Anyone following the US presidential race may have noticed independent candidate Robert F. Kennedy Jr. has a particularly harsh-sounding voice. The cause is a neurological condition called spasmodic dysphonia.
Author
Adam Taylor
Professor and Director of the Clinical Anatomy Learning Centre, Lancaster University
Spasmodic dysphonia, also known as laryngeal dysphonia, often results in a shaky, tight or strained-sounding voice. It does not affect other functions of the vocal cords, such as laughing, crying or shouting.
It affects about one in every 50,000 people - with women being more prone to it than men. It usually develops between the ages of 30 and 50.
The causes aren't clear, but one study found that 65% of people with the condition previously had measles or mumps - compared with the US national average of 15%.
A separate study found the measles and mumps vaccines helped protect against developing the condition. An interesting finding, if confirmed, given that RFK Jr. is a noted vaccine sceptic.
Other studies have suggested that a history of throat and sinus illnesses, mumps and rubella, intense occupational voice use, tremor, tics and compulsive behaviour are all associated with spasmodic dysphonia.
There are three types of spasmodic dysphonia, the most common being "adductor spasmodic dysphonia", accounting for 85-95% of cases. In this version of the condition, the muscles that bring the vocal cords together are affected, making the cords stiffen or slam shut as a result of the spasms. This causes a strained or strangulated sound during speech.
The less common type is "abductor spasmodic dysphonia", which causes spasms that trigger the cords to open. The reason this is rarer is there is only one muscle (posterior cricoarytenoid) on each side that opens the cords. This results in speech being quieter or weak.
Finally, incredibly rare is a spasmodic dysphonia that affects both the adductors and abductors.
There is no cure for spasmodic dysphonia, but there are treatments that can help alleviate the symptoms.
Botox injections have become the gold standard therapy. However, this is a short-term solution and requires an injection every three to six months. Speech therapy can also help by strengthening the defective muscles or enabling other muscles to compensate. Sometimes Botox and speech therapy are combined.
A more invasive treatment involves severing some of the adductor muscles (for the more common form of the condition). This mimics a permanent Botox injection.
A recent small study also showed that deep-brain stimulation (a type of pacemaker for the brain) can improve the voice quality of people with adductor spasmodic dysphonia.
Voice changes can signal other health problems
Ageing causes our voices to change. Over time, our vocal cords become stiffer and less flexible, which alters the sound of our voice. People who use their vocal cords regularly - such as singers - show significantly less change in sound than those who don't sing.
But voice changes over a shorter period can suggest an illness.
Respiratory illnesses
Our respiratory system is lined by a special layer of cells called "pseudostratified columnar ciliated epithelium". Among the columnar cells are specialised cells called goblet cells that produce mucus. The role of mucus is to prevent microbes (common cold, COVID and many other things) from getting deep into the respiratory system, by causing microbes to stick.
The cilia then beat the mucus upwards, about ten to 14 times a second, towards the larynx where the microbe-containing-mucus is swallowed and neutralised by stomach acid.
This accumulation of mucus is increased in people with vocal disorders, because the cords move less and so they are less likely to be able to clear the mucus.
Studies have shown that the most efficient way to remove excess mucus is by hard throat clearing.
Acid reflux
Acid reflux can make the voice hoarse. The rising stomach acid can cause swelling and scarring in the larynx. This changes the shape and structure of the cords, affecting their function and the sound they make.
Allergies
Allergies are a significant contributor to vocal changes. The inflammatory reaction caused by exposure and activation by allergens, such as pollen, cause swelling in the vocal cords and increased mucus.
Antihistamines are often used to treat allergies. But, because they reduce the amount of mucus produced, they tend to dry out the larynx, making the voice very raspy.
Cancer
Changes in vocal sounds without other symptoms or identifiable causes may be caused by cancer tumour growth in the chest. The nerve that controls a muscle that abducts (opens) the vocal cords can become compressed by tumours in the chest. This is because it travels down from the skull, into the chest, wrapping under the aorta before returning to supply the larynx.
Studies have shown that between 18% and 24% of people with tumours that are in the chest - but not their larynx - have vocal cord paralysis that causes their voice to change.
Vocal changes happen subtly with ageing, but there are many other causes. Any changes that persist for weeks should be checked by a GP, particularly if there are other symptoms accompanying it.
Adam Taylor does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
