Communication, Language and Speech Deficits in Dementia

Communication, language and speech deficits in dementia

Nasios G, MD, PhD

Department of Speech and Language Therapy, TEI of Epirus, Ioannina, GREECE

Summary

Communication disorders, especially aphasia, is a core characteristic in dementias, but its qualitative nature and severity vary substantially as functions of disease process and localization. These disorders are now recognized as one of the strongest predictors for discriminating among dementia subtypes. Language assessments in dementias help in differentiating different subtypes, staging severity, providing a unique understanding of the evolution and progression of deterioration, correlating different clinical profiles to different brain pathologies and designing therapeutic interventions. It is rather clear that differential diagnosis in dementias will rely on identification of these disorders, as it is already the fact for the different subtypes of frotontemporal dementias and primary progressive aphasias. Knowledge of these clinical profiles may be useful in educating patients, families and caregivers regarding the cognitive-linguistic behavioral deficits expected from onset to progression of the disease, and the possible therapeutic interventions.

Review

Aphasia represents an acquired disorder of language comprehension, production, and/or symbolic knowledge (1). Given this broad definition, aphasia is evident across all of the dementias, and indeed is included in formal diagnostic criteria across them. (2,3). Alzheimer’s first patient was also aphasic, suggesting that language impairment is a component of Alzheimer’s disease (AD). Nonetheless, aphasia as a prominent feature of AD has been emphasized only recently. Despite the ubiquity of aphasia in dementia, its qualitative nature and severity vary substantially as functions of disease process and localization. (4) ICD-10, DSM-IV-TR, and the NINCDS criteria for diagnosing dementias lack specificity in discriminating among the many dementia variants. Differential diagnosis of dementias is complicated by a high degree of overlap in the initial presenting symptoms across dementia subtypes. Communication disorders seem to be among the strongest predictors for discriminating among dementia subtypes. As such, evaluation of speech and language disorders could make an important contribution to dementia diagnosis and its ongoing management. This review goes through the disorders of speech and language in Alzheimer’s disease (AD),Vascular dementia(s) (VaDs), Frontotemporal dementias (FTDs), Parkinson’s disease dementia (PDD), Lewy Body Disease Dementia (LBD), and Primary progressive aphasias (PPAs Emphasis is given in FTDs’ and PPAs’, as they represent unique paradigms in which recent research advances broaden our knowledge on correlations among different speech and language impairments with different clinical profiles and different neuropathological findings.

Alzheimer’s disease (AD)

Language decline is apparent even in the early stage of the disease. (5) All AD patients have aphasia. Its severity correlates with increasing severity of dementia. (6) AD accelerates this decline regardless of patients’ age, in respect with the decline in normal aging or in Mild Cognitive impairment. (7) The pattern of the language disorder is different in AD than in VADs (8, 9), or in FTDs (10). In a recent study, Karrasch M et al (11) showed that an incidental memory modification of the Boston Naming Test could be used in clinical settings especially to differentiate between normal aging and mild AD.Golden Z et al, (12) conducted a study to examine the differences in neuropsychological test performance between groups with Alzheimer's and vascular dementia. They showed that the two groups did differ on more basic tests and all the memory tests, but not on the more complex tests.

In a longitudinal study of language decline in Alzheimer’s disease and frontotemporal dementia (10), Blair et al showed that FTD-fv and PPA patients showed a faster language decline than AD patients. A general conclusion was that longitudinal language assessment provides a unique understanding of the evolution and progression of language deterioration in various dementias.

Vascular Dementias (VaDs)

VaDs represent a heterogeneous group of dementias associated with cerebrovascular damage (13). VaD can evolve due to multiple cortical or subcortical strokes, cerebral hypoxemia, aneurysm, small vessel ischemic disease and genetic cerebrovascular disease.Phenotypic heterogeneity is further increased by the fact almost half of all VaD patients have mixed vascular and Alzheimer’s disease pathologies (14,15,16). ICD-10 identifies the following VaD variants: 1) VaD acute onset, 2) Multi-infarct dementia, 3) Subcortical vascular dementia, 4) Mixed subcortical and cortical vascular dementia, 5) Other VaD, 6) VaD unspecified (16).

