What is dysphonia?
Dysphonia is the medical term for a speech disturbance (phonation), usually resulting in a hoarse voice or whispering voice, due to problems with the larynx (voice box). Spasmodic dysphonia is a form of dystonia where there is involuntary spasms of the vocal cords. This causes interruptions in speech , or the voice may appear to be strained.
The most common cause of dysphonia is laryngitis and this causes a temporary disturbance in phonation (sound production). Dysphonia may also be due to a structural problem with the larynx (cartilage, muscles, cavities) or disorders of the nerves innervating the laryngeal muscles, namely the vagus nerve (CN X) and its branches. In these cases, the problem is longer lasting or even permanent.
How does dysphonia occur?
Thoughts processed in the Wernicke’s area along with the choice of words initiate the voluntary control of the larynx, mouth, lips, tongue and breathing by the Broca’s area to verbalize these words in set patterns that are learned in early life.
Motor impulses via the vagus nerve alter the tension of the vocal folds (vocal cords) and tilt the cords as necessary by manipulating the surrounding laryngeal cartilages through the action of the laryngeal muscles. This allows for the production of sound (phonation) in the larynx as air flows through it and causes the vocal cords to vibrate. Articulation is the process of moving the mouth, lips and tongue to verbalize actual words by manipulating the sound produced within the larynx.
In dysphonia, it is the phonation within the larynx that is affected. It should not be confused with other speech disturbances like dysarthria where there is a problem with articulation leading to slurred speech or dysphasia where there is a problem with the language content of speech.
Dysphonia means that some phonation is possible even though it is affected whereas in aphonia, phonation is completely impaired.
Dysphonia is a disturbance of the speech which presents as a hoarse voice or whispered speech. It is usually indicative of pathology isolated to the larynx or affecting the function of the larynx in producing sound (phonation). Most cases of hoarseness of the voice is due to laryngitis as a result of an infection, injury or strain. However, smokers should be cautious about the structural changes of the vocal cords that occur with long term tobacco smoking. This also increases the risk of developing cancer of the larynx.
Causes of Voice Hoarseness
This would be detected when the infant is crying.
- Congenital abnormality like laryngomalacia, where the immature larynx folds inwards due to an abnormality in the laryngeal cartilages.
- Neurological disorder affecting the vagus nerve or its branches (laryngeal branches).
Toddlers and Children
- Laryngitis – bacterial, viral, in childhood diseases like mumps, measles and chickenpox
- Voice strain (screamer’s nodes)
- The entire upper respiratory tract may be infected or only the larynx (laryngitis).
- Viral infections are more common and often associated with the common cold or influenza.
- Bacterial infections are the second most common infectious cause and includes infections with S.aureus, H.influenzae and in tuberculosis.
- Fungal infections, while rare, may be related to the spread of oral infections like candidiasis. This is common in immunocompromised patients, especially in HIV/AIDS.
- This may be due to mechanical or chemical injury.
- Cigarette smoking and air pollution cause a combination of mechanical and chemical injury.
- Gastroesophageal reflux disease (GERD) – reflux laryngitis.
- Prolonged strain – vocal cord nodules (singer’s nodes)
- Age-related changes
- Atrophy of the vocal folds seen with age (presbylarynx).
- Asthma inhalers
- Laryngeal carcinoma
- Lung cancer
- Myasthenia gravis
- Dystonia (spasmodic dysphonia)
- Vagal/laryngeal nerve disorders or lesions may result in unilateral or bilateral paralysis.
- Unilateral laryngeal paralysis is more likely to result in persistent dysphonia and other symptoms associated with laryngeal obstruction may be absent.
- Bilateral paralysis will lead to an obstruction of air flow within the larynx.
- Idiopathic (unknown)
- Breathlessness, cyanosis and stridor may also be present.
- Allergic edema
- Spasm of laryngeal muscles
- Foreign body including inhaled blood clots or food
- Bilateral laryngeal paresis
- May present as aphonia, which is a loss of the voice, or dysphonia, which is hoarseness or whispering speech.