Apraxia of speech (AOS) can be caused by neurodegenerative disease and sometimes is its presenting sign (i.e., primary progressive apraxia of speech, PPAOS). During the last several decades, our ...understanding of PPAOS has evolved from clinical recognition to a fuller understanding of its core and associated clinical features, its distinction from but relationship with primary progressive aphasia, its temporal course and eventual progression to include other neurological deficits, and its neuroimaging correlates and underlying pathology.
This paper provides a comprehensive summary of the literature that has built the current knowledge base about PPAOS and progressive AOS as it co-occurs with progressive aphasia. It reviews the history of its emergence as a recognized syndrome; its relationship with the agrammatic/nonfluent variant of primary progressive aphasia; its salient perceptual features and subtypes; the acoustic and structural/physiological imaging measures that index its presence, severity, and distinction from aphasia; and principles and available data regarding its management and care.
A broad summary of what is known about AOS as a manifestation of neurodegenerative disease.
Primary progressive apraxia of speech is a recognizable syndrome that can be distinguished from other neurodegenerative conditions that affect speech and language.
Abbreviations
AAC = augmentative and alternative communication; AES = Articulatory Error Score; ALS = amyotrophic lateral sclerosis; AOS = apraxia of speech; AOS+PAA = AOS plus the agrammatic/nonfluent variant of PPA; ASRS = Apraxia of Speech Rating Scale; CBD = corticobasal degeneration; CBS = corticobasal syndrome; DAOS = dominant AOS - aphasia present but AOS more severe; MSD = motor speech disorders; nfPPA = nonfluent variant of PPA, with or without AOS; NVOA = nonverbal oral apraxia; PAOS = progressive AOS, with or without aphasia; PAA = agrammatic variant of PPA, without AOS; PPA = primary progressive aphasia, with or without AOS; PPAOS = primary progressive AOS - no aphasia; PSP = progressive supranuclear palsy; SMA = supplementary motor area.
The logopenic variant of primary progressive aphasia is an atypical clinical variant of Alzheimer's disease which is typically characterized by left temporoparietal atrophy on magnetic resonance ...imaging and hypometabolism on F-18 fluorodeoxyglucose positron emission tomography. We aimed to characterize and compare patterns of atrophy and hypometabolism in logopenic primary progressive aphasia, and determine which brain regions and imaging modality best differentiates logopenic primary progressive aphasia from typical dementia of the Alzheimer's type.
A total of 27 logopenic primary progressive aphasia subjects underwent fluorodeoxyglucose positron emission tomography and volumetric magnetic resonance imaging. These subjects were matched to 27 controls and 27 subjects with dementia of the Alzheimer's type. Patterns of atrophy and hypometabolism were assessed at the voxel and region-level using Statistical Parametric Mapping. Penalized logistic regression analysis was used to determine what combinations of regions best discriminate between groups.
Atrophy and hypometabolism was observed in lateral temporoparietal and medial parietal lobes, left greater than right, and left frontal lobe in the logopenic group. The logopenic group showed greater left inferior, middle and superior lateral temporal atrophy (inferior p = 0.02; middle p = 0.007, superior p = 0.002) and hypometabolism (inferior p = 0.006, middle p = 0.002, superior p = 0.001), and less right medial temporal atrophy (p = 0.02) and hypometabolism (p<0.001), and right posterior cingulate hypometabolism (p<0.001) than dementia of the Alzheimer's type. An age-adjusted penalized logistic model incorporating atrophy and hypometabolism achieved excellent discrimination (area under the receiver operator characteristic curve = 0.89) between logopenic and dementia of the Alzheimer's type subjects, with optimal discrimination achieved using right medial temporal and posterior cingulate hypometabolism, left inferior, middle and superior temporal hypometabolism, and left superior temporal volume.
Patterns of atrophy and hypometabolism both differ between logopenic primary progressive aphasia and dementia of the Alzheimer's type and both modalities provide excellent discrimination between groups.
To determine how well the consensus criteria could classify subjects with primary progressive aphasia (PPA) using a quantitative speech and language battery that matches the test descriptions ...provided by the consensus criteria.
A total of 105 participants with a neurodegenerative speech and language disorder were prospectively recruited and underwent neurologic, neuropsychological, and speech and language testing and MRI in this case-control study. Twenty-one participants with apraxia of speech without aphasia served as controls. Select tests from the speech and language battery were chosen for application of consensus criteria and cutoffs were employed to determine syndromic classification. Hierarchical cluster analysis was used to examine participants who could not be classified.
