Brain Connectivity and Information-Flow Breakdown Revealed by a Minimum Spanning Tree-Based Analysis of MRI Data in Behavioral Variant Frontotemporal Dementia

Brain functional disruption and cognitive shortfalls as consequences of neurodegeneration are among the most investigated aspects in current clinical research. Traditionally, specific anatomical and behavioral traits have been associated with neurodegeneration, thus directly translatable in clinical terms. However, these qualitative traits, do not account for the extensive information flow breakdown within the functional brain network that deeply affect cognitive skills. Behavioural variant Frontotemporal Dementia (bvFTD) is a neurodegenerative disorder characterized by behavioral and executive functions disturbances. Deviations from the physiological cognitive functioning can be accurately inferred and modeled from functional connectivity alterations. Although the need for unbiased metrics is still an open issue in imaging studies, the graph-theory approach applied to neuroimaging techniques is becoming popular in the study of brain dysfunction. In this work, we assessed the global connectivity and topological alterations among brain regions in bvFTD patients using a minimum spanning tree (MST) based analysis of resting state functional MRI (rs-fMRI) data. Whilst several graph theoretical methods require arbitrary criteria (including the choice of network construction thresholds and weight normalization methods), MST is an unambiguous modeling solution, ensuring accuracy, robustness, and reproducibility. MST networks of 116 regions of interest (ROIs) were built on wavelet correlation matrices, extracted from 41 bvFTD patients and 39 healthy controls (HC). We observed a global fragmentation of the functional network backbone with severe disruption of information-flow highways. Frontotemporal areas were less compact, more isolated, and concentrated in less integrated structures, respect to healthy subjects. Our results reflected such complex breakdown of the frontal and temporal areas at both intra-regional and long-range connections. Our findings highlighted that MST, in conjunction with rs-fMRI data, was an effective method for quantifying and detecting functional brain network impairments, leading to characteristic bvFTD cognitive, social, and executive functions disorders

Premorbid vulnerability and disease severity impact on Long-COVID cognitive impairment

Background Cognitive deficits have been increasingly reported as possible long-term manifestations after SARS-CoV-2 infection. Aims In this study we aimed at evaluating the factors associated with cognitive deficits 6 months after hospitalization for Coronavirus Disease 2019 (COVID-19). Methods One hundred and six patients, discharged from a pneumology COVID-19 unit between March 1 and May 30 2020, accepted to be evaluated at 6 months according to an extensive neurological protocol, including the Montreal Cognitive Assessment (MoCA). Results Abnormal MoCA scores at 6 months follow-up were associated with higher pre-hospitalization National Health System (NHS) score (Duca et al. in Emerg Med Pract 22:1-2, 2020) (OR 1.27; 95% CI 1.05-1.6; p = 0.029) and more severe pulmonary disease expressed by the Brescia-COVID Respiratory Severity Scale (Duca et al. in Emerg Med Pract 22:1-2, 2020) (BCRSS > 1OR 4.73; 95% CI 1.53-14.63; p = 0.003) during the acute phase of the disease. Discussion This longitudinal study showed that the severity of COVID-19, indicated by BCRSS, and a complex score given by age and premorbid medical conditions, expressed by NHS, play a major role in modulating the long-term cognitive consequences of COVID-19 disease. Conclusions These findings indicate that the association of age and premorbid factors might identify people at risk for long-term neurological consequences of COVID-19 disease, thus deserving longer and proper follow-up

Mild Cognitive Impairment and Progression to Dementia in Progressive Supranuclear Palsy

&lt;b&gt;&lt;i&gt;Background:&lt;/i&gt;&lt;/b&gt; Cognitive deficits are common in progressive supranuclear palsy (PSP), but their relevance and the progression to dementia are still poorly described. The recently revised criteria for PSP consider cognitive dysfunction in the diagnostic work-up. &lt;b&gt;&lt;i&gt;Methods:&lt;/i&gt;&lt;/b&gt; The study retrospectively evaluated a series of 99 PSP patients with Richardson syndrome (PSP-RS), subgrouped according to cognitive and behavioural performances into PSP with normal cognition (PSP-NC), PSP with mild cognitive impairment (PSP-MCI), and PSP with dementia (PSP-D). The progression to dementia at the 3-year follow-up was assessed. &lt;b&gt;&lt;i&gt;Results:&lt;/i&gt;&lt;/b&gt; At baseline, 15.2% of patients were classified as PSP-NC, 43.4% as PSP-MCI, and 41.4% as PSP-D. During the 3-year follow-up, 21 out of 29 patients, previously classified as PSP-NC or PSP-MCI, converted to dementia, with an incidence rate of 241 per 1,000 patients/year. Nineteen out of 21 PSP patients (90%) developed the behavioural variant frontotemporal dementia phenotype. The only factor associated with conversion to dementia was MCI diagnosis at baseline (&lt;i&gt;p&lt;/i&gt; = 0.023). &lt;b&gt;&lt;i&gt;Conclusion:&lt;/i&gt;&lt;/b&gt; Cognitive decline occurs in a great proportion of PSP-RS patients early during the disease course. In the absence of a specific phenotype, the diagnosis of MCI might identify PSP patients at greatest risk of developing dementia and should be considered further in the diagnostic assessment.</jats:p

