Negin Holland

Corticobasal degeneration (CBD) is a late onset progressive neurodegenerative condition of the 4-repeat-tauopathy-type, classically presenting with asymmetrical rigidity, dystonia and myoclonus. In the most recent diagnostic criteria, Armstrong and colleagues (2013) described four clinical phenotypes associated with this pathology, including corticobasal syndrome (CBS), through a large retrospective analysis of published cases and confirmed brain bank cases of CBD. However, predicting CBD pathology remains challenging. With the advent of disease-modifying therapies, it has become particularly important to distinguish Alzheimer’s disease pathology from other underlying pathologies. We therefore combined two prospectively recruited cohorts of patients with CBS and analysed their key demographic, clinical and biomarker features. We included a separate cohort from UK brain banks who were diagnosed with CBS in life. We divided patients into three groups: CBS-Alzheimer’s (CBS-AD), CBS-non-Alzheimer’s (CBS-non-AD) and CBS-indeterminate (CBS-IDT) based on biomarkers and pathology, comparing clinical features, regional volumetric MRI measures and Nucleic Acid-Linked Immuno-Sandwich Assay with detection by next generation sequencing (NULISAseq) blood protein levels between groups. We performed additional analyses of pathologically verified cases. We included 397 participants, of which 57.7% were female. The mean age at symptom onset was 65.9 years. AD biomarkers and pathology permitted classifying 47 (11.8%) of the cases as CBS-AD, 134 (33.8%) as CBS-non-AD and 216 (54.4%) as CBS-IDT. Patients with CBS-AD had a younger age at onset (61.8 years vs 66.1 years, P < 0.01 and less severe motor deficits (non-significantly lower scores on MDS-UPDRS and PSPRS) and more severe cognitive impairment (non-significantly lower scores on MoCA). Patients with CBS-AD had higher rates of cortical sensory impairment (P = 0.087) and lower rates of limb dystonia (P < 0.01) and falls (P < 0.01) compared to the CBS-non-AD group. Volumetric MRI analysis revealed smaller parietal lobe volumes in CBS-AD (P = 0.01). The most common pathological diagnoses were PSP, CBD and AD. Limb dystonia was more common in people with CBD and PSP pathology (P = 0.077). Falls, impaired verbal fluency and impaired vertical saccades were confirmed as more common in PSP (P = 0.046, P = 0.040, P = 0.012, respectively). In summary, younger onset, less parkinsonism and more cognitive and cortical sensory impairment, along with reduced MRI parietal volumes point to CBS-AD, while limb dystonia, falls and worse verbal fluency relate to CBS-non-AD. Clinical, imaging and blood-biomarkers in can augment the Armstrong criteria in predicting the underlying pathology of corticobasal syndromes.

Background/Objectives: Corticobasal syndrome (CBS) shows weak clinicopathological correlation, with only half of cases attributable to corticobasal degeneration (CBD). Common alternative aetiologies include Alzheimer’s disease (AD) and progressive supranuclear palsy (PSP). Emerging disease modifying therapies are likely to require accurate antemortem differentiation. While plasma biomarkers have potential, clinical/cognitive tools such as the Addenbrooke’s Cognitive Examination-Revised (ACE-R), Cambridge Behavioural Inventory-Revised (CBI-R), and PSP Rating Scale (PSP-RS) may provide a cost-effective and scalable alternative. Methods: We retrospectively analysed 226 people diagnosed with CBS between 1997–2024, of whom 72 had post-mortem neuropathological assessment. We compared ACE-R, CBI-R, and PSP-RS subdomain scores across pathologies and trained predictive models to differentiate them. In a subset of 52 patients, we also evaluated plasma biomarkers (Neurofilament Light Chain, pTau217, Aβ42/Aβ40 ratio) as indicators of AD pathology. Results: People with CBS with AD pathology showed significantly worse scores in ACE-R memory (p=0.002), visuospatial (p=0.002) and attention (p=0.012), and CBI-R memory & orientation (p=0.022) domains. Principal component analysis identified a ‘global cognition’ factor (PC2), with higher scores in AD cases (i.e: worse cognition; p=<0.001). Multiple predictive models trained on ACE-R/CBI-R subdomain scores predicted AD pathology with 84.9-85.6% accuracy (AUC 0.874-0.926). Plasma biomarkers failed to reliably distinguish the dominant underlying pathology, in our cohort. Conclusions: Neurocognitive assessments offer a rapid, inexpensive, and scalable method to identify AD pathology in CBS, outperforming current plasma biomarkers. These tools may facilitate targeted trial recruitment and clinical management decisions, while additional development of blood biomarkers is required in the context of corticobasal syndrome.

