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Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease associated with axonal injury, and neurofilament light chains in serum (sNfL) are considered a biomarker for this damage. We aimed to investigate the relationship between sNfL and the axonal damage in early MS lesions in a special cohort of biopsied patients. sNfL from 106 biopsied patients with 26 follow-up samples were analyzed using single-molecule array (SiMoA) technology. Findings were correlated with clinical parameters and histological findings of acute axonal damage (APP-positive spheroids) and axonal loss in different lesion stages. A median of 59 pg/ml sNfL was found (range 8-3101 pg/ml). sNfL levels correlated with APP-positive spheroids in early active demyelinating lesions that represent the earliest lesion stages (p < 0.01). A significant negative correlation between sNfL levels in follow-up blood samples and axonal density in normal-appearing white matter was also observed (p = 0.02). sNfL levels correlated with the Expanded Disability Status Score at biopsy (p < 0.01, r = 0.49) and at last clinical follow-up (p < 0.01, r = 0.66). In conclusion, sNfL likely represent a compound measure of recent and ongoing neuroaxonal damage. We found that sNfL in biopsied MS patients correlate with acute axonal damage in the earliest MS lesion stages. Determination of sNfL levels thus allows insight into brain pathology and underlines the relevance of relapse-associated lesional pathology. Axonal loss in normal-appearing white matter contributes to sNfL levels independent of relapses. Since sNfL levels correlate with clinical disability, they may predict the future disability of patients and help with individual treatment decisions., (© 2022. The Author(s).)

The following review summarizes the progress in multiple sclerosis research published in the Journal of Neurology in 2009.

Mutations in the mitofusin 2 (MFN2) gene are a major cause of primary axonal Charcot- Marie-Tooth (CMT) neuropathy. This study aims at further characterization of cerebral white matter alterations observed in patients with MFN2 mutations. Molecular genetic, magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and diffusion tensor imaging (DTI) investigations were performed in four unrelated patients aged 7 to 38 years with early onset axonal CMT neuropathy. Three distinct and so far undescribed MFN2 mutations were detected. Two patients had secondary macrocephaly and mild diffuse predominantly periventricular white matter alterations on MRI. In addition, one boy had symmetrical T2-hyperintensities in both thalami. Two patients had optic atrophy, one of them with normal MRI. In three patients proton MRS revealed elevated concentrations of total N-acetyl compounds (neuronal marker), total creatine (found in all cells) and myo-inositol (astrocytic marker) in cerebral white and gray matter though with regional variation. These alterations were most pronounced in the two patients with abnormal MRI. DTI of these patients revealed mild reductions of fractional anisotropy and mild increase of mean diffusivity in white matter. The present findings indicate an enhanced cellular density in cerebral white matter of MFN2 neuropathy which is primarily due to a reactive gliosis without axonal damage and possibly accompanied by mild demyelination.

The neuropathology of multiple sclerosis is characterised by focal damage to white matter. However, tissue damage is also present in the cortical grey matter, with a particularly high prevalence of cortical demyelination being observed in secondary progressive and primary progressive forms of the disease. The presence of meningeal B-cell follicle-like structures, which frequently appear during the secondary progressive phase of disease, may be involved in the formation of these subpial cortical lesions. Diffuse white matter inflammation accompanied by axonal damage can also be observed in normal appearing white matter and, again, this is more prominent in chronic progressive forms of multiple sclerosis than in acute stages of disease. Axonal damage is a particularly important component of the pathology of multiple sclerosis and appears to be a critical determinant of clinical outcome. Axons appear to become vulnerable to injury as a result of loss of their myelin sheaths. Remyelination represents an important mechanism of tissue repair in multiple sclerosis and already occurs at an early stage of lesion development and in both white and grey matter lesions. The extent of remyelination appears to be greater in cortical lesions and in lesions further from the ventricles. There is important heterogeneity between patients in terms of the extent of remyelination, which may reflect underlying differences in pathogenetic mechanisms between patients.

Multiple sclerosis is a disease of the central nervous system that destroys myelin, oligodendrocytes, neurons and axons. Historically considered to be caused by an autoimmune process mainly affecting myelin and oligodendrocytes in the white matter, recent data provide evidence that a generalized, diffuse neurodegenerative process plays an important role in the pathogenesis of MS. There is a high density of axonal transections in active demyelinating lesions, but also persistent low-level axonal damage in inactive plaques and diffuse axonal and neuronal loss throughout the nervous system. Initial axonal injury appears to be closely related to inflammation, but is not restricted to the lesions themselves. Damage may be propagated throughout the nervous system by anterograde Wallerian, retrograde or transynaptic degeneration. Cumulative tissue loss in the grey and white matter, especially of axons, is important and probably the principal determinant of accumulation of irreversible neurological disability and of conversion to a progressive disease course.

