Anatomy and physiology of the vocal mechanism
To better understand voice disorders, it is important to first understand the anatomy and physiology of the vocal mechanism. Voicing occurs in the larynx, at the level of the vocal folds. There is both a motoric/neurological and aerodynamic component to normal vocal function. Laryngeal muscles actively work to bring vocal folds together (adduction) and pull them apart (abduction). When the vocal folds come together, the airflow below from the lungs set the vocal folds into vibration at an exceptional rate per second, creating our voice. Besides for speech, vocal folds serve additional purposes, including maintaining an open airway during breathing and protecting the airway during swallowing. Although the vocal folds can serve different functions, difficulty in one function can indicate difficulty in another.
Causes for a voice disorder
Voice disorders can occur for a variety of reasons with the origins being neurological, organic, traumatic, or behavioral. Neurological impairment can be the result of progressive, degenerative diseases (i.e. Parkinson’s disease, Huntington’s disease, ALS) or through sudden onset damage (i.e. brain injury or damage to the peripheral nervous system). Nerve damage could impair both the motor function of the vocal folds (responsible for voicing) and the sensory function (responsible for protecting the airway).
The cause of voice disorders may also be organic in nature, such that they can be secondary to different laryngeal cancers, a congenital anomaly, or gastrointestinal reflux (GERD). Trauma, which could be from endotracheal intubation or inhalation of chemical gases or smoke, could also significantly injure laryngeal structures.
Possibly the most well-known cause for a voice disorder is a result of phonotrauma. This term is often interchanged with the terms vocal misuse or abuse, which refer to engaging in poor vocal behaviors such as persistent yelling, screaming or extensive voice use without voice rest. However, it should be noted that vocal misuse does not necessarily imply behavioral trauma to vocal folds. It could be considered vocal misuse if an individual continues to present with a high-pitched voice past the age of puberty (i.e. puberphonia).
Identifying and evaluating a voice disorder
Signs of a voice disorder can be identified perceptually but also quantified objectively through instrumentation. Perceptual signs are characteristics of the voice that are directly perceived by a listener/observer. Abnormalities may be observed in one’s pitch, loudness, and vocal quality. An indication of a problem could be when an individual exhibits a lack of variation, excessive variation, or a reduction in pitch range or loudness. Voice quality can be described as rough, breathy, tensed/strained, and/or unsteady (tremor).
These perceptual characteristics can also be measured objectively through instrumentation. For example, obtaining acoustic measures for fundamental frequency (the rate at which vocal folds vibrate per second) is directly related to a person’s pitch. A laryngoscopy can also be used to view anatomical structures or physiological signs of abnormality. A stroboscopy specifically examines vocal fold movement to identify a wide range of irregularities.
Voice disorders in pediatric, adolescent, and geriatric populations
Voice disorders in the pediatric population may be congenital or acquired. However, congenital anomalies may not be identified until later in life as laryngeal structures experience maturation and change. Disorders present at birth may include laryngomalacia, laryngeal paralysis, or a laryngeal web. In general, primary signs of a congenital disorder include difficulty voicing, difficulty breathing, and possibly feeding difficulty. The most common condition in the pediatric population is vocal nodules. These are small calluses that form on the vocal folds as a result of vocally abusive behaviors. Most often, vocal nodules can resolve through behavioral therapy. Vocal fold paralysis can also occur in children after experiencing trauma, such as from cardiac surgery, which may damage the recurrent laryngeal nerve.
As children age into adolescence and young adulthood, some unique problems may develop. Some problems may be related to using the appropriate pitch, whether it is related to puberphonia or transitioning the transsexual voice. Another unique condition is vocal fold dysfunction (VCD), which refers to the vocal folds closing during inhalation, making it difficult to breath. Since this often occurs during periods of sustained physical activity, it is often mistaken for asthma. Vocal rehabilitation then involves teaching breathing strategies for the athlete to utilize prior to and during activity. VCD can be caused by chemical irritation such as from perfumes or soaps. However, it can be treated through vocal rehabilitation.
Physical changes to the larynx, such as laryngeal atrophy, that occur in geriatric populations (65+) can lead to perceptual voice characteristics that include breathiness, roughness, low pitch, and imprecise articulation. Neurological disorders mentioned above are also causes for voice disorders in the geriatric population.
When it comes to treating a voice disorder, it is very important that an individual is evaluated by a team of professionals. A voice team often includes speech pathologists, otolaryngologists, and nurses, although other disciplines may be involved. Evaluation involves gathering an extensive patient history, a perceptual and acoustic analysis, and possibly imaging through laryngoscopy or stroboscopy. The patient’s diagnosis will help to determine the best course of action for treatment. A patient may be treated through vocal rehabilitation, surgical management, and/or medical management. Vocal rehabilitation assumes significant responsibility from the patient, as a good portion of therapy involves changing lifestyle habits and teaching healthy vocal behaviors. A patient’s progress in therapy often depends on his or her willingness to participate. Vocal rehabilitation is the most common treatment for vocal nodules but is also the method of treatment for less common disorders, such as vocal fold dysfunction and transitioning a transsexual voice. Voice therapy may be recommended in conjunction with invasive measures, such as surgery. The goal of surgical management is to conserve, reconstruct, or improve laryngeal functions. Surgeries often involve removal of pathological tissue (abnormal growths), correction in position or shape of the vocal folds, vocal fold injections, or repair of a laryngeal deformity. For instances in which voice disorders are the result of or exacerbated by infection, allergies, or laryngopharyngeal reflux, medicine may be the best course of treatment. Overall, it is very important that an individual is evaluated by a team of specialists with expertise in voice disorders to develop the most effective plan of care.
Written by Marissa Habeshy, M.S., CCC-SLP
Resource: Casper, J. K., & Leonard, R. (2006). Understanding voice problems: A physiological perspective for diagnosis and treatment. Lippincott Williams & Wilkins.