Also known as vocal folds, the vocal cords are two bands of muscle tissue that stretch across the interior cavity of the voice box. They produce sound by vibrating and adjusting the flow of exhaled air as it is passed through them from the lungs.
Vocal cord lesions are benign growths that occur along the edges or just below the surface membrane of one or both vocal cords. These lesions are categorized into three main groups, namely nodules, polyps and cysts. All these lesions may arise as a result of:
- Voice abuse
- Thyroid deficiency which leads to thickening of the vocal cords
- Chronic sinusitis with post-nasal drip which irritates the vocal cords and also leads to repeated forceful clearing of the throat
- Irradiation of the neck region
Nodules are callus-like masses that tend to occur symmetrically on both vocal cords, usually at the midpoint and in pairs, with the two nodules located opposite each other. Also referred to as ‘singer’s nodules’, these masses are caused by overuse or misuse of the voice such as occurs with repetitive yelling, shouting, screaming or speaking in a strained voice. If the person stops using the voice in such a way, these lesions often disappear.
The underlying reason for the development of the lesion is that the misuse of the voice in this way causes the vocal cords to slap together with increased force. It is at the point where they meet together that the lesions often form.
In the initial phase of the disease, the vocal cord tissue changes appearance, from being whitish to reddish in color. It then swells and thickens. When the mechanism of voice production continues to be strained, a nodule eventually forms, which can then harden, if left untreated.
More rarely, nodules may form as a result of vocal cord paralysis, where the nerves that regulate vocal cord movement fail to function. Other causes include allergy problems, smoke inhalation, acid reflux and hypothyroidism.
Vocal cord polyps, which are softer and more gelatinous than nodules, are more likely to occur along one vocal cord only.
A reactive nodule, however, may develop at the point where a polyp makes contact with the opposing cord.
Polyps are also more likely to be supplied with blood vessels and therefore to be reddish in color.
Singing or shouting causes fluid to build up within the traumatised part of the vocal cord.
This initially forms a blister, which progresses to become a tissue pocket of fluid. As with nodules, vocal cord polyps may be caused by misuse or overuse of the voice.
In contrast to nodules, however, they may also occur as a result of a single incident of gross misuse of the voice, such as prolonged and loud yelling during a concert.
One type of polyp formation, referred to as polypoid corditis, is mainly associated with smoking.
A vocal cyst is a collection of fluid or semi-solid material contained within a membrane, and which forms inside a vocal cord. Vocal cysts are spherical and tend to arise from deeper inside the vocal cord than nodules or polyps.
A solid cyst is referred to as a keratin cyst, while a cyst filled with fluid is called a fluid-retention cyst. These cysts may lead to hoarseness of the voice.
Vocal cysts usually arise as a result of misuse or overuse of the voice, or vocal cord trauma. When a person is speaking or singing in a normal way, the vocal cords close together more than 100 times a second.
When the voice is overused or misused, the prolonged repetition of this kind of impact begins to cause injury and inflammation, leading to swelling of the cords.
If the person continues to use the voice in a way as to cause strain, the fluid trapped within the inflamed vocal cord tissue becomes walled in, creating a cyst within the cord.
Other common causes of injury to the vocal cords include:
- throat clearing
- acid reflux
- postnasal drip
Since people tend to ignore the fact that their voice has become hoarse, they do not rest their voices. This it is often difficult for an injured cord to heal, and continued use of the swollen cords often leads to the formation of a cyst.
Vocal cord lesions alter the contour of the vocal cords and impair the ability of the vocal cords to close properly on vibration when a person is speaking or singing. During certain phases of vibration, there may be a gap between the vocal cords that would not usually be present. This leads to a leaking vocal valve.
This type of leakage causes patients with these lesions to often experience vocal fatigue. Singers, for example, may find that they can no longer reach high notes that they could previously, particularly if they are trying to sing gently or softly.
The lesions also commonly cause a raspy voice because they can cause the cords to become stiffer and less compliant, as well as impeding complete closure of the vocal cords. Stiff vocal cords also cannot vibrate properly. This can give rise to a strained and gravelly voice.
This premalignant lesion is characterized by thickened whitish or grayish patches on the vocal cords. These show cellular abnormalities on microscopic examination, and are usually due to exposure to tobacco, alcohol, or other irritant substances.