Vocal Fold Polyps and Cysts
Vocal fold polyps and cysts are considered vocal masses because they add weight and may displace the existing microanatomy. As such, these masses have a direct effect on the vibrating margin, so video or digital stroboscopy is especially helpful in characterizing these lesions. Although the terms polyp and cyst imply different types of lesions, there is actually a continuum of vocal fold masses with overlap in features between these lesions in some cases.1 Both types of lesions may be associated with intracordal scarring (within the lamina propria), sulcus deformities (epithelial indentations or defects bridging superficial to the deeper layers of the vocal fold microanatomy), as well as reactive callus or hyperkeratosis on the contralateral vocal fold. In this latter situation, bilateral lesions may initially appear as “nodules” if one were not to have the benefit of stroboscopy. Therefore, an understanding of the pathogenesis of these lesions and an understanding of typical findings on stroboscopy will improve accuracy of diagnosis, surgical planning, and ultimately prognosis to treatment.
Pathogenesis of Polyps and Cysts
Both polyps and cysts are believed to have similar initiating factors involving mucosal injury due to a multiple of factors, although they are believed to have different final steps in their pathogenesis. Vocal overuse and misuse are central to the development of vocal fold masses. This initial trauma is exacerbated by baseline inflammation often caused by laryngopharyngeal reflux. Another source of baseline inflammation may be sinonasal or pulmonary diseases. The resulting mucosal injury leads to increased shearing forces at the midportion of the membranous vocal fold, which is the most common site of vocal fold polyps and cysts.2 In many cases, the presence of the mass causes impaired glottic closure during phonation resulting in excess air egress, so there is a tendency for the patient to compensate for resulting voice limitations with hyperfunctional voice behavior.3 This maladaptation further increases shear and prevents the natural healing process.
In the case of vocal fold polyps, it is believed that capillary hemorrhage in the superficial lamina propria leads to extravasation of blood, resultant local edema, and ultimate organization with hyalinized stroma.4 Pathologically, polyps are acellular, with thickened epithelium over superficial lamina propria, and increased vascularity in an abundant delicate fibrin stromal matrix. They have more vasculature and less organized collagen than do nodules, but the distinction may be difficult for the pathologist.4 Immunohistochemistry studies reveal clustered fibronectin and disruption of laminar pattern suggesting diffuse injury in the region of the polyp.5
The resulting mass may be broad-based (sessile) or pedunculated (fusiform) and hemorrhagic versus nonhemorrhagic (Fig. 22.1). Hemorrhagic polyps may also have an associated blood vessel or varix. Though the gross appearance may vary, the lesion is generally considered to be an out-pouching of inflamed and organized Reinke’s space. Therefore, a superficial nonhemorrhagic, broad-based polyp may be interpreted as a pseudocyst, as a true cyst has an intact epithelial lining.
Vocal fold cysts are subepidermal epitheliallined sacs located within the lamina propria and may be mucus retention or epidermoid in origin (Fig. 22.2). Mucusretention cysts form when a mucous gland duct becomes obstructed (usually during an upper respiratory infection or with overuse), retaining glandular secretions. Epidermoid cysts develop either from congenital cell rests in the subepithelium (from the 4th and 6th branchial arches) or from healing injured mucosa burying epithelium. A ruptured cyst may result in scarring within the lamina propria or in a sulcus. Varices are also often associated with vocal cysts.
Indications and Usefulness of Stroboscopy
As one may infer from the discussion above, a two-dimensional picture of the vocal folds is not sufficient to characterize features that may be used to distinguish polyps from cysts. Transoral mirror evaluation and traditional indirect laryngoscopy may recognize a vocal fold mass, but the displacement of normal architecture in the vocal fold microanatomy lends itself to characteristic stroboscopic findings in the two lesions.6 Therefore, in addition to the use of traditional indirect laryngoscopy to visualize the larynx, stroboscopy is uniquely useful and indicated to characterize a lesion and its relationship to the layered microanatomy of the vocal fold and to help determine the etiology of dysphonia in patients when a lesion, or cause, is not apparent.
As these masses have distinct histology, the prognosis is different, and the best treatment is also different. Treatment modalities may include behavioral, medical, surgical, or office-based procedures. For example, a hemorrhagic vocal polyp with associated varix may be amenable to an office-based angiolytic laser treatment, sparing an epithelial dissection and potentially facilitating recovery of the voice.7 A vocal polyp may be amenable to resolution with strict voice rest and behavior modification in selected individuals.8 Conversely, a true cyst will not resolve with conservative management. The phonosurgical approach for cyst removal requires more extensive dissection than does that with a polyp, as the cyst is in the submucosal plane. The cyst may also be associated with intracordal scarring, requiring a more elaborate dissection. Consequently, recovery of the mucosal wave is prolonged and may never return to being completely normal. Furthermore, leaving behind a minute fragment of epithelium in the cyst sac may result in recurrence of the cyst.9 In a large series of patients, Sataloff et al. recognized the usefulness of videostroboscopy to help distinguish between polyps and cysts and thus improve surgical planning and preoperative patient counseling.10
Interpretation: Impact of Polyps and Cysts on Vibratory Parameters
As discussed elsewhere in this text, stroboscopy features may help distinguish polyps from cysts. These features include glottic configuration, amplitude of vibration, mucosal wave phase (closed, open, irregular, hourglass, anterior/posterior chink), mucosal wave symmetry/asymmetry, and periodicity (regular, irregular). Common to both lesions is the impact of the mass on the linearity of the vocal fold, which often results in premature contact at the site of the lesion and subsequently an hourglass or irregular glottic configuration on phonation.
