The SLN  is responsible for sensory input to the vocal folds. Due to its variable nature, the progression of vocal fold paresis may fluctuate, so it may be characterized differently from one evaluation to the next. Fluctuating vocal fold paresis has been observed in neurodegenerative disorders like Guillain–Barré syndrome or myasthenia gravis.The posterior cricoarytenoid (PCA) is a muscle of the larynx that is responsible for pulling the vocal folds apart from one another. Vocal fold paresis describes the weakness of the PCA and an impairment to its functioning. Unilateral vocal fold paresis is the term used when there is damage to the RLN on one side of the body. In unilateral vocal fold paresis, there is a lack of nerve supply to one side of the vocal folds PCA muscle. This lack of nerve supply renders the arytenoid cartilage immobile. The RLN may be damaged during surgical procedures. The right RLN in particular, has a greater chance of being damaged during surgery due to its position in the neck. When both of the vocal folds PCA muscles lack a nerve supply, the term bilateral vocal fold paresis is used. With bilateral vocal fold paresis, a persons airway may become blocked as the muscles are unable to pull the vocal folds apart fully. Treatment
The treatment of vocal fold paralysis varies depending on its cause and main symptoms. For example, if laryngeal nerve paralysis is caused by a tumor, suitable therapy should be initiated.
Vocal cord paresis, also known as recurrent laryngeal nerve paralysis or vocal fold paralysis, is an injury to one or both recurrent laryngeal nerves (RLNs), which control all intrinsic muscles of the larynx except for the cricothyroid muscle. The RLN is important for speaking, breathing and swallowing.The primary larynx-related functions of the mainly efferent nerve fiber RLN, include the transmission of nerve signals to the muscles responsible for regulation of the vocal folds position and tension to enable vocalization, as well as the transmission of sensory nerve signals from the mucous membrane of the larynx to the brain. A unilateral injury of the nerve typically results in hoarseness caused by a reduced mobility of one of the vocal folds. It may also cause minor shortages of breath as well as aspiration problems especially concerning liquids. A bilateral injury causes the vocal folds to impair the air flow resulting in breathing problems, stridor and snoring sounds, and fast physical exhaustion. This strongly depends on the median or paramedian position of the paralyzed vocal folds. Hoarseness rarely occurs in bilaterally paralyzed vocal folds. Signs and symptoms
Typically, patients with vocal fold paresis or paralysis are able to identify the onset of their symptoms. The most commonly reported symptom patients with either vocal fold paresis or paralysis make is having a rough voice quality. It is important to note that the symptoms of vocal fold paresis are not specific to the condition and tend to be common symptoms of other voice disorders as well.