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What is aphasia and how does magnetic resonance imaging help?

As a child, learning to speak and then to write was extremely important. Speech typically begins at an extremely young age, unless the child has a reason not to speak. However, even in cases where a child doesn't speak, they are immediately checked for deafness or issues with the area of the brain that deals with language. At around age four or five, children begin to learn to write. After that language becomes the main path to communication, whereas drawing, crying, or motioning were the primary ways that a child communicated before learning to speak or write.

Imagine growing up with these abilities. You had no problem communicating with others and were able to understand what was being said. Then, you suddenly suffered some form of brain damage in the form of a stroke or head injury of some kind. After the injury, you are unable to speak, write or communicate. What causes these issues?

What is aphasia?

The answer is a medical condition called aphasia. Aphasia causes patients to lose the ability to communicate in some way.1,2 This loss of communication could be spoken, written, or a combination of both that causes trouble with understanding language. Aphasia is typically due to a stroke or head injury, but also from things that cause degeneration (progressive permanent damage) in the brain.

People should watch for signs of aphasia after a loved one suffers a brain injury, stroke and as their loved one ages. There are a few different signs of aphasia in everyday life. There are also three different types of aphasia that can occur.

Signs of aphasia1,2

  • The patient may speak in short or incomplete sentences
  • They may speak or write in sentences that don't make sense
  • They may have issues with words and sounds and substitute words or sounds for other words or sounds
  • They may speak unintelligibly
  • The patient may not understand conversations

Types of aphasia

  • Nonfluent aphasia, also referred to as Broca aphasia, results from damage to the area in the left frontal area of the brain that houses the language network.1,2 Patients who have nonfluent aphasia may struggle to get words out, speak in short sentences and omit words. Listeners can usually understand what the patient is trying to say. This type of aphasia leads patients to understand what others are saying better than they can respond. These patients may be aware of their communication issue and may get frustrated with it. Nonfluent aphasia patients may also have trouble with paralysis or weakness on the right side of their body.
  • Mixed nonfluent aphasia appears similar to nonfluent aphasia. Patients may have sparse and effortful speech.2 They will also have a limited ability to comprehend speech and may not read or write beyond an elementary level.
  • Fluent aphasia allows patients to speak easily and fluently in long, complex sentences, but these sentences do not make sense and sometimes include unrecognizable, incorrect, or unnecessary words.1,2 Patients with fluent aphasia don't normally understand others who are speaking well and may not be aware that others can't understand them. Fluent aphasia is also referred to as Wernicke aphasia and results from damage to the middle of the left side of the brain, which also stores part of the language network.
  • Anomic aphasia patients are persistently unable to supply words for what they are talking about, especially nouns and verbs. They may understand speech well and typically read adequately. Their difficulty find words can be evident in both speech and writing.
  • Global aphasia is the final type of aphasia.1,2 It results from severe damage to the language network within the brain. Global aphasia can cause severe issues with expression and comprehension. Patients with global aphasia cannot read or write. It may occur after stroke, but not immediately, and may rapidly improve if the damage is not too extensive.
  • Primary progressive aphasia is less common.3 Symptoms begin slowly, often before the age of 65. Patients with primary progressive aphasia lose the ability to communicate, just like the other forms of aphasia. This condition progresses slowly and results from atrophy (a loss of brain tissue) from dementia. This is considered part of frontotemporal dementia. There are three types of primary progressive aphasia: progressive nonfluent aphasia, semantic dementia and logopenic progressive aphasia.2,3

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What does magnetic resonance imaging do for aphasia?

Magnetic resonance imaging (MRI) uses a superconducting magnet to create and alter a magnetic field around the scanner, which the patient enters for their MR scan. This allows the computer to use antenna-like objects, called coils, to detect signals released by the patient's body. These signals occur in response to the pulse sequences used for the scan and the alignment of protons within the body.

MRI is particularly useful for measuring, monitoring, and visualizing the tissue structures within the body, including the brain. It can also be used to image other organs and areas of the body. However, in imaging for aphasia, it is primarily used to image the head. MRI may help to image primary progressive aphasia.3

MRI may show differences between the three types of primary progressive aphasia. One study, including 8 patients with progressive nonfluent aphasia, 13 patients with semantic dementia, 7 patients with logopenic progressive aphasia and 29 neurologically healthy patients, has shown that there is some basis for this classification.4 They monitored the gray matter in the brain over a year. Each of the types of aphasia affected different areas of the brain. Progressive nonfluent aphasia appeared as increased atrophy (gray matter contraction) in the left frontal and subcortical areas of the brain. Semantic dementia appeared as a gray matter contraction in the medial and lateral temporal lobe. Finally, logopenic progressive aphasia showed as atrophy in the lateral and posterior temporal and medial parietal regions.

Magnetic resonance imaging has provided additional information on the progression of each type of primary progressive aphasia. The information provided by MRI could help doctors to better understand what is happening in their patient's brains. This understanding could help patients with aphasia feel more comfortable in their or their family's knowledge of the disease. When someone loses the ability to communicate, it becomes a major obstacle for them. Hopefully, in the future, there will be some sort of improvement in aphasia treatment.

References

1. Mayo Clinic Staff. "Aphasia." MayoClinic.org. 3 April 2018. Web. 11 June 2019. <https://www.mayoclinic.org/diseases-conditions/aphasia/symptoms-causes/syc-20369518>.

2. "Aphasia Definitions." National Aphasia Association. Web. 11 June 2019. <https://www.aphasia.org/aphasia-definitions/>.

3. Mayo Clinic Staff. "Primary progressive aphasia." MayoClinic.org. 27 December 2018. Web. 11 June 2019. <https://www.mayoclinic.org/diseases-conditions/primary-progressive-aphasia/diagnosis-treatment/drc-20350504>.

4. Simona Maria Brambati, et al. "Longitudinal gray matter contraction in three variants of primary progressive aphasia: A tenser-based morphometry study." NeuroImage: Clinical. 2015; 8: 345-355. Web. 11 June 2019. doi: 10.1016/j.nicl.2015.01.011.