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Primary progressive aphasia and the parts of the brain affected

Hausarbeit (Hauptseminar) 2018 17 Seiten

Anglistik - Linguistik

Leseprobe

Contents

1. Introduction

2. Primary progressive aphasia

3. Language impairments and the affected parts of the brain of Primary progressive aphasia patients

4. Case Study

4.1. Critical review of the case study

5. Conclusion

6. Bibliography

1. Introduction

Primary progressive aphasia is a relatively newly recognized subtype of dementia. Dementia is a clinical condition, in which a progressive decline of mental and emotional capacities occurs (Mesulam 2000:159). It affects fifty million people worldwide, with ten million new cases yearly (N.U. Dementia 2017). There is a wide variety of symptoms, including the loss or decline of memory, ability to focus, difficulties with reasoning, communication and language (Alzheimer's Society 2005:3), interfering with the independence of the daily living situation and activities (Mesulam 2000:159).

To this day, Primary progressive aphasia is often misdiagnosed, because of its unpopularity and therefore lack of knowledge of many people. Those misdiagnoses steal valuable time to find effective treatments, which, at least, could slow down the progressive nature of the illness. Studying the relationship between language impairments and affected parts of the brain in Primary progressive aphasia, allows us to reach a better understanding of the language network in the brain and pushes forward the search for effective treatments or even a cure.

This termpaper presents a review of literature, especially by Mesulam, on Primary progressive aphasia and the language impairments, declining progressively throughout the illness. The question this paper tries to answer is, what kinds of language impairments can be present in Primary progressive aphasia and which parts of the brain are responsible for certain deficits, when affected by different diseases. It will give information about the most common language impairments seen in patients, because no case is exactly the same and not everybody experiences the same difficulties. Furthermore, the paper will explore the language network of the brain, where it is located, which parts it includes and which parts play a role in Primary progressive aphasia, for short PPA.

To look at the clinical picture from another perspective, a 14- years follow-up case study will give an example of speech impairments of a patient diagnosed with Primary progressive aphasia and show the neuropathological findings of the affected brain parts, which are responsible for the specific impairments.

2. Primary progressive aphasia

Aphasia in general is described as an error in the communicative handling of speech. It is different from dysarthria, which is the dysfunction of the articulation, for example cerebellar coordination disorder or stuttering (Poeck 1982:109).

Primary progressive aphasia is a subtype of Frontotemporal lobar degeneration. Frontotemporal lobar degeneration is a form of dementia, which gets its name from the parts of the brain affected, which are the frontal lobe and the temporal lobe. Frontotemporal lobar degeneration is divided into three clinically defined subtypes. Frontotemporal dementia, Semantic dementia and Primary progressive aphasia (Schulte-Overberg 2008:7).

Every subtype is marked by an insidious beginning with a progressive development. The average age of people diagnosed with a form of frontotemporal lobar degeneration lies between forty-five and sixty-five years (Ibach 2006:8-9).

Primary progressive aphasia is a progressive disorder, which was first described by Arnold Pick in 1890 (Gorno-Tempini, Hillis, et al. 2011). The aphasia is caused by different impacts on the brain, because of which, atrophy[1] forms on parts of the brain, which are responsible for language. Those impacts vary between stroke, traumatic brain injury, infection (Mandell 2002:1) and neurodegenerative diseases, such as Alzheimer's disease or Frontotemporal lobar degeneration (N.U. Primary Progressive Aphasia). The impairments cause a progressive dissolution of language function, that gets progressively worse in the course of the illness (Mesulam 2000:12). This gets caused by degeneration in parts of the brain responsible for speech and language, the so called language network (Rader). People with the average age of fifty years to sixty years old are usually the patients, that are getting diagnosed with primary progressive aphasia (Hallowell 2017:205).

The left hemisphere of the brain is the one dominant for language function and it is the location of the language network. The right hemisphere is rarely impaired, when it comes to Primary progressive aphasia patients (Mesulam 2001).

“In several PPA patients with marked left hemisphere hypometabolism, the metabolic state of the contralateral right hemisphere remains within normal range.”(Mesulam 2000:455)

The aphasia starts out barely noticeable, as a difficulty in thinking of common words in spoken or written form. The symptoms then worsen to slow or halting speech, decreased use of language, word-finding hesitations, substitution of words and also difficulty in understanding or following conversations, despite no lack of hearing ability. The symptoms differ in every case and never are exactly the same. First, the memory, reasoning and visual perception are not impacted, and the patients diagnosed with PPA are able to function normally in their daily routines and to live independently (Rader). When diagnosed, other mental faculties are not impaired, for at least the first two years of the disease. In some cases, the patients only impairment is the aphasia, for up to five to ten years (Mesulam 2000:455).

There are three clinical variants of Primary progressive aphasia, which the patients are divided into after being diagnosed: Nonfluent/agrammatic variant PPA, Semantic variant PPA and Logopenic variant PPA.

Those three subtypes got identified by a group of clinicians in the time span from 2006 to 2009. They used video presentations of twelve Primary progressive aphasia patients. The group rated the patients with a list of seventeen speech and language features and each clinician determined the presents of the specific language functions (Gorno-Tempini, Hillis, et al. 2011). The evaluations produced the results of three clinical presentations of PPA, which are most applicable at the early stages of the aphasia and are only the most common presentations of PPA (Gorno-Tempini, Hillis, et al. 2011), so not every single case of Primary progressive aphasia will fit into those specific three symptom groups. Those patients are described as ,,PPA unclassifiable'', but in later progress of the disease they may become assignable to one of the classifications (Gorno-Tempini, Hillis, et al. 2011).

