The evolution of parkinsonism in primary progressive apraxia of speech: A 6-year longitudinal study

Clinicopathologic and Neuroimaging Correlations of Nonverbal Oral Apraxia in Patients With Neurodegenerative Disease

BACKGROUND AND OBJECTIVES

Nonverbal oral apraxia (NVOA) is the inability to plan, sequence, and execute voluntary oromotor movements in the absence of weakness. In the context of neurodegenerative disease, it remains unclear whether it is linked to a specific underlying pathologic, clinical, or neuroimaging finding. Thus, we aimed to assess the clinicopathologic and neuroimaging associations of NVOA.

METHODS

We conducted a retrospective study of autopsy-confirmed patients previously assessed through an NVOA evaluation tool with a previously published cutpoint to screen for NVOA. We compared demographic and clinical characteristics and postmortem pathology between those who developed NVOA and those who did not. We also compared clinicopathologic characteristics in mild vs greater than mild NVOA and early vs late-emerging NVOA. SPM12 was used to assess patterns of gray matter loss in NVOA vs non-NVOA with age and sex included as covariates.

RESULTS

A total of 104 patients (median age at symptom onset 63 years, 43% female) were included in the study. 63 (60.6%) developed NVOA. NVOA appeared at a median of 4.3 years from symptom onset. 29% developed NVOA within the first 3 years. Primary progressive apraxia of speech and the nonfluent variant of primary progressive aphasia were the most common baseline diagnoses in the NVOA group while progressive supranuclear palsy (PSP) syndrome and logopenic progressive aphasia (LPA) were the most common in patients without NVOA. Atrophy of the left lateral and medial posterior frontal cortex was related to NVOA. The most common pathologies associated with NVOA were PSP (36.5%) and corticobasal degeneration (CBD) (33.3%). In patients without NVOA, PSP (26.8%) and other pathologies (26.8%) were the most frequent. 11% of patients with NVOA had persistently mild NVOA and were more likely to have baseline diagnoses of LPA, PSP syndrome, or semantic dementia. The most frequent pathologies in this group were Alzheimer disease and PSP. The pathologic associations of greater than mild NVOA were CBD and PSP.

DISCUSSION

NVOA is present in several clinical syndromes. It is most associated with PSP and CBD. NVOA is a manifestation of left lateral and medial posterior frontal cortex damage rather than a particular pathology.

Radiomics-Guided Deep Learning Networks Classify Differential Diagnosis of Parkinsonism

The differential diagnosis between atypical Parkinsonian syndromes may be challenging and critical. We aimed to proposed a radiomics-guided deep learning (DL) model to discover interpretable DL features and further verify the proposed model through the differential diagnosis of Parkinsonian syndromes. We recruited 1495 subjects for 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) scanning, including 220 healthy controls and 1275 patients diagnosed with idiopathic Parkinson's disease (IPD), multiple system atrophy (MSA), or progressive supranuclear palsy (PSP). Baseline radiomics and two DL models were developed and tested for the Parkinsonian diagnosis. The DL latent features were extracted from the last layer and subsequently guided by radiomics. The radiomics-guided DL model outperformed the baseline radiomics approach, suggesting the effectiveness of the DL approach. DenseNet showed the best diagnosis ability (sensitivity: 95.7%, 90.1%, and 91.2% for IPD, MSA, and PSP, respectively) using retained DL features in the test dataset. The retained DL latent features were significantly associated with radiomics features and could be interpreted through biological explanations of handcrafted radiomics features. The radiomics-guided DL model offers interpretable high-level abstract information for differential diagnosis of Parkinsonian disorders and holds considerable promise for personalized disease monitoring.

Progression to corticobasal syndrome: a longitudinal study of patients with nonfluent primary progressive aphasia and primary progressive apraxia of speech

BACKGROUND AND OBJECTIVES

Nonfluent variant primary progressive aphasia (nfvPPA) and primary progressive apraxia of speech (PPAOS) can be precursors to corticobasal syndrome (CBS). Details on their progression remain unclear. We aimed to examine the clinical and neuroimaging evolution of nfvPPA and PPAOS into CBS.

METHODS

We conducted a retrospective longitudinal study in 140 nfvPPA or PPAOS patients and applied the consensus criteria for possible and probable CBS for every visit, evaluating limb rigidity, akinesia, limb dystonia, myoclonus, ideomotor apraxia, alien limb phenomenon, and nonverbal oral apraxia (NVOA). Given the association of NVOA with AOS, we also modified the CBS criteria by excluding NVOA and assigned every patient to either a progressors or non-progressors group. We evaluated the frequency of every CBS feature by year from disease onset, and assessed gray and white matter volume loss using SPM12.

RESULTS

Asymmetric akinesia, NVOA, and limb apraxia were the most common CBS features that developed; while limb dystonia, myoclonus, and alien limb were rare. Eighty-two patients progressed to possible CBS; only four to probable CBS. nfvPPA and PPAOS had a similar proportion of progressors, although nfvPPA progressed to CBS earlier (p-value = 0.046), driven by an early appearance of limb apraxia (p-value = 0.0041). The non-progressors and progressors both showed premotor/motor cortex involvement at baseline, with spread into prefrontal cortex over time.

DISCUSSION

An important proportion of patients with nfvPPA and PPAOS progress to possible CBS, while they rarely develop features of probable CBS even after long follow-up.

Efficacy of LSVT LOUD® on Phonatory Control and Voice Quality in Patients with Primary Progressive Apraxia of Speech: Case Studies

Primary progressive apraxia of speech (PPAOS) is a neurodegenerative syndrome characterized by the progressive and initially isolated or predominant onset of difficulties in the planning/programming of movements necessary for speech production and can be accompanied by dysarthria. To date, no study has used an evidence-based treatment to address phonation control in patients with PPAOS. The aim of this study was to evaluate the feasibility and efficacy of LSVT LOUD® as a treatment for phonatory control in speakers with PPAOS. Three speakers with PPAOS received LSVT LOUD® therapy, and changes in phonatory control, voice quality and prosody were measured immediately, and one, four and eight weeks after the end of the treatment. Overall, the results suggest that the treatment is feasible and could improve voice quality, intensity, and control in some patients with PPAOS. The generalization of the results is also discussed.

Altered structural and functional connectivity in Posterior Cortical Atrophy and Dementia with Lewy bodies

Posterior cortical atrophy (PCA) and dementia with Lewy bodies (DLB) show distinct atrophy and overlapping hypometabolism profiles, but it is unknown how disruptions in structural and functional connectivity compare between these disorders and whether breakdowns in connectivity relate to either atrophy or hypometabolism. Thirty amyloid-positive PCA patients, 24 amyloid-negative DLB patients and 30 amyloid-negative cognitively unimpaired (CU) healthy individuals were recruited at Mayo Clinic, Rochester, MN, and underwent a 3T head MRI, including structural MRI, resting state functional MRI (rsfMRI) and diffusion tensor imaging (DTI) sequences, as well as [18F] fluorodeoxyglucose (FDG) PET. We assessed functional connectivity within and between 12 brain networks using rsfMRI and the CONN functional connectivity toolbox and calculated regional DTI metrics using the Johns Hopkins atlas. Multivariate linear-regression models corrected for multiple comparisons and adjusted for age and sex compared DTI metrics and within-network and between-network functional connectivity across groups. Regional gray-matter volumes and FDG-PET standard uptake value ratios (SUVRs) were calculated and analyzed at the voxel-level using SPM12. We used univariate linear-regression models to investigate the relationship between connectivity measures, gray-matter volume, and FDG-PET SUVR. On DTI, PCA showed degeneration in occipito-parietal white matter, posterior thalamic radiations, splenium of the corpus collosum and sagittal stratum compared to DLB and CU, with greater degeneration in the temporal white matter and the fornix compared to CU. We observed no white-matter degeneration in DLB compared to CU. On rsfMRI, reduced within-network connectivity was present in dorsal and ventral default mode networks (DMN) and the dorsal-attention network in PCA compared to DLB and CU, with reduced within-network connectivity in the visual and sensorimotor networks compared to CU. DLB showed reduced connectivity in the cerebellar network compared to CU. Between-network analysis showed increased connectivity in both cerebellar-to-sensorimotor and cerebellar-to-dorsal attention network connectivity in PCA and DLB. PCA showed reduced anterior DMN-to-cerebellar and dorsal attention-to-sensorimotor connectivity, while DLB showed reduced posterior DMN-to-sensorimotor connectivity compared to CU. PCA showed reduced dorsal DMN-to-visual connectivity compared to DLB. The multimodal analysis revealed weak associations between functional connectivity and volume in PCA, and between functional connectivity and metabolism in DLB. These findings suggest that PCA and DLB have unique connectivity alterations, with PCA showing more widespread disruptions in both structural and functional connectivity; yet some overlap was observed with both disorders showing increased connectivity from the cerebellum.

