Pathophysiology 1A

Introduction to Voice Disorders

• Instructor: Doctor Weldon - Focus: Voice disorders and their pathophysiology, understanding the underlying mechanisms that lead to voice changes.

• Previous Modules: Anatomy, physiology of the larynx (including respiration and phonation cycles), voice evaluation techniques (perceptual, acoustic analysis of voice, video stroboscopic imaging for vocal fold vibratory patterns, aerodynamic measures of airflow and pressure).

• Upcoming Focus: Different larynges with various lesions causing dysphonia and developing a comprehensive understanding of the etiology of these anatomical problems.

Types of Voice Disorders

Structural Pathologies

• Definition: Affect the physical structure of the larynx (e.g., lesions, masses, or mucosal changes) that directly interfere with vocal fold vibration.

• Categories:

  • Inflammatory Conditions: Causes inflammation, swelling, erythema, edema, and mucosal issues (e.g., acute laryngitis, reflux laryngitis, vocal fold thickening due to chronic irritation).

  • Trauma or Injury: Examples include arytenoid dislocation from external trauma, intubation-related trauma (such as granulomas or scarring), chemical burns, or excessive vocal abuse leading to acute injury.

  • Systemic Conditions: Endocrine imbalances (e.g., hormone issues like hypothyroidism affecting vocal fold mass and stiffness), dehydration, autoimmune disorders, or allergies that cause widespread effects impacting vocal function.

  • Non-Laryngeal Aerodigestive Disorders: Swallowing issues (dysphagia) or gastroesophageal reflux disease (GERD)/laryngopharyngeal reflux (LPR) impacting laryngeal function due to chronic irritation and inflammation of the vocal folds and surrounding tissues.

  • Psychiatric and Psychological Disorders: Functional voice disorders linked to mental health where voice reflects emotions and identity, often presenting without clear organic pathology (e.g., psychogenic dysphonia, muscle tension dysphonia with psychological roots).

  • Neurologic Disorders: Progressive neurodegenerative diseases (e.g., Parkinson's disease, amyotrophic lateral sclerosis (ALS), multiple sclerosis, stroke affecting neural control of the larynx) that impact voice due to muscle and nerve dysfunction affecting laryngeal movement and coordination.

  • Miscellaneous Disorders: Various other voice disorders that do not fit neatly into categories, such as congenital anomalies or rare idiopathic conditions.

Focus on Structural Pathologies: Malignant Laryngeal Lesions

Laryngeal Cancer

• Overview: Malignant lesions in the larynx that can aggressively grow and spread, potentially leading to severe health consequences including airway compromise and metastasis.

• Current Statistics: Approximately 89,000 individuals in the U.S. living with laryngeal cancer; relatively rare compared to other cancers (3% of all head and neck cancers), with higher incidence in men.

• Predisposing Factors:

  • Smoking: Major cause, with very few cases emerging in non-smokers. Tobacco smoke contains carcinogens that directly irritate and damage the mucosal lining of the larynx, leading to cellular changes.

  • Alcohol Abuse: Increased risk, especially when combined with smoking, as alcohol acts as a co-carcinogen, enhancing the effects of tobacco.

  • Chemical Exposures: Rarely highlightable causes for laryngeal cancer, but sustained exposure to certain industrial chemicals (e.g., asbestos, paint fumes) can increase risk.

Types of Laryngeal Cancer

• Squamous Cell Carcinoma: Most common (over 90% of cases); begins in the mucosal epithelium, which lines the larynx.

• Characterization:

  • Cancer can present at various sites: glottic (on the true vocal folds), supraglottic (above the vocal folds), or subglottic (below the vocal folds).

  • Glottic cancer referred to based on involvement of true vocal folds and often causes early voice change due to interference with vocal fold vibration.

  • T staging system based on tumor size, location, and movement of vocal folds (e.g., T1A, T1B, T2, T3).

  • $T1A$: Tumor confined to one true vocal fold, with normal vocal fold mobility.

  • $T1B$: Tumor involves both true vocal folds, with normal vocal fold mobility.

  • $T2$: Tumor extends to the supraglottis and/or subglottis, or impairs vocal fold movement.

  • $T3$: Tumor is confined to the larynx but with vocal fold fixation (immobility) and/or invades the paraglottic space.

