Uncommon 18F-FDG-PET/CT findings in patients affected by limbic encephalitis: Hyper-hypometabolic pattern with double antibody positivity and migrating foci of hypermetabolism

Autoimmune limbic encephalitis (LE) is a rare disorder; its diagnosis can be challenging.We report two uncommon cases of LE evaluated by brain 2-deoxy-2-[18F]fluoro-d-glucose (18F-FDG) positron emission tomography/ computed tomography describing themetabolic imaging patterns, which were different from those observed in previous studies: the first one presented an unprecedented 18F-FDG brain mixed pattern, involving also themidbrain, despite negative magnetic resonance imaging exams; the second one showed migrating foci of hypermetabolism, one of which turned into hypometabolism at a later examination

Prevention of dental caries: a review of effective treatments

The objective of this study is to review medical and non medical treatments for prevention of caries. A comprehensive literature search of the most relevant and updated published studies from 01/01/2002 through December 2015 in PubMed/MEDLINE, Embase and Scopus databases regarding the efficacy of strategies and treatments aiming to prevent the development of caries was performed selecting papers on the basis of the Evidence-based Medicine Criteria. We identified thirty systematic reviews on prevention of caries. Analyzing the data the retrieved literature, performance of prevention treatments seems to be high. Prevention treatments may have a relevant impact on the avoiding the development of caries planning

Role of PET and SPECT in the study of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis has been defined as a "heterogeneous group of neurodegenerative syndromes characterized by progressive muscle paralysis caused by the degeneration of motor neurons allocated in primary motor cortex, brainstem, and spinal cord." A comprehensive diagnostic workup for ALS usually includes several electrodiagnostic, clinical laboratory and genetic tests. Neuroimaging exams, such as computed tomography, magnetic resonance imaging and spinal cord myelogram, may also be required. Nuclear medicine, with PET and SPECT, may also play a role in the evaluation of patients with ALS, and provide additional information to the clinicians.This paper aims to offer to the reader a comprehensive review of the different radiotracers for the assessment of the metabolism of glucose (FDG), the measurement of cerebral blood flow (CBF), or the evaluation of neurotransmitters, astrocytes, and microglia by means of newer and not yet clinically diffuse radiopharmaceuticals

Metabolic spatial connectivity in Amyotrophic Lateral Sclerosis as revealed by independent component analysis

Objectives. Positron emission tomography (PET) and volume of interest (VOI) analysis have recently shown in amyotrophic lateral sclerosis (ALS) an accuracy of 93% in differentiating patients from controls. The aim of this study was to disclose by spatial independent component analysis (ICA) the brain networks involved in ALS pathological processes and evaluate their discriminative value in separating patients from controls. Experimental design. Two hundred fifty-nine ALS patients and 40 age- and sex-matched control subjects underwent brain 18F-2-fluoro-2-deoxy-D-glucose PET (FDG-PET). Spatial ICA of the preprocessed FDG-PET images was performed. Intensity values were converted to z-scores and binary masks were used as data-driven VOIs. The accuracy of this classifier was tested versus a validated system processing intensity signals in 27 brain meta-VOIs. A support vector machine was independently applied to both datasets and the \u27leave-one-out\u27 technique verified the general validity of results. Principal observations: The 8 components selected as pathophysiologically meaningful discriminated patients from controls with 99.0% accuracy, the discriminating value of bilateral cerebellum/midbrain alone representing 96.3%. Among the meta-VOIs, right temporal lobe alone reached an accuracy of 93.7%. Conclusions: Spatial ICA identified in a very large cohort of ALS patients distinct spatial networks showing a high discriminatory value, improving substantially on the previously obtained accuracy. The cerebellar/midbrain component accounted for the highest accuracy in separating ALS patients from controls. Spatial ICA and multivariate analysis perform better than univariate semi-quantification methods in identifying the neurodegenerative features of ALS and pave the way for inclusion of PET in clinical trials and early diagnosis

Functional pattern of Brain FDG-PET in Amyotrophic Lateral Sclerosis

Objective: We investigated a large sample of patients with amyotrophic lateral sclerosis (ALS) at rest in order to assess the value of 18F-2-fluoro-2-deoxy-D-glucose (18F-FDG) PET as a biomarker to discriminate patients from controls. Methods: A total of 195 patients with ALS and 40 controls underwent brain 18F-FDG-PET, most within 5 months of diagnosis. Spinal and bulbar subgroups of ALS were also investigated. Twenty-five bilateral cortical and subcortical volumes of interest and cerebellum were taken into account, and 18F-FDG uptakes were individually normalized by whole-brain values. Group analyses investigated the ALS-related metabolic changes. Discriminant analysis investigating sensitivity and specificity was performed using the 51 volumes of interest as well as age and sex. Metabolic connectivity was explored by voxel-wise interregional correlation analysis. Results: Hypometabolismwas found in frontal, motor, and occipital cortex and hypermetabolismin midbrain, temporal pole, and hippocampus in patients with ALS compared to controls. A similar metabolic pattern was also found in the 2 subgroups. Discriminant analysis showed a sensitivity of 95% and a specificity of 83% in separating patients from controls. Connectivity analysis found a highly significant positive correlation between midbrain and white matter in corticospinal tracts in patients with ALS. Conclusions: 18F-FDG distribution changes in ALS showed a clear pattern of hypometabolism in frontal and occipital cortex and hypermetabolism in midbrain. The latter might be interpreted as the neurobiological correlate of diffuse subcortical gliosis. Discriminant analysis resulted in high sensitivity and specificity in differentiating patients with ALS from controls. Once validated by diseased-control studies, the present methodology might represent a potentially useful biomarker for ALS diagnosis. Classificaton of evidence: This study provides Class III evidence that 18F-FDG-PET accurately distinguishes patients with ALS from normal controls (sensitivity 95.4%, specificity 82.5%)

The metabolic signature of C9ORF72-related ALS: FDG PET comparison with nonmutated patients

Purpose Recently, a GGGGCC hexanucleotide repeat expansion in the C9ORF72 gene, located on chromosome 9p21 has been demonstrated to be the commonest cause of familial amyotrophic lateral sclerosis (ALS) and to account for 5 to 10 % of apparently sporadic ALS. Relatively little is known about the brain metabolism profile of patients carrying the expansion. Our aim was to identify the [18F]FDG PET profile in ALS patients with the C9ORF72 expansion (C9ORF72-ALS). Methods Fifteen C9ORF72-ALS patients were compared with 12 patients with ALS and comorbid frontotemporal dementia (FTD) without the C9ORF72 expansion (ALSFTD) and 30 cognitively normal patients with ALS without mutations of ALS-related genes (sALS). The three groups were then cross-matched to 40 neurologically normal controls. All patients underwent FDG PET within 4 months of diagnosis. Results The C9ORF72-ALS patients compared with the sALS patients showed significant hypometabolism in the anterior and posterior cingulate cortex, insula, caudate and thalamus, the left frontal and superior temporal cortex, and hypermetabolism in the midbrain, bilateral occipital cortex, globus pallidus and left inferior temporal cortex. The ALS FTD patients compared with the sALS patients showed more limited hypometabolic areas, including the orbitofrontal, prefrontal, anterior cingulate and insular cortex, and hypermetabolic areas, including the bilateral occipital cortex, the left precentral and postcentral cortex and superior temporal gyrus. The C9ORF72-ALS patients compared with the ALS-FTD patients showed hypometabolism in the left temporal cortex. Conclusion ALS patients with the C9ORF72 hexanucleotide repeat expansion had a more widespread central nervous system involvement than ALS patients without genetic mutations, with or without comorbid FTD, consistent with their more severe clinical picture

18F-FDG-PET correlates of cognitive impairment in ALS

Objective: To identify the metabolic signature of the various levels of cognitive deficits in amyotrophic lateral sclerosis (ALS) using 18F-2-fluoro-2-deoxy-D-glucose-PET (18F-FDG-PET). Methods: A total of 170 ALS cases consecutively enrolled at the ALS Center of Turin underwent brain 18F-FDG-PET and were classified as displaying normal cognition (ALS-Cn; n 5 94), full-blown frontotemporal dementia (ALS-FTD; n 5 20), executive or nonexecutive cognitive impairment not fulfilling FTD criteria (ALS-Ci; n 5 37), prevalent behavioral changes (n 5 9), or nonclassifiable impairment (n 5 10) according to neuropsychological testing. Group comparisons of 18F-FDG-PET pattern were carried out among the cognitive subgroups. Results: We found a significantly reduced frontal and prefrontal metabolism in ALS-FTD as compared to ALS-Cn, while ALS-Ci showed an intermediate metabolic behavior in frontal cortex, being hypometabolic as compared to ALS-Cn, and relatively hypermetabolic as compared to ALS-FTD. Hypometabolism in frontal regions was associated in all comparisons to hypermetabolism in cerebellum, midbrain, and corticospinal tracts: the more severe the cognitive decline, the larger the size of the cluster and the statistical significance of 18F-FDG uptake differences. Conclusions: This study demonstrated in a large cohort of patients with ALS a continuum of frontal lobe metabolic impairment reflecting the clinical and anatomic continuum ranging from pure ALS, through ALS with intermediate cognitive deficits, to ALS-FTD, and showing that patients with intermediate cognitive impairment display a characteristic metabolic pattern. Since 18F-FDG-PET allows us to estimate the cerebral lesion load in vivo in neurodegenerative diseases, it might be helpful to investigate in ALS its association with neuropsychological testing along the disease course to disclose the early metabolic signature of possible cognitive impairment