Frontotemporal dementia, FTD

FTD is the second most common dementia after Alzheimer’s disease below the age of 65 years and it is characterized initially by progressive atrophy of regions of frontal and temporal cortex. There are at least three distinct FTD phenotypes, each having a particular distribution of cortical damage : a. Progressive Nonfluent Aphasia (PNFA),b. Semantic Dementia (SD), and

c. Frontal variant FTD, (FvFTD)

Progressive Nonfluent Aphasia is characterized by nonfluent speech (3), combined with agrammatism, phonemic paraphasias, and anomia, with relatively preserved episodic memory, visuospatial functioning, and temporal orientation (3, 17). PNFA reflects asymmetric damage to left posterior inferior frontal cortex, including the anterior insula, basal ganglia, left inferior and middle frontal gyri, dorsal, premotor and supplementary motor cortices (18). The distribution of left hemisphere damage in PNFA corresponds to that commonly seen in nonfluent stroke aphasia (e.g., Broca’s Aphasia). Direct comparison between nonfluent stroke aphasia and PNFA showed that the extent of syntactic loss in production (i.e., agrammatism) was worse in the stroke aphasia group relative to PNFA (19).

In Semantic Dementia loss of meaning is a core diagnostic feature that affects both language production and comprehension. Other core features of SD include empty spontaneous speech, semantic paraphasias, and a perceptual disorder characterized by prosopagnosia and/or associative visual agnosia (3). For a diagnosis of SD, patients must also show relatively preserved perceptual matching abilities (e.g., pure tones, pictures of different people, nonsense objects), intact single word repetition, and an ability to read aloud orthographically regular words (3). SD patients experience profound communicative impairment. On structural imaging patients with SD show circumscribed atrophy affecting anterior, lateral, and ventral temporal lobe structures with relative sparing of the medial temporal lobe (20).

Frontal variant FTD, is characterized by decreased speech output, reduced conversational initiation, echolalia, and changes in the pragmatics of conversation. In FvFTD, cortical atrophy affects inferior, anterior regions of the frontal lobe (i.e., orbitofrontal cortex) (21,22). Unlike PNFA and SD, individuals with FvFTD exhibit early changes in personality, organization, and attention (3, 20). Core diagnostic criteria for FvFTD include a gradual decline in social conduct (i.e., inappropriate jokes, risk taking, hypersexuality), with loss of insight and early emotional blunting (3).

Semantic dementia is distinguishable from other presentations of FTD and AD, not only by fluent speech and impaired comprehension without loss of episodic memory, syntax, and phonology but also by empty speech with thematic perseverations, semantic paraphasias, and poor category fluency (23). Questioning the meaning of words is an important diagnostic clue not seen in other groups, and behavior change is prevalent.

Parkinson’s disease dementia (PDD)
As PD progresses 70 to 80% of individuals convert to PD with dementia (PDD) and this conversion limits survival duration to aprox. 5 years (similar to LBD) (24,25). Predictors of survival duration in PDD are among others fluctuating cognition, and degree of concurrent Alzheimer’s disease neuropathology. Core diagnostic criteria for PDD include an established diagnosis of PD and impairment in at least two of the following four domains: 1) attention, 2) executive functioning, 3) visuospatial processing, and 4) verbal free recall. Communication deficits include impaired concept formation, perseveration, and reduced verbal fluency (24). Reduced action word (i.e., verb) fluency predicts conversion from PD to PDD (26). As PDD progresses, the cognitive and language deficits become more pronounced.

Lewy Body Disease Dementia (LBD)
Lewy Body Dementia (LBD) is a relatively new dementia classification with prevalence estimates varying from 15% to 35% of all dementia cases (25, 27). Diagnosis of LBD is based on presence of dementia as well as two of the following three features: fluctuating cognition, visual hallucinations, and movement disorder. Language disturbance in LBD is characterized by confabulation, incoherence, and perseveration during conversation, difficulty naming common objects, and a reduction in verbal fluency (28).

