Focus on disorders caused by issues with the central or peripheral nervous system.
Discussion will also include miscellaneous disorders, such as endocrine disorders and functional disorders related to the larynx.
Acknowledgment of Dr. Keltner and Dr. Ishikawa's contributions to the lecture series.
Endocrine Disorders Affecting Voice
1. Hypothyroidism
Definition: A condition characterized by low thyroid hormone levels affecting the thyroid gland located in the neck above the thyroid cartilage.
This leads to a decreased metabolic rate and systemic effects on multiple body systems.
Effects on Voice:
Swelling of the true vocal folds due to prolonged low thyroid hormone levels. This occurs from the accumulation of mucopolysaccharides (e.g., hyaluronic acid) in the extracellular matrix of the vocal folds, increasing their mass and stiffness.
Symptoms include vocal fatigue, mild dysphonia, rough voice quality (due to irregular vocal fold vibration caused by increased mass and edema), and changes in frequency (often lower pitch) and intensity (reduced loudness).
Voice changes can be insidious, developing slowly over months.
Risk Factors:
Low dietary iodine levels.
Thyroid gland damage (e.g., thyroidectomy due to cancer or benign nodules).
Radiation exposure for head and neck cancers.
Autoimmune conditions like Hashimoto's thyroiditis are a common cause.
Identification: Hypothyroidism can often be overlooked as a cause of dysphonia. Diagnosis involves blood tests measuring TSH (Thyroid-Stimulating Hormone), free T3, and free T4 levels.
Treatment:
Pharmacologic treatment using Synthroid (levothyroxine) to supplement thyroid hormone, aiming to normalize TSH levels in the bloodstream.
Voice therapy focusing on vocal hygiene, resonance improvement, and hydration, which can help mitigate symptoms as medication takes effect.
2. Hyperthyroidism
Definition: A condition with elevated thyroid hormone levels, leading to various ailments such as unexplained weight loss, anxiety, tremors, heat intolerance, and cardiac irregularities.
Voice Quality Changes:
Symptoms often include breathy or tremulous voice quality along with reduced loudness.
The increased metabolic rate can alter muscle tension and breath support, contributing to vocal instability and fatigue.
Mild dysphonia is typically reported, where individuals might not identify the specific cause of their voice changes.
Causes:
Hashimoto's thyroiditis (can initially present with fluctuating thyroid hormones that may include hyperthyroid phases, though more commonly hypothyroid), Graves' disease (an autoimmune disorder causing overproduction of thyroid hormones), and idiopathic cases with unknown causes.
Management:
Similar treatment approaches as hypothyroidism in principle, including pharmacologic regulation (e.g., anti-thyroid medications like methimazole, beta-blockers for symptom control) and voice therapy to address specific vocal symptoms.
Miscellaneous Voice Disorders
3. Dysphonia Related to Rheumatoid Arthritis
Overview: A type of autoimmune arthritis that impairs joint movement and can affect the voice, primarily by affecting the cricoarytenoid joints of the larynx (the only true synovial joints in the larynx).
Characteristics of Voice Change:
Potential development of "bamboo nodules," which are submucosal swellings resembling typical vocal fold nodules but must be bilateral and are histologically characterized as inflammatory pseudotumors.
Restricted movement of the arytenoid cartilages can lead to incomplete glottic closure, resulting in a breathy or hoarse voice.
Symptoms and Best Practices:
Risk factors include joint impairment similar to osteoarthritis but often at a younger age and with systemic inflammatory markers.
Patients may experience laryngeal pain, dysphagia, and inspiratory stridor if joint movement is severely restricted.
Treatment typically consists of pharmacologic therapy for rheumatoid arthritis (e.g., DMARDs, biologics) and voice therapy to improve vocal quality and resonance, as well as to manage any compensatory muscle tension.
4. Allergic Reactions and Voice Disorders
Cause of Dysphonia: Seasonal or environmental allergies causing inflammation in the mucous membranes of the throat, nasopharynx, and larynx.
Physiological Response:
Release of histamine and other inflammatory mediators leads to vasodilation and increased vascular permeability, contributing to the inflammation, characterized by upper respiratory symptoms, red watery eyes, sneezing, nasal congestion, and throat irritation.
Chronic inflammation can lead to structural changes over time.
Voice Changes:
Possible vocal edema, increased laryngeal sensitivity, urge to cough, or postnasal drip draining into the larynx.
Resulting voice quality may be wet, gurgly, raspy, or rattly due to secretions and irritation. Acute reactions can cause sudden, significant dysphonia, while chronic exposure leads to persistent subtle changes.
