Shared imaging markers of fatigue across multiple sclerosis, aquaporin-4 antibody neuromyelitis optica spectrum disorder and MOG antibody disease

Fatigue is frequently reported by patients with multiple sclerosis, aquaporin-4-antibody neuromyelitis optica spectrum disorder and myelin-oligodendrocyte-glycoprotein antibody disease; thus they could share a similar pathophysiological mechanism. In this cross-sectional cohort study, we assessed the association of fatigue with resting-state functional MRI, diffusion and structural imaging measures across these three disorders. Sixteen patients with multiple sclerosis, 17 with aquaporin-4-antibody neuromyelitis optica spectrum disorder and 17 with myelin-oligodendrocyte-glycoprotein antibody disease assessed, outside of relapses, at the Oxford Neuromyelitis Optica Service underwent Modified Fatigue Impact Scale, Hospital Anxiety and Depression Scale and Expanded Disability Status Scale scoring. A 3T brain and spinal cord MRI was used to derive cortical, deep grey and white matter volumetrics, lesions volume, fractional anisotropy, brain functional connectivity metrics, cervical spinal cord cross-sectional area, spinal cord magnetic transfer ratio and average functional connectivity between the ventral and the dorsal horns of the cervical cord. Linear relationships between MRI measures and total-, cognitive- and physical-fatigue scores were assessed. All analyses were adjusted for correlated clinical regressors. No significant differences in baseline clinical characteristics, fatigue, depression and anxiety questionnaires and disability measures were seen across the three diseases, except for older age in patients with aquaporin-4-antibody neuromyelitis optica spectrum disorder (P = 0.0005). In the total cohort, median total-fatigue score was 35.5 (range 3-72), and 42% of patients were clinically fatigued. A positive correlation existed between the total-fatigue score and functional connectivity of the executive/fronto-temporal network in the in left middle temporal gyrus (P = 0.033) and between the physical-fatigue score and functional connectivity of the sensory-motor network (P = 0.032) in both pre- and post-central gyri. A negative relationship was found between the total-fatigue score and functional connectivity of the salience network (P = 0.023) and of the left fronto-parietal network (P = 0.026) in the right supramarginal gyrus and left superior parietal lobe. No clear relationship between fatigue subscores and the average functional connectivity of the spinal cord was found. Cognitive-fatigue scores were positively associated with white matter lesion volume (P = 0.018) and negatively associated with white matter fractional anisotropy (P = 0.032). Structural, diffusion and functional connectivity alterations were not influenced by the disease group. Functional and structural imaging metrics associated with fatigue relate to brain rather than spinal cord abnormalities. Salience and sensory-motor networks alterations in relation to fatigue might indicate a disconnection between the perception of the interior body state and activity and the actual behavioural responses and performances (reversible or irreversible). Future research should focus on functional rehabilitative strategies

Sodium channel Nav1.6 accumulates at the site of infraorbital nerve injury

<p>Abstract</p> <p>Background</p> <p>Sodium channel (NaCh) expressions change following nerve and inflammatory lesions and this change may contribute to the activation of pain pathways. In a previous study we found a dramatic increase in the size and density of NaCh accumulations, and a remodeling of NaChs at intact and altered myelinated sites at a location just proximal to a combined partial axotomy and chromic suture lesion of the rat infraorbital nerve (ION) with the use of an antibody that identifies all NaCh isoforms. Here we evaluate the contribution of the major nodal NaCh isoform, Na_v1.6, to this remodeling of NaChs following the same lesion. Sections of the ION from normal and ION lesioned subjects were double-stained with antibodies against Na_v1.6 and caspr (contactin-associated protein; a paranodal protein to identify nodes of Ranvier) and then z-series of optically sectioned images were captured with a confocal microscope. ImageJ (NIH) software was used to quantify the average size and density of Na_v1.6 accumulations, while additional single fiber analyses measured the axial length of the nodal gap, and the immunofluorescence intensity of Na_v1.6 in nodes and of caspr in the paranodal region.</p> <p>Results</p> <p>The findings showed a significant increase in the average size and density of Na_v1.6 accumulations in lesioned IONs when compared to normal IONs. The results of the single fiber analyses in caspr-identified typical nodes showed an increased axial length of the nodal gap, an increased immunofluorescence intensity of nodal Na_v1.6 and a decreased immunofluorescence intensity of paranodal caspr in lesioned IONs when compared to normal IONs. In the lesioned IONs, Na_v1.6 accumulations were also seen in association with altered caspr-relationships, such as heminodes.</p> <p>Conclusion</p> <p>The results of the present study identify Na_v1.6 as one isoform involved in the augmentation and remodeling of NaChs at nodal sites following a combined partial axotomy and chromic suture ION lesion. The augmentation of Na_v1.6 may result from an alteration in axon-Schwann cell signaling mechanisms as suggested by changes in caspr expression. The changes identified in this study suggest that the participation of Na_v1.6 should be considered when examining changes in the excitability of myelinated axons in neuropathic pain models.</p