Exciton migration in two-dimensional materials

Excitons play an essential role in the optical response of two-dimensional materials. These are bound states showing up in the band gaps of many-body systems and are conceived as quasiparticles formed by an electron and a hole. By performing real-time simulations in hBN, we show that an ultrashort (few-fs) UV pulse can produce a coherent superposition of excitonic states that induces an oscillatory motion of electrons and holes between different valleys in reciprocal space, leading to a sizeable exciton migration in real space. We also show that an ultrafast spectroscopy scheme based on the absorption of an attosecond pulse in combination with the UV pulse can be used to read out the laser-induced coherences, hence to extract the characteristic time for exciton migration. This work opens the door towards ultrafast electronics and valleytronics adding time as a control knob and exploiting electron coherence at the early times of excitation

Exciton migration in two-dimensional materials

Excitons play an essential role in the optical response of two-dimensional materials. These are bound states showing up in the band gaps of many-body systems and are conceived as quasiparticles formed by an electron and a hole. By performing real-time simulations in hBN, we show that an ultrashort (few-fs) UV pulse can produce a coherent superposition of excitonic states that induces an oscillatory motion of electrons and holes between different valleys in reciprocal space, leading to a sizeable exciton migration in real space. We also show that an ultrafast spectroscopy scheme based on the absorption of an attosecond pulse in combination with the UV pulse can be used to read out the laser-induced coherences, hence to extract the characteristic time for exciton migration. This work opens the door towards ultrafast electronics and valleytronics adding time as a control knob and exploiting electron coherence at the early times of excitationThis publication is based upon work from COST Action AttoChem, CA18222 supported by COST (European Cooperation in Science and Technology). M. Malakhov, G. Cistaro, and A. Pic\u00F3n acknowledge grants ref. PID2021-126560NB-I00 and CNS2022-135803 (MCIU/AEI/FEDER, UE), and the \u201CMar\u00EDa de Maeztu\" Programme for Units of Excellence in R&D (CEX2023-001316-M), and FASLIGHT network (RED2022-134391-T), and grants refs. 2017-T1/IND-5432 and 2021-5A/IND-20959 (Comunidad de Madrid through TALENTO program). M. Malakhov\u2019s work also carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation (theme \u201CQuantum\u201D No. 122021000038-7).\u00A0MM acknowledges funding from the Spanish Ministerio de Ciencia, Innovaci\u00F3n y Universidades grants (TED2021-1327 57B-I00, PID2022-143013OB-I00). F. Mart\u00EDn acknowledges the projects PID2019-105458RB-I00 funded by MCIN/AEI/10.13039/501100011033 and by the European Union \u201CNextGenerationEU\"/PRTRMICINN programs, and the \u201CSevero Ochoa\" Programme for Centres of Excellence in R&D (CEX2020-001039-S). Calculations were performed at the Centro de Computaci\u00F3n Cient\u00EDfica de la Universidad Aut\u00F3noma de Madrid (FI-2021-1-0032), Instituto de Biocomputaci\u00F3n y F\u00EDsica de Sistemas Complejos de la Universidad de Zaragoza (FI-2020-3-0008), and Barcelona Supercomputing Center (FI-2020-1-0005, FI-2021-2-0023, FI-2021-3-0019) and Picasso (FI-2022-1-0031,FI-2022-2-0031,FI-2022-3-0022

Primary CNS Lymphomas: Challenges in Diagnosis and Monitoring

Primary Central Nervous System Lymphoma (PCNSL) is a rare neoplasm that can involve brain, eye, leptomeninges, and rarely spinal cord. PCNSL lesions most typically enhance homogeneously on T1-weighted magnetic resonance imaging (MRI) and appear T2-hypointense, but high variability in MRI features is commonly encountered. Neurological symptoms and MRI findings may mimic high grade gliomas (HGGs), tumefactive demyelinating lesions (TDLs), or infectious and granulomatous diseases. Advanced MRI techniques (MR diffusion, spectroscopy, and perfusion) and metabolic imaging, such as Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) or amino acid PET (usually employing methionine), may be useful in distinguishing these different entities and monitoring the disease course. Moreover, emerging data suggest a role for cerebrospinal fluid (CSF) markers in predicting prognosis and response to treatments. In this review, we will address the challenges in PCNSL diagnosis, assessment of response to treatments, and evaluation of potential neurotoxicity related to chemotherapy and radiotherapy