Risk Factors:
Family history and exposure to common allergens like pollen, dust, animal hair, mold, and smoke.
Management:
Combination of medical therapies, including antihistamines (e.g., Zyrtec, fexofenadine) and nasal sprays (e.g., corticosteroids for inflammation, saline rinses), alongside environmental controls (e.g., air purifiers) and allergy assessments (e.g., skin prick tests, RAST tests).
Neurologic Disorders Affecting the Voice
5. Vocal Fold Paralysis
Definition: A condition arising from unilateral right or left recurrent laryngeal nerve paralysis affecting the movement of vocal folds. This nerve is responsible for the abduction and adduction of the vocal folds.
Voice Characteristics:
One vocal fold remains immobile, possibly leading to different vocal fold positions (e.g., midline, paramedian, or lateral).
Voice quality can range from normal to breathy or weak, depending on the position of the paralyzed fold and compensatory abilities of the functioning fold to achieve glottic closure.
Risk Factors:
Surgical interventions near the recurrent laryngeal nerve (e.g., thyroidectomy, cervical spine surgeries, carotid endarterectomy).
Viral infections (e.g., post-viral neuropathy), neuropathy (from diabetes or chemotherapy), or lung cancer compressing the left recurrent laryngeal nerve due to its longer course through the chest (inferior to the aortic arch) before ascending to the larynx.
Diagnosis and Treatment:
Voice therapy is employed to improve glottic closure, particularly in cases where the vocal fold can approximate midline or where compensatory strategies can be developed by the healthy vocal fold.
Surgical interventions may include vocal fold injections (e.g., using hyaluronic acid, calcium hydroxylapatite, or fat) to bulk the paralyzed side and move it closer to the midline, or medialization procedures (e.g., thyroplasty) to permanently reposition the vocal fold.
Important Clinical Note:
Left-sided vocal fold paralysis can often be an early symptom of lung cancer, necessitating thorough evaluation via CT scans of neck and chest to rule out tumors, especially in patients with a smoking history or other risk factors.
6. Superior Laryngeal Nerve Paralysis
Definition: Characterized by absent or abnormal function of the external branch of the superior laryngeal nerve, which innervates the cricothyroid muscle to regulate pitch by elongating and tensing the vocal folds.
Characteristics:
No direct impact on vocal fold abduction or adduction due to the preserved role of the recurrent laryngeal nerve.
Difficulty with pitch changes, particularly in reaching higher pitches, and subtle visible changes can be observed on stroboscopy, such as asymmetry in mucosal wave excursion, ipsilateral vocal fold bowing, and laryngeal obliquity (tilt).
Patients may report vocal fatigue or a monotonous voice.
Risk Factors:
As with recurrent laryngeal nerve paralysis, similar risk factors apply, including surgical trauma (e.g., during thyroid or carotid surgery), viral infections, and trauma to the neck. Excludes lung cancer due to the different, higher course of the superior laryngeal nerve.
Management:
Therapy often includes working on pitch variability and resonance improvement through exercises that focus on gliding techniques, increasing vocal range, and improving vocal fold adduction during phonation.
7. Bilateral Recurrent Laryngeal Nerve Paralysis
Definition: Both vocal folds are paralyzed, which may significantly affect breathing and voice quality depending on the position of the vocal folds.
Symptoms:
Stridor may be present, indicating severe airway obstruction during inhalation, particularly if the folds are juxtaposed or in a paramedian position. Stridor is a high-pitched, harsh inspiratory sound caused by turbulent airflow through a narrowed airway.
Voice quality can be relatively normal if the vocal folds are in a paramedian position (allowing some glottic closure), but significant breathing difficulties often take precedence.
Surgical Interventions:
Options include procedures to widen the glottis, such as arytenoidectomy (removal of an arytenoid cartilage), posterior cordectomy (removal of a portion of the vocal fold posteriorly), or tracheostomies if severe breathing difficulties arise and cannot be managed by other means.
Risks:
Similar causes apply (surgical trauma, infection, and cancer affecting both nerves), adding potential brainstem compression or tumors impacting lower cranial nerves and their nuclei.
Treatment Options:
Medical or surgical options, including voice therapy to optimize voice quality; however, breathing concerns may take precedence in management, often requiring immediate intervention to secure the airway.
Conclusion
Discussion and examples of practical clinical applications will continue in subsequent videos, providing further insight into voice pathology and relevant diagnostic/therapeutic strategies.