Spasmodic dysphonia (VoQS ), also known as laryngeal dystonia, is a disorder in which the muscles that generate a person's voice go into periods of spasm. This results in breaks or interruptions in the voice, often every few sentences, which can make a person difficult to understand. The person's voice may also sound strained or they may be nearly unable to speak. Onset is often gradual and the condition is lifelong.
The cause is unknown. Risk factors may include family history. Triggers may include an upper respiratory infection, injury to the larynx, overuse of the voice, and psychological stress. The underlying mechanism is believed to typically involve the central nervous system, specifically the basal ganglia. Diagnosis is typically made following examination by a team of healthcare providers. It is a type of focal dystonia.
While there is no cure, treatment may improve symptoms. Most commonly this involves injecting botulinum toxin into the affected muscles of the larynx. This generally results in improvement for a few months. Other measures include voice therapy, counselling, and amplification devices. If this is not effective, surgery may be considered; evidence to support surgery is limited, but some have recovered following surgery.
The disorder affects an estimated 2 per 100,000 people. Women are more commonly affected. Onset is typically between the ages of 30 and 50. Severity is variable between people. In some, work and social life are affected. Life expectancy is normal.
Signs and symptoms Symptoms of spasmodic dysphonia can come on suddenly or gradually appear over the span of years. They can come and go for hours or even weeks at a time, or remain consistent. Gradual onset can begin with the manifestation of a hoarse voice quality, which may later transform into a voice quality described as strained with breaks in phonation.Colton, R. H., & Casper, J. K. (2006). Understanding voice problems: A physiological perspective for diagnosis and treatment. Baltimore, MD: Lippincott Williams & Wilkins. These phonation breaks have been compared to stuttering in the past, but there is a lack of research in support of spasmodic dysphonia being classified as a fluency disorder. It is commonly reported by people with spasmodic dysphonia that symptoms almost only occur on vocal sounds that require phonation. Symptoms are less likely to occur at rest, while whispering, or on speech sounds that do not require phonation. It is hypothesized that this occurs because of an increase in sporadic, sudden, and prolonged tension found in the muscles around the larynx during phonation. This tension affects the abduction and adduction (opening and closing) of the vocal folds. Consequently, the vocal folds are unable to retain subglottal air pressure (required for phonation) and breaks in phonation can be heard throughout the speech of people with spasmodic dysphonia.
Regarding types of spasmodic dysphonia, the main characteristic of spasmodic dysphonia, breaks in phonation, is found along with other varying symptoms. The voice quality of adductor spasmodic dysphonia can be described as "strained-strangled" from tension in the glottal region. Voice quality for abductor spasmodic dysphonia can be described as breathy from variable widening of the glottal region. Vocal tremor may also be seen in spasmodic dysphonia. A mix and variance of these symptoms are found in mixed spasmodic dysphonia.
Symptoms of spasmodic dysphonia typically appear in middle-aged people, but have also been seen in people in their twenties, with symptoms emerging as young as teenage years.
Cause
Although the exact cause of spasmodic dysphonia is still unknown, epidemiological, genetic, and neurological pathogenic factors have been proposed in recent research.
Risk factors include: Being female Being middle aged Having a family history of neurological diseases (e.g., tremor, dystonia, meningitis, and other neurological diseases) Stressful events Upper respiratory tract infections Sinus and throat illnesses Heavy voice use Cervical dystonia Childhood measles or mumps Pregnancy and parturition It has not been established whether these factors directly affect the development of spasmodic dysphonia, but they could be used to identify at-risk patients.
Researchers have also explored the possibility of a genetic component to SD. Three genes have been identified that may be related to the development of focal or segmental dystonia: TUBB4A, THAP1, and TOR1A genes. However, a recent study that examined the mutation of these three genes in 86 SD patients found that only 2.3% of the patients had novel/rare variants in THAP1, but none in TUBB4A and TOR1A. Evidence of a genetic contribution for dystonia involving the larynx is still weak, and more research is needed in order to establish a causal relationship between SD and specific genes.
SD is a neurological disorder rather than a disorder of the larynx, and as in other forms of dystonia, interventions at the end organ (i.e., larynx) have not offered a definitive cure, only symptomatic relief. The pathophysiology underlying dystonia is becoming better understood as a result of discoveries about genetically based forms of the disorder, and this approach is the most promising avenue to a long-term solution.
