Aphasia is damage to the brain which affects speech. It is used for all forms of brain damage which negatively affects speech. The damage may cause muteness, in which case treatment depends on knowing exactly what caused the aphasia.
The condition primary progressive aphasia is serious because it is progressive. It gets worse with time.
- Damasio AR 1992. Aphasia. The New England Journal of Medicine. 326 (8): 531–9.