Background/Objective: The corticobasal syndrome (CBS) is a complex asymmetric movement disorder, with cognitive impairment. Although commonly associated with the primary 4‐repeat‐tauopathy of corticobasal degeneration, clinicopathological correlation is poor, and a significant proportion is due to Alzheimer's disease (AD). Synaptic loss is a pathological feature of many clinical and preclinical tauopathies. We therefore measured the degree of synaptic loss in patients with CBS and tested whether synaptic loss differed according to β‐amyloid status.Methods: Twenty‐five people with CBS, and 32 age‐/sex‐/education‐matched healthy controls participated. Regional synaptic density was estimated by [¹¹C]UCB‐J non‐displaceable binding potential (BP_ND), AD‐tau pathology by [¹⁸F]AV‐1451 BP_ND, and gray matter volume by T1‐weighted magnetic resonance imaging. Participants with CBS had β‐amyloid imaging with ¹¹C‐labeled Pittsburgh Compound‐B ([¹¹C]PiB) positron emission tomography. Symptom severity was assessed with the progressive supranuclear palsy‐rating‐scale, the cortical basal ganglia functional scale, and the revised Addenbrooke's Cognitive Examination. Regional differences in BP_ND and gray matter volume between groups were assessed by ANOVA.Results: Compared to controls, patients with CBS had higher [¹⁸F]AV‐1451 uptake, gray matter volume loss, and reduced synaptic density. Synaptic loss was more severe and widespread in the β‐amyloid negative group. Asymmetry of synaptic loss was in line with the clinically most affected side.Discussion: Distinct patterns of [¹¹C]UCB‐J and [¹⁸F]AV‐1451 binding and gray matter volume loss, indicate differences in the pathogenic mechanisms of CBS according to whether it is associated with the presence of Alzheimer's disease or not. This highlights the potential for different therapeutic strategies in CBSs. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Background: There is growing evidence for early and extensive synaptic loss in frontotemporal lobar degeneration syndromes from in vivo and post‐mortem studies. We proposed that synaptic loss would affect behaviour, in relation to changes in functional connectivity.Method: We recruited 29 participants with progressive supranuclear palsy, 16 participants with amyloid‐negative corticobasal syndrome, 8 participants with behavioural variant frontotemporal dementia and 24 similarly‐aged healthy volunteers. All participants underwent resting‐state functional 3T MRI and positron emission tomography with [¹¹C]UCB‐J, that binds synaptic vesicle 2A. We compared the connectivity metrics of nodal weighted degree and voxelwise regional homogeneity with [¹¹C]UCB‐J non‐displaceable binding potential (BP_ND), in associative and commonality analyses. We then used independent component analysis to extract [¹¹C]UCB‐J BP_ND signal variance across participants, followed by derivation of participant‐specific scores of functional spatial covariance with the [¹¹C]UCB‐J components. We applied model selection to assess whether connectivity scores would improve prediction of and moderate the effect of synaptic loss on clinical severity.Result: Reduced [¹¹C]UCB‐J BP_ND was associated with reduced connectivity, with synaptic density predicting both measures of connectivity over and above grey matter volume (Figure 1). The anatomical distribution of synaptic loss partially overlapped in PSP, bvFTD and CBS, but there were also disease‐specific effects (Figure 2). The effect of synaptic loss on functional connectivity was expressed local to the regions of severe synaptic loss, and in remote regions. Moreover, functional connectivity explained additional variance and moderated the relationship between synaptic density and clinical severity (Figure 3).Conclusion: In vivo synaptic loss is associated with reduced connectivity, and changes in behaviour, with implications for modelling disease pathogenesis and translational studies.

