Seeing is believing: in vivo evolution of multiple sclerosis pathology with magnetic resonance

Evaluation of MS related central fatigue using MR neuroimaging methods: Scoping review

BACKGROUND

Fatigue is a common and debilitating symptom in multiple sclerosis (MS). Over the past decade, a growing body of research has focussed on the pathophysiological mechanisms underlying central (cognitive and physical) fatigue in MS. The precise mechanisms causing fatigue in MS patients are complex and poorly understood, and may differ between patients. Advanced quantitative magnetic resonance imaging (MRI) techniques allow for objective assessment of disease pathology and have been used to characterise the pathophysiology of central fatigue in MS.

OBJECTIVE

To systematically review the existing literature of MRI-based studies assessing the pathophysiological mechanisms of MS-related central fatigue.

METHODS

A systematic literature search of four major databases (PubMed, Medline, Embase, Scopus and Google Scholar) was conducted to identify MRI-based studies of MS-related fatigue published in the past 20 years. Studies using the following MRI-based methods were included: structural (lesion load/atrophy), T1 relaxation time/magnetisation transfer ratio (MTR), diffusion tensor imaging (DTI), functional MRI (fMRI) and magnetic resonance spectroscopy (MRS).

RESULTS

A total of 92 studies were identified as meeting the search criteria and included for review. Structurally, regional gray/white matter atrophy, cortical thinning, decreased T1 relaxation times and reduced fractional anisotropy were associated with central fatigue in MS. Functionally, hyperactivity and reduced functional connectivity in several regional areas of frontal, parietal, occipital, temporal and cerebellum were suggested as causes of central fatigue. Biochemically, a reduction in N-acetyl aspartate/creatine and increased (glutamine+glutamate)/creatine ratios were correlated with fatigue severity in MS.

CONCLUSION

Several advanced quantitative MRI methods have been employed in the study of central fatigue in MS. Central fatigue in MS is associated with macro/microstructural and functional changes within specific brain regions (frontal, parietal, temporal and deep gray matter) and specific pathways/networks (cortico-cortical and cortico-subcortical). Alternations in the cortico-striatal-thalamocortical (CSTC) loop are correlated with the development of fatigue in MS patients.

Relationship between symptom change, relapse activity and disability progression in multiple sclerosis

BACKGROUND

Symptom changes may serve as a risk factor for relapse activity (RA) and disability progression (DP), which could facilitate multiple sclerosis (MS) treatment decisions.

OBJECTIVE

To assess the relationship of symptom change with RA and DP.

METHODS

We evaluated the relationship of symptom change with subsequent RA and DP using NARCOMS registry data reported over a five-year period. Symptom change was evaluated using both symptom worsening (SW) and average of Performance Scales (APS) scores. Disability progression was defined as a one-point or more increase in Patient-Determined Disease Steps (PDDS) score between two consecutive updates. Repeated measures logistic regression was used to investigate the relationship between symptom change and RA and DP.

RESULTS

SW and APS were both significant predictors of subsequent RA and DP. Both SW and APS have a significant interaction with levels of disability (Mildly Impaired versus Highly Impaired) for the prediction of the subsequent RA or DP. For Mildly Impaired MS subjects, both SW and APS were significant predictors of both RA and DP. However, for Highly Impaired MS subjects, SW did not significantly predict future RA and neither SW nor APS predicted disability progression.

CONCLUSION

Changes in self-reported overall symptomatology may precede and predict clinical relapse and future disability progression. The predictive power of symptom changes may only be present at lower levels of disability.

Oxidative and Nitrosative Stress and Immune-Inflammatory Pathways in Patients with Myalgic Encephalomyelitis (ME)/Chronic Fatigue Syndrome (CFS)

Myalgic Encephalomyelitis (ME) / Chronic Fatigue Syndrome (CFS) has been classified as a disease of the central nervous system by the WHO since 1969. Many patients carrying this diagnosis do demonstrate an almost bewildering array of biological abnormalities particularly the presence of oxidative and nitrosative stress (O&NS) and a chronically activated innate immune system. The proposal made herein is that once generated chronically activated O&NS and immune-inflammatory pathways conspire to generate a multitude of self-sustaining and self-amplifying pathological processes which are associated with the onset of ME/CFS. Sources of continuous activation of O&NS and immune-inflammatory pathways in ME/CFS are chronic, intermittent and opportunistic infections, bacterial translocation, autoimmune responses, mitochondrial dysfunctions, activation of the Toll-Like Receptor Radical Cycle, and decreased antioxidant levels. Consequences of chronically activated O&NS and immune-inflammatory pathways in ME/CFS are brain disorders, including neuroinflammation and brain hypometabolism / hypoperfusion, toxic effects of nitric oxide and peroxynitrite, lipid peroxidation and oxidative damage to DNA, secondary autoimmune responses directed against disrupted lipid membrane components and proteins, mitochondrial dysfunctions with a disruption of energy metabolism (e.g. compromised ATP production) and dysfunctional intracellular signaling pathways. The interplay between all of these factors leads to self-amplifying feed forward loops causing a chronic state of activated O&NS, immune-inflammatory and autoimmune pathways which may sustain the disease.

Concurrent saturation transfer contrast in in vivo brain by a uniform magnetization transfer MRI

The development of chemical exchange saturation transfer (CEST) and magnetization transfer (MT) contrast in MRI has enabled the enhanced detection of metabolites and biomarkers in vivo. In brain MRI, the separation between CEST and MT contrast has been particularly difficult due to overlaps in the frequency responses of the contrast mechanisms. We demonstrate here that MT and CEST contrast can be separated in the brain by the so-called uniform-MT (uMT) technique, thus opening the door to addressing long-standing ambiguities in this field. These methods could be useful for keeping track of important endogenous metabolites and for providing an improved understanding of neurological and neurodegenerative disorders. Examples are shown from white and gray matter regions in healthy volunteers and patients with multiple sclerosis, which demonstrated that the MT effects in the brain were asymmetric and that the uMT method could make them uniform.

Review of MR elastography applications and recent developments

The technique of MR elastography (MRE) has emerged as a useful modality for quantitatively imaging the mechanical properties of soft tissues in vivo. Recently, MRE has been introduced as a clinical tool for evaluating chronic liver disease, but many other potential applications are being explored. These applications include measuring tissue changes associated with diseases of the liver, breast, brain, heart, and skeletal muscle including both focal lesions (e.g., hepatic, breast, and brain tumors) and diffuse diseases (e.g., fibrosis and multiple sclerosis). The purpose of this review article is to summarize some of the recent developments of MRE and to highlight some emerging applications.

Axonal degeneration as a therapeutic target in the CNS

Degeneration of the axon is an important step in the pathomechanism of traumatic, inflammatory and degenerative neurological diseases. Increasing evidence suggests that axonal degeneration occurs early in the course of these diseases and therefore represents a promising target for future therapeutic strategies. We review the evidence for axonal destruction from pathological findings and animal models with particular emphasis on neurodegenerative and neurotraumatic disorders. We discuss the basic morphological and temporal modalities of axonal degeneration (acute, chronic and focal axonal degeneration and Wallerian degeneration). Based on the mechanistic concepts, we then delineate in detail the major molecular mechanisms that underlie the degenerative cascade, such as calcium influx, axonal transport, protein aggregation and autophagy. We finally concentrate on putative therapeutic targets based on the mechanistic prerequisites.

Chemokines and chemokine receptors in neurological disease: raise, retain, or reduce?

Chemokines and chemokine receptors comprise a large number of molecules implicated in a wide range of physiological and pathological functions. Numerous studies have demonstrated the roles of chemokines and chemokine receptors: 1) during development, by regulating hematopoiesis, cardiogenesis, and vascular and cerebellar development; 2) during tumor biology, by controlling cell proliferation, angiogenesis, and metastasis; and 3), especially during leukocyte migration, by acting on firm adhesion, locomotion, diapedesis, and chemotaxis. This review focuses on chemokine and chemokine receptor involvement in diverse neurological diseases and their therapeutic potentials. Because of its induction or upregulation during CNS pathologies, members of the chemokine system can be used as biological markers. CXCR4 and CXCL12, by the correlation between their expression and the glioblastoma tumor progression, could be a marker to grade this type of CNS tumor. CCR1, by virtue of specific expression in Abeta plaques, may be a marker for Alzheimer pathology. Downregulation of CCL2 in cerebrospinal fluid may be a candidate to characterize multiple sclerosis (MS), but needs additional investigation. Moreover, chemokines and chemokine receptors represent interesting therapeutic targets. Using chemokine receptor antagonists, several studies provided exciting findings for potential neurological disease treatment. Chemokine receptor antagonists reduce disease severity in animal models of MS. In glioblastoma, a CXCR4 antagonist (AMD3100) showed an inhibition of tumor growth. Inhibition of chemokine receptor signaling is not the only therapeutic strategy: for example, CXCR4-CXCL12 has anti-inflammatory properties and CX3CL1-CX3CR1 controls neurotoxicity. Thus, chemokine biology suggests several approaches for treating neurological disease.