SD is classified as a neurological disorder.Dystonias Fact Sheet: National Institute of Neurological Disorders and Stroke (NINDS) However, because the voice can sound normal or near normal at times, some practitioners believe it to be psychogenic, originating in the affected person's mind rather than from a physical cause. This was especially true in the 19th and 20th centuries. No medical organizations or groups take this position. A comparison of SD patients compared with vocal fold paralysis (VFP) patients found that 41.7% of the SD patients met the DSM-IV criteria for psychiatric comorbidity compared with 19.5% of the VFP group. However, another study found the opposite, with SD patients having significantly less psychiatric comorbidity compared to VFP patients: "The prevalence of major psychiatric cases varied considerably among the groups, from a low of seven percent (1/14) for spasmodic dysphonia, to 29.4 percent (5/17) for functional dysphonia, to a high of 63.6 percent (7/11) for vocal cord paralysis."Newswise Medical News | Patients with Selected Voice Disorders Are Subject to Psychiatric Problems A review in the journal Swiss Medicine Weekly states that "Psychogenic causes, a 'psychological disequilibrium', and an increased tension of the laryngeal muscles are presumed to be one end of the spectrum of possible factors leading to the development of the disorder". Alternatively, many investigations into the condition feel that the psychiatric comorbidity associated with voice disorders is a result of the social isolation and anxiety that patients with these conditions feel as a consequence of their difficulty with speech, as opposed to the cause of their dysphonia. The opinion that SD is psychogenic is not upheld by experts in the scientific community.Spasmodic Dysphonia is a Neurological Disorder Current Evidence and References , by Christy L. Ludlow, Ph.D.
SD is formally classified as a movement disorder; it is a type of focal dystonia known as laryngeal dystonia.
Diagnosis Diagnosis of spasmodic dysphonia requires a multidisciplinary team and consideration of both perceptual and physiological factors. There is currently no universally accepted diagnostic test for spasmodic dysphonia, which presents a challenge for diagnosis. Additionally, diagnostic criteria have not been agreed upon as the distinguishing features of this disorder have not been well-characterized.
A team of professionals including a speech–language pathologist, an otolaryngologist, and a neurologist, are typically involved in spasmodic dysphonia assessment and diagnosis. The speech–language pathologist conducts a speech assessment including case history questions to gather information about voice use and symptoms. This is followed by clinical observation and perceptual rating of voice characteristics such as voice breaks or strain, which are selectively present in normal speech over other voice activities such as whispering or laughing. Symptoms also vary across types of spasmodic dysphonia. For example, voiced sounds are more affected in adductor spasmodic dysphonia, while unvoiced sounds are more affected in abductor spasmodic dysphonia. Following the speech assessment, the otolaryngologist conducts a flexible transnasal laryngoscopy to view the vocal folds and activity of the muscles controlling them in order to eliminate other possible causes of the voice disorder. In spasmodic dysphonia, producing long vowels or speaking sentences results in muscle spasms that are not observed during other vocal activities such as coughing, breathing, or whispering. To evaluate the individual for any other neurological problems, this examination is followed up with an assessment by the neurologist.
Voice quality symbol
The voice quality symbol for spasmodic dysphonia is ꟿ.
Differential diagnosis Because spasmodic dysphonia shares many characteristics with other voice disorders, misdiagnosis frequently occurs. A common misdiagnosis is muscle tension dysphonia, a functional voice disorder that results from use of the voice, rather than a structural abnormality. Some parameters can help guide the clinician towards a decision. In muscle tension dysphonia, the vocal folds are typically hyperadducted in a constant way, not in a spasmodic way. Additionally, the voice difficulties found in spasmodic dysphonia can be task specific, as opposed to those found in muscle tension dysphonia. Being able to differentiate between muscle tension dysphonia and spasmodic dysphonia is important because muscle tension dysphonia typically responds well to behavioral voice treatment, but spasmodic dysphonia does not. This is crucial to avoid providing inappropriate treatment, but in some cases, a trial of behavioral voice treatment can also be helpful to establish a differential diagnosis.
Spasmodic dysphonia can also be misdiagnosed as voice tremor. The movements that are found in this disorder are typically rhythmic in nature, as opposed to the muscle spasms of spasmodic dysphonia. Voice tremor and spasmodic dysphonia can co-occur in some patients.
Differential diagnosis is particularly important for determining appropriate interventions, as the type and cause of the disorder determine the most effective treatment. Differences in treatment effectiveness are present even between the types of spasmodic dysphonia. Diagnosis of spasmodic dysphonia is often delayed due to these challenges, which in turn presents difficulties in choosing the proper interventions.
Types The three types of spasmodic dysphonia (SD) are adductor spasmodic dysphonia, abductor spasmodic dysphonia, and mixed spasmodic dysphonia. A fourth type called whispering dysphonia has also been proposed. Adductor spasmodic dysphonia is the most common type.
Adductor spasmodic dysphonia