Background: Novel, validated imaging biomarkers for assessing disease severity and progression in dementia with Lewy Bodies (DLB) are needed as standard neuroimaging changes such as atrophy are not pronounced. Both multi‐modal MR and PET offer opportunities, for example cortical microstructure and dendritic imaging can be assessed using advanced MR diffusion weighted imaging (DWI) methods such as neurite orientation dispersion and density imaging (NODDI) and PET with UCB‐J can assess synaptic density. We applied these and other markers to people with DLB and controls.Method: In linked studies, people with probable DLB and similarly aged controls (n = 10‐30 per group depending on study) underwent multimodal 3T‐MRI (including structural, multi‐shell DWI and arterial spin labelling imaging) and PET imaging with AV1451 (for assessment of tau), PiB (for amyloid status) and [11C]UCB‐J PET/MR. For MR, T1‐MRI and DWI datasets were processed using FreeSurfer 7.2 and FSL 6.0.4 respectively with whole‐brain ODI derived from the Microstructure Diffusion Toolbox. The [11C]UCB‐J and [18F]AV1451 binding potentials (BPND) were assessed using a simplified reference tissue model (reference centrum semiovale for UCBJ and cerebellum for AV1451). Group differences in ODI, UCB‐J and AV1451 BPND were examined and correlated with structural changes and clinical and cognitive variables (ACE‐R score).Result: Compared to controls, people with DLB showed significantly thinner neocortex (T = ‐2.8, p = 0.01) in temporo‐parietal regions but more widespread reductions in cortical microstructure (ODI, T = ‐3.9, p < 0.001)(Figure 1). Within the DLB group, hippocampal ODI was positively correlated with cognitive performance (robust linear regression: p < 0.001)(Figure 2). Reduced synaptic density (UCB‐J BP_ND) was found for the DLB group in posterior regions (p<0.05, FWE corrected)(Figure 3), with a trend for greater reductions in those who were amyloid positive. ACE‐R scores significantly correlated with synaptic density (p<0.05, FWE corrected). There were no significant differences in AV1451 binding between DLB and controls.Conclusion: Extensive reductions in ODI and reduced synaptic density, both associated with cognitive impairment and occurring in regions without significant atrophy or tau deposition, suggests that NODDI and synaptic PET imaging are promising biomarkers for DLB which merit further investigation, including in longitudinal studies.

Parkinson's disease (PD) and progressive supranuclear palsy (PSP) both impair response inhibition, exacerbating impulsivity. Inhibitory control deficits vary across individuals and are linked with worse prognosis, and lack improvement on dopaminergic therapy. Motor and cognitive control are associated with noradrenergic innervation of the cortex, arising from the locus coeruleus (LC) noradrenergic system. Here we test the hypothesis that structural variation of the LC explains response inhibition deficits in PSP and PD. Twenty-four people with idiopathic PD, 14 with PSP-Richardson's syndrome, and 24 age- and sex-matched controls undertook a stop-signal task and ultrahigh field 7T magnetization-transfer-weighted imaging of the LC. Parameters of “race models” of go- versus stop-decisions were estimated using hierarchical Bayesian methods to quantify the cognitive processes of response inhibition. We tested the multivariate relationship between LC integrity and model parameters using partial least squares. Both disorders impaired response inhibition at the group level. PSP caused a distinct pattern of abnormalities in inhibitory control with a paradoxically reduced threshold for go responses, but longer nondecision times, and more lapses of attention. The variation in response inhibition correlated with the variability of LC integrity across participants in both clinical groups. Structural imaging of the LC, coupled with behavioral modeling in parkinsonian disorders, confirms that LC integrity is associated with response inhibition and LC degeneration contributes to neurobehavioral changes. The noradrenergic system is therefore a promising target to treat impulsivity in these conditions. The optimization of noradrenergic treatment is likely to benefit from stratification according to LC integrity.SIGNIFICANCE STATEMENTResponse inhibition deficits contribute to clinical symptoms and poor outcomes in people with Parkinson's disease and progressive supranuclear palsy. We used cognitive modeling of performance of a response inhibition task to identify disease-specific mechanisms of abnormal inhibitory control. Response inhibition in both patient groups was associated with the integrity of the noradrenergic locus coeruleus, which we measuredin vivousing ultra-high field MRI. We propose that the imaging biomarker of locus coeruleus integrity provides a trans-diagnostic tool to explain individual differences in response inhibition ability beyond the classic nosological borders and diagnostic criteria. Our data suggest a potential new stratified treatment approach for Parkinson's disease and progressive supranuclear palsy.

Background: Synaptic loss is characteristic of many neurodegenerative diseases; it occurs early and is strongly related to functional deficits.Objective: In this longitudinal observational study, we determine the rate at which synaptic density is reduced in the primary tauopathies of progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD), and we test the relationship with disease progression.Methods: Our cross‐sectional cohort included 32 participants with probable PSP and 16 with probable CBD (all amyloid‐negative corticobasal syndrome), recruited from tertiary care centers in the United Kingdom, and 33 sex‐ and age‐matched healthy control subjects. Synaptic density was estimated by positron emission tomography imaging with the radioligand [¹¹C]UCB‐J that binds synaptic vesicle 2A. Clinical severity and cognition were assessed by the PSP Rating Scale and the Addenbrooke's cognitive examination. Regional [¹¹C]UCB‐J nondisplaceable binding potential was estimated in Hammersmith Atlas regions of interest. Twenty‐two participants with PSP/CBD had a follow‐up [¹¹C]UCB‐J positron emission tomography scan after 1 year. We calculated the annualized change in [¹¹C]UCB‐J nondisplaceable binding potential and correlated this with the change in clinical severity.Results: We found significant annual synaptic loss within the frontal lobe (−3.5%, P = 0.03) and the right caudate (−3.9%, P = 0.046). The degree of longitudinal synaptic loss within the frontal lobe correlated with the rate of change in the PSP Rating Scale (R = 0.47, P = 0.03) and cognition (Addenbrooke's Cognitive Examination–Revised, R = −0.62, P = 0.003).Conclusions: We provide in vivo evidence for rapid progressive synaptic loss, correlating with clinical progression in primary tauopathies. Synaptic loss may be an important therapeutic target and outcome variable for early‐phase clinical trials of disease‐modifying treatments. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Objective: Synaptic loss is an early feature of neurodegenerative disease models, and is severe in post mortem clinical studies, including frontotemporal dementia. Positron emission tomography (PET) with radiotracers that bind to synaptic vesicle glycoprotein 2A enables quantification of synaptic density in vivo. This study used [¹¹C]UCB‐J PET in participants with behavioral variant frontotemporal dementia (bvFTD), testing the hypothesis that synaptic loss is severe and related to clinical severity.Methods: Eleven participants with clinically probable bvFTD and 25 age‐ and sex‐matched healthy controls were included. Participants underwent dynamic [¹¹C]UCB‐J PET, structural magnetic resonance imaging, and a neuropsychological battery, including the revised Addenbrooke Cognitive Examination, and INECO frontal screening. General linear models compared [¹¹C]UCB‐J binding potential maps and gray matter volume between groups, and assessed associations between synaptic density and clinical severity in patients. Analyses were also performed using partial volume corrected [¹¹C]UCB‐J binding potential from regions of interest (ROIs).Results: Patients with bvFTD showed severe synaptic loss compared to controls. [¹¹C]UCB‐J binding was reduced bilaterally in medial and dorsolateral frontal regions, inferior frontal gyri, anterior and posterior cingulate gyrus, insular cortex, and medial temporal lobe. Synaptic loss in the frontal and cingulate regions correlated significantly with cognitive impairments. Synaptic loss was more severe than atrophy. Results from ROI‐based analyses mirrored the voxelwise results.Interpretation: In accordance with preclinical models, and human postmortem evidence, there is widespread frontotemporal loss of synapses in symptomatic bvFTD, in proportion to severity. [¹¹C]UCB‐J PET could support translational studies and experimental medicine strategies for new disease‐modifying treatments for neurodegeneration. ANN NEUROL 2023;93:142–154