Of the 84 participants, 58 (69%) could be classified as agrammatic (27%), semantic (7%), or logopenic (35%) variants of PPA. The remaining 31% of participants could not be classified. Of the unclassifiable participants, 2 clusters were identified. The speech and language profile of the first cluster resembled mild logopenic PPA and the second cluster semantic PPA. Gray matter patterns of loss of these 2 clusters of unclassified participants also resembled mild logopenic and semantic variants.
Quantitative application of consensus PPA criteria yields the 3 syndromic variants but leaves a large proportion unclassified. Therefore, the current consensus criteria need to be modified in order to improve sensitivity.
Highlights • The ASRS quantifies the frequency/severity of the characteristics associated with AOS. • ASRS correlates with clinical diagnosis and severity of AOS. • Overall intra-judge and ...inter-judge reliability is acceptable. • Sensitivity and specificity of the ASRS are acceptable.
•Phonetic PPAOS is characterized predominantly by distorted sound substitutions.•Prosodic PPAOS is characterized predominantly by slow, segmented speech.•The predominant clinical characteristics of ...PPAOS can be quantified reliably.•PPAOS subtypes are associated with distinct imaging patterns on MRI, DTI, and FDG-PET.
Primary progressive apraxia of speech (PPAOS) is a clinical syndrome in which apraxia of speech is the initial indication of neurodegenerative disease. Prior studies of PPAOS have identified hypometabolism, grey matter atrophy, and white matter tract degeneration in the frontal gyri, precentral cortex, and supplementary motor area (SMA). Recent clinical observations suggest two distinct subtypes of PPAOS may exist. Phonetic PPAOS is characterized predominantly by distorted sound substitutions. Prosodic PPAOS is characterized predominantly by slow, segmented speech. Demographic, clinical, and neuroimaging data (MRI, DTI, and FDG-PET) were analyzed to validate these subtypes and explore anatomic correlates. The Phonetic subtype demonstrated bilateral involvement of the SMA, precentral gyrus, and cerebellar crus. The Prosodic subtype demonstrated more focal involvement in the SMA and right superior cerebellar peduncle. The findings provide converging evidence that differences in the reliably determined predominant clinical characteristics of AOS are associated with distinct imaging patterns, independent of severity.
We assessed whether clinical and imaging features of subjects with apraxia of speech (AOS) more severe than aphasia (dominant AOS) are more similar to agrammatic primary progressive aphasia (agPPA) ...or to primary progressive AOS (PPAOS).
Sixty-seven subjects (PPAOS = 18, dominant AOS = 10, agPPA = 9, age-matched controls = 30) who all had volumetric MRI, diffusion tensor imaging, F18-fluorodeoxyglucose and C11-labeled Pittsburgh compound B (PiB)-PET scanning, as well as neurologic and speech and language assessments, were included in this case-control study. AOS was classified as either type 1, predominated by sound distortions and distorted sound substitutions, or type 2, predominated by syllabically segmented prosodic speech patterns.
The dominant AOS subjects most often had AOS type 2, similar to PPAOS. In contrast, agPPA subjects most often had type 1 (p = 0.01). Both dominant AOS and PPAOS showed focal imaging abnormalities in premotor cortex, whereas agPPA showed widespread involvement affecting premotor, prefrontal, temporal and parietal lobes, caudate, and insula. Only the dominant AOS and PPAOS groups showed midbrain atrophy compared with controls. No differences were observed in PiB binding across all 3 groups, with the majority being PiB negative.
These results suggest that dominant AOS is more similar to PPAOS than agPPA, with dominant AOS and PPAOS exhibiting a clinically distinguishable subtype of progressive AOS compared with agPPA.
