Ryota Satoh

[¹⁸F]flortaucipir PET imaging has shown relatively low sensitivity for detecting four-repeat (4R) tau, which limits its utility in 4R tauopathies such as progressive supranuclear palsy (PSP). Previous studies have suggested that the first component of principal-component analysis includes non-disease-related uptake in non-Alzheimer tauopathies. In this study, we tested the hypothesis that subtracting this component could increase sensitivity to 4R tau using a large PSP cohort. Methods: Prospectively recruited patients with PSP (n = 141; 80 Richardson syndrome, 44 PSP-subcortical, and 17 PSP-cortical variants) and controls (n = 102) underwent [¹⁸F]flortaucipir PET. The first principal component (PC1) was extracted from the SUV ratio (SUVR) images of 62 controls and then subtracted from the remaining controls (n = 40) and all PSP patients. We compared the diagnostic performance before and after PC1 subtraction by evaluating SUVR differences between PSP and controls, as well as across PSP clinical variants, and by calculating correlation coefficients between SUVR and the severity of tau pathology. Results: Area under the receiver operating characteristic curves differentiating PSP and controls were improved by PC1 subtraction in the frontal white matter (0.54 to 0.67; P = 0.002) and subcortical (0.69 to 0.87; P < 0.001) regions. In the frontal regions, no differences were observed across PSP clinical variants before PC1 subtraction, whereas the PSP-cortical variant showed an SUVR higher than that of the PSP Richardson syndrome and PSP-subcortical variants after PC1 subtraction (adjusted P < 0.05). A correlation with the severity of tau pathology was observed only in the red nucleus before PC1 subtraction, whereas correlations were observed in the precentral, superior frontal gyrus, and red nucleus after PC1 subtraction (adjusted P < 0.05). Conclusion: Our approach enhanced the diagnostic performance of [¹⁸F]flortaucipir PET in PSP and increased sensitivity to 4R tau, suggesting that subtracting the first principal component improves the detectability of subtle 4R tau uptake and the potential utility of [¹⁸F]flortaucipir PET imaging for non-Alzheimer tauopathies.

Background: The cerebellar dentate is a known site of iron accumulation and tau deposition in progressive supranuclear palsy (PSP); however, detailed iron distribution and localized volume and shape changes remain unclear across PSP clinical variants. Objective: The study aimed to clarify details about regional susceptibility distribution, volume, and shape deformation in the cerebellar dentate across PSP clinical variants. Methods: Sixty‐seven PSP patients, including 31 PSP‐Richardson syndrome, 12 PSP‐parkinsonism, 10 PSP‐progressive gait freezing, and 14 PSP‐cortical variants (PSP‐frontal, PSP‐speech/language, and PSP‐corticobasal syndrome), and 31 healthy controls underwent 3 Tesla magnetic resonance imaging to reconstruct quantitative susceptibility maps. Manual dentate segmentation was performed to extract magnetic susceptibility and volume adjusted for total intracranial volume. Shape deformation was assessed using Deformetrica atlas construction. Group comparisons were evaluated with Kruskal–Wallis tests and receiver operating characteristic analysis. Results: Patients with PSP‐Richardson syndrome, PSP‐parkinsonism, and PSP‐cortical variants showed significantly increased dentate susceptibility compared with controls ( P < 0.05). Patients with PSP‐progressive gait freezing showed no significant susceptibility differences. Volume loss was most prominent in PSP‐cortical variants, bilaterally, and PSP‐Richardson syndrome, left hemisphere only ( P < 0.05). Shape analysis revealed subregion‐specific deformation patterns, especially in the anterior and posterior deformation in PSP‐progressive gait freezing and the ventroanterior deformation in PSP‐cortical variants. Conclusions: The PSP clinical variants had different patterns of susceptibility, volume, and shape metrics, reflecting distinct neurodegenerative patterns of the cerebellar dentate. These findings contribute to our understanding of the neurobiology of PSP and may help to improve phenotypic differentiation of PSP clinical variants. © 2026 International Parkinson and Movement Disorder Society.

