Aphonia is loss of the sound of the voice, necessitating mouthing or whispering of words. As for dysphonia, this most frequently follows laryngeal inflammation, although it may follow bilateral recurrent laryngeal nerve palsy. Dystonia of the abductor muscles of the larynx can result in aphonic segments of speech (spasmodic aphonia, or abductor laryngeal dystonia); this may be diagnosed by hearing the voice fade away to nothing when asking the patient to keep talking; patients may comment that they cannot hold any prolonged conversation. Aphonia of functional or hysterical origin is also recognized. Aphonia should be differentiated from mutism, in which patients make no effort to speak, and anarthria in which there is a failure of articulation.