What is spasmodic dysphonia?

Spasmodic dysphonia is a condition affecting the voice in which the muscles of the voice box experience sudden involuntary contractions or spasms which interfere with the ability to produce a clear voice.

These spasms produce breaks in the voice, which may make the voice sound choppy when speaking. Breaks can occur every few sentences, or sometimes even every word when the condition is severe. It can be difficult for a person with the condition to be understood when they speak. It can also be strenuous and hard work to speak. Patients are often distressed and frustrated by their condition.

Spasmodic dysphonia is a rare condition. It occurs most often in people between 30 and 50 years of age, and affects women more commonly than men. However it can occur in anyone, and affects different people to different extents.


What causes spasmodic dysphonia?

The precise cause is unknown. However spasmodic dysphonia is thought to arise from the disordered functioning of the central nervous system. In particular, it may involve part of the brain known as the basal ganglia. The basal ganglia are clusters of nerve cells deep in the brain that help coordinate muscle movements throughout the body. Despite the brain being involved, it is usually not possible to identify any structural abnormality, meaning that a brain scan such as an MRI is likely to be normal.

Genetic factors may predispose a person to the condition, and environmental factors such as a viral illness, voice overuse, injury to the voice box, or even stress can precipitate it. Symptoms can also develop with no obvious explanation.

In the past, people considered spasmodic dysphonia to be a psychological illness, mainly because it is difficult to identify a physical cause. While it is true that stress can worsen symptoms, or even precipitate the disorder, it is very rare for stress to be the cause. Conversely, having a disabling disorder can contribute to a lot of stress.


What other symptoms occur in spasmodic dysphonia?

Spasmodic dysphonia is considered to be a movement disorder known as a “dystonia”, and is sometimes referred to as laryngeal dystonia. The term dystonia describes abnormal involuntary repetitive muscle contractions. These abnormal muscle contractions tend to be localised to the voice box rather than affect all muscles in the body, and the condition is therefore referred to as a “focal dystonia”.

Focal dystonias can also affect other parts of the body, and these dystonias can sometimes occur together with spasmodic dysphonia. Examples of other focal dystonias include cervical dystonia in which there are abnormal movements in the neck muscles, blepharospasm causing abnormal contraction of the muscles around the eyes and blinking, oromandibular dystonia causing distortions of the mouth and tongue, and writer’s cramp affecting the hand muscles.

Finally, spasmodic dysphonia can also occur as part of a generalised dystonia in which muscles are affected in multiple regions of the body or the entire body. This is rare.

Sometimes dystonias, including spasmodic dysphonia can run in families, and a number of genes have been associated with various dystonias. However only mutations of a gene known as THAP1 have been associated with a form of dystonia that begins in childhood and can affect the whole body including the voice box or larynx.

Patients with spasmodic dysphonia can also sometimes have a vocal tremor. This makes the muscles of the voice box quake, resulting in a shaky or wobbly voice quality.


Are there different types of spasmodic dysphonia?

There are three main types of spasmodic dysphonia:

Adductor spasmodic dysphonia is the most common. It is characterised by spasms in the muscles that close the vocal folds during speech. As a result, words often sound as though they are being cut off or are difficult to start. Speech may therefore sound choppy, and is sometimes described as strained-strangled or tight. The voice may be better or even normal while laughing, crying, or shouting, and is usually worse under stress. Adductor spasmodic dysphonia can sometimes be difficult to distinguish from severe muscle tension dysphonia, a condition in which the voice muscles are habitually held tight during speech.

Abductor spasmodic dysphonia is characterized by spasms that force the vocal folds open during voicing, instead of allowing them to close and vibrate normally. This results in excessive air escaping during speech. As in adductor spasmodic dysphonia, spasms occur in an uncontrolled and repetitive fashion, so the voice also has a choppy quality. However in abductor spasmodic dysphonia, the spasms create a weak and breathy sound, that is accentuated during certain voicing tasks. As with adductor spasmodic dysphonia, spasms are often absent during activities such as laughing, crying, or shouting.

Mixed spasmodic dysphonia can occur occasionally, and is a combination of adductor and abductor spasmodic dysphonia. In mixed spasmodic dysphonia, both the muscles that open and close the vocal folds can be affected by spasm, and the voice has both tight and breathy features.


How do we diagnose spasmodic dysphonia?

