This article recapitulates the evidence on the role of mammalian targets of rapamycin (mTOR) complex pathways in multiple sclerosis (MS). Key biological processes that intersect with mTOR signaling cascades include autophagy, inflammasome activation, innate (e.g., microglial) and adaptive (B and T cell) immune responses, and axonal and neuronal toxicity/degeneration. There is robust evidence that mTOR inhibitors, such as rapamycin, ameliorate the clinical course of the animal model of MS, experimental autoimmune encephalomyelitis (EAE). New, evolving data unravel mechanisms underlying the therapeutic effect on EAE, which include balance among T-effector and T-regulatory cells, and mTOR effects on myeloid cell function, polarization, and antigen presentation, with relevance to MS pathogenesis. Radiologic and preliminary clinical data from a phase 2 randomized, controlled trial of temsirolimus (a rapamycin analogue) in MS show moderate efficacy, with significant adverse effects. Large clinical trials of indirect mTOR inhibitors (metformin) in MS are lacking; however, a smaller prospective, non-randomized study shows some potentially promising radiological results in combination with ex vivo beneficial effects on immune cells that might warrant further investigation. Importantly, the study of mTOR pathway contributions to autoimmune inflammatory demyelination and multiple sclerosis illustrates the difficulties in the clinical application of animal model results. Nevertheless, it is not inconceivable that targeting metabolism in the future with cell-selective mTOR inhibitors (compared to the broad inhibitors tried to date) could be developed to improve efficacy and reduce side effects.

Background: The diagnostic accuracy for Parkinson’s disease (PD), a synucleinopathy, based on diagnostic criteria is suboptimal. A biomarker for synucleinopathies is pivotal both from a clinical and from a research point of view. CSF a-synuclein has been extensively studied over the past two decades as a candidate biomarker of synucleinopathies. Herein, we present data on studies focusing on total, phosphorylated and oligomeric CSF a-synuclein in PD. Methods: Pubmed, Scopus and Web of Science were searched for studies with >10 PD patients and control subjects, with data (mean, SD) on total, phosphorylated or oligomeric a-synuclein. Cohen’s d, as a measure of effect size, was calculated for all a-synuclein forms. Subgroup analysis and meta-regression were performed in an effort to explain between-study heterogeneity. Results: Thirty studies on total, six studies on oligomeric and one study on phosphorylated a-synuclein were included. Total a-synuclein was decreased and oligomeric a-synuclein increased in PD patients vs. controls. The effect size was medium for total and high for oligomeric a-synuclein. A-syn forms provided suboptimal combined sensitivity/specificity for the differentiation of PD from controls. There was significant between-study heterogeneity. The PD cohort characteristics (sex, age, disease duration, UPDRS, H & Y) and study characteristics (study design, healthy vs. neurological controls, control for CSF blood contamination, method of a-syn measurement) could not account for between-study heterogeneity. Publication bias was limited. Conclusions: CSF a-synuclein levels lack sufficient accuracy to be used as biomarkers for PD. The standardization of (pre)analytical variables may improve the discriminatory power of a-synuclein forms in the future.

Background: Various MRI markers—including midbrain and pons areas (M_area, P_area) and volumes (M_vol, P_vol), ratios (M/P_area, M/P_vol), and composite markers (magnetic resonance imaging Parkinsonism Indices 1,2; MRPI 1,2)—have been proposed as imaging markers of Richardson’s syndrome (RS) and multiple system atrophy–Parkinsonism (MSA-P). A systematic review/meta-analysis of relevant studies aiming to compare the diagnostic accuracy of these imaging markers is lacking. Methods: Pubmed and Scopus were searched for studies with >10 patients (RS, MSA-P or CBS) and >10 controls with data on M_area, P_area, M_vol, P_vol, M/P_area, M/P_vol, MRPI 1, and MRPI 2. Cohen’s d, as a measure of effect size, was calculated for all markers in RS, MSA-P, and CBS. Results: Twenty-five studies on RS, five studies on MSA-P, and four studies on CBS were included. Midbrain area provided the greatest effect size for differentiating RS from controls (Cohen’s d = −3.10; p < 0.001), followed by M/P_area and MRPI 1. MSA-P had decreased midbrain and pontine areas. Included studies exhibited high heterogeneity, whereas publication bias was low. Conclusions: Midbrain area is the optimal MRI marker for RS, and pons area is optimal for MSA-P. M/P_area and MRPIs produce smaller effect sizes for differentiating RS from controls.

(1) Background: Frontotemporal lobar degeneration (FTLD) is a generic term which refers to multiple pathologies, including FTLD-tau. The most common FTLD-tau diseases are Pick’s disease (PiD), progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). These diseases share four major syndromes: behavioral variant frontotemporal dementia (bvFD), Richardson syndrome (RS), corticobasal syndrome (CBS) and non-fluent agrammatic primary progressive aphasia (nfa-PPA). The primary aim of this meta-analysis was to examine the diagnostic performance of CSF total (t-tau) and phosphorylated (p-tau) protein in bvFTD, RS, CBS, nfa-PPA and pathologically or genetically defined tauopathy. (2) Methods: A systematic review and meta-analysis was performed on all studies with >10 subjects in a bvFTD/RS/CBS/nfa-PPA group and control group and available data on CSF t-tau or p-tau (mean, SD). Cohen’s d was used to quantify the effect size of each study (3) Results: The PSP/tauopathy patients exhibited decreased levels of CSF p-tau compared to the control subjects. The CBS/bvFTD/nfa-PPA cohorts exhibited an increase in t-tau compared to the control groups. (4) Conclusions: Tauopathies may exhibit an inherent decrease in CSF p-tau. The admixture of AD patients in FTD cohorts and high heterogeneity among studies on rare diseases are significant confounding factors in FTLD studies.

Background: Diagnostic accuracy of Parkinson’s disease (PD), a synucleinopathy, based on diagnostic criteria is suboptimal. A biomarker for synucleinopathies is pivotal both from a clinical and from a research aspect. CSF a-synuclein has been extensively studied over the past two decades as a candidate biomarker of synucleinopathies. Herein we present data on studies focusing on total, phosphorylated and oligomeric CSF a-synuclein in PD. Methods: Pubmed, Scopus and Web of Science were searched for studies with >10 PD patients and control subjects, with data (mean, SD) on total, phosphorylated or oligomeric a-synuclein. Cohen’s d, as a measure of effect size, was calculated for all a-synuclein forms. Subgroup analysis and meta-regression were performed in an effort to explain between-study heterogeneity. Results: Thirty studies on total, six studies on oligomeric and one study on phosphorylated a-synuclein were included. Total a-synuclein was decreased and oligomeric a-synuclein increased in PD patients vs. controls. Effect size was medium for total and high for oligomeric a-synuclein. A-syn forms provided suboptimal combined sensitivity/specificity for the differentiation of PD from controls. There was significant between-study heterogeneity. PD cohort characteristics (sex, age, disease duration, UPDRS, H&Y) and study characteristics (study design, healthy vs. neurological controls, control for CSF blood contamination, method of a-syn measurement) could not account for between-study heterogeneity. Publication bias was limited. Conclusions: CSF a-synuclein levels lack sufficient accuracy to be used as biomarkers for PD. Standardization of (pre)analytical variables may improve the discriminatory power of a-synuclein forms in the future.

Introduction: Multiple MRI markers have been introduced as surrogate markers of progressive supranuclear palsy (PSP). Midbrain surface, midbrain/pons surface ratio (M/P) and the Magnetic Resonance Parkinsonism Index (MRPI) have produced high diagnostic accuracy in differentiating PSP from other parkinsonian disorders. A systematic comparison of the diagnostic accuracy of available MRI markers, and the effect of disease duration, clinical presentation, level of clinical certainty on the performance of these markers is lacking. Materials and methods: In this single-center, retrospective study, 244 subjects were included (80 PSP, 38 corticobasal degeneration, 45 multiple system atrophy, 36 Parkinson’s disease patients, 45 control subjects). All patients underwent a standardized MRI acquisition protocol and automated MRI data preprocessing through Freesurfer for volumetric data. Midbrain distance, surface and volume, superior cerebellar peduncle (SCP) width and volume, and composite markers including the M/P and M/P 2.0 ratios and the MRPI and MRPI 2.0 were measured. The diagnostic accuracy of these markers was calculated, and the effect of clinical phenotype, level of disease certainty and disease duration were investigated. Results: Surface-based MRI markers were superior to distance- and volume-based markers. Midbrain surface was the optimal MRI marker for PSP (AUC = 0.937; sensitivity 88.8%; specificity 84.2%). MRI markers were more accurate in diagnosing probable PSP vs. possible/suggestive PSP and PSP-Richardson syndrome vs. PSP variants. MRI markers exhibited comparable diagnostic accuracy in early (≤ 24 months) vs. late (≤ 48 months) disease stages. Midbrain atrophy correlated with PSP disease severity as well as ocular motor, gait and bulbar deficit severity. Discussion: Planimetric MRI markers are optimal for PSP diagnosis. Level of disease certainty (i.e. probable vs. possible/suggestive) and clinical presentation (PSP-RS vs. PSP variants) affect the diagnostic accuracy of MRI markers. MRI markers are useful even in early (≤ 24 months) stages of PSP.