Microglia-neuron interaction at nodes of Ranvier depends on neuronal activity through potassium release and contributes to remyelination.

Microglia, the resident immune cells of the central nervous system, are key players in healthy brain homeostasis and plasticity. In neurological diseases, such as Multiple Sclerosis, activated microglia either promote tissue damage or favor neuroprotection and myelin regeneration. The mechanisms for microglia-neuron communication remain largely unkown. Here, we identify nodes of Ranvier as a direct site of interaction between microglia and axons, in both mouse and human tissues. Using dynamic imaging, we highlight the preferential interaction of microglial processes with nodes of Ranvier along myelinated fibers. We show that microglia-node interaction is modulated by neuronal activity and associated potassium release, with THIK-1 ensuring their microglial read-out. Altered axonal K+ flux following demyelination impairs the switch towards a pro-regenerative microglia phenotype and decreases remyelination rate. Taken together, these findings identify the node of Ranvier as a major site for microglia-neuron interaction, that may participate in microglia-neuron communication mediating pro-remyelinating effect of microglia after myelin injury.

IVIg increases interleukin-11 levels, which in turn contribute to increased platelets, VWF and FVIII in mice and humans.

The mechanisms of action of intravenous immunoglobulins (IVIg) in autoimmune diseases are not fully understood. The fixed duration of efficacy and noncumulative effects of IVIg in immune thrombocytopenia (ITP) and acquired von Willebrand disease (AVWD) suggest other mechanisms besides immunological ones. Additionally to the peripheral destruction of platelets in ITP, their medullary hypoproduction emerged as a new paradigm with rescue of thrombopoietin receptor agonists (TPO-RA). In an ITP mouse model, interleukin (IL)-11 blood levels increase following IVIg. IL-11 stimulates the production of platelets and other haemostasis factors; recombinant IL-11 (rIL-11) is thus used as a growth factor in post-chemotherapy thrombocytopenia. We therefore hypothesized that IVIg induces IL-11 over-production, which increases platelets, VWF and factor VIII (FVIII) levels in humans and mice. First, in an ITP mouse model, we show that IVIg or rIL-11 induces a rapid increase (72 h) in platelets, FVIII and VWF levels, whereas anti-IL-11 antibody greatly decreased this effect. Secondly, we quantify for the first time in patients with ITP, AVWD, inflammatory myopathies or Guillain-Barré syndrome the dramatic IL-11 increase following IVIg, regardless of the disease. As observed in mice, platelets, VWF and FVIII levels increased following IVIg. The late evolution (4 weeks) