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Characterizing a neurodegenerative syndrome: primary progressive apraxia of speech.

ABSTRACT: 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.

SUBMITTER: Josephs KA

PROVIDER: S-EPMC3338923 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Purpose Individuals with primary progressive apraxia of speech (PPAOS) have apraxia of speech (AOS) in which disruptions in articulation or prosody predominate the speech pattern, referred to, respectively, as phonetic or prosodic subtypes. Many develop aphasia and/or dysarthria. Past research has demonstrated that simple temporal acoustic measures are sensitive to the presence of AOS. The aim of this study was to describe the change in temporal acoustic measures over time and assess if specific patterns of AOS or co-occurring aphasia or dysarthria impact the rate of change over time. Method Durations for multiple productions of the words cat, catnip, catapult, and catastrophe, in an imitative speech task, were recorded for 73 patients, with two to six visits each. A linear mixed-effects model was used to assess the cross-sectional differences and longitudinal influence of AOS subtype and presence of aphasia/dysarthria on speech rate. Pearson correlations were calculated between rate measures and performance on other clinical measures. Results Cross-sectionally, patients with prosodic-predominant PPAOS produced words more slowly than those with phonetic-predominant PPAOS. Patients with either aphasia or dysarthria produced words more slowly than those without. Longitudinally, the speech rate of patients with phonetic-predominant PPAOS had a reduction of 0.5 syllables per second per year. Patients with prosodic-predominant AOS changed less quickly, as did those who developed aphasia. Dysarthria did not impact rate of change. There were strong associations between speech rate measures and other clinical indices of speech and language functioning. Conclusion Simple temporal acoustic measures may reflect the subtype of AOS (phonetic or prosodic predominant), serve as an index of progression of AOS, and inform prognostication relative to the presenting combination of speech and language features. Supplemental Material https://doi.org/10.23641/asha.13564724.

Project description:Apraxia of speech is a motor speech disorder thought to result from impaired planning or programming of articulatory movements. It can be the initial or only manifestation of a degenerative disease, termed primary progressive apraxia of speech (PPAOS). The aim of this study was to use task-free functional magnetic resonance imaging (fMRI) to assess large-scale brain network pathophysiology in PPAOS. Twenty-two PPAOS participants were identified from a prospective cohort of degenerative speech and language disorders patients. All participants had a comprehensive, standardized evaluation including an evaluation by a speech-language pathologist, examination by a behavioral neurologist and a multimodal imaging protocol which included a task-free fMRI sequence. PPAOS participants were age and sex matched to amyloid-negative, cognitively normal participants with a 1:2 ratio. We chose a set of hypothesis driven, predefined intrinsic connectivity networks (ICNs) from a large, out of sample independent component analysis and then used them to initialize a spatiotemporal dual regression to estimate participant level connectivity within these ICNs. Specifically, we evaluated connectivity within the speech and language, face and hand sensorimotor, left working memory, salience, superior parietal, supramarginal, insular and deep gray ICNs in a multivariate manner. The spatial maps for each ICN were then compared between PPAOS and control participants. We used clinical measures of apraxia of speech severity to assess for clinical-connectivity correlations for regions found to differ between PPAOS and control participants. Compared to controls, PPAOS participants had reduced connectivity of the right supplementary motor area and left posterior temporal gyrus to the rest of the speech and language ICN. The connectivity of the right supplementary motor area correlated negatively with an articulatory error score. PPAOS participants also had reduced connectivity of the left supplementary motor area to the face sensorimotor ICN, between the left lateral prefrontal cortex and the salience ICN and between the left temporal-occipital junction and the left working memory ICN. The latter connectivity correlated with the apraxia of speech severity rating scale, although the finding did not survive correction for multiple comparisons. Increased connectivity was noted in PPAOS participants between the dorsal posterior cingulate and the left working memory ICN. Our results support the importance of the supplementary motor area in the pathophysiology of PPAOS, which appears to be disconnected from speech and language regions. Supplementary motor area connectivity may serve as a biomarker of degenerative apraxia of speech severity.