Vocal folds with small polyps generally have intact mucosal waves but phase asymmetry due to the impaired phase closure and the mass effect of the polyp (Video Clips 23 and 46). Vocal folds with larger polyps may have increased mucosal wave amplitude due to a shearing effect tethering a pedunculated polyp to the normal adjacent mucosa or decreased amplitude due to overwhelming mass effect. As polyps are asymmetric masses of the vocal folds, they are more prone to result in chaotic vibrations and aperiodic mucosal waves.11 Examples of vocal polyps and their impact on vibratory patterns seen on stroboscopy are shown and discussed in Figs. 22.3 to 22.6.
The history of a patient with a vocal cyst is similar to those of patients with nodules and polyps, but often with less vocal limitation than expected from its size. The voice may sound diplophonic (particularly with epidermoid cysts), where there is great pitch instability and there is splitting of the fundamental frequency overtones.
Though it is often possible to distinguish some cysts solely by still-light endoscopy, visualizations of the outline of the cyst, associated capillary patterns, and characteristic changes in the edge or free margin are not always present. On stroboscopy, the vocal folds appear asymmetric with occasional evidence of the subepithelial mass. The free edges of the vocal folds are generally smooth.12
Due to displacement of the lamina propria and the fibrosis that frequently occurs around vocal fold cysts, there is a significant decreased or absent mucosal wave on the side of the cyst (Video Clip 26). Whereas vocal fold polyps have intact mucosal waves in 80% of all cases, Shohet et al. demonstrated the mucosal wave to be diminished or absent in 100% of vocal fold cysts.13 This can be explained by changes in the elastic coefficient of the lamina propria surrounding the cyst.14 If light reflection indicates an intact mucosal wave, the vocal fold with a cyst will not reflect light. In contrast with a polyp, a cyst would have a dynamic segment of mucosa adjacent to the cyst, lacking reflected light, with an intact mucosal wave over the contralateral cord-corresponding segment.13 The amplitude and vibration of the wave are also diminished and absent.9 Examples of vocal cysts and their impact on vibratory patterns seen on stroboscopy are shown and discussed in Figs. 22.7 to 22.10.
Pearls and Pitfalls in the Diagnosis of Polyps and Cysts on Stroboscopy
The general pearls that may be assumed from the above discussion follow:
- Polyps are out-pouchings of Reinke’s space, may be pedunculated (fusiform) or broad-based (sessile), and may or may not show signs of hemorrhage.
- Cysts are epithelial-lined sacs within Reinke’s space and may be mucus or epidermoid related.
- Polyps and cysts result in an hourglass or irregular vocal fold glottic configuration on phonation.
- The amplitude of the mucosal wave is generally decreased with vocal cysts, whereas it is generally normal or increased with vocal fold polyps.
- The amplitude of vibration will likely be decreased secondary to the mass of the lesion combined with an incomplete glottic closure.
- Vocal fold vibration will likely be asymmetric and possibly aperiodic.
Despite these pearls, there are pitfalls in the use of stroboscopy to distinguish vocal fold polyps from cysts or other lesions. The presence of a polyp or cyst may cause a reactive lesion, or “callus,” on the contralateral vocal fold secondary to contact irritation. A unilateral lesion with reactive callus formation may look like bilateral lesions, in other words nodules, which may confound the diagnosis, prognosis, and ultimate management. Also, though the glottic closure of the vocal folds with cysts may often be complete (for example), it depends on the cyst size and whether there is development of the callus on the contralateral vocal fold (Video Clip 26).
Rosen et al. evaluated a series of 85 patients with bilateral vocal fold lesions and found 21 to have nodules and 64 to have a unilateral vocal fold lesion with a contralateral reactive lesion (UVFL/RL).15 When comparing patients with nodules and those with UVFL/RL, they found statistically significant differences in (1) symmetry of vocal fold vibration, (2) amplitude perturbations, (3) estimated subglottic pressure, and (4) voice handicap index, suggesting that these parameters be used as tools to differentiate nodules from UVFL/RL.
Repeated inflammation, vocal trauma, vocal hemorrhage, and the presence of an intracordal cyst predispose to scarring in Reinke’s space. Intracordal scarring is often found in association with a cyst, particularly if it is epidermoid in origin and has ruptured. Intracordal scarring is suspected on stroboscopy when there is markedly reduced or absent mucosal wave (usually asymmetric) that often affects phase closure (Video Clip 33). It is crucial to differentiate between an uncomplicated subepithelial cyst and an intracordal scar, as the latter is a more complex problem with worse prognosis for voice rehabilitation. With these factors in mind, the typical “pearls” used to distinguish polyps from cysts on stroboscopy have understandable limitations. Nevertheless, the utility of stroboscopy in appropriate diagnosis, patient counseling, and treatment intervention is vital to obtaining the best outcome.
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