An often puzzling form of hoarseness is "functional" dysponia. Functional refers to the fact that anatomically and physiologically, the larynx is working properly. But through some environmental, psychologic, or subconscious mechanism the brain has retrained the individual to speech in an abnormal way. The voice can range from being absent, very high pitched, or strained.
Functional dysphonia tends to occur after a respiratory infection, when acute laryngitis may lead to vocal fold swelling and inflammation. This may trigger the patient to change the way that they speak, and when the laryngitis resolves, they may get stuck in this particular pattern.
Stress or trauma can trigger episodes, as a form of conversion disorder. This may occur with or without physical trauma. Occasionally, a strangling injury will lead the patient to "guard" their voice by misusing the neck muscles.
As opposed to common neurologic causes of hoarseness like vocal cord paralysis and spasmodic dysphonia, functional dysphonia has the ability to come and go.
Additional contributing factors include vocal fold inflammation from acid reflux, sinus inflammation, cough, or vocal abuse.