Phonomicrosurgery for Benign Vocal Fold Lesions

Introduction

Patients complaining of hoarseness, vocal fatigue, diminished vocal range, strain, or other vocal issues require a complete laryngeal examination. Based on the findings of this examination, several treatments may be indicated, including surgery. Phonomicrosurgery (PMS) encompasses a variety of elective operations whose primary goal is to improve the quality of the voice. These procedures focus on precision microsurgical techniques to remove benign vocal fold lesions, while not disrupting surrounding normal tissue. Hirano’s body cover theory of vocal fold vibration is paramount in the design of current microsurgical principles and surgical procedures. The delicate interface between the mucosa (cover) and the deeper lamina propria layers and muscle (body) allows for the creation of a mucosal wave ( Fig. 2.1 ). Alterations in the muscosal wave result in dysphonia. Stroboscopy, which provides vital information about the mucosal wave, is absolutely essential in the evaluation of dysphonic patients. Wound healing is optimized by preserving the mucosa whenever possible and limiting surgery to the vocal fold layers involved with pathology (staying as superficial in the vocal fold as possible). The higher content of fibroblasts in the vocal ligament may result in increased scar deposition if surgery extends to this region. Fortunately, the majority of bilateral vocal fold lesions are located within the superficial lamina propria, resulting in expected better postoperative mucosal wave vibration, and thereby likely improving vocal outcomes. Our improved knowledge of vocal fold microanatomy and the use of stroboscopy have led to improved patient care and surgical advancement in PMS.

Sound is the product of subglottic airflow forcing closed vocal folds to open, thereby leading to the generation of a mucosal wave along the medial edge of the vocal fold. Closure of the vocal folds during this vibratory cycle is achieved by the inherent elastic recoil of the vocal fold and the Bernoulli effect. This is called the myoelastic aerodynamic theory of phonation. This cycle usually occurs 100 to 1200 times per second. A mass on the vocal fold can disrupt this normal process and lead to hoarseness and other vocal complaints. Therefore the use of stroboscopy, which allows visualization of the mucosal wave, is indispensable in the care of these patients. Depending on the patient’s history and laryngeal examination, either flexible transnasal laryngoscopy with stroboscopy (vocal fold motion abnormalities), or rigid, per-oral, endoscopy with stroboscopy (lesions), or both may need to be performed to fully evaluate the larynx. Such laryngeal examinations will provide the surgeon with an idea of the depth and type of the lesion. Although all vocal fold lesions are sent to pathology for evaluation, it is difficult for pathologists to distinguish between various vocal fold lesions based on their histologic characteristics. Precise classification of benign vocal fold lesions is therefore based on the surgeon’s evaluation in the operating room, including magnification with the operating microscope, palpation of the vocal fold, identification of the physical features of the lesion or lesions, such as a cystic or fibrous mass, and location of the pathology.

Key Operative Learning Points

• The key surgical anatomy related to PMS for benign vocal fold lesions involves the layered structure of the membranous true vocal fold.

  • Major components to the layered structure of the vocal fold

    • Epithelium

    • Lamina propria

    • Muscle (thyroarytenoid-lateral cricoarytenoid)

  • The most medial aspect of the muscle that runs from the vocal process of the arytenoid to the thyroid cartilage is named the vocalis muscle.

• Excluding epithelial diseases of the vocal folds, all benign vocal fold lesions arise within the lamina propria, which can be defined as the anatomic space between the epithelium and the muscle of the vocal fold. There are anatomically (or histologically) three distinct layers of the lamina propria.

  • Superficial layer

  • Intermediate layer

  • Deep layer

    • The intermediate and deep layers, also called the vocal ligament, are not surgically distinct.

• From a surgical perspective, there are two key operative locations within the lamina propria

  • Subepithelial space

  • Ligamentous region

• The mucosa of the vocal fold is defined as being composed of the epithelium and the superficial layer of the lamina propria.

• The majority of benign vocal fold lesions occur within the subepithelial space. The most common pathology that occurs in this region includes :

  • Vocal fold nodules

  • Vocal fold polyp(s)

  • Subepithelial cyst(s)

  • Subepithelial fibrous mass(es)

  • Reinke edema

• Lesions that occur in the area of the vocal fold ligament include:

  • Ligamentous vocal fold cyst(s)

  • Ligamentous fibrous mass(es)

  • Rheumatologic lesion(s)

• The majority of benign vocal fold lesions occur in the midportion of the membranous vocal fold, which is positioned halfway between the anterior commissure and the vocal process of the true vocal fold.

