Vocal cord paralysis (VCP) occurs when the nerve impulses to the voice box, or larynx, are interrupted, causing the muscles controlling the vocal cords to become immobile. These two bands of tissue, also known as vocal folds, are responsible for generating sound, protecting the airway, and assisting with breathing. The resulting sound of VCP is a direct consequence of the cords’ inability to move together properly, leading to a range of auditory symptoms that affect speech, breathing, and swallowing.
The Core Characteristics of the Voice Change
The primary acoustic signature of vocal cord paralysis is dysphonia, a term for any abnormality in vocal sound. This condition presents with a combination of breathiness, hoarseness, and a noticeable reduction in volume. These qualities stem from a failure of the paralyzed vocal cord to meet the functioning cord, leaving an open gap, or glottal insufficiency, during speech.
The most prominent feature is often breathiness, resulting from air leaking past the cords without being fully converted into sound. This gives the voice an airy, whispery quality. Because the air escapes so quickly, the speaker is forced to take frequent breaths, significantly shortening the length of sentences they can speak comfortably.
Hoarseness introduces a rough, raspy, or strained element to the voice. This occurs because the vibrating vocal cords do so irregularly, a phenomenon measured by acoustic analysis parameters known as jitter and shimmer. These terms describe the cycle-to-cycle variations in the frequency (jitter) and amplitude (shimmer) of the vocal sound wave, resulting in an acoustically unstable and rough voice.
The voice also suffers from a significant loss of volume, making it difficult for the individual to speak loudly or shout. This weakness results from diminished subglottic pressure; without tight closure, the air pressure needed to produce a strong sound cannot build up beneath the cords. The overall effect is a voice that requires excessive effort to project, leading to vocal fatigue after short periods of speaking.
How the Sound Differs in Unilateral Versus Bilateral Paralysis
The auditory experience of VCP varies depending on whether one cord (unilateral) or both (bilateral) are immobilized. Unilateral paralysis is the more common form, defined by the voice quality itself. With one paralyzed cord, the mobile cord attempts to compensate by moving past the midline to meet its immobile partner.
This compensatory movement is often insufficient, resulting in the characteristic breathy and hoarse voice and a reduced ability to modulate pitch. The voice is weak and lacks projection because of persistent air escape through the glottal gap. The airway generally remains open, meaning breathing sounds are not the primary concern.
In bilateral paralysis, the primary auditory issue shifts from voice quality to severe breathing sounds. When both vocal cords are paralyzed, they often settle close to the midline. Paradoxically, the voice can sound nearly normal because the cords are close enough to vibrate together when air is forced through them, though the voice may be limited in intensity.
This near-closed position severely restricts the passage of air for breathing. The obstruction creates a harsh, high-pitched, or wheezing sound known as stridor, which is most prominent when inhaling. Stridor is an urgent symptom, indicating a dangerously narrow airway, and this noisy breathing becomes the overriding sound of bilateral VCP.
Related Sounds and Non-Vocal Symptoms
VCP impairs the larynx’s protective functions, resulting in distinct non-speech sounds. The inability of the vocal cords to close tightly compromises the airway’s defense mechanisms, often leading to a wet or gurgling voice quality. This “wet” dysphonia occurs when saliva, food, or liquids accumulate above the vocal cords because the larynx cannot fully close during swallowing, leading to aspiration.
Another common auditory symptom is a weak or ineffective cough. A healthy, forceful cough requires the vocal cords to snap shut momentarily to build up high pressure before suddenly releasing the air. When the cords are paralyzed and cannot close tightly, the resulting cough is soft, puffy, and lacks the concussive force needed to clear the throat or lungs.
The frequent, strained sound of throat clearing is also common, as the individual attempts to dislodge accumulated mucus or foreign material that the ineffective cough cannot remove. This repetitive, effortful sound is often a sign of sensory irritation or an attempt to improve the perceived vocal quality. The loss of a gag reflex is a related non-vocal symptom that highlights the compromised protective function of the paralyzed larynx.
Adjusting the Voice Through Treatment
Medical interventions for VCP are designed to improve the voice’s sound by physically closing the glottal gap. Temporary bulk injections involve injecting a filling agent, such as hyaluronic acid or collagen, directly into the paralyzed cord to augment its volume. This procedure pushes the immobile cord closer to the midline, allowing the functioning cord to make better contact.
The resulting sound is immediately less breathy and stronger, as improved closure means less air escapes during phonation. The voice’s volume and durability are enhanced, and the rough, hoarse quality is reduced because the cords can vibrate more regularly. For more permanent results, surgical repositioning, such as medialization laryngoplasty, uses an implant to hold the paralyzed cord in a more medial, or central, position.
Following these physical adjustments, voice therapy plays a crucial role in shaping the final sound quality. A speech-language pathologist works with the patient to retrain the remaining laryngeal muscles to use the newly positioned cord effectively. This therapy aims to maximize the clarity and stability of the voice, teaching the patient to produce a sound that is less effortful and closer to their natural speaking voice.