Background: Posterior cortical atrophy (PCA) patients typically show progressive visual decline, although language impairment can be a prominent feature. Previous studies have explored language connectivity impairment in PCA; not much is known about the exact nature of language processing disruptions in PCA. Methods: Thirty-seven PCA patients were compared with 39 cognitively unimpaired (CU) individuals. Functional connectivity was evaluated for the language processing system, which consisted of language, perceptual, motor, and cognitive networks. Linear regression was performed to compare within- and between-network connectivity across networks and within the language network in PCA compared to CU individuals. Relationships between language network connectivity, clinical performance, and gray matter volumes were also evaluated. Results: PCA showed reduced connectivity within the language and perceptual networks, along with reduced between-network connectivity compared to CU individuals. Regional connectivity breakdown within the language network was also noted. Language processing system connectivity was not associated with clinical performance on language processing tests. However, a breakdown in Broca-Wernicke, Wernicke-middle frontal gyrus, and Wernicke-frontal orbital gyrus connectivity was related to worse performance on sentence repetition. Lastly, gray matter volume was not associated with language network connectivity. Discussion: Together, these results reiterate the breakdown of language network connectivity in PCA and highlight the disruption in connectivity at the regional level within the language network. Reduced connectivity within the perceptual network and associations between reduced language network connectivity and worse performance on sentence repetition imply a breakdown within the language processing systems in PCA.

Background: Quantitative susceptibility mapping ( QSM ) is a promising neuroimaging biomarker for detecting abnormal iron deposition in progressive supranuclear palsy ( PSP ); however, the QSM profile and its accuracy in autopsy‐confirmed PSP remain unexplored. Objective: The aim of the study was to elucidate and validate the QSM profiles in autopsy‐confirmed PSP. Methods: Eight patients with a clinically diagnosed PSP syndrome ( PSPS ) underwent antemortem 3 T magnetic resonance imaging ( MRI) scanning and subsequent pathological diagnosis, confirming 6 PSP pathology and 2 multiple system atrophy ( MSA ) pathology cases. QSM analysis and Prussian blue staining were performed across subcortical regions. Results: PSP cases showed higher susceptibility than age‐matched controls in the pallidum, subthalamic nucleus, substantia nigra, and cerebellar dentate (false discovery rate [ FDR] ‐corrected P < 0.05). PSP had higher susceptibility in the subthalamic nucleus and lower susceptibility in the putamen than the clinically atypical MSA ( P = 0.08). Subcortical susceptibilities correlated with Prussian blue–stained areas ( r = 0.63, P < 0.001). Conclusions: QSM could be a reliable measure to evaluate abnormal iron accumulation patterns in PSP.

Background The length of the tectal plate, which sits above the midbrain, is reduced in both the Richardson’s syndrome (RS) and parkinsonism (P) variants of progressive supranuclear palsy (PSP). However, it is unclear whether tectal measurements could be useful biomarkers in other PSP variants or predict PSP pathology. Methods The Neurodegenerative Research Group, Mayo Clinic, enrolled 115 PSP (including seven variants), 19 corticobasal syndrome (CBS), 21 Parkinson’s disease (PD), and 50 controls. Forty-seven PSP patients had PSP at autopsy, and 15 had a non-PSP pathology. Tectal plate length and area and area of the superior/inferior colliculi were measured. Measurements were compared across clinical and pathological groups, and associations were assessed with clinical severity. Effect sizes were evaluated using the area under the receiver operator characteristic curves (AUROCs). Results All PSP variants showed reduced tectal plate length compared to controls, with good differentiation (AUROC > 0.80). Excellent differentiation was observed for PSP-RS and PSP-P from controls (AUROC = 0.93/0.86), and PD (AUROC = 0.92/0.83), and PSP-RS showed good differentiation from CBS (AUROC = 0.80). Tectal plate and superior colliculus areas were reduced in all PSP variants, except PSP-Speech-language (SL), compared to controls. PSP-RS and PSP-P showed reduced area measurements compared to PSP-SL. No differences were observed between PSP and non-PSP pathology. Reduced tectal plate length was associated with worse clinical severity in PSP. Conclusion Tectal plate length may have utility as a disease biomarker across PSP variants, although tectal plate measurements could not predict pathology within patients clinically diagnosed with PSP.