Synaptic loss occurs early in many neurodegenerative diseases and contributes to cognitive impairment even in the absence of gross atrophy. Currently, for human disease there are few formal models to explain how cortical networks underlying cognition are affected by synaptic loss. We advocate that biophysical models of neurophysiology offer both a bridge from clinical to preclinical models of pathology, and quantitative assays for experimental medicine. Such biophysical models can also disclose hidden neuronal dynamics generating neurophysiological observations like electro- and magneto-encephalography (MEG). Here, we augment a biophysically informed mesoscale model of human cortical function by inclusion of synaptic density estimates as captured by [ ¹¹ C]UCB-J positron emission tomography, and provide insights into how regional synapse loss affects neurophysiology. We use the primary tauopathy of progressive supranuclear palsy (Richardson’s syndrome) as an exemplar condition, with high clinicopathological correlations. Progressive supranuclear palsy causes a marked change in cortical neurophysiology in the presence of mild atrophy and is associated with a decline in cognitive functions associated with the frontal lobe. Using (parametric empirical) Bayesian inversion of a conductance-based canonical microcircuit model of MEG data, we show that the inclusion of regional synaptic density—as a subject-specific prior on laminar specific neuronal populations—markedly increases model evidence. Specifically, model comparison suggests that a reduction in synaptic density in inferior frontal cortex affects superficial and granular layer glutamatergic excitation. This predicted individual differences in behaviour, demonstrating the link between synaptic loss, neurophysiology, and cognitive deficits. The method we demonstrate is not restricted to progressive supranuclear palsy or the effects of synaptic loss: such pathology-enriched dynamic causal models can be used to assess the mechanisms of other neurological disorders, with diverse non-invasive measures of pathology, and is suitable to test the effects of experimental pharmacology.

Synaptic loss is prominent in several human neurodegenerative diseases. We tested the hypothesis that synaptic density is reduced by the primary tauopathies of progressive supranuclear palsy (PSP) and cor- ticobasal syndrome (CBS). Thirty-three participants (10 CBS, 10 PSP, and thirteen age-/sex-/education- matched controls) underwent clinical and neuropsychological assessment, 3T-magnetic resonance imaging, and positron emission tomography with the radioligand [11C]UCB-J which targets the Synaptic Vesicle Glycoprotein 2A (SV2A). Eight CBS patients had negative β-amyloid biomarker. As expected, PSP and CBS groups were impaired in executive, memory and visuospatial tasks. [11C]UCB-J binding was reduced across frontal, temporal, parietal, and occipital lobes, cingulate, hippocampus, insula, amygdala and subcortical structures in both PSP and CBS patients compared to controls (p<0.001), with reductions up to 50%, consistent with post mortem data. The revised Addenbrooke’s Cognitive Examination score correlated positively with cortical [11C]UCB-J binding (frontal, temporal, parietal, and occipital lobes, hippocampus, insula and amygdala, all p<0.05); putamen and precentral [11C]UCB-J binding correlated inversely with the PSP rating scale (both p<0.05). In conclusion, we confirm severe synaptic loss in PSP and CBS, which correlates with disease severity, providing critical insights into the underlying pathophysiology of primary degenerative tauopathies and supporting potential treatment strategies based on synaptic maintenance or restoration. nda26@cam.ac.uk