The vocal folds are the parallel folds of tissue that play a major role in the formation of sounds and the voice. They are part of the larynx in the throat. From the outside, they are protected and shielded from externally palpable cricoid cartilage. They are covered with mucous membrane and consist mainly of the voice muscle, the "vocalis muscle".
The vocal folds in the larynx are attached to various cartilages, which can be moved and adjusted by other laryngeal muscles. These muscles cause the glottis to close or to open like a cleft, a triangle or a rhombus. This results in different tones, which provide the basis for our articulation and language. The sound production through the vocal folds is called "phonation".
In a so-called paralysis of the vocal folds, especially the laryngeal muscles are paralyzed, which allow opening of the glottis and movement of the vocal folds, or the vocal folds irritated.
This can sometimes lead to serious symptoms, such as long-lasting hoarseness or speech problems.
The cause may be irritation of the vocal folds or damage to the supplying nerve, the so-called recurrent nerve, which supplies the laryngeal musculature.
The underlying cause of vocal cord paralysis is a loss or weakness of the laryngeal muscles. The reasons for muscular failure can be different. A small nerve branch sends its impulses to almost all the laryngeal muscles of its side. Due to its anatomical position, it is often impaired in various diseases of the neck, but especially in medical interventions. Even slight irritation of the nerve, but also a complete transection lead to weakness and the loss of almost all laryngeal muscles.
Tumors can also affect the laryngeal muscles. In particular, laryngeal and thyroid tumors can affect the sensitive nerve and the sensitive structures in the larynx.
Rarely, inflammation, circulatory disorders or viral diseases in the neck area can cause vocal cord paralysis.
Complications after surgery on the thyroid, for example, in a goiter therapy, are the most common cause of vocal cord paralysis. In the case of complete or partial removal of the thyroid, in rare cases, often inexperienced surgeons, the so-called "recurrent nerve" is damaged or severed. Through embryological development, the nerve passes completely through the neck and under the large arterial vessels in the upper chest. Then he pulls behind the thyroid gland back toward the larynx. He lies on both sides closely behind the thyroid gland. This exposed location of the thin nerve makes him very vulnerable to any injury.
Today, attempts are made to minimize the risk of recurrent nerve palsy. For this purpose, intraoperative probes are used, which constantly check the function of the nerve. Immediately after completion of the operation, the larynx is viewed by means of a mirror or a small camera or the patient is asked to speak in order to detect potential damage in good time.
Typical symptom of vocal cord paralysis on one side is hoarseness. Due to the failure of one side of the laryngeal muscles, the phonation in the larynx can no longer run properly and it creates a permanent hoarseness. The vibration and tone formation are disturbed, depending on how pronounced the paralysis of the laryngeal muscles is. Normal speech therefore also requires more air consumption.
If both sides are affected by a vocal cord paralysis, the glottis can not open by itself and there is an acute shortness of breath. The air can no longer escape through the closed vocal folds and thus, in the event of complete failure, the patient must be intensively medically ventilated.
The anatomy of the recurrent nerves is different on both sides. Like the large arterial vessels, which branch off from the aorta in the direction of the neck, the laryngeal nerves on both sides also differ.
On the right side, the fine recurrent nerve branches off the main nerve and snakes around the main artery of the neck and arm at the level of the clavicle. On the left, on the other hand, the nerve pulls much deeper into the chest and winds around the aorta itself just above the heart. Its course is significantly longer than on the right side and thus the nerve is also more susceptible to damage in its long course. As a result, the left side is nearly twice as likely to be affected by vocal cord paralysis as the right side.
Unilateral vocal cord paralysis is significantly more common than bilateral. Hoarseness is the typical consequence of one-sided missing vibrations of the glottis. Although there is no breathlessness, normal speech is consumed more air.
Bilateral vocal cord paralysis is rare. If it occurs, it will lead to serious symptoms and intensive care needs. In the normal relaxed state the glottis is closed. In particular, the muscles that open the glottis wide are affected in vocal cord paralysis. As a result, the larynx does not open, causing shortness of breath, severe hoarseness, and a hissing attempt to breathe.
In case of severe acute respiratory distress, the patient must be assisted if necessary by artificial respiration. If there is no improvement or the prospect of a cure, surgery can help to permanently dilate the glottis. Sometimes it is necessary to continue to ventilate via the artificial access. In particular, infections of the lungs and respiratory tract are a common consequence, as mucus and germs can no longer reliably be coughed up.
An important part of the diagnosis of vocal cord injury is the patient's history and speech. A typical permanent hoarseness is already groundbreaking for the diagnosis. The ENT surgeon can then examine the larynx using either a laryngoscope mirror, which the doctor holds in the patient's throat, or endoscopy of the larynx. In this so-called "laryngoscopy", a camera with light is pushed into the larynx of the patient and the glottis is viewed on a display. Especially in the page comparison to the left with the right paresis of a page fall quickly.
To ensure the diagnosis, an "electromyography", ie a control of the muscle ability by electrical stimulation, take place. If no thyroid surgery has taken place beforehand, the cause of the vocal cord paralysis should be determined. A CT or MRI scan of the neck and chest can show any abnormalities well.
The treatment depends on the extent of the injury. If the nerve has been completely severed, for example as part of a thyroid operation, there is no prospect of improvement through exercises. A surgical procedure can help to align the vocal cord so that the symptoms are as small as possible. In the case of bilateral vocal cord paralysis, surgical intervention can also extend the glottis so that acute respiratory distress does not occur.
If the nerve of the larynx is irritated and limited in function, its function can be restored by exercise. Certain speaking exercises can help to regain movement possibilities.
In case of irritation and partial laryngeal muscle failure, there is a good chance of getting the original functions back. The exercises aim to produce as many different sounds as possible. Like a normal muscle training to build the larynx muscles must be used evenly.
To ensure successful rehabilitation, a speech therapist should be consulted. By constantly practicing different vowels with increased emphasis, much of the ability to speak can often be regained over time.
Electrostimulation procedures are also used today. Targeted stimulation of certain muscles can trigger the contraction. Electrostimulation to strengthen the muscles has the same effect as a conscious tension through phonation exercises.
The possibility of complete healing of vocal cord paralysis depends on the cause of the paralysis. In rare cases, especially in accidents or after operations, the responsible nerve is completely severed or severely damaged, so that a paralysis is not curable.
In many cases, however, the nerve is merely irritated. If there is a tumor that presses on the nerves, this cause must be corrected. If the nerve has a residual function and is not severed, the muscles can often recover in part through subsequent therapy.
Nerve tissue is very sensitive and still difficult to treat today. However, the more severely damaged the nerve, the less likely it is to regain much of the function.