Pathophysiology

• Dysplasia: Abnormal changes in cells; a pre-malignant condition where cells are altered but have not yet become invasive cancer. It is often graded as mild, moderate, or severe.

• Leukoplakia: Whitish mucosal patches or plaques indicating dysplastic cells; often needs monitoring and biopsy to rule out malignancy, as it represents hyperkeratosis with or without dysplasia.

• Hyperkeratosis: Thickening of the mucosa, resembling a callus or rough patch, indicating dysplastic conditions. Biopsy is essential to determine the extent of cellular atypia.

Treatment Options for Laryngeal Cancer

• Surgical Intervention: Biopsy to confirm diagnosis; various procedures ranging from endoscopic removal of small lesions to partial or total laryngectomy (removal of part or all of the larynx) if necessary.

• Radiation Therapy: Often combined with surgery or chemotherapy depending on cancer stage and spread. It uses high-energy rays to kill cancer cells, sometimes as a primary treatment for early-stage cancers.

• Chemotherapy: Used in various combinations for treatment effectiveness, especially for advanced cancers, as an adjunct to surgery and radiation, or as a palliative measure.

Importance of Early Diagnosis

• Necessity of Evaluation: Any persistent hoarseness for more than a few weeks (typically two to three weeks) must lead to laryngoscopic imaging for thorough diagnosis, as early detection significantly improves prognosis.

• Critical Role of Speech Pathologists: Ensuring imaging occurs before any voice intervention to prevent treating underlying malignancies that could worsen outcomes or delay life-saving treatment.

Voice Function Impacted by Laryngeal Cancer

• Degree of impact on voice can vary significantly with tumor size, location (e.g., glottic lesions cause more immediate hoarseness), and the extent of vocal fold involvement.

• Vocal fold paralysis or fixation (due to tumor invasion or nerve damage) can lead to respiratory issues affecting speech production, including dysphagia, chronic cough, and reduced vocal intensity and pitch control.

Healing Process in Voice Lesions

Stages of Wound Healing

• Hemostasis: Initial phase of injury where blood supply to the area is reduced through vasoconstriction, and platelets aggregate to form a temporary plug, stopping bleeding.

• Inflammation: Reaction to injury, characterized by vasodilation and increased permeability, allowing immune cells (neutrophils, macrophages) to migrate to the site to clear debris and fight infection, promoting healing.

• Proliferation: Cell growth and formation of granulation tissue, a good sign indicating healing. This stage involves fibroblasts laying down collagen, angiogenesis (formation of new blood vessels), and production of extracellular matrix components.

• Re-epithelialization: Formation of a new layer of skin or mucus membrane as epithelial cells migrate from the wound edges to cover the defect, restoring the protective barrier.

• Remodeling: Involves contraction of tissue and can lead to scarring, which can impact vocal fold pliability. This long phase (weeks to years) reorganizes collagen fibers, increases tensile strength of the tissue, and reduces scar tissue over time.

Vocal Fold Nodules

• Alternative Names: Singer's nodes, Screamer's nodes, vocal abuse nodules.

• Characteristics:

  • Localized, benign (non-cancerous) masses on the true vocal folds, typically found in the junction of anterior one-third and posterior two-thirds, which is the point of maximal vibratory excursion and impact.

  • Associated with phonotraumatic behaviors such as yelling, chronic throat clearing, excessive loud talking, or prolonged improper voice use.

  • More common in women, especially vocal professionals (e.g., teachers, singers, call-center operators) due to higher vocal loading and differential vibratory mechanics compared to men.

  • Microscopically, nodules present with a thickened basement membrane zone, edema, and often fibrosis.

• Presentation: Often create an hourglass-shaped glottal closure during phonation due to bilateral swelling on the medial edge of the vocal folds, preventing complete adduction.

• Symptoms: Variable degree of dysphonia, ranging from roughness, breathiness, and pitch breaks to vocal fatigue, reduced pitch range, and effortful voice production during voice use.

• Management:

  • Initial approach almost always favors voice therapy to change phonotraumatic behaviors, promote voice rest, optimize vocal hygiene, and potentially use amplification. This is the primary and most effective treatment.

  • Surgery considered only if therapy is unsuccessful and nodules are persistent or significantly impacting voice function, largely due to the risk of recurrence if behaviors are not modified and potential tissue scarring which can permanently alter vocal fold vibration.

Conclusion of Current Module

• Next topic will cover vocal fold polyps