Nerves fulfilling motor and sensory functions in human body are the Cranial Nerves with a double structure, one on the right and one on the left, that exit the central nervous system in the brain and distribute throughout the body. They consist of 12 pairs in total and each has a different task.
After exiting the skull, the tenth of these pairs, the Nervus Vagus (10th Cranial Nerve Pair) distributes to the mouth, ear, larynx, heart, lungs, stomach, and intestines and enables these systems to fulfill their functions. It provides sense function to the larynx and the motor functions to the vocal cords independently of other nerve pairs.
The failure of one or both of the nerve pairs which make the systems in the body work to do transmission or do limited transmission is called as paralysis or stroke.
The vocal cords have a function moving laterally, opening mutually while breathing and closing while talking. The inability or restricted movement of the vocal cords due to damage or deformation of the Nervus Vagus, which controls the movements of the vocal cords in the larynx, is called as Vocal Cord Paralysis.
There are different types of vocal cord paralysis depending on the area in which they occur and affect:
Unilateral Vocal Cord Paralysis: A single vocal cord is affected. Before one of the vocal cords is completely closed, it remains in a half-open position and loses its ability to move. Synchronization with the completely closed vocal cord is lost. It causes problems in breathing due to shortness of breath or exhaustion, and in speaking due to low voice.
Bilateral Vocal Cord Paralysis: Both vocal cords are affected. Before the vocal cords are completely closed, they remain in a semi-open position and lose their ability to move. The voice utters well if the clearance is little, but since there is no opening, breathing becomes difficult and immediate intervention is required. A hole is opened in the trachea (tracheostomy) from the outer part of the neck to ensure respiration and prevent foreign substances from entering the trachea while eating.
Vocal Cord Paralysis Causing Sensory Loss in Larynx: It is the loss of sense in the larynx due to the function loss of the Nervus Vagus, which alone provides sense in the larynx. Tension of the vocal cord is affected. The voice is hoarse while speaking, food may get into the gorge, the voice changes while singing, a feeling of pressure occurs in the throat, and throat cleansing is needed.
The common symptoms of vocal cord paralysis are hoarse, cracked or breathy voice, shortness of breath and exhaustion, air mixture with voice during speech, vocal fatigue and difficulty in swallowing saliva, food escape into the trachea while eating, choking hazard with a cough attack and return of beverages from the nose.
The position of the vocal cords during vocal cord paralysis causes the symptoms of paralysis to differ. Voice hoarseness or difficulty in breathing appears as the most visible symptom, depending on the clearance of the vocal cords. In general, if paralysis occurs when the vocal cords are in the middle, namely, nearby their closed position, breathing problems prevail; however, if paralysis occurs in the sides, namely, nearby their open position, hoarseness problems prevail. Although it is rare, if paralysis occurs when both vocal cords are completely closed or slightly opened, breathing is blocked and immediate treatment is required.
The first examination should be performed by an ear, nose and throat specialist to diagnose vocal cord paralysis. With this examination, it is determined whether the problem is paralysis in the vocal cords, whether the paralysis is in one vocal cord or both cords, the level of paralysis, and whether there is any other factor causing it. In the first examination, the structure and functionality of the vocal cords are examined with endoscopic devices named as laryngoscopy or stroboscopy and sound analysis programs, in which vocal cords and their surroundings are monitored. The functionality of the muscles in the larynx that move the vocal cords is examined by entering into the muscle with a needle (electrode) and using an electromyography (EMG) that measures the electrical potential of the muscle. If the patient has problems in swallowing and eating, the patient is given contrast agents such as barium and nonionic iodine, and the fluoroscopy method is used to examine the course of this agent in the body, particularly between the mouth and gorge.
If necessary, the doctor may ask x-ray, ultrasonography, computed tomography (CT), and magnetic resonance (MR) examinations simultaneously.
As a result of the diagnosis performed in the light of the complaints and symptoms, it is decided whether treatment method and surgical intervention are needed.
Although there is no precise cause of some vocal cord paralyses, it is usually caused by a trauma or operational damages to the Nervus Vagus nerve during neck, throat, thyroid, heart and lung surgeries, or due to infection and neurological problems that occur after these interventions. In addition to these causes, infections not caused by surgery, vestibular neuritis, goiter surgery, and neck region traumas, tumors in the larynx and the surrounding organs, reflux, and head trauma that damage the nerve system may also cause vocal cord paralysis.
For patients diagnosed with vocal cord paralysis, vocal therapy is primarily applied to restore functionality of the vocal cord muscles and the necessary medication is provided. If no improvement is observed after voice therapy and medication, a surgical intervention is administered. The surgical method to be applied is determined based on the type of the nerve affected, the position of the vocal cords at the time of paralysis, and whether the paralysis is unilateral or bilateral.
Breath deprivation requires immediate treatment in surgical intervention. This occurs when both vocal cords remain immobile in a closed or slightly open position as a result of the loss of sense of larynx due to the loss of function in the Nervus Vagus. In such a case, a hole is made between the 2nd and 3rd rings of the trachea (tracheostomy) and an artificial tubular channel (cannula) is placed in the outer part of the neck to ensure respiration and prevent foreign substances from entering the trachea while eating and drinking. Afterwards, Endoscopic CO2 Laser Cordotomy (Kashima Procedure) or Arytenoidectomy Surgery used for the treatment of bilateral paralysis is applied.
In the endoscopic CO2 laser cordotomy method, the region is entered from the mouth area with an endoscopic laser apparatus under general anesthesia and enlarged by incising the back of one of the vocal cords. Thus, a space is formed for breathing.
In arytenoidectomy surgery, the arytenoid cartilage in the larynx is removed.
Surgical intervention is possible by means of the methods such as Tissue Transplantation or Nerve Transplantation, Type 1 Thyroplasty (Isshiki Thyroplasty Type I - Medialization) and Filling (Injection) Treatment in unilateral vocal cord paralysis.
In Tissue Transplantation method, the paralyzed vocal cord is pushed into the middle area and the tissue taken from another area of the patient is placed from the outside into the inside of voice box. The non-paralyzed vocal cord is better vibrated than the damaged vocal cord. In the Nerve Replacement method, the damaged nerve is replaced with a healthy nerve from the neck area. Full recovery lasts 6-9 months.
In the Thyroplasty method, a permanent piece (implant) is placed on the paralyzed vocal cord or fold under sedation or local anesthesia, so the two vocal cords contact each other and the opening between them is filled. A second surgery is required in general to fix the position of the implant. The patient is discharged the following day after the operation and recovery period takes about a week.
In Filling Treatment method, the paralyzed vocal cord is reached with the incision from the mouth or neck, and filler (fat or collagen) is injected into the cord to increase the width of the vocal cord. Thus, the paralyzed vocal cord is approached to the middle area. The patient is discharged on the same day and recovers within 2-3 days.
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