[2] For voice to be classified as "dysphonic", abnormalities must be present in one or more vocal parameters: pitch, loudness, quality, or variability.
[7] Perceptually, dysphonia can be characterised by hoarse, breathy, harsh, or rough vocal qualities, but some kind of phonation remains.
[7] Dysphonia can be categorized into two broad main types: organic and functional, and classification is based on the underlying pathology.
While the causes of dysphonia can be divided into five basic categories, all of them result in an interruption of the ability of the vocal folds to vibrate normally during exhalation, which affects the voice.
The assessment and diagnosis of dysphonia is done by a multidisciplinary team, and involves the use of a variety of subjective and objective measures, which look at both the quality of the voice as well as the physical state of the larynx.
[9] The distinction between these broad classes stems from their cause, whereby organic dysphonia results from some sort of physiological change in one of the subsystems of speech (for voice, usually respiration, laryngeal anatomy, and/or other parts of the vocal tract are affected).
[14][15][16][17] (Note that this list is not exhaustive): It has been suggested that certain occupational groups may be at increased risk of developing dysphonia[5][6] due to the excessive or intense vocal demands of their work.
[19] Research on this topic has primarily focused on teachers and singers, although some studies have examined other groups of heavy voice users (e.g. actors, cheerleaders, aerobic instructors, etc.).
[22] However, the exact prevalence rates for occupational voice users are unclear, as individual studies have varied widely in the methodologies used to obtain data (e.g. employing different operational definitions for "singer").
[19][21] Located in the anterior portion of the neck is the larynx (also known as the voice box), a structure made up of several supporting cartilages and ligaments, which houses the vocal folds.
[23] In normal voice production, exhaled air moves out of the lungs and passes upward through the vocal tract.
[23] At the level of the larynx, the exhaled air causes the vocal folds to move toward the midline of the tract (a process called adduction).
Furthermore, a voice can be classified as dysphonic when it poses problems in the functional or occupational needs of the individual or is inappropriate for their age or sex.
[7] Auditory-perceptual measures are the most commonly used tool by clinicians to evaluate the voice quality due to its quick and non-invasive nature.
[17] The GRBAS (Grade, Roughness, Breathiness, Asthenia, Strain) and the CAPE-V (Consensus Auditory Perceptual Evaluation—Voice) are two formal voice rating scales commonly used for this purpose.
Signal processing algorithms are applied to voice recordings made during sustained phonation or during spontaneous speech.
[29] The acoustic parameters which can then be examined include fundamental frequency, signal amplitude, jitter, shimmer, and noise-to-harmonic ratios.
The normal aerodynamic parameters of voice vary considerably among individuals, which leads to a large overlapping range of values between dysphonic and non-dysphonic patients.
Direct prevention describes efforts to reduce conditions that may serve to increase vocal strain (such as patient education, relaxation strategies, etc.
), while indirect prevention strategies refer to changes in the underlying physiological mechanism for voice production (e.g., adjustments to the manner in which vocal fold adduction occurs, respiratory training, shifting postural habits, etc.).
The professional has to keep in mind there is not one universal treatment, but rather the clinical approach must find what the optimal effective course of action for that particular patient is.
[34] Laryngologists also recommend this type of treatment to patients who have an organic voice disorder - such as vocal fold nodules, cysts or polyps as well as to treat functional dysphonia.
[9] Techniques work to either modify vocal fold contact, manage breathing patterns, and/or change the tension at level of the larynx.
An effective treatment for spasmodic dysphonia (hoarseness resulting from periodic breaks in phonation due to hyperadduction of the vocal folds) is botulinum toxin injection.
[20] Dysphonia is more common in adult females than males,[20][42] possibly due to sex-related anatomical differences of the vocal mechanism.
[20] Among the elderly, dysphonia is associated with both naturally occurring anatomical and physiological changes as well as higher rates of pathological conditions.