Aphasia is a language disorder occurring after a brain injury. It can be caused by a car accident, a head trauma, a stroke, or any other events during which you hit your head hard enough. When the language areas are damaged, it can cause problems in terms of understanding and / or producing the language.

The 3 factors of Aphasia

There are three main factors to consider when categorizing the different types of aphasia.

Broca's area, Wernicke area and arcuate fasciculus, Aphasia

Fluence Repetition Comprehension

The state of these factors depends on the brain region injured.

Fluence

Fluence is associated with the mouth and throat muscles motor activity controlled in the frontal lobe. Non-fluency, which is difficulty producing language, is caused by an injury in Broca’s area. This area is used to coordinate the many movements needed for the language production. It’s located right next to the primary motor area responsible for sending messages from the brain to the mouth muscles.

Broca's area and primary motor area, Aphasia

A person with non-fluent aphasia could, depending on the case, understand very well their interlocutor. However, that same person will respond with a speech containing short sentences, hesitation and / or grammatical errors. The most serious cases can express themselves with only one sound.

Fluence problem, Aphasia

People with non-fluent aphasia can have enormous difficulty in formulating sentences in their daily life. However, they are able to sing song lyrics they know well without errors. This is explained by the neural connections strengthening through repetition. Since they had said these phrases over and over, they are somewhat less vulnerable to the consequences of aphasia. This phenomenon also applies to the expressions they often said before the injury.

Comprehension

Whether fluent or not, aphasia can also come or not with a comprehension deficit. In this case, people not only have difficulty understanding what others are communicating to them, they lack coherence in their speech. They tend to speak in paraphrases (describing instead of naming) and make syntax errors. It therefore leads them sometimes to speak using very long sentences hard to understand.

Comprehension problem, Aphasia

When the understanding is impaired, we can suspect that the Wernicke’s area is affected. It’s located near the hearing area which, after processing the sound stimuli, sends the information to the Wernicke area.

Hearing area and Wernicke area, Aphasia

Being hard of hearing doesn’t mean it’s impossible to deal with aphasia symptoms. Language areas are not used only to process verbal information, but all forms of communication. Thus, if these regions are injured, they could lose their ability to understand sign language. They may also have difficulty communicating, resulting in signs which are not appropriate to the context or a set of signs which, taken together, do not make it possible to create a coherent sentence.

Repetition

Some people with aphasia are able to repeat a sentence, others cannot. A repetition problem results in difficulty in reproducing a sentence orally or in writing (as in dictation exercices).

Repetition problem, aphasia

This is explained by an arcuate fasciculus lesion, that is the white matter which connects the Broca’s area and the Wernicke’s area. This link allows the communication between these two areas so that we can associate the sounds with articulatory representations (of the motor commands) allowing us to reproduce the sounds hear.

Broca's area, Wernicke area and arcuate fasciculus, Aphasia

All types of Aphasia

Here is a tree summarizing the different types of aphasia. Depending on the fluency level, understanding and repetition of the patient, a different diagnosis will be made. The different combinations of criteria (eg fluent, understands, doesn’t repeat VS non-fluent, doesn’t understand, doesn’t repeat, etc.) can be explained by the different lesion locations and their extent. If several of the areas mentioned above are damaged, the consequences will be different than if only a small part of the Broca’s area, for example, is affected.

Types of aphasia

Fine observers will have noticed that anomic aphasia is characterized by an ability to speak normally (verbal fluency), to understand our interlocutor and to repeat. So why are they diagnosed with aphasia? Simply because, in general, they can express themselves coherently and at a normal rate. However, they face difficulty remembering certain specific vocabulary words. So, they search for their words more often than most people.

English isn’t my first language so there might be some mistakes. If you want, let me know in the comments bellow if you found any so I can fix them. Thank you!


Sources 

Le H, Lui MY. Aphasia. [Updated 2020 Jun 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK559315/

Falchook, A. D., Mayberry, R. I., Poizner, H., Burtis, D. B., Doty, L., & Heilman, K. M. (2013). Sign language aphasia from a neurodegenerative disease. Neurocase19(5), 434–444. https://doi.org/10.1080/13554794.2012.690427

Tomaino C. M. (2012). Effective music therapy techniques in the treatment of nonfluent aphasia. Annals of the New York Academy of Sciences1252, 312–317. https://doi.org/10.1111/j.1749-6632.2012.06451.x

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