Voice is a critical medium of human communication and social interaction; therefore, partial or total loss of voice may have profound implications for quality of life and safety. Problems with the voice can also lead to severe functional and occupational impairment for professionals who rely heavily on vocalization, such as singers, teachers, lawyers, actors, media personalities, and myriad others. Most people, in fact, would be affected significantly by a major impairment in their speech.
The human voice is produced by the passage of exhaled air from the lungs over the vibrating vocal folds; this requires synchronization of diaphragmatic and laryngeal function as well as the shaping of the sound by the tongue, cheeks, and lips. In order to preserve optimal function, it is best to avoid activities that can strain the vocal folds, such as prolonged or excessively loud screaming or shouting. Organic abnormalities of the anatomy, such as nodules, scars, cartilage subluxations, and nerve injuries, are likely to cause voice anomalies. A functional voice disorder should be suspected when vocal quality is compromised without any identifiable anatomical or neurological factors.
Voice disorders can be classified as follows:
Structural organic voice disorders result from physical changes in the laryngeal anatomy, such as edema, vocal nodules, and presbylarynx.
Neurogenic organic voice disorders include vocal tremors, spasmodic dysphonia, paralysis of the vocal folds, etc. These problems relate to abnormalities of central or peripheral nervous system innervation to the larynx.
Functional voice disorders (FVD) are caused by insufficient or improper use of the larynx and diaphragm without any identifiable physical structural abnormality or neurological dysfunction. These disorders often have a noticeable adverse impact on social and occupational function. Although there is a vast amount of literature relating to the topic, there is no consensus regarding foundational concepts or methodology of evaluation of voice disorders, as very few authors have rigorously investigated the most effective vocal assessment or video laryngoscopic examination techniques required to produce a consistent and definitive diagnosis of FVD. The most common FVDs are vocal fatigue, muscle tension dysphonia or aphonia, diplophonia, and ventricular phonation. Vocal fatigue is caused by overuse of the voice and resultant tiring of the laryngeal musculature. Muscle tension dysphonia or aphonia is caused by hypertonicity of the laryngeal musculature, which in turn limits the vocal folds' ability to abduct and adduct with coordination and rapidity. Diplophonia is the phenomenon in which two separate fundamental frequencies are being produced during phonation, which may result from waves of different phases passing through the vocal fold mucosal surface or from different oscillatory frequencies occurring in the left and right vocal folds. Lastly, ventricular phonation occurs when the false vocal folds, also known as the ventricular folds, become the primary vibratory surfaces of the larynx due to stiffness of the true vocal folds or maladaptive voicing habits. All of these phenomena tend to present with hoarseness.
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