Background: Progressive apraxia of speech (PAOS) is a neurodegenerative disorder most commonly arising from a 4-repeat tauopathy that affects the programming or planning of speech, although many patients develop a Parkinson-plus syndrome. The role of neuroinflammation as a disease mechanism is unknown. We investigated the spatial pattern of neuroinflammation in PAOS using PET and evaluated whether it is associated with disease severity, presence of Parkinson-plus features, and tau PET uptake. Patients and Methods: Twenty-five PAOS patients (13 with Parkinson-plus features) and 30 controls underwent inflammatory ¹¹C-ER176 and tau ¹⁸F-flortaucipir PET scans as well as detailed clinical assessments. Multiple linear regression analyses compared the inflammatory standardized uptake value ratio (SUVR) between PAOS and controls and assessed the relationship with clinical test scores. Pearson correlation analysis examined the relationship between inflammatory and tau SUVRs. Results: PAOS had greater neuroinflammatory SUVR than controls in the precentral, supplementary motor area, frontal gyri, putamen, pallidum, subthalamic nucleus, and red nucleus (adjusted P < 0.05). Greater neuroinflammation was associated with worse parkinsonism, and patients who had developed Parkinson-plus features showed a broader pattern of neuroinflammation, extending to prefrontal, temporal and parietal cortices. Neuroinflammation correlated with tau uptake in most (96%) PAOS patients (r > 0.3, P < 0.05). The higher correlation was associated with worse parkinsonism (r = 0.61, P < 0.05) and disease severity (r = 0.54, P < 0.05). Conclusions: ¹¹C-ER176 PET analysis demonstrates neuroinflammation in frontal and subcortical regions in PAOS which is particularly severe and widespread with the development of Parkinson-plus clinical features. The colocalization of neuroinflammation and tau may support a relationship between these disease mechanisms.

Objectives: The four‐repeat (4R) tauopathies are a group of neurodegenerative diseases, including progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and globular glial tauopathy (GGT). This study aimed to characterize spatiotemporal atrophy progression using structural magnetic resonance imaging (MRI) and to examine its relationship with clinical course and neuropathology in a cohort of autopsy‐confirmed 4R tauopathies.Methods: The study included 85 autopsied patients (54 with PSP, 28 with CBD, and 3 with GGT) who underwent multiple 3T MRI scans, as well as neuropsychological, neurological, and speech/language examinations, and standardized postmortem neuropathological evaluations. An unsupervised machine‐learning algorithm, Subtype and Stage Inference (SuStaIn), was applied to the cross‐sectional brain volumes to estimate spatiotemporal atrophy patterns and data‐driven subtypes and stages in each patient. The relationships among estimated subtypes, pathological diagnoses, and longitudinal changes in clinical testing were examined.Results: The SuStaIn algorithm identified 2 distinct subtypes: (1) the subcortical subtype, in which atrophy progresses from the midbrain to the cortex, and (2) the cortical subtype, in which atrophy progresses from the frontal cortex to the subcortical regions. The subcortical subtype was more associated with typical PSP, whereas the cortical subtype was more associated with atypical PSP with a cortical distribution of pathology and CBD (p < 0.001). The cortical subtype had a faster rate of change on the PSP Rating Scale than the subcortical subtype (p < 0.05).Interpretation: SuStaIn analysis revealed 2 MRI‐driven subtypes with distinct spatiotemporal atrophy patterns, clinical courses, and neuropathology. Our findings contribute to a comprehensive and improved understanding of disease progression and its relationship to tau pathology in 4R tauopathies. ANN NEUROL 2025;98:492–507

