Aphasia is caused by damage to the language centers of the brain. In most people, these language centers are located in the left hemisphere, but aphasia can also occur as a result of damage to the right hemisphere; this is often referred to as crossed aphasia, to denote that the right hemisphere is language dominant in these individuals.
Common causes of aphasia include the following:
- Ischemic—caused by a blockage that disrupts blood flow to a region of the brain
- Hemorrhagic—caused by a ruptured blood vessel that damages surrounding brain tissue
- Traumatic brain injury
- Brain tumors
- Brain surgery
- Brain infections
- Progressive neurological diseases (e.g., dementia)
Stroke is the most common cause of aphasia. According to the National Aphasia Association (n.d.), about 25%–40% of stroke survivors experience aphasia. Approximately 35%–40% of adults who are admitted to an acute-care hospital with a diagnosis of stroke are diagnosed with aphasia by the time they are discharged (Dickey et al., 2010; Pedersen, Jorgensen, Nakayama, Raaschou, & Olsen, 1995).