Project description:The consensus criteria for the diagnosis and classification of primary progressive aphasia (PPA) have served as an important tool in studying this group of disorders. However, a large proportion of patients remain unclassifiable whilst others simultaneously meet criteria for multiple subtypes. We prospectively evaluated a large cohort of patients with degenerative aphasia and/or apraxia of speech using multidisciplinary clinical assessments and multimodal imaging. Blinded diagnoses were made using operational definitions with important differences compared to the consensus criteria. Of the 130 included patients, 40 were diagnosed with progressive apraxia of speech (PAOS), 12 with progressive agrammatic aphasia, 9 with semantic dementia, 52 with logopenic progressive aphasia, and 4 with progressive fluent aphasia, while 13 were unclassified. The PAOS and progressive fluent aphasia groups were least impaired. Performance on repetition and sentence comprehension was especially poor in the logopenic group. The semantic and progressive fluent aphasia groups had prominent anomia, but only semantic subjects had loss of word meaning and object knowledge. Distinct patterns of grey matter loss and white matter changes were found in all groups compared to controls. PAOS subjects had bilateral frontal grey matter loss, including the premotor and supplementary motor areas, and bilateral frontal white matter involvement. The agrammatic group had more widespread, predominantly left sided grey matter loss and white matter abnormalities. Semantic subjects had bitemporal grey matter loss and white matter changes, including the uncinate and inferior occipitofrontal fasciculi, whereas progressive fluent subjects only had left sided temporal involvement. Logopenic subjects had diffuse and bilateral grey matter loss and diffusion tensor abnormalities, maximal in the posterior temporal region. A diagnosis of logopenic aphasia was strongly associated with being amyloid positive (46/52 positive). Our findings support consideration of an alternative way of identifying and categorizing subtypes of degenerative speech and language disorders.

Project description:Apraxia of speech is a motor speech disorder characterized by combinations of slow speaking rate, abnormal prosody, distorted sound substitutions, and trial-and-error articulatory movements. Apraxia of speech is due to abnormal planning and/or programming of speech production. It is referred to as primary progressive apraxia of speech (PPAOS) when it is the only symptom of a neurodegenerative condition. Past reports suggest an association of PPAOS with primary 4-repeat (4R) tau (e.g., progressive supranuclear palsy, corticobasal degeneration), rather than amyloid, pathology. The goal of the current study was to investigate the distribution of tau tracer uptake using [18F]AV-1451 positron emission tomography (PET) imaging in patients with PPAOS. Fourteen PPAOS patients underwent [18F]AV-1451 PET (tau-PET) imaging, [C11] Pittsburgh Compound B (PiB) PET and structural MRI and were matched 3:1 by age and sex to 42 cognitively normal controls. Tau-PET uptake was assessed at the region-of-interest (ROI) level and at the voxel-level. The PPAOS group (n = 14) showed increased tau-PET uptake in the precentral gyrus, supplementary motor area and Broca's area compared to controls. To examine whether tau deposition in Broca's area was related to the presence of aphasia, we examined a subgroup of the PPAOS patients who had predominant apraxia of speech, with concomitant aphasia (PPAOSa; n = 7). The PPAOSa patients showed tau-PET uptake in the same regions as the whole group. However, the remaining seven patients who did not have aphasia showed uptake only in superior premotor and precentral cortices, with no uptake observed in Broca's area. This cross-sectional study demonstrates that elevated tau tracer uptake is observed using [18F]AV-1451 in PPAOS. Further, it appears that [18F]AV-1451 is sensitive to the regional distribution of tau deposition in different stages of PPAOS, given the relationship between tau signal in Broca's area and the presence of aphasia.

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Characterizing a neurodegenerative syndrome: primary progressive apraxia of speech.

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