Primary progressive apraxia of speech is a recently described neurodegenerative disorder in which patients present with an isolated apraxia of speech and show focal degeneration of superior premotor ...cortex. Little is known about how these individuals progress over time, making it difficult to provide prognostic estimates. Thirteen subjects with primary progressive apraxia of speech underwent two serial comprehensive clinical and neuroimaging evaluations 2.4 years apart median age of onset = 67 years (range: 49-76), seven females. All underwent detailed speech and language, neurological and neuropsychological assessments, and magnetic resonance imaging, diffusion tensor imaging and (18)F-fluorodeoxyglucose positron emission tomography at both baseline and follow-up. Rates of change of whole brain, ventricle, and midbrain volumes were calculated using the boundary-shift integral and atlas-based parcellation, and rates of regional grey matter atrophy were assessed using tensor-based morphometry. White matter tract degeneration was assessed on diffusion-tensor imaging at each time-point. Patterns of hypometabolism were assessed at the single subject-level. Neuroimaging findings were compared with a cohort of 20 age, gender, and scan-interval matched healthy controls. All subjects developed extrapyramidal signs. In eight subjects the apraxia of speech remained the predominant feature. In the other five there was a striking progression of symptoms that had evolved into a progressive supranuclear palsy-like syndrome; they showed a combination of severe parkinsonism, near mutism, dysphagia with choking, vertical supranuclear gaze palsy or slowing, balance difficulties with falls and urinary incontinence, and one was wheelchair bound. Rates of whole brain atrophy (1.5% per year; controls = 0.4% per year), ventricular expansion (8.0% per year; controls = 3.3% per year) and midbrain atrophy (1.5% per year; controls = 0.1% per year) were elevated (P ≤ 0.001) in all 13, compared to controls. Increased rates of brain atrophy over time were observed throughout the premotor cortex, as well as prefrontal cortex, motor cortex, basal ganglia and midbrain, while white matter tract degeneration spread into the splenium of the corpus callosum and motor cortex white matter. Hypometabolism progressed over time in almost all subjects. These findings demonstrate that some subjects with primary progressive apraxia of speech will rapidly evolve and develop a devastating progressive supranuclear palsy-like syndrome ∼ 5 years after onset, perhaps related to progressive involvement of neocortex, basal ganglia and midbrain. These findings help improve our understanding of primary progressive apraxia of speech and provide some important prognostic guidelines.
Apraxia of speech is a disorder of speech motor planning and/or programming that is distinguishable from aphasia and dysarthria. It most commonly results from vascular insults but can occur in ...degenerative diseases where it has typically been subsumed under aphasia, or it occurs in the context of more widespread neurodegeneration. The aim of this study was to determine whether apraxia of speech can present as an isolated sign of neurodegenerative disease. Between July 2010 and July 2011, 37 subjects with a neurodegenerative speech and language disorder were prospectively recruited and underwent detailed speech and language, neurological, neuropsychological and neuroimaging testing. The neuroimaging battery included 3.0 tesla volumetric head magnetic resonance imaging, (18)F-fluorodeoxyglucose and (11)C Pittsburg compound B positron emission tomography scanning. Twelve subjects were identified as having apraxia of speech without any signs of aphasia based on a comprehensive battery of language tests; hence, none met criteria for primary progressive aphasia. These subjects with primary progressive apraxia of speech included eight females and four males, with a mean age of onset of 73 years (range: 49-82). There were no specific additional shared patterns of neurological or neuropsychological impairment in the subjects with primary progressive apraxia of speech, but there was individual variability. Some subjects, for example, had mild features of behavioural change, executive dysfunction, limb apraxia or Parkinsonism. Voxel-based morphometry of grey matter revealed focal atrophy of superior lateral premotor cortex and supplementary motor area. Voxel-based morphometry of white matter showed volume loss in these same regions but with extension of loss involving the inferior premotor cortex and body of the corpus callosum. These same areas of white matter loss were observed with diffusion tensor imaging analysis, which also demonstrated reduced fractional anisotropy and increased mean diffusivity of the superior longitudinal fasciculus, particularly the premotor components. Statistical parametric mapping of the (18)F-fluorodeoxyglucose positron emission tomography scans revealed focal hypometabolism of superior lateral premotor cortex and supplementary motor area, although there was some variability across subjects noted with CortexID analysis. (11)C-Pittsburg compound B positron emission tomography binding was increased in only one of the 12 subjects, although it was unclear whether the increase was actually related to the primary progressive apraxia of speech. A syndrome characterized by progressive pure apraxia of speech clearly exists, with a neuroanatomic correlate of superior lateral premotor and supplementary motor atrophy, making this syndrome distinct from primary progressive aphasia.
Objective
The objective of this study was to describe clinical features, 18F‐fluorodeoxyglucose (FDG)‐positron emission tomography (PET) metabolism and digital pathology in patients with logopenic ...progressive aphasia (LPA) and pathologic diagnosis of diffuse Lewy body disease (DLBD) and compare to patients with LPA with other pathologies, as well as patients with classical features of probable dementia with Lewy bodies (pDLB).