Diffusion tensor imaging-based multi-fiber tracking reconstructions can regionally differentiate phonetic versus prosodic subtypes of progressive apraxia of speech

Two subtypes of progressive apraxia of speech (PAOS) have been recognized: phonetic PAOS (PAOS_ph) where speech output is dominated by distorted sound substitutions and prosodic PAOS (PAOS_pr) which is dominated by segmented speech. We investigate whether these PAOS subtypes have different white matter microstructural abnormalities measured by diffusion tensor tractography. Thirty-three patients with PAOS (21 PAOS_ph and 12 PAOS_pr) and 19 healthy controls were recruited by the Neurodegenerative Research Group (NRG) and underwent diffusion MRI. Using a whole-brain tractography approach, fractional anisotropy (FA) and mean diffusivity (MD) were extracted for cortico-cortical, cortico-subcortical, cortical-projection, and cerebello-cortical white matter tracts. A hierarchical linear model was applied to assess tract-level FA and MD across groups. Both PAOS_ph and PAOS_pr showed degeneration of cortico-cortical, cortico-subcortical, cortical-projection, and cerebello-cortical white matter tracts compared to controls. However, degeneration of the body of corpus callosum, superior thalamic radiation, and superior cerebellar peduncle was greater in PAOS_pr compared to PAOS_ph, and degeneration of the inferior segment of the superior longitudinal fasciculus (SLF) was greater in PAOS_ph compared to PAOS_pr. Worse parkinsonism correlated with greater degeneration of cortico-cortical and cortico-subcortical tracts in PAOS_ph. Apraxia of speech articulatory error score correlated with degeneration of the superior cerebellar peduncle tracts in PAOS_pr. Phonetic and prosodic PAOS involve the compromise of a similar network of tracts, although there are connectivity differences between types. Whereas clinical parameters are the current gold standard to distinguish PAOS subtypes, our results allege the use of DTI-based tractography as a supplementary method to investigate such variants.

Combined assessment of progressive apraxia of speech brain microstructure by diffusion tensor imaging tractography and multishell neurite orientation dispersion and density imaging

BACKGROUND

Progressive apraxia of speech (PAOS) is characterized by difficulties with motor speech programming and planning. PAOS targets gray matter (GM) and white matter (WM) microstructure that can be assessed using diffusion tensor imaging (DTI) and multishell applications, such as neurite orientation dispersion and density imaging (NODDI). In this study, we aimed to apply DTI and NODDI to add further insight into PAOS tissue microstructure.

METHODS

Twenty-two PAOS patients and 26 age- and sex-matched controls, recruited by the Neurodegenerative Research Group (NRG) at Mayo Clinic, underwent diffusion MRI on 3T MRI. Brain maps of fractional anisotropy (FA) and mean diffusivity (MD) from DTI and intracellular volume fraction (ICVF) and isotropic volume fraction (IsoVF) from NODDI were generated. Global WM and GM, and specific WM tracts were identified using tractography and lobar GM regions.

RESULTS

Global WM differences between PAOS and controls were greatest for ICVF, and global GM differences were greatest for MD and IsoVF. Abnormalities in key WM tracts involved in PAOS, including the body of the corpus callosum and frontal aslant tract, were identified with FA, MD, and ICVF, with excellent differentiation of PAOS from controls (area under the receiver operating characteristic curves >.90). MD and ICVF identified abnormalities in arcuate fasciculus, thalamic radiations, and corticostriatal tracts. Significant correlations were identified between an index of articulatory errors and DTI and NODDI metrics from the arcuate fasciculus, frontal aslant tract, and inferior longitudinal fasciculus.

CONCLUSIONS

DTI and NODDI represent different aspects of brain tissue microstructure, increasing the number of potential biomarkers for PAOS.

