A patient produces no spoken speech at all over several days of observation, despite being otherwise physically capable of speaking, and communicates instead only through gesture and occasional handwritten notes. What is this?

This is mutism: a complete loss of speech in a person otherwise capable of speaking, here with communication maintained through gesture and writing, a pattern particularly seen in catatonic presentations. It is not specifically pure word-dumbness, a particular named sub-type of speechlessness distinguished by the specific and consistent preservation of reading and writing alongside a total absence of speech; the general term mutism covers a broader range of presentations and causes than this specific pattern. It is not expressive aphasia, in which written language is also typically affected to some degree, unlike the preserved writing described here. And it is not thought blocking, which concerns a sudden gap in the flow of thought, not a complete and sustained loss of speech.