Aphasia is a partial or total loss of the language already learned. Such a loss of speech can occur when certain areas of the brain are damaged.
Because aphasia impairs the ability to communicate, aphasic persons can – depending on the severity of their speech disorders – be psychologically or mentally handicapped. But: Aphasia does not indicate a mental or psychological disability, but is pure speech disorder!
The most common causes of aphasia are circulatory disturbances in the brain due to changes in blood vessels (e.g. as a result of arteriosclerosis or diabetes mellitus): This can lead to a stroke, which can lead to aphasia in around four out of ten cases. Other possible triggers of speech disorders are:
- Skull-brain traumas
- inflammation or lack of oxygen in the brain
- gradual brain breakdown (e.g. progressive dementia)
After a stroke or due to dementia, a speech disorder can often occur.
In adults, stroke is by far the most common cause of aphasia.
In children, on the other hand, speech impairment is usually caused by traumatic brain injury.
Usually an aphasia affects all components of speech, so that the use of language – with different emphases – leads to deviations in word finding (lexis), understanding the meaning of words (semantics), grammar (syntax) and sound formation (phonology). In addition, speaking, writing, comprehension and reading may have aphasic disorders.
Depending on which symptoms predominate in aphasia, there are different forms of speech disorder. The most important forms of aphasia, most of which can be clearly classified as damage to certain regions of the brain, are
- Broca aphasia (or motor aphasia), the most important symptom of which is speech formation,
- Wernicke’s aphasia (or sensory aphasia), the main symptoms of which are impaired speech comprehension,
- amnestic aphasia, characterised by dyslexia, and
- global aphasia, which is considered the most severe form.
A sudden aphasia often improves by itself – especially in the first six months after brain damage caused by reduced blood flow.
However, acquired speech disorders can also last longer. In any case:
With every aphasia, it is advisable to start speech therapy as early as possible, as this often significantly improves the aphasic’s ability to communicate.
In order to prevent aphasia, it is particularly important to minimise the risk of stroke and head injuries (e.g. wearing a safety helmet when cycling).
The term aphasia by definition refers to a speech disorder acquired after completed speech development or an impairment of speech formation or speech comprehension caused by brain damage. The partial or complete loss of speech impairs the ability to communicate, but aphasia is not a sign of psychological or mental disabilities.
The foundations of our knowledge about aphasia date back to the first half of the 19th century, when research into brain diseases began to establish a connection between motor and sensory functions (or their disorders) and certain regions of the brain. At the centre of this development was the French physician Paul Broca (1824 to 1880), who succeeded for the first time in 1861 in assigning the motor speech centre of right-handed people to the left half of the cerebrum in a person with motor speech disorder, which is today also known as the Broca speech centre. Broca’s work on the localization of brain functions was groundbreaking for the further development of brain anatomy and physiology.
Particularly in the first quarter of the 20th century, there were intensive efforts to investigate the structure of each individual brain region and to create maps of the entire brain. In 1909 Korbinian Brodmann already distinguished 52 different fields, which he called “Area 1” to “Area 52”. Brodmann’s figures are still widely used today.
Research into the brain regions was associated with the hope of gaining insight into its functions through knowledge of the fine structure of the brain. Later research, however, showed that it had not always been possible to precisely assign brain regions and functions. This may be partly due to the fact that the investigations were usually carried out on only a few people.
Recent comparative studies have shown that the fine structure of the brain varies greatly from person to person. Nevertheless, it is possible to establish relationships between disorders of certain motor or sensory functions and damage to local areas of the brain. The most important forms of aphasia can also be more or less clearly attributed to damage to certain brain regions:
Broca aphasia, for example, is mainly caused by damage to the so-called Broca speech centre, which is located in the frontal lobe of the brain in Area 44 according to Brodmann,
whereas in Wernicke’s aphasia the so-called Wernicke speech centre in the upper temporal lobe of the brain is essentially damaged.