Mutism is absence of speech output. This may be psychogenic, as in schizophrenia or affective disorders, with or without catatonia; or a consequence of neurological disease, for example:
Dementia syndromes, especially frontal lobe dementia, late stages of primary progressive aphasia
Damage to Broca’s area, supplementary motor area; severe pseudobulbar palsy, bilateral thalamic damage
Cerebellar mutism: rare, following midline cerebellar surgery in children
Bilateral vocal cord paralysis (although this may be better termed aphonia)
In neurological disorders there may be difficulty initiating movements, completing motor sequences, or inhibition of appropriate responses.
Altshuler LL, Cummings JL, Mills MJ. Mutism: review, differential diagnosis and report of 22 cases. American Journal of Psychiatry 1986; 143: 1409-1414 (erratum: American Journal of Psychiatry 1987; 144: 542) Ersahin Y, Mutluer S, Cagli S, Duman Y. Cerebellar mutism: report of seven cases and review of the literature. Neurosurgery 1996; 38: 60-66