Types of Benign Vocal Fold Lesions

• Vocal Nodules

Vocal nodules are benign bilateral lesions, not always symmetrical, located within the lamina propria, with normal overlying epithelium. The mucosal wave is normal or near-normal. They are typically located at the midpoint of the musculomembranous vocal fold. Breathy and raspy dysphonia is the result of incomplete vocal fold closure. Vocal nodules tend to occur in patients who use their voices aggressively (i.e., children, cheerleaders). After the inciting phonotraumatic behavior is eliminated and voice therapy is implemented, these lesions always resolve. Accordingly, surgery is not indicated for vocal nodules.

• Nonspecific Vocal Fold Lesion(s)

These vocal fold lesions are similar to vocal fold nodules. However, these lesions persist after voice therapy, despite resolution or significant improvement of the patient’s dysphonia. Because the patients’ dysphonia resolves and the lesions are benign, no surgery is indicated.

• Vocal Fold Polyp

A vocal fold polyp is located in the subepithelial space, usually at the midpoint of the musculomembranous vocal fold. It is generally unilateral, sometimes with a contralateral reactive lesion. A vocal fold polyp can be sessile (broadly attached to a vocal fold) or pedunculated (hanging from a stalk). This lesion is believed to be the product of intense phonotrauma or vocal fold hemorrhage. Inflammatory agents, dehydration, hormone treatment, and anti-inflammatory medications may be predisposing factors. Truncation or microflap excision is performed for a vocal fold polyp if the voice is functionally impaired after conservative therapy.

• Vocal Fold Cyst

A vocal fold cyst, both subepithelial and ligamentous, is often unilateral and located at the edge of the midmusculomembranous portion of the vocal fold. The encapsulated structure is thought to be due to glandular duct blockage or phonotrauma or may be congenital. The mucosal wave is more reduced with a ligamentous vocal fold cyst. Proper voice use and voice therapy are often the initial treatments. If this is not adequate to meet the vocal demands of the patient, microflap excision is performed.

• Fibrous Mass

A fibrous mass is composed of irregular fibrous material without clearly defined borders. This lesion can occur in either the subepithelial space or near the ligament of the vocal fold, both with normal overlying epithelium. This mass is often located in the midmembranous vocal fold, either unilateral or bilateral, and therefore incomplete vocal fold closure is common. Unilateral lesions are frequently associated with a contralateral reactive lesion. Development of a fibrous mass is often associated with chronic phonotrauma or hemorrhage. Voice therapy is often the initial treatment. If this fails, surgical excision with a microflap technique is indicated.

Subepithelial fibrous mass(es) have a reduced mucosal wave but not usually as severely reduced as ligamentous fibrous mass(es). When deep dissection is needed to excise these lesions, there is a greater risk of reduced postoperative voice improvement than with more subepithelial fibrous masses.

• Reactive Lesion

Reactive lesions are believed to result from altered contact forces from a primary contralateral lesion, such as a polyp, cyst, or fibrous mass. Videostroboscopy will demonstrate a convex lesion (primary lesion) that fits into a concave reactive lesion (secondary lesion). This lesion can be surgically removed at the same time the primary lesion is removed or left to resolve during the postoperative period. This decision is based on the surgeon’s preference and experience.

• Reinke Edema (Polypoid Degeneration, Diffuse Polyposis, Chronic Polypoid Corditis)

Reinke edema involves the deposition of gelatinous material within the subepithelial space. It is usually bilateral but may be asymmetrical or unilateral. These patients’ voices are lower in pitch and dysphonic. Clinically, women are affected more often by Reinke edema; however, this may be due to selection bias because women are more bothered by lower vocal pitch and roughness and thus are more prone to seek treatment. The largest risk factor is smoking, followed by reflux and phonotrauma. When the pathologic accumulation is severe, airway obstruction can occur. Primary treatment is to remove the offending agents that led to the development of Reinke edema. Smoking cessation is vital. Voice therapy can occasionally be helpful if the probable cause is phonotrauma. Only after several months of compliance with smoking cessation and other conservative treatments (acid suppression and voice therapy) should surgery be considered, except in the case of airway obstruction. Conservative removal of a portion of the gelatinous material is achieved through a lateral cordotomy on the superior aspect of the vocal fold, followed by suctioning and/or near complete removal of material from the subepithelial space and excision of redundant tissue. Care must be taken because overly aggressive removal of redundant superficial lamina propria will lead to scarring and permanent hoarseness. Laser treatment with the potassium titanyl phosphate (KTP) laser may be a reasonable alternative treatment option.

Preoperative Period

Operative Period