig. 4). Types of laryngoceles are defined by their relationship to the thyrohyoid membrane—internal and external/mixed [4]. Internal (or simple) laryngoceles are confined to the paraglottic space of the supraglottis, and are found lateral to the thyrohyoid membrane. If the laryngocele extends superiorly through the thyrohyoid membrane into the submandibular space, then it is termed a mixed laryngocele. An external laryngocele does not have an internal component and is rare; it may present as a lateral neck mass and can be intimately associated with the superior laryngeal nerve.
Benign inflammatory laryngeal lesions
Repetitive insult to the laryngeal mucosa—such as with singing, yelling, smoking, gastroesophageal reflux—can lead to a number of benign inflammatory lesions, especially of the vocal cords. Although related in etiology, these lesions differ in mechanics of origin and appearance [6, 7]. Vocal cord nodules occur bilaterally and symmetrically at the midpoint of the cords due to high shear force during apposition and subsequent remodeling, similar to a callous. A laryngeal polyp forms after trauma to the submucosal capillary bed, with subsequent exudative inflammatory changes and outpouching of the mucosa (Fig. 5). A laryngeal cyst can appear similar to a laryngocele and may be of two types: retention, due to glandular obstruction and resultant trapped secretions, or epidermoid, which are congenital or due to trauma. Reinke’s edema is not a discrete lesion, but is diffuse edema of the vocal cords due to fluid accumulation between the membranous folds (Reinke’s space). These lesions do not warrant imaging as they are readily seen by laryngoscopy; however, they may be seen incidentally on head and neck imaging obtained for other reasons [8].
Squamous cell carcinoma
Squamous cell carcinoma (SCC) is by far the most common (98%) primary tumor of the larynx, and can also secondarily involve the larynx when the primary is elsewhere in the oropharynx. SCC generally occurs in men over 50 and was previously associated with smoking and alcohol abuse; however, SCC related to human papilloma virus (HPV) is now more prevalent, and is seen in the younger population with better prognosis. Classification is based on subsite of location in relation to the glottis—supraglottic (20–30%), glottic (50–60%), subglottic (5%), and transglottic (spanning two or more subsites)—and presentation depends on the subsite involved. Glottic lesions often present earlier with dysphonia or aspiration, while subglottic lesions typically present with dyspnea and/or stridor. Purely supraglottic lesions are asymptomatic, thus usually present later with symptoms due to lymphadenopathy or trans-spatial spread, such as tender neck mass, sore throat, dysphagia/odynophagia, or referred ear pain.
As laryngoscopy can be performed by the otolaryngologist, imaging is used for staging rather than diagnosis. SCC appears as an enhancing soft tissue mass on both computed tomography (CT) and MRI; either may be used for disease surveillance. The lesion is usually isoattenuating to the surrounding mucosa on CT, but may be identified due to architectural distortion and loss of tissue planes (Figs. 6 and 7). On MRI, the lesion is usually T1-hyperintense, T2-hyperintense, and demonstrates high STIR signal due to edema. Positron emission tomography (PET) may be used in conjunction to identify metastatic lymphadenopathy or post-treatment occurrence.
Small lesions may be treated locally with laser or radiation ablation; larger tumors usually necessitate laryngectomy and radiation therapy, although supraglottic tumors without vocal cord fixation may be treated with voice-sparing surgery. Compared to similarly staged SCC elsewhere in the head and neck, laryngeal SCC portends a better prognosis, but 15–20% will develop a second primary site SCC that is most certainly fatal.
Recurrent respiratory papillomatosis
Respiratory papillomatosis is caused by human papilloma virus (HPV); it has a propensity for the larynx but can also occur elsewhere in the airway [9]. It is the most common laryngeal tumor in children, but can be seen in adults. In juvenile-onset respiratory papillomatosis, HPV is transmitted from a mother to her child during passage through the birth canal; an infected mother has a 1% risk for transmission to her child. In adult-onset respiratory papillomatosis, transmission is thought to occur via oral sex [10, 11]. The most common strains in respiratory papillomatosis are HPV 6 and HPV 11; however, HPV 16 carries the highest risk for malignant transformation. Respiratory papillomatosis results in airway obstruction, which may be due to either blockage by an intraluminal lesion or infiltration of the structural tissues; tissue infiltration can also result in dysphonia due to morphologic alteration of the laryngeal components. Imaging characteristics are nonspecific; intraluminal lesions tend to be sessile and verrucoid, while infiltrative lesions appear as irregular soft tissue thickening. Lesions tend not to enhance avidly or at all; however, they will demonstrate fluorodeoxyglucose (FDG)-avidity on PET (Fig. 8). Treatment is antiretroviral therapy and surgical resection, possibly complemented by airway reconstruction in cases of wide resection necessitated by large lesions or extensive infiltration; as implied by the name, however, papillomatosis tends to recur [12].
Laryngeal amyloidosis
Amyloidosis is the extracellular deposition of a variety of fibrils that are composed of various low molecular weight subunits of proteins that are found normally in blood serum; this abnormal tissue is called amyloid. Laryngeal amyloidosis is a rare entity, accounting for only 1% of laryngeal masses [13, 14]. Amyloidosis is a slow progressive process that results in hoarseness due to tissue infiltration by amyloid, which alters the structure and mechanics of the vocal apparatus. Deposition in laryngeal tissue is most often a localized process, but systemic amyloidosis with laryngeal involvement is usually due to a monoclonal plasma cell dyscrasia. Imaging findings in amyloidosis are nonspecific and result from architectural distortion of laryngeal structures due to tissue infiltration (Fig. 9). Treatment consists of endoluminal microsurgical resection or debulking, and often requires multiple sessions due to extent and recurrence [15].