New Perspectives in Radiological and Radiopharmaceutical Hybrid Imaging in Progressive Supranuclear Palsy: A Systematic Review

Progressive supranuclear palsy (PSP) is a neurodegenerative disease characterized by four-repeat tau deposition in various cell types and anatomical regions, and can manifest as several clinical phenotypes, including the most common phenotype, Richardson's syndrome. The limited availability of biomarkers for PSP relates to the overlap of clinical features with other neurodegenerative disorders, but identification of a growing number of biomarkers from imaging is underway. One way to increase the reliability of imaging biomarkers is to combine different modalities for multimodal imaging. This review aimed to provide an overview of the current state of PSP hybrid imaging by combinations of positron emission tomography (PET) and magnetic resonance imaging (MRI). Specifically, combined PET and MRI studies in PSP highlight the potential of [18F]AV-1451 to detect tau, but also the challenge in differentiating PSP from other neurodegenerative diseases. Studies over the last years showed a reduced synaptic density in [11C]UCB-J PET, linked [11C]PK11195 and [18F]AV-1451 markers to disease progression, and suggested the potential role of [18F]RO948 PET for identifying tau pathology in subcortical regions. The integration of quantitative global and regional gray matter analysis by MRI may further guide the assessment of reduced cortical thickness or volume alterations, and diffusion MRI could provide insight into microstructural changes and structural connectivity in PSP. Challenges in radiopharmaceutical biomarkers and hybrid imaging require further research targeting markers for comprehensive PSP diagnosis.

Longitudinal characterization of patients with progressive apraxia of speech without clearly predominant phonetic or prosodic speech features

Most recent studies of progressive apraxia of speech (PAOS) have focused on patients with phonetic or prosodic predominant PAOS to understand the implications of the presenting clinical phenotype. Patients without a clearly predominating speech quality, or mixed AOS, have been excluded. Given the implications for disease progression, it is important to understand these patients early in the disease course to inform appropriate education and prognostication. The aim of this study was to describe a cohort of ten patients with initially mixed PAOS and how their clinical course evolves. Four patients were rated prosodic predominant later on (mild AOS at first visit); five were later designated phonetic (four with more than mild AOS at first visit); one was judged mixed at all visits. The study suggests patients without a clear predominance of speech featuresshould still be included in PAOS studies and thought of on the continuum of the disease spectrum.

An Update on Apraxia of Speech

PURPOSE OF REVIEW

Apraxia of speech (AOS) is a motor speech disorder that has long been recognized to occur secondary to acute neurologic insults and, more recently, to neurodegenerative diseases as a harbinger for progressive supranuclear palsy and corticobasal syndrome. This article reviews recent findings regarding the clinic phenotypes of AOS, neuroimaging correlates, and the underlying disease processes.

RECENT FINDINGS

Two clinical subtypes of AOS map onto two underlying 4-repeat tauopathies. New imaging techniques have recently been applied to the study of progressive AOS. There is no data on the impact of behavioral intervention, although studies of nonfluent/agrammatic primary progressive aphasia that include patients with AOS suggest some benefit in speech intelligibility and maintenance. While recent findings suggest subtypes of AOS exist that are linked to molecular pathology and have important implications for disease progression, further research is needed to assess outcome of behavioral and other types of intervention.

Speech Motor Profiles in Primary Progressive Aphasia

PURPOSE

Previous research on motor speech disorders (MSDs) in primary progressive aphasia (PPA) has largely focused on patients with the nonfluent/agrammatic variant of PPA (nfvPPA), with few systematic descriptions of MSDs in variants other than nfvPPA. There has also been an emphasis on studying apraxia of speech, whereas less is known about dysarthria or other forms of MSDs. This study aimed to examine the qualitative and quantitative characteristics of MSDs in a prospective sample of individuals with PPA independent of subtype.

METHOD

We included 38 participants with a root diagnosis of PPA according to current consensus criteria, including one case with primary progressive apraxia of speech. Speech tasks comprised various speech modalities and levels of complexity. Expert raters used a novel protocol for auditory speech analyses covering all major dimensions of speech.

RESULTS

Of the participants, 47.4% presented with some form of MSD. Individual speech motor profiles varied widely with respect to the different speech dimensions. Besides apraxia of speech, we observed different dysarthria syndromes, special forms of MSDs (e.g., neurogenic stuttering), and mixed forms. Degrees of severity ranged from mild to severe. We also observed MSDs in patients whose speech and language profiles were incompatible with nfvPPA.

CONCLUSIONS

The results confirm that MSDs are common in PPA and can manifest in different syndromes. The findings emphasize that future studies of MSDs in PPA should be extended to all clinical variants and should take into account the qualitative characteristics of motor speech dysfunction across speech dimensions.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.22555534.

