The patient may have a hoarse voice (dysphonia) or no voice (aphonia). The most common cause of dysphonia is laryngitis. The inflammation causes the vocal cords to swell up and function poorly. Other causes of poorly-functioning vocal cords are incorrect use of the voice, overuse of the voice and morphological abnormalities such as polyps and malignancies. Constitutional morphological abnormalities can also cause a hoarse voice.
A neurological cause of a hoarse voice can be loss of function of a recurrent laryngeal nerve (a branch of the vagus nerve) caused, for example, by a thyroid tumour, thyroid surgery or a lung tumour (left-sided). Idiopathic loss of function of the recurrent laryngeal nerve can also occur.
Vocal cord paralysis can be diagnosed after indirect laryngoscopy. During the acute phase of the lesion to the recurrent laryngeal nerve, the vocal cord is at rest and during phonation it is in the paramedian position (refer to ‘The cranial nerves’, CNIX, CN X). If there is loss of function of both recurrent laryngeal nerves, the patient will display stridor as well as aphonia or dysphonia. Because the tone of the adductor muscles of the vocal cords is dominant, the vocal cords will be in the median position.
