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.

Association of Performance on the Financial Capacity Instrument-Short Form With Brain Amyloid Load and Cortical Thickness in Older Adults.

Background and Objectives: To investigate the association of the Financial Capacity Instrument-Short Form (FCI-SF) performance and timing total scores with brain ß-amyloid and cortical thickness in cognitively unimpaired (CU) (at baseline) older adults. Methods: A total of 309 participants (aged 70 years or older) of the Mayo Clinic Study of Aging underwent 11C-Pittsburgh compound B PET amyloid imaging and MRI, and completed the FCI-SF. Abnormal amyloid PET was defined as standardized uptake value ratio ≥1.48 in an Alzheimer disease (AD)-related region of interest and reduced AD signature cortical thickness as ≤2.68 mm (neurodegeneration). A cohort of 218 (of the 309) participants had follow-up visits (every 15 months) with FCI-SF data for longitudinal analysis (number of visits including baseline, median [range]: 2 [2-4]). In the analysis, we used linear regression and mixed-effects models adjusted for age, sex, education, apolipoprotein E ε4 allele status, global cognitive z score, and previous FCI-SF testing. Results: Participants' mean age (SD) was 80.2 (4.8) years (56.3% male individuals). In cross-sectional analysis, abnormal amyloid PET (vs normal) was associated with a lower FCI-SF total score and slower total composite time. In longitudinal analysis, FCI-SF total score declined faster (difference in annualized rate of change, beta coefficient [ß] [95% confidence interval (CI)] = -1.123 [-2.086 to -0.161]) and FCI-SF total composite time increased faster (difference in annualized rate of change, ß [95% CI] = 16.274 [5.951 to 26.597]) for participants with neurodegeneration at baseline (vs those without). Participants who exhibited both abnormal amyloid PET and neurodegeneration at baseline had a greater increase in total composite time when compared with the group without abnormal amyloid and without neurodegeneration (difference in annualized rate of change, ß [95% CI] = 16.750 [3.193 to 30.307]). Discussion: Performance and processing speed on the FCI-SF were associated with imaging biomarkers of AD pathophysiology in CU (at baseline) older adults. Higher burdens of imaging biomarkers were associated with longitudinal worsening on FCI-SF performance. Additional research is needed to delineate further these associations and their predictive utility at the individual person level.

Cross-Sectional and Longitudinal Assessment of Behavior in Primary Progressive Apraxia of Speech and Agrammatic Aphasia.

INTRODUCTION: Progressive agrammatic aphasia (PAA) can be associated with abnormal behaviors; however, it is unknown whether behaviors occur and/or are different in patients with primary progressive apraxia of speech (PPAOS). We aimed to compare baseline and longitudinal behavioral symptomatology between PPAOS, patients with PAA, and patients with both apraxia of speech and PAA (AOS-PAA). METHODS: We recruited 89 patients for this study, 40 with PPAOS, 11 with PAA, and 38 with AOS-PAA. Behavioral disturbances were evaluated using the frontal behavior inventory (FBI) which was also split into negative behaviors and disinhibition, and the 20-item behavioral assessment scale (20-BAS). Data analysis was performed using linear regression and linear mixed models. RESULTS: Of the 89 patients in the study, 54% were women and the mean age at onset was 68 years. All patients, regardless of diagnosis, endorsed at least one symptom on the FBI at baseline, most frequently verbal apraxia (100%), logopenia (95.6%), irritability (55.9%), and apathy (42.6%). On the 20-BAS, 47.6% of the patients endorsed at least one symptom, most commonly "crying more easily" (19.5%) and personality change (18.3%). PPAOS was the least behaviorally affected group, with differences between PPAOS and AOS-PAA mainly driven by negative behaviors as opposed to disinhibition for PPAOS and PAA. The behavioral metrics showed average sensitivity and specificity to distinguish between groups. Behavioral disturbances worsened over time although rate of behavioral change across groups was similar. CONCLUSION: Behavioral disturbances are more common and severe in patients with agrammatic aphasia with or without AOS compared to patients with isolated apraxia of speech.

Tau polygenic risk scoring: a cost-effective aid for prognostic counseling in Alzheimer's disease.

