Aphasia is a condition in which the person affected becomes unable to use or understand language effectively. It is primarily a language disorder that leads to problems in word-finding, word recognition and grammar.

Aphasia can affect people of all age groups, but is most common in older people, particularly those who have had a stroke.

Aphasia symptoms

In its most extreme form, aphasia prevents understanding and use of spoken language. Although aphasia is often accompanied by a speech disorder, pronunciation of words is usually not the main problem. Symptoms of milder forms (called dysphasia) include:

  • Not being able to construct meaningful sentences.
  • Finding it difficult to understand any but the simplest instructions.
  • Having difficulty finding the ‘right’ word.
  • Finding it hard to articulate words.
  • Being unable to repeat phrases back after someone else has said them.
  • Forgetting or being unaware of how to use grammar.
  • Trouble with reading or writing.

Many aphasic people have normal intelligence when they are not trying to use language.

The regions of the brain affected by aphasia

Aphasia results from damage to the language-related areas of the brain. These are mainly located in the ‘language hemisphere’. In about 90% of people, this is the left cerebral hemisphere. Important areas of the hemisphere include:

  • Wernicke’s area – this is involved in how we perceive sound, including speech, animal sounds and inanimate noises. The area is in the temporal lobe of the cerebrum in the brain. 
  • Broca’s area – this area is important in understanding the meaning of language, particularly how grammar works. The area is in the rear of the frontal front lobe of the cerebral hemisphere, lying immediately above the temporal lobe.

In rare cases, aphasia may result from damage to sub-cortical (deep) regions of the brain, including the thalamus and the basal ganglia.

What causes aphasia or dysphasia?

Anything that causes brain damage can cause aphasia. Stroke, physical injury to the brain, neurological disorders such as Alzheimer’s disease and brain tumours can cause people to lose the power of speech.

Damage to the brain is most likely to cause aphasia if they affect the language hemisphere and the language-related areas within it. Stroke that results in hemiparesis, partial paralysis of the right side of the body, is often associated with damage to Broca’s area. People who lose movement on their right side often experience loss of speech. 

How is aphasia classified and diagnosed?

Aphasia has several recognised categories:

  • Fluent (receptive): someone has good use of grammar, but otherwise incomprehensible speech, peppered with completely original words, as in ‘I cooked the limbo and ate the mellifluid’.
  • Non-fluent (expressive): this type of aphasia is characterised by difficulty in forming sentences and word-finding. Questions can be reduced to the bare minimum; ‘Want drink’.
  • Global: completely unable to understand or use spoken language.

A formal diagnosis of aphasia involves taking a standardised test, such as the Boston Diagnostic Aphasia Examination.1 This may be followed up by magnetic resonance imaging (MRI) scanning of the brain. MRI scanning is a non-invasive technique that can visualise the body’s soft tissues: an MRI scan is routine in people who have had a stroke. 

Aphasia or dysphasia after a stroke

A stroke is caused by the interruption of blood supply to an area of the brain. An ischaemic stroke decreases the blood supply to an area of the brain, often because of a blood clot. Haemorrhagic stroke is due to bleeding within the brain as a result of a burst blood vessel. Any stroke that affects the language hemisphere, especially the specific language areas within it, can cause aphasia.

After emergency treatment has been successful, stroke rehabilitation starts early to increase the chances of recovering movement and speech. Aphasia treatment is usually given by a speech therapist; each case of aphasia is different, so treatment is tailored to individual people and taken at their pace.

Frequent treatment over a short period of time tends to be more effective than infrequent training over a longer time period and several techniques are recommended:

  • Multisensory teaching uses many different types of stimuli – pictures, sounds, music and textures to engage with the different senses.
  • Structured teaching starts off gradually but then asks more of the patient over time, using encouragement to push their own skills.

Everyone who has a stroke should be encouraged to use language skills, even if these are very limited at first as avoiding speech in the early days can lead to loss of important nerve connections in the brain. If possible, family are encouraged to help with the therapy.

Recovering from aphasia

How well people recover depends on what caused the aphasia in the first place and on the severity of the language disorder. The brain is to an extent plastic; cases are known in which Broca’s area has been damaged, and then other areas of the brain have taken over its functions.

Despite serious brain damage, the person affected has recovered the ability to understand and use speech. No matter how severe the aphasia is at first, some degree of recovery is possible.