Primary Progressive Aphasia (PPA)

Mesulam (1982) proposed this term to describe a slowly progressive language impairment that persists for a period of at least two years without dementia (29). Further diagnostic criteria for PPA include an insidious onset and gradual worsening of language (syntax, naming, word finding, word comprehension) in the absence of other causes of aphasia. PPA has been described as a “language-based dementia”(32) and as “slowly progressive aphasia without generalized dementia”(29) and other amnesic, personality, or dysexecutive deficits that impair activities of daily living (30,31). PPA patients are now divided in 3 main variants based on specific speech and language features characteristic of each subtype (33):

a. nonfluent (nfvPPA), b. semantic (svPPA), and c. logopenic (lvPPA)

PPA – nonfluent variant (nfvPPA)

Initially almost all individuals present with increasing anomia and word finding difficulties (34-36). In this respect patients are not much different from aphasics with AD, except they have relatively preserved memory and non-verbal cognition (37). As the disease progresses, speech fluency decreases. Subjects experience progressive problems with sentence construction and syntax so that their speech becomes agrammatic and difficult to understand (38, 39, 40). Agrammatism is among the core features of nfvPPA (33), and may resemble Broca’s aphasia (39), is typically less severe than that seen after stroke (35,36). Many patients with nfvPPA may be classified as having conduction aphasia characterized due to their poor repetition with intact auditory comprehension and fluent yet paraphasic speech (34).

PPA – semantic variant (svPPA)

Semantic variant PPA is the second most extensively described variety of progressive aphasia. This condition has been usually characterized by a progressive and multimodal loss of semantic knowledge (41,42). Patients progressively lose the meaning of words, but are fluent and repeat well, resembling to “transcortical sensory aphasia”. As the disease progresses, their speech is still considered fluent, but characterized by semantic jargon, frequently unrelated to the questions being asked or the topic discussed (23). Severe, progressive anomia and markedly impaired comprehension of single words, with patients themselves frequently asking the meaning of words, usually nouns, are the hallmark of svPPA (10, 23, 31, 32, 33). Semantic variant is strongly associated with FvFTD, and so early behavioral and personality changes are almost always seen in svPPA patients (23,31,32,43).

PPA – logopenic variant (lvPPA or PPA-L)

Logopenic variant PPA, or logopenic primary progressive aphasia has been only recently described as a distinct form of PPA (41). Although the speech output of both nfvPPA and lvPPA is slowed, with frequent word-finding pauses and phonemic paraphasias, patients with the logopenic type do not present with agrammatism, impaired motor control of speech, and aprosodia (33, 44, 45). Given that patients typically have severe difficulty repeating sentences and longer phrases, while reproduction of short, single words remaining spared, the core impairment that underlies most language deficits in lvPPA has been suggested to be a phonological short-term memory deficit (44). As the lvPPA progresses, problems with single-word comprehension and deficits with sentence-level grammar emerge. Patients with lvPPA frequently have episodic memory impairment (37) and poor arithmetic abilities (40), and so their clinical picture resembles AD. Behavioral abnormalities may be present, with apathy, anxiety, irritability, and agitation (43).

Rogalski et al, investigatetd the progression of language decline and cortical atrophy in subtypes of primary progressive aphasia (46). Neuropsychological language performance patterns lost the sharp distinctions that differentiated one PPA variant from another. Peak atrophy sites spread beyond the initial distinctive locations that characterized each of the 3 subtypes and displayed a more convergent distribution encompassing all 3 major components of the language network: the inferior frontal gyrus, the temporoparietal junction, and lateral temporal cortex.

Conclusions

Evaluation of speech and language disorders, in demented population proved to be very helpful in differentiating dementias’ subtypes, as the examples of frotontemporal dementias and primary progressive aphasias had showed. Furthermore this provides evidence for staging disease severity, tracking progression of deterioration, and conducting interventions. Designing and validating proper clinical scales for this evaluation will improve our clinical practice both for diagnosing and managing patients with dementia. Towards a standardized and cost-effective neuropsychological rehabilitation the role of speech and language therapists should be central.

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