Microstructural changes across different clinical milestones of disease in amyotrophic lateral sclerosis

Neurodegenerative process in amyotrophic lateral sclerosis (ALS) has been proven to involve several cortical and subcortical brain regions within and beyond motor areas. However, how ALS pathology spreads progressively during disease evolution is still unknown. In this cross-sectional study we investigated 54 ALS patients, divided into 3 subsets according to the clinical stage, and 18 age and sex-matched healthy controls, by using tract-based spatial statistics (TBSS) diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) analyses. We aimed to identify white (WM) and gray matter (GM) patterns of disease distinctive of each clinical stage, corresponding to specific clinical milestones. ALS cases in stage 2A (i.e., at diagnosis) were characterized by GM and WM impairment of left motor and premotor cortices and brainstem at ponto-mesenchephalic junction. ALS patients in clinical stage 2B (with impairment of two functional regions) exhibited decreased fractional anisotropy (FA) (p<0.001, uncorrected) and increased mean (MD) and radial diffusivity (RD) (p<0.001, uncorrected) in the left cerebellar hemisphere and brainstem precerebellar nuclei, as well as in motor areas, while GM atrophy (p<0.001, uncorrected) was detected only in the left inferior frontal gyrus and right cuneus. Finally, ALS patients in stage 3 (with impairment of three functional regions) exhibited decreased FA and increased MD and RD (p<0.05, corrected) within WM underneath bilateral pre and postcentral gyri, corpus callosum midbody, long associative tracts and midbrain, while no significant clusters of GM atrophy were observed. Our findings reinforce the hypothesis that the neurodegenerative process propagates along the axonal pathways and develops beyond motor areas from early stages, involving progressively several frontotemporal regions and their afferents and efferents, while the detection of GM atrophy in earlier stages and its disappearance in later stages may be the result of reactive gliosis

Neuropsychological assessment in different King's clinical stages of amyotrophic lateral sclerosis

Emerging evidence shows that cognitive deficits associated with frontal lobe dysfunction occur from early stages of amyotrophic lateral sclerosis (ALS). We aimed to assess neuropsychological functioning at different stages of ALS to further delineate the occurrence of cognitive impairment alongside the trajectory of ALS as defined by standard assessment procedures. We investigated several cognitive domains in 74 ALS patients classified into four different clinical stages of disease, according to a recently validated staging system for ALS (known as King's system), and evaluated and compared the corresponding cognitive profiles. We found that data derived from global cognitive assessment and several executive (i.e. Frontal Assessment Battery and Trail Making Test B-A) and long-term memory (i.e. memory prose) tests were significantly different among the subsets of ALS patients, showing poorer performances with increasing clinical disability. In conclusion, our preliminary results support the notion that mainly frontotemporal abilities may be impaired during the ALS course and suggest that neuropsychological information could supplement the current clinical staging of patients. However, ALS-specific multi-domain screening instruments, which allow to correct neuropsychological scores for physical disability, should be validated in larger populations worldwide and routinely introduced in clinical practice

Neuropsychological assessment in different King's clinical stages of amyotrophic lateral sclerosis

<p>Emerging evidence shows that cognitive deficits associated with frontal lobe dysfunction occur from early stages of amyotrophic lateral sclerosis (ALS). We aimed to assess neuropsychological functioning at different stages of ALS to further delineate the occurrence of cognitive impairment alongside the trajectory of ALS as defined by standard assessment procedures. We investigated several cognitive domains in 74 ALS patients classified into four different clinical stages of disease, according to a recently validated staging system for ALS (known as ‘King's’ system), and evaluated and compared the corresponding cognitive profiles. We found that data derived from global cognitive assessment and several executive (i.e. Frontal Assessment Battery and Trail Making Test B-A) and long-term memory (i.e. memory prose) tests were significantly different among the subsets of ALS patients, showing poorer performances with increasing clinical disability. In conclusion, our preliminary results support the notion that mainly frontotemporal abilities may be impaired during the ALS course and suggest that neuropsychological information could supplement the current clinical staging of patients. However, ALS-specific multi-domain screening instruments, which allow to correct neuropsychological scores for physical disability, should be validated in larger populations worldwide and routinely introduced in clinical practice.</p