Vocal cord polyps are benign, non-cancerous growths that develop on the vocal folds (vocal cords) inside the larynx, or voice box. These lesions are fluid-filled, blister-like swellings that interfere with the smooth vibration of the vocal folds necessary for clear speech. When a polyp forms, it disrupts the wave-like motion of the vocal fold mucosa, resulting in symptoms like hoarseness, a breathy voice, or vocal fatigue. Understanding the causes involves looking beyond simple voice strain to the specific mechanisms of injury and underlying conditions.
The Immediate Cause: Acute Vocal Trauma
The formation of a vocal cord polyp is often triggered by a single, high-impact event of vocal misuse, medically known as phonotrauma. This involves acute, intense physical stress on the delicate vocal fold tissues. Forceful actions, such as screaming, yelling during an argument, or a prolonged, violent coughing fit, create immense shear forces.
This intense force can cause a localized injury to the small blood vessels beneath the mucosal surface, leading to a micro-hemorrhage, or bruise. The resulting lesion is typically a soft, fluid-filled growth that is highly vascularized. Polyps usually form on only one vocal fold, often at the midpoint, which is the site of the greatest impact stress during voicing.
Systemic and Environmental Contributing Factors
While acute trauma may be the direct trigger, systemic and environmental factors often create a vulnerable tissue environment, lowering the threshold for injury. Chronic exposure to irritants like tobacco smoke causes inflammation and drying of the vocal fold mucosa. Smoking accelerates degenerative changes, making the tissue less resilient to the physical stresses of voicing. A specific type of polyp, Reinke’s edema, is almost exclusively associated with heavy smoking.
Another contributing factor is Laryngopharyngeal Reflux (LPR), the backflow of stomach acid and enzymes like pepsin into the throat and voice box. This chemical irritation causes the vocal fold tissue to become chronically inflamed and thickened, making it fragile and highly susceptible to damage. The presence of pepsin in the laryngeal tissue is particularly associated with polyp formation.
Dehydration also plays a significant role by reducing the protective mucus layer that covers the vocal folds. Factors promoting dehydration, such as excessive consumption of caffeine or alcohol, or the use of drying medications like antihistamines, leave the vocal folds less lubricated and more prone to friction injury. Additionally, occupations requiring chronic, high-demand voice use (e.g., teaching, singing, or sales) place the tissue under constant strain, increasing the likelihood of an acute injury developing into a polyp.
Distinguishing Polyps from Vocal Nodules
Vocal polyps are frequently confused with vocal nodules, but they have distinct causes and appearances. Polyps are typically unilateral, appearing on only one vocal fold, and result from a single, acute hemorrhagic event. This acute trauma causes a rupture in blood vessels and fluid accumulation in the deeper layer of the vocal fold.
In contrast, vocal nodules, sometimes called “singer’s nodes,” result from chronic, repetitive friction and collision of the vocal folds over time. Nodules are bilateral, forming mirror-image calluses at the point of maximum impact on both vocal folds. They are denser and more callous-like than the fluid-filled polyp. While both lesions relate to voice misuse, a polyp is the result of a sudden, intense blow, often superimposed on tissue made vulnerable by underlying conditions like smoking or reflux.