Spasmodic dysphonia is a rare condition that can have similar characteristics to other voice disorders. It is frequently misunderstood and underdiagnosed, and yet can be very debilitating for people who suffer from it. The diagnosis is often best made by an ENT (ear nose and throat) specialist, specialising in voice disorders (also known as a laryngologist). The diagnosis can also be made by a speech therapist with experience managing voice disorders. Sometimes it is diagnosed by a neurologist, a doctor specialising in nervous system disorders.

There are three important aspects to the diagnosis: The first involves listening to the voice for characteristics typical of spasmodic dysphonia, and to determine the type of spasmodic dysphonia. The patient is asked to perform a number of different voicing tasks that bring out the key characteristics. Factors that contribute to symptoms, and the impact that the condition has on the patient are also assessed.

Secondly, a careful examination of the voice box and associated structures is carried out. This is important to evaluate the structure and function of the voice box, and the pattern of vocal fold movement during speech, and determine if there are other possible causes for the voice disorder. The external components of the voice box as well as internal structures are examined. Internal structures are examined by passing a small camera, usually through the nose (and sometimes through the mouth) to view the vocal folds. A strobe light may be used to visualise vibration of the vocal folds in slow motion and assess certain features in more detail. This procedure is known as video-laryngoscopy or video-laryngo-stroboscopy.

The third part of the assessment is to rule out other muscle movement disorders or neurological conditions. Evaluation by a neurologist may be necessary for this purpose.

Frequently a multidisciplinary approach involving the ENT specialist, speech therapist and neurologist provides the most comprehensive diagnosis and treatment plan at the outset of the condition.


What treatments are available?

Spasmodic dysphonia is a chronic condition, and although there is currently no known cure, treatments are available that can alleviate symptoms often very effectively. Symptoms can fluctuate, and so can the impact that they have on daily functioning, meaning that there can be good and bad phases for the condition. We also occasionally see instances where the condition recovers spontaneously.

Injecting botulinum toxin into the affected muscles of the voice box is the most established method of treating spasmodic dysphonia, and can produce significant improvements in voice and quality of life. Botulinum toxin is produced by the bacteria Clostridium botulinum. It works by blocking nerve impulses to muscle at the site of the injection. In doing so makes the muscle weak, which is desirable when that muscle is prone to spasm.

Botulinum toxin injections are usually carried out by passing a fine needle through the skin of the neck. Two methods can be used to pinpoint the muscle for injection. The first utilises laryngeal electromyography (LEMG), in which an electrical signal indicates that the needle is in the correct muscle. Anaesthetic is not normally required for this method. The second method uses a flexible endoscope or camera passed through the nose to visually guide the needle to the correct location. Local anaesthesia is usually used to reduce the sensitivity of the larynx, and the procedure is typically achieved comfortably for the patient.

Side effects that can occur after botulinum toxin injection include temporary weakness and breathiness of the voice, and occasional swallowing difficulties. Usually these subside after a few days to a few weeks. Following this period the voice generally improves for up to three to four months, after which voice spasms gradually return. Reinjections are necessary to maintain a good speaking voice. Botulinum toxin will relieve symptoms in most cases of adductor spasmodic dysphonia, and is helpful in many cases of abductor spasmodic dysphonia.

In milder cases, speech therapy may help to reduce symptoms and it is often advisable for patients to undergo a trial of speech therapy with a speech therapist. Other aspects of caring for the voice including maintaining good hydration, and reducing gastric reflux are also important to optimise the voice. Some people may benefit from psychological counselling to help them accept and live with their voice problem.

When more conventional measures have failed, surgery on the larynx may be performed. Three main surgical approaches are currently in use:

  • Thyroarytenoid neuro-myectomy is probably the least invasive. In this method, the vocal folds are accessed under general anaesthetic through the mouth, so that no cuts are made in the skin. A laser is used to cut into the voicing muscle and reduce its bulk, as well as divide the nerve entering the muscle. By reducing the bulk of the muscle its ability to spasm is reduced.
  • Another method known as selective denervation and re-innervation accesses the nerve to the voicing muscle through an incision in the neck.
  • A third method known as thyroplasty involves dividing the voice box cartilage and spreading it apart so that the voice muscles cannot close as tightly even though spasm may still be present.

While these surgical procedures can improve the voice, long-term benefits and effects are unknown.


What we are able to offer at David Lau ENT Centre

Dr Lau is experienced in the diagnosis and management of spasmodic dysphonia. He performs both EMG-guided as well as endoscopy-guided botulinum toxin injections. He emphasises the importance of careful evaluation and tailoring treatment to the patient’s needs, with a multi-disciplinary approach where required. He also has experience in thyro-arytenoid myectomy and selective denervation and re-innervation as surgical options.


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