Setting a national consensus for managing mild and blast traumatic brain injury: post-meeting consensus report

A meeting was held on Wednesday 15 January 2020 to examine the current evidence for non-routine imaging and for neuroendocrine screening in the management of military personnel with brain injury and overlapping symptom domains. The Summit aimed to specifically address the relative utility of magnetoencephalography (MEG), diffusion tensor imaging (DTI) and susceptibility weighted imaging (SWI) in the UK context. This Consensus Report discusses points of consensus, points for further discussion/points of equipoise and recommendations that arose during, and following, the meeting

Local Translation in Primary Afferent Fibers Regulates Nociception

Recent studies have demonstrated the importance of local protein synthesis for neuronal plasticity. In particular, local mRNA translation through the mammalian target of rapamycin (mTOR) has been shown to play a key role in regulating dendrite excitability and modulating long-term synaptic plasticity associated with learning and memory. There is also increased evidence to suggest that intact adult mammalian axons have a functional requirement for local protein synthesis in vivo. Here we show that the translational machinery is present in some myelinated sensory fibers and that active mTOR-dependent pathways participate in maintaining the sensitivity of a subpopulation of fast-conducting nociceptors in vivo. Phosphorylated mTOR together with other downstream components of the translational machinery were localized to a subset of myelinated sensory fibers in rat cutaneous tissue. We then showed with electromyographic studies that the mTOR inhibitor rapamycin reduced the sensitivity of a population of myelinated nociceptors known to be important for the increased mechanical sensitivity that follows injury. Behavioural studies confirmed that local treatment with rapamycin significantly attenuated persistent pain that follows tissue injury, but not acute pain. Specifically, we found that rapamycin blunted the heightened response to mechanical stimulation that develops around a site of injury and reduced the long-term mechanical hypersensitivity that follows partial peripheral nerve damage - a widely used model of chronic pain. Our results show that the sensitivity of a subset of sensory fibers is maintained by ongoing mTOR-mediated local protein synthesis and uncover a novel target for the control of long-term pain states

Validating the portal population of the United Kingdom Multiple Sclerosis Register

MS Society. Award 64

Promoting remyelination in multiple sclerosis-recent advances

We review the current state of knowledge of remyelination in multiple sclerosis (MS), concentrating on advances in the understanding of the pathology and the regenerative response, and we summarise progress on the development of new therapies to enhance remyelination aimed at reducing progressive accumulation of disability in MS. We discuss key target pathways identified in experimental models, as although most identified targets have not yet progressed to the stage of being tested in human clinical trials, they may provide treatment strategies for demyelinating diseases in the future. Finally, we discuss some of the problems associated with testing this class of drugs, where they might fit into the therapeutic arsenal and the gaps in our knowledge

The node of Ranvier in CNS pathology.

Healthy nodes of Ranvier are crucial for action potential propagation along myelinated axons, both in the central and in the peripheral nervous system. Surprisingly, the node of Ranvier has often been neglected when describing CNS disorders, with most pathologies classified simply as being due to neuronal defects in the grey matter or due to oligodendrocyte damage in the white matter. However, recent studies have highlighted changes that occur in pathological conditions at the node of Ranvier, and at the associated paranodal and juxtaparanodal regions where neurons and myelinating glial cells interact. Lengthening of the node of Ranvier, failure of the electrically resistive seal between the myelin and the axon at the paranode, and retraction of myelin to expose voltage-gated K(+) channels in the juxtaparanode, may contribute to altering the function of myelinated axons in a wide range of diseases, including stroke, spinal cord injury and multiple sclerosis. Here, we review the principles by which the node of Ranvier operates and its molecular structure, and thus explain how defects at the node and paranode contribute to neurological disorders