3. Language impairments and the affected parts of the brain of Primary progressive aphasia patients

The language network is located in the left hemisphere of the brain, in the frontal, temporal and parietal lobes (Abbott 2016). Especially six left hemisphere regions are activated by PPA, including the left posterior[2] fusiform gyrus, which is part of the temporal lobe, the posterior superior[3] temporal region, also known as Wernicke's area, the inferior[4] parietal lobule, the intraparietal sulcus, the ventral premotor cortex and the inferior frontal gyrus, also known as Broca's area (Sreepadma, Mesulam, et al. 2007).

The language impairment varies in every patient. A few of the most common impairments are word-finding difficulties, difficulty in understanding the meaning of words and also object naming difficulties. The speech of a patient gets categorized as either fluent or as nonfluent. Fluent aphasia leaves the patient with nearly intact articulation and word flow (Mesulam 2003), whereas nonfluent aphasia expresses itself, amongst other things, through effortful speech and agrammatism in language production (Gorno-Tempini, Hillis, et al. 2011). “Agrammatism denotes inappropriate word order and the misuse of word endings, prepositions, pronouns, conjunctions, and verb tenses.”(Mesulam 2003)

Mesulam calls anomia the single most common sign for PPA. Anomia gets described as the “inability to retrieve the right word in conversation or to name objects.”(Mesulam 2003) Anomia gets diagnosed by testing the affected person, asking them to name geometric shapes, body parts and commonly known objects. Many patients experience a gradual intensification of word-finding deficits in an anomic stage (Mesulam 2003).

The language network is located in the left hemisphere of the brain. It includes the Broca's area and the Wernicke's area. Paul Broca discovered the area which is responsible for phonetic production, after he did a postmortem examination of the brain of a patient with speech disorder. Near the lateral sulcus[5], he found a great lesion in the left frontal lobe, which he then declared as responsible (Mayer). The Broca's area is located within the inferior and middle gyri of the left frontal lobe. The function of this particular area is to generate articulatory sequences and to form statements with proper phonology and syntax. Its dysfunction would lead to difficulties with articulation, word order, grammar and lexical retrieval (Mesulam 2001).

Carl Wernicke discovered, that the receptive aspect, like the speech comprehension, is also part of the language system. The area responsible for the speech comprehension is located near the parietal lobe (Mayer), at the left temporoparietal junction (Mesulam 2001). It is responsible for “linking the sensory pattern of words to the distributed associations that encode their meaning.”(Mesulam 2001) If it dysfunctions, the patient struggles with the comprehension of words and the translation of thoughts into words (Mesulam 2001).

Also active in language impairment are the surrounding areas of frontal, parietal and temporal cortex. Those areas often show atrophy or decreased blood flow. Metabolic dysfunction and atrophy in perisylvian regions, also including the left inferior frontal cortex, are seen in patients with nonfluent aphasia and intact language comprehension. On the other hand, metabolic dysfunction and atrophy are found in the middle, inferior and polar regions of the temporal lobe, by patients diagnosed with fluent aphasia and comprehension deficits (Mesulam 2003).

Mesulam, Thompson, Weintraub and Rogalski wrote an article in the magazine “A Journal of Neurology” (Mesulam, et al. 2015), which deals with a study, testing sentence comprehension and word comprehension of seventy-two patients with diagnosed PPA, caused by neurodegenerative diseases. The test results show, that impaired sentence comprehension is associated with atrophy in the left supramarginal and angular gyri, which are posterior parts of the Wernicke area, inferior frontal gyrus, which is the Broca's area, dorsal frontal cortex and anterior[6] orbifrontal cortex. If those parts of the brain are affected, the patients word comprehension is relatively intact. Also, the patients show no atrophy in the temporal pole (Mesulam, et al. 2015). Impaired word comprehension gets associated with atrophy in the left anterior temporal lobe, including its polar component and temporal pole. “It appears, then, that anterior temporal lobe neuronal loss causes major word comprehension impairments only if it extends anteriorly all the way into the polar region.”(Mesulam, et al. 2015) Patients with the most severe comprehension impairments also showed severe object naming abnormalities, but their sentence comprehension was almost intact. The results showed, that the territory assigned to Wernicke's area does not impair single word comprehension, when infested with atrophy (Mesulam, et al. 2015).

[...]


[1] Weakening of parts of the body, in this case parts of the brain, by decreasing in size or completely wasting away (McFerran 2008:42)

[2] Refers to the axes. Posterior labels the horizontal axis, which is located towards the back of the brain (N.U. Ways to view the brain).

[3] Is the vertical axis, located more towards the top of the brain (N.U. Ways to view the brain).

[4] Is the vertical axis, located more towards the bottom of the brain (N.U. Ways to view the brain).

[5] The lateral sulcus is a fissure, which separates the frontal lobe and the temporal lobe, also called the sylvian fissure (Griffiths 2010:7-34).

[6] Refers to the horizontal axis, located in the front of the brain (N.U. Ways to view the brain).

Details

Seiten
17
Jahr
2018
ISBN (eBook)
9783668986480
ISBN (Buch)
9783668986497
Sprache
Englisch
Katalognummer
v493030
Institution / Hochschule
Universität zu Köln
Note
2,3
Schlagworte
primary

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Titel: Primary progressive aphasia and the parts of the brain affected