Acoustic Analysis and Neuroimaging Correlates of Diadochokinetic Rates in Mild-Moderate Primary Progressive Apraxia of Speech

Speech rate can be judged clinically using diadochokinetic (DDK) tasks, such as alternating motion rates (AMR) and sequential motion rates (SMR). We evaluated whether acoustic AMR/SMR speech rates would differentiate primary progressive apraxia of speech (PPAOS) from healthy controls, and determined how DDK rates relate to phonetic and prosodic speech characteristics and brain metabolism on FDG-PET. Rate was calculated for each of three AMRs (repetitions of 'puh', 'tuh', and 'kuh') and for SMRs (repetitions of 'puhtuhkuh') for 27 PPAOS patients and 52 controls who underwent FDG-PET. PPAOS patients were slower than controls on all DDK tasks. All DDK rates correlated with apraxia of speech severity, with strongest associations with prosodic speech features. Slower DDK rates were associated with hypometabolism in the right cerebellar dentate and left supplementary motor area. Performance on AMR rate, not just SMR rate, may be impaired in mild PPAOS, but sensitivity and specificity require further study.

Spatial patterns of elevated magnetic susceptibility in progressive apraxia of speech

PURPOSE

Progressive apraxia of speech (PAOS) is a neurodegenerative disorder affecting the planning or programming of speech. Little is known about its magnetic susceptibility profiles indicative of biological processes such as iron deposition and demyelination. This study aims to clarify (1) the pattern of susceptibility in PAOS patients, (2) the susceptibility differences between the phonetic (characterized by predominance of distorted sound substitutions and additions) and prosodic (characterized by predominance of slow speech rate and segmentation) subtypes of PAOS, and (3) the relationships between susceptibility and symptom severity.

METHODS

Twenty patients with PAOS (nine phonetic and eleven prosodic subtypes) were prospectively recruited and underwent a 3 Tesla MRI scan. They also underwent detailed speech, language, and neurological evaluations. Quantitative susceptibility maps (QSM) were reconstructed from multi-echo gradient echo MRI images. Region of interest analysis was conducted to estimate susceptibility coefficients in several subcortical and frontal regions. We compared susceptibility values between PAOS and an age-matched control group and performed a correlation analysis between susceptibilities and an apraxia of speech rating scale (ASRS) phonetic and prosodic feature ratings.

RESULTS

The magnetic susceptibility of PAOS was statistically greater than that of controls in subcortical regions (left putamen, left red nucleus, and right dentate nucleus) (p < 0.01, also survived FDR correction) and in the left white-matter precentral gyrus (p < 0.05, but not survived FDR correction). The prosodic patients showed greater susceptibilities than controls in these subcortical and precentral regions. The susceptibility in the left red nucleus and in the left precentral gyrus correlated with the prosodic sub-score of the ASRS.

CONCLUSION

Magnetic susceptibility in PAOS patients was greater than controls mainly in the subcortical regions. While larger samples are needed before QSM is considered ready for clinical differential diagnosis, the present study contributes to our understanding of magnetic susceptibility changes and the pathophysiology of PAOS.

Long-duration progressive supranuclear palsy: clinical course and pathological underpinnings

OBJECTIVES

To identify the clinical characteristics of the subgroup of benign progressive supranuclear palsy with particularly long disease duration; to define neuropathological determinants underlying variability in disease duration in progressive supranuclear palsy.

METHODS

Clinical and pathological features were compared among 186 autopsy-confirmed cases with progressive supranuclear palsy with ≥10 years and shorter survival times.

RESULTS

45 cases (24.2%) had a disease duration of ≥10 years. The absence of ocular motor abnormalities within the first 3 years from disease onset was the only significant independent clinical predictor of longer survival. Histopathologically, the neurodegeneration parameters in each survival group were paralleled anatomically by the distribution of neuronal cytoplasmic inclusions, whereas the tufted astrocytes displayed anatomically an opposite severity pattern. Most interestingly, we found significantly less coiled bodies in those who survive longer, in contrast to patients with less favorable course.

INTERPRETATIONS

A considerable proportion of patients had a more 'benign' disease course with ≥10 years survival. They had a distinct pattern and evolution of core symptoms compared to patients with short survival. The inverted anatomical patterns of astrocytic tau distribution suggest distinct implications of these cell types in trans-cellular propagation. The tempo of disease progression appeared to be determined mostly by oligodendroglial tau, where high degree of oligodendroglial tau pathology might affect neuronal integrity and function on top of neuronal tau pathology. The relative contribution of glial tau should be further explored in cellular and animal models. This article is protected by copyright. All rights reserved.