Objective: To determine whether a machine learning model of voxel level [¹⁸f]fluorodeoxyglucose positron emission tomography (PET) data could predict progressive supranuclear palsy (PSP) pathology, as well as outperform currently available biomarkers.Methods: One hundred and thirty‐seven autopsied patients with PSP (n = 42) and other neurodegenerative diseases (n = 95) who underwent antemortem [¹⁸f]fluorodeoxyglucose PET and 3.0 Tesla magnetic resonance imaging (MRI) scans were analyzed. A linear support vector machine was applied to differentiate pathological groups with sensitivity analyses performed to assess the influence of voxel size and region removal. A radial basis function was also prepared to create a secondary model using the most important voxels. The models were optimized on the main dataset (n = 104), and their performance was compared with the magnetic resonance parkinsonism index measured on MRI in the independent test dataset (n = 33).Results: The model had the highest accuracy (0.91) and F‐score (0.86) when voxel size was 6mm. In this optimized model, important voxels for differentiating the groups were observed in the thalamus, midbrain, and cerebellar dentate. The secondary models found the combination of thalamus and dentate to have the highest accuracy (0.89) and F‐score (0.81). The optimized secondary model showed the highest accuracy (0.91) and F‐scores (0.86) in the test dataset and outperformed the magnetic resonance parkinsonism index (0.81 and 0.70, respectively).Interpretation: The results suggest that glucose hypometabolism in the thalamus and cerebellar dentate have the highest potential for predicting PSP pathology. Our optimized machine learning model outperformed the best currently available biomarker to predict PSP pathology. ANN NEUROL 2025;98:410–420

Quantitative susceptibility mapping (QSM) is an advanced MRI technique for evaluating the distribution of magnetic susceptibility related to substances such as iron, hemosiderin, and deoxyhemoglobi... Quantitative susceptibility mapping (QSM), one of the advanced MRI techniques for evaluating magnetic susceptibility, offers precise quantitative measurements of spatial distributions of magnetic s...

Objectives Voxel-based morphometry (VBM) is widely used to quantify the progression of Alzheimer’s disease (AD), but improvement is still needed for accurate early diagnosis. We evaluated the feasibility of a novel diagnosis index for early diagnosis of AD based on quantitative susceptibility mapping (QSM) and VBM. Methods Thirty-seven patients with AD, 24 patients with mild cognitive impairment (MCI) due to AD, and 36 cognitively normal (NC) subjects from four centers were included. A hybrid sequence was performed by using 3-T MRI with a 3D multi-echo GRE sequence to obtain both a T1-weighted image for VBM and phase images for QSM. The index was calculated from specific voxels in QSM and VBM images by using a linear support vector machine. The method of voxel extraction was optimized to maximize diagnostic accuracy, and the optimized index was compared with the conventional VBM-based index using receiver operating characteristic analysis. Results The index was optimal when voxels were extracted as increased susceptibility (AD > NC) in the parietal lobe and decreased gray matter volume (AD < NC) in the limbic system. The optimized proposed index showed excellent performance for discrimination between AD and NC (AUC = 0.94, p = 1.1 × 10⁻¹⁰) and good performance for MCI and NC (AUC = 0.87, p = 1.8 × 10⁻⁶), but poor performance for AD and MCI (AUC = 0.68, p = 0.018). Compared with the conventional index, AUCs were improved for all cases, especially for MCI and NC (p < 0.05). Conclusions In this preliminary study, the proposed index based on QSM and VBM improved the diagnostic performance between MCI and NC groups compared with the VBM-based index. Key Points • We developed a novel diagnostic index for Alzheimer’s disease based on quantitative susceptibility mapping (QSM) and voxel-based morphometry (VBM). • QSM and VBM images can be acquired simultaneously in a single sequence with little increasing scan time. • In this preliminary study, the proposed diagnostic index improved the discriminative performance between mild cognitive impairment and normal control groups compared with the conventional VBM-based index.