Multiple sclerosis is a chronic inflammatory demyelinating disease of the central nervous system manifested morphologically by inflammation, demyelination, axonal loss and gliosis. The inflammatory lesions are characterized by massive infiltration by a heterogeneous population of cellular and soluble mediators of the immune system, including T cells, B cells, macrophages and mi croglia, as well as a broad range of cytokines, chemokines, antibodies, complement and other toxic substances. The appearance of such lesions is associated with clinical relapses. Recent detailed immunopathological studies of early, acute lesions revealed profound heterogeneity in the patterns of demyelination and the factors of the immune system involved. During remission, resolution of inflammation is the main factor which leads to clinical improvement of patients. However, the immune system can play a beneficial role at this stage, promoting remyelination perhaps by production of growth factors such as BDNF. In contrast, the progressive irreversible neurological deficit in multiple sclerosis is associated with neurodegenerative processes resulting in axonal and neuronal loss. The mechanisms behind damage to axons in multiple sclerosis lesions are poorly understood. However, the close proximity of areas with prominent axonal loss and areas containing inflammatory infiltrates (e. g., T cells, macrophages) suggest that axonal damage is closely associated with inflammation. Different soluble or cellular mediators of the immune response have been shown to damage axons in experimental systems, and these may be responsible for neurodegeneration in human disease.

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system. The pathological hallmarks of MS lesions in the brain and spinal cord are inflammation, demyelination, axon loss and gliosis. Recent studies revealed heterogeneity in the mechanisms leading to the formation of lesions, which include typical autoimmune patterns of demyelination involving T cells and macrophages, as well as antibody/complement as characteristic effector mechanisms. Additionally, oligodendrocyte dystrophy patterns of demyelination, with disturbances of oligodendroglial myelin protein expression and oligodendrocyte apoptosis, were observed. Treatment of MS has advanced dramatically in recent years, with the introduction of beta-interferons, glatiramer acetate and mitoxantrone. However, not all MS patients respond well to treatment with these drugs, and this may be a consequence of disease heterogeneity. Although immunomodulatory therapy has been clinically proven to be effective in patients with relapsing-remitting MS, studies in secondary-progressive MS patients have only demonstrated a positive therapeutic effect with interferon beta-1b. The pathology and pathogenesis of lesions suggest the need for a subtype-specific treatment, which may be possible when observations from pathology can be acted upon in the living MS patient. In addition to myelin and oligodendrocyte damage, the loss of axons represents another key element of MS lesions that lacks a therapeutic approach. However, axon-protective therapy is yet to be established and the mechanisms and effector molecules involved in axonal degeneration are still to be defined.

Recent clinical studies in multiple sclerosis (MS) provide new data on the treatment of clinically isolated syndromes, on secondary progression, on direct comparison of immunomodulatory treatments and on dosing issues. All these studies have important implications for the optimized care of MS patients. The multiple sclerosis therapy consensus group (MSTCG) critically evaluated the available data and provides recommendations for the application of immunoprophylactic therapies. Initiation of treatment after the first relapse may be indicated if there is clear evidence on MRI for subclinical dissemination of disease. Recent trials show that the efficacy of interferon beta treatment is more likely if patients in the secondary progressive phase of the disease still have superimposed bouts or other indicators of inflammatory disease activity than without having them. There are now data available, which suggest a possible dose-effect relation for recombinant beta-interferons. These studies have to be interpreted with caution, as some potentially important issues in the design of these studies (e. g. maintenance of blinding in the clinical part of the study) were not adequately addressed. A meta-analysis of selected interferon trials has been published challenging the value of recombinant IFN beta in MS. The pitfalls of that report are discussed in the present review as are other issues relevant to treatment including the new definition of MS, the problem of treatment failure and the impact of cost-effectiveness analyses. The MSTCG panel recommends that the new diagnostic criteria proposed by McDonald et al. should be applied if immunoprophylactic treatment is being considered. The use of standardized clinical documentation is now generally proposed to facilitate the systematic evaluation of individual patients over time and to allow retrospective evaluations in different patient cohorts. This in turn may help in formulating recommendations for the application of innovative products to patients and to health care providers. Moreover, in long-term treated patients, secondary treatment failure should be identified by pre-planned follow-up examinations, and other treatment options should then be considered.

The effect of CSF filtration on inflammation and neuronal damage was studied in experimental Streptococcus pneumoniae meningitis. New Zealand white rabbits received either antibiotic therapy alone (ceftriaxone i.v., 20 mg/kg bolus, 10 mg/kg maintenance dose; n = 10) or ceftriaxone plus CSF filtration (n = 11) 12 h after intracisternal infection. Immediately after the onset of antibiotic therapy 300 microliters cisternal CSF was removed, passed through a miniaturized CSF-1 filter at a constant flow of 20 microliters/min, and then reinjected. This procedure was repeated six times at intervals of 20 min. Antibiosis plus CSF filtration caused a transient reduction in CSF bacterial titers and leukocyte counts compared with antibiosis alone (P = 0.04 and 0.02 5 h after initiation of therapy). CSF lipoteichoic acid concentrations were not reduced. The concentration of neuron-specific enolase in CSF and the density of apoptotic neurons in the dentate gyrus were almost equal 12 h after the onset of treatment. Adjuvant CSF filtration accelerated the elimination of viable bacteria from CSF in comparison to antibiotic treatment alone. Parameters of neuronal destruction, however, were not reduced.