Autopsy Validation of Progressive Supranuclear Palsy-Predominant Speech/Language Disorder Criteria

BACKGROUND

Progressive supranuclear palsy (PSP) may present as a speech/language disorder (PSP-SL).

OBJECTIVE

We assessed pathological correlates of patients with PSP-SL who retained the suggestive of PSP-SL (s.o. PSP-SL) diagnosis versus those who progressed to possible/probable (poss./prob.) PSP.

METHODS

Thirty-four prospectively recruited patient with s.o. PSP-SL completed comprehensive speech/language and neurological assessments longitudinally, died, and underwent autopsy.

RESULTS

Twelve patients (35%) evolved to poss./prob PSP, while 22 (65%) remained as s.o. PSP-SL. Pathological diagnoses differed across the groups (P = 0.025). Patients with s.o. PSP-SL had four different neuropathologies (corticobasal degeneration [59%], PSP [13%], Pick's disease [14%], and frontotemporal lobar degeneration with TDP-43 [14%]), while all patients with poss./prob. PSP had a 4R-tauopathy (PSP [67%] and corticobasal degeneration [33%]). Development of poss./prob. PSP increased the chance of having PSP pathology by 2.38 times.

CONCLUSIONS

PSP-SL is associated with heterogenous pathologies. Evolution of PSP-SL into poss./prob. PSP is more predictive of underlying PSP pathology than s.o. PSP-SL. © 2021 International Parkinson and Movement Disorder Society.

Assessing Change in Communication Limitations in Primary Progressive Apraxia of Speech and Aphasia: A 1-Year Follow-Up Study

Purpose Individuals with primary progressive apraxia of speech have apraxia of speech (AOS) as the initial and predominant symptom. Many develop aphasia and/or dysarthria later in the disease course. It was previously demonstrated that patients with neurodegenerative AOS experience reduced participation in communication that is further exacerbated by co-occurring language deficits (Utianski et al., 2020). Measures of disease severity did not necessarily correlate with measures of participation restrictions. The aim of this follow-up study was to describe changes in communication limitations in these patients, again measured by (a) the patient via the Communicative Participation Item Bank (CPIB) and (b) the speech-language pathologist via the American Speech-Language-Hearing Association's (ASHA's) Functional Communication Measures (FCMs) and an adapted motor speech disorder (MSD) severity rating to determine if there are significant changes in these and other objective speech and language measures at follow-up after 1 year. Method Of the 24 patients reported in the study of Utianski et al. (2020), 17 (10 men, seven women) returned for a second visit approximately 1 year following the first visit. Identical procedures were utilized; the communication measures collected at each visit were statistically compared. Correlations were calculated between the participation ratings and other clinical assessment measures at the second visit and for the change in scores on those measures between the first and second visits. Results There were statistically significant differences in AOS and aphasia severity between visits. There were significant changes in clinical assessments, MSD severity rating, and all ASHA FCMs between visits, but not the CPIB. Correlation analyses suggest the relationships among clinical and participation measures are complex; overall, patients with more severe changes in AOS experienced greater changes in participation restrictions. Conclusions The findings of this study support the use of patient-reported outcome measures as they may better reflect the patient experience, including the influence of factors such as ongoing speech therapy and the emergence of neuropsychiatric features, and associated changes in day-to-day functioning, when other measures may simply index the progression of the disease. Supplemental Material https://doi.org/10.23641/asha.16528512.

Metabolic and Structural Signatures of Speech and Language Impairment in Corticobasal Syndrome: A Multimodal PET/MRI Study

Introduction: Corticobasal syndrome (CBS) is a progressive neurological disorder related to multiple underlying pathologies, including four-repeat tauopathies, such as corticobasal degeneration and progressive supranuclear palsy, and Alzheimer's disease (AD). Speech and language are commonly impaired, encompassing a broad spectrum of deficits. We aimed to investigate CBS speech and language impairment patterns in light of a multimodal imaging approach.

Materials and Methods: Thirty-one patients with probable CBS were prospectively evaluated concerning their speech–language, cognitive, and motor profiles. They underwent positron emission tomography with [¹⁸F]fluorodeoxyglucose (FDG-PET) and [¹¹C]Pittsburgh Compound-B (PIB-PET) on a hybrid PET-MRI machine to assess their amyloid status. PIB-PET images were classified based on visual and semi-quantitative analyses. Quantitative group analyses were performed on FDG-PET data, and atrophy patterns on MRI were investigated using voxel-based morphometry (VBM). Thirty healthy participants were recruited as imaging controls.