Methods
This is a clinicopathologic case‐control study of 45 patients, including 20 prospectively recruited patients with LPA among whom 6 were diagnosed with LPA‐DLBD. We analyzed clinical features and compared FDG‐PET metabolism in LPA‐DLBD to an independent group of patients with clinical pDLB and regional α‐synuclein burden on digital pathology to a second independent group of autopsied patients with DLBD pathology and antemortem pDLB (DLB‐DLBD).
Results
All patients with LPA‐DLBD were men. Neurological, speech, and neuropsychological characteristics were similar across LPA‐DLBD, LPA‐Alzheimer's disease (LPA‐AD), and LPA‐frontotemporal lobar degeneration (LPA‐FTLD). Genetic screening of AD, DLBD, and FTLD linked genes were negative with the exception of APOE ε4 allele present in 83% of LPA‐DLBD patients. Seventy‐five percent of the patients with LPA‐DLBD showed a parietal‐dominant pattern of hy pometabolism; LPA‐FTLD – temporal‐dominant pattern, whereas LPA‐AD showed heterogeneous patterns of hypometabolism. LPA‐DLBD had more asymmetrical hypometabolism affecting frontal lobes, with relatively spared occipital lobe in the nondominantly affected hemisphere, compared to pDLB. LPA‐DLBD had minimal atrophy on gross brain examination, higher cortical Lewy body counts, and higher α‐synuclein burden in the middle frontal and inferior parietal cortices compared to DLB‐DLBD.
Interpretation
Whereas AD is the most frequent underlying pathology of LPA, DLBD can also be present and may contribute to the LPA phenotype possibly due to α‐synuclein‐associated functional impairment of the dominant parietal lobe. ANN NEUROL 2021;89:520–533
Converging evidence suggests a role for microglia-mediated neuroinflammation in Parkinson's disease (PD). Animal models of PD can serve as a platform to investigate the role of neuroinflammation in ...degeneration in PD. However, due to features of the previously available PD models, interpretations of the role of neuroinflammation as a contributor to or a consequence of neurodegeneration have remained elusive. In the present study, we investigated the temporal relationship of neuroinflammation in a model of synucleinopathy following intrastriatal injection of pre-formed alpha-synuclein fibrils (α-syn PFFS).
Male Fischer 344 rats (N = 114) received unilateral intrastriatal injections of α-syn PFFs, PBS, or rat serum albumin with cohorts euthanized at monthly intervals up to 6 months. Quantification of dopamine neurons, total neurons, phosphorylated α-syn (pS129) aggregates, major histocompatibility complex-II (MHC-II) antigen-presenting microglia, and ionized calcium-binding adaptor molecule-1 (Iba-1) immunoreactive microglial soma size was performed in the substantia nigra. In addition, the cortex and striatum were also examined for the presence of pS129 aggregates and MHC-II antigen-presenting microglia to compare the temporal patterns of pSyn accumulation and reactive microgliosis.
Intrastriatal injection of α-syn PFFs to rats resulted in widespread accumulation of phosphorylated α-syn inclusions in several areas that innervate the striatum followed by significant loss (~ 35%) of substantia nigra pars compacta dopamine neurons within 5-6 months. The peak magnitudes of α-syn inclusion formation, MHC-II expression, and reactive microglial morphology were all observed in the SN 2 months following injection and 3 months prior to nigral dopamine neuron loss. Surprisingly, MHC-II immunoreactivity in α-syn PFF injected rats was relatively limited during the later interval of degeneration. Moreover, we observed a significant correlation between substantia nigra pSyn inclusion load and number of microglia expressing MHC-II. In addition, we observed a similar relationship between α-syn inclusion load and number of microglia expressing MHC-II in cortical regions, but not in the striatum.
Our results demonstrate that increases in microglia displaying a reactive morphology and MHC-II expression occur in the substantia nigra in close association with peak numbers of pSyn inclusions, months prior to nigral dopamine neuron degeneration, and suggest that reactive microglia may contribute to vulnerability of SNc neurons to degeneration. The rat α-syn PFF model provides an opportunity to examine the innate immune response to accumulation of pathological α-syn in the context of normal levels of endogenous α-syn and provides insight into the earliest neuroinflammatory events in PD.
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