Elective mutism
Complete lack of speech (mutism) that is believed to be volitional (willed) on the part of the patient.
True elective mutism may be a reaction to a traumatic event, the aftermath of an injury to the mouth or throat, particularly if it is painful, or a symptom of extreme shyness.
In some cases, the lack of speech is eventually found not to be volitional, but a sign of damage or deformity of the speech apparatus, or a feature of infantile autism.
See also selective mutism.