Tau deposition is one of two hallmark features of biologically defined Alzheimer's disease (AD) and is more closely related to cognitive decline than amyloidosis. Further, not all amyloid-positive individuals develop tauopathy, resulting in wide heterogeneity in clinical outcomes across the population with AD. We hypothesized that a polygenic risk score (PRS) based on tau PET (tau PRS) would capture the aggregate inherited susceptibility/resistance architecture influencing tau accumulation, beyond solely the measurement of amyloid-ß burden. Leveraging rich multimodal data from a population-based sample of older adults, we found that this novel tau PRS was a strong surrogate of tau PET deposition and captured a significant proportion of the variance in tau PET levels as compared with amyloid PET burden, APOE (apolipoprotein E) ε4 (the most common risk allele for AD), and a non-APOE PRS of clinical case-control AD risk variants. In independent validation samples, the tau PRS was associated with cerebrospinal fluid phosphorylated tau levels in one cohort and with postmortem Braak neurofibrillary tangle stage in another. We also observed an association of the tau PRS with longitudinal cognitive trajectories, including a statistical interaction of the tau PRS with amyloid burden on cognitive decline. Although additional study is warranted, these findings demonstrate the potential utility of a tau PRS for capturing the collective genetic background influencing tau deposition in the general population. In the future, a tau PRS could be leveraged for cost-effective screening and risk stratification to guide trial enrollment and clinical interventions in AD.

Comparison of the Short Test of Mental Status and the Montreal Cognitive Assessment Across the Cognitive Spectrum.

OBJECTIVE: To compare the Short Test of Mental Status (STMS) with the Montreal Cognitive Assessment (MoCA) for predicting and detecting mild cognitive impairment (MCI). PARTICIPANTS AND METHODS: Participants from the community-based Mayo Clinic Study of Aging (MCSA) (November 24, 2010, through May 19, 2012) and an academic referral Alzheimer's Disease Research Center (ADRC) (March 16, 2015, through September 5, 2018) were analyzed. All participants were evaluated using a standardized neuropsychological battery, and a multidisciplinary consensus diagnosis was assigned. The MCSA and ADRC samples included 313 and 106 stable cognitively normal (CN) participants, 72 and 8 CN participants at baseline who developed incident MCI or dementia, 114 and 96 participants with prevalent MCI, and 25 and 132 participants with dementia, respectively. RESULTS: There were no statistically significant differences between the 2 tests in 6 of 7 diagnostic comparisons across academic referral and community populations. The STMS had a better area under the curve (0.90; 95% CI, 0.87-0.93) for differentiating prevalent MCI from CN participants in the MCSA cohort compared with the MoCA cohort (0.85; 95% CI, 0.81-0.89; P=.01). In addition, 53% of the stable CN participants (222 of 419) scored less than 26 on the MoCA, with specificity of 47% for diagnosing prevalent MCI. CONCLUSION: We provide evidence that the STMS performs similarly to the MoCA in a variety of settings and neurodegenerative syndromes. These results suggest that the current recommended MoCA cutoff score may be overly sensitive, consistent with previous studies. We also provide a conversion table for comparing the 2 cognitive tests.

Quantitative assessment of grammar in amyloid-negative logopenic aphasia.

Logopenic primary progressive aphasia (lvPPA) typically results from underlying Alzheimer's disease, but subjects have been reported that do not show beta-amyloid (Aß) deposition. These subjects do not differ on neurological and speech-language testing from Aß-positive lvPPA, but they impressionistically show increased grammatical deficits. We performed a quantitative linguistic analysis of grammatical characteristics in Aß-negative lvPPA compared to Aß-positive lvPPA and agrammatic PPA, which is characterized by increased grammatical difficulties. Aß-negative lvPPA used fewer function words and correct verbs but more syntactic and semantic errors compared to Aß-positive lvPPA. These measures did not differ between Aß-negative lvPPA and agPPA. Both lvPPA cohorts showed a higher mean length of utterance, more complex sentences, and fewer nouns than agPPA. Aß-negative lvPPA subjects appear unique and share linguistic features with both agPPA and Aß-positive lvPPA. Quantitative language analysis in lvPPA may be able to distinguish those with and without Aß deposition.