Results: Aphasia was the second most prominent cognitive impairment, presented in 67.7% of the cases, following apraxia (96.8%). We identified a wide linguistic profile, ranging from nonfluent variant-primary progressive aphasia to lexical–semantic deficits, mostly with impaired verbal fluency. PIB-PET was classified as negative (CBS-A– group) in 18/31 (58%) and positive (CBS-A+ group) in 13/31 (42%) patients. The frequency of dysarthria was significantly higher in the CBS-A– group than in the CBS-A+ group (55.6 vs. 7.7%, p = 0.008). CBS patients with dysarthria had a left-sided hypometabolism at frontal regions, with a major cluster at the left inferior frontal gyrus and premotor cortex. They showed brain atrophy mainly at the opercular frontal gyrus and putamen. There was a positive correlation between [¹⁸F]FDG uptake and semantic verbal fluency at the left inferior (p = 0.006, R² = 0.2326), middle (0.0054, R² = 0.2376), and superior temporal gyri (p = 0.0066, R² = 0.2276). Relative to the phonemic verbal fluency, we found a positive correlation at the left frontal opercular gyrus (p = 0.0003, R² = 0.3685), the inferior (p = 0.0004, R² = 0.3537), and the middle temporal gyri (p = 0.0001, R² = 0.3993).

Discussion: In the spectrum of language impairment profile, dysarthria might be helpful to distinguish CBS patients not related to AD. Metabolic and structural signatures depicted from this feature provide further insights into the motor speech production network and are also helpful to differentiate CBS variants.

Brain changes underlying progression of speech motor programming impairment

Aquired apraxia of speech is a disorder that impairs speech production, despite intact peripheral neuromotor function. Its pathomechanism remains to be established. Neurodegenerative lesion models provide an unequalled opportunity to explore the neural correlates of apraxia of speech, which is present in a subset of patients diagnosed with non-semantic variants of primary progressive aphasia. The normalized pairwise variability index, an acoustic measure of speech motor programming, has shown high sensitivity and specificity for apraxia of speech in cross-sectional studies. Here, we aimed to examine the strength of the pairwise variability index and overall word duration (i.e. articulation rate) as markers of progressive motor programming deficits in primary progressive aphasia with apraxia of speech. Seventy-nine individuals diagnosed with primary progressive aphasia (39 with non-fluent variant and 40 with logopenic variant) and 40 matched healthy controls participated. Patients were followed-up annually (range 1-6 years, median number of visits = 2). All participants completed a speech assessment task and a high-resolution MRI. Our analyses investigated trajectories of speech production (e.g. pairwise variablity index and word duration) and associations with cortical atrophy in the patients. At first presentation, word duration differentiated the nonfluent and logopenic cases statistically, but the range of scores overlapped substantially across groups. Longitudinally, we observed progressive deterioration in pairwise variability index and word duration specific to the non-fluent group only. The pairwise variability index showed particularly strong associations with progressive atrophy in speech motor programming brain regions. Of novelty, our results uncovered a key role of the right frontal gyrus in underpinning speech motor programming changes in non-fluent cases, highlighting the importance of right-brain regions in responding to progressive neurological changes in the speech motor network. Taken together, our findings validate the use of a new metric, the pairwise variability index, as a robust marker of apraxia of speech in contrast to more generic measures of speaking rate. Sensitive/specific neuroimaging biomarkers of the emergence and progression of speech impairments will be useful to inform theories of the pathomechanisms underpinning impaired speech motor control. Our findings justify developing more sensitive measures of rhythmic temporal control of speech that may enable confident detection of emerging speech disturbances and more sensitive tracking of intervention-related changes for pharmacological, neuromodulatory and behavioural interventions. A more reliable detection of speech disturbances has relevance for patient care, with predominance of progressive apraxia of speech a high-risk factor for later diagnosis of progressive supranuclear palsy or corticobasal degeneration.

Coming to Terms with a Conundrum: A Case of Primary Progressive Apraxia of Speech due to Corticobasal Degeneration?

Primary progressive apraxia of speech (PPAOS) is a progressive disorder impairing the motor speech act leaving linguistic function unattained. Although apraxia of speech frequently co-occurs with other neurodegenerative conditions, PPAOS defines a clinical syndrome where apraxia of speech is the sole or prominent symptom for much of the disease's natural history. Mounting evidence is beginning to fully define this disease as the epiphenomenon of 4-repeat (4R) tau pathology although other pathologic signatures have been reported. Indeed, PPAOS patients generally present a parkinsonian syndrome late into their natural history mostly qualifying for either corticobasal syndrome (CBS) or progressive supranuclear palsy (PSP). This is starting to be reflected in diagnostic criteria for PSP, namely, in the PSP speech and language (SL) subcategory; however, this inclusion is not reflected for CBS. Here, we present a single case of a patient with PPAOS and her clinical follow-up lasting 6 years, from the time she sought our attention to her death which occurred 8 years into the disease. PPAOS was the only and prominent symptom for most of the illness with extrapyramidal signs overtly presenting in the last months of its course. Clinical evaluation, imaging, genetic, and cerebrospinal fluid biomarkers all pointed toward an underlying CBD pathology, albeit the eventual anatomopathological confirmation was not performed. Had her clinical course been more suggestive of PSP, she would have qualified for criteria as PSP-SL. Our case therefore suggests the hypothetic need to discuss the broadening of the existing CBS criteria to encompass isolated PPAOS.

A Preliminary Look Into the Clinical Evolution of Motor Speech Characteristics in Primary Progressive Apraxia of Speech in Québec French

Purpose This study aimed to track changes in acoustical and perceptual features of motor speech in patients with phonetic and prosodic primary progressive apraxia of speech (PPAOS) in Québec French over an 18-month period. Method A prospective multiple-case series with multiple testing periods, including four participants with a diagnosis of PPAOS, was conducted. Participants were 0.5-4 years postonset of disease at baseline. They underwent comprehensive motor speech and language assessments and cognitive screening every 6 months for up to 18 months. Acoustical and perceptual analyses of motor speech were conducted. Results Results showed a considerable impairment in motor speech abilities for patients with PPAOS at all time points and a significant decrease in performance for almost all articulatory and prosodic measures over time. Passage reading and diadochokinesis seemed particularly promising for the tracking of changes in PPAOS motor speech characteristics and PPAOS classification. Quantifying length of speech runs made it possible to distinguish phonetic from prosodic PPAOS. Finally, the patients who evolved to phonetic PPAOS developed aphasia, and the two with prosodic PPAOS showed greater motor symptoms such as unequivocal dysarthria. Conclusion This study extends the growing literature on PPAOS and its subtypes by describing specific changes in articulatory and prosodic abilities over a period of at least 6 months, which are important for the diagnosis and management of PPAOS.

A molecular pathology, neurobiology, biochemical, genetic and neuroimaging study of progressive apraxia of speech

Progressive apraxia of speech is a neurodegenerative syndrome affecting spoken communication. Molecular pathology, biochemistry, genetics, and longitudinal imaging were investigated in 32 autopsy-confirmed patients with progressive apraxia of speech who were followed over 10 years. Corticobasal degeneration and progressive supranuclear palsy (4R-tauopathies) were the most common underlying pathologies. Perceptually distinct speech characteristics, combined with age-at-onset, predicted specific 4R-tauopathy; phonetic subtype and younger age predicted corticobasal degeneration, and prosodic subtype and older age predicted progressive supranuclear palsy. Phonetic and prosodic subtypes showed differing relationships within the cortico-striato-pallido-nigro-luysial network. Biochemical analysis revealed no distinct differences in aggregated 4R-tau while tau H1 haplotype frequency (69%) was lower compared to 1000+ autopsy-confirmed 4R-tauopathies. Corticobasal degeneration patients had faster rates of decline, greater cortical degeneration, and shorter illness duration than progressive supranuclear palsy. These findings help define the pathobiology of progressive apraxia of speech and may have consequences for development of 4R-tau targeting treatment.

Progressive apraxia of speech (PAOS) is a neurodegenerative syndrome of multiple etiologies which affects spoken communication. Here, the authors characterized the molecular pathology, biochemistry, genetics and longitudinal neuroimaging of 32 autopsy-confirmed patients with PAOS who were followed over 10 years.

Primary Progressive Apraxia of Speech: From Recognition to Diagnosis and Care

BACKGROUND

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.

AIMS

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.

MAIN CONTRIBUTION

A broad summary of what is known about AOS as a manifestation of neurodegenerative disease.

CONCLUSIONS

Primary progressive apraxia of speech is a recognizable syndrome that can be distinguished from other neurodegenerative conditions that affect speech and language.