Aphasia - originally from the Greek, 'a' and 'phasis', which mean 'without' and 'speech' respectively - is a condition caused by malfunctioning or damaged sectors of the brain dealing with language. It severely affects the production of speech and/or the comprehension of words, including during reading and writing. Sufferers use the wrong words, sounds, or put them in the incorrect order, and sometimes require a great deal of support to be understood.
Aphasia is actually a blanket term for a number of conditions, which differ according to the brain areas involved and the extent, onset, and prognosis of the damage. It can be categorised in terms of the specific deficits experienced. Expressive aphasia means having difficulties putting your coherent thoughts into words. Receptive aphasia is when a person is able to hear or see words, yet they cannot make sense of them. Not knowing the words for nouns - objects, places and events - is known as anomic aphasia. Finally, global aphasia means a generalised failure to speak, understand, read or write language. The underlying issue is an inability to access and process speech, though it may still appear in tact in the mind.
Global aphasia usually occurs when multiple brain regions have been damaged, but more discrete deficits can be linked to specific areas. For example, Wernicke's area is a section of the brain involved in assigning meaning to words. Thus, those with Wernicke's aphasia do not struggle to talk, but the sentences they produce may be long and nonsensical. In contrast, a person with Broca's aphasia will speak coherently, but slowly and with great effort, as Broca's area mediates the production of language. Fortunately, both these types have the potential for improvement, as the brain and individual can adapt, though it is stressed that appropriate language therapy should be sought as soon as possible after diagnosis. On the other hand, primary progressive aphasia, such as that resulting from Alzheimer's disease or dementia, means language skills will deteriorate over time, the aphasia and associated deficits gradually worsening as the damage increases.
But for most, therapy can help. It is essential that both sufferers, professionals, and the social support networks of friends and family are patient, as aphasia can be a very frustrating disorder. Indeed, some might think they are being helpful by finishing off sentences before they are uttered, but for a person struggling to talk this can be demoralising and patronising. Looking at it from this perspective, it is perhaps not surprising that sometimes a diagnosis of aphasia is associated with depression, anxiety, and angry outbursts, an understandable reaction to a difficult situation. Nonetheless, with the correct professional support and encouragement, often these side effects are only temporary.
Although aphasia arises from a variety of injuries and diseases such as brain tumours and head trauma, it affects almost a third of surviving stroke victims. This has meant that the literature and treatment is highly focused around this patient group. Therefore, you can find a number of good resources at https://www.stroke.org.uk/finding-support/aphasia-and-communicating and http://www.strokeassociation.org, as well as those available at the dedicated aphasia site, http://www.aphasia.org. It can be difficult to communicate for sufferers and their loved ones, but it is important to remember that there is support available. Aphasia does not affect a person's intelligence, so it is just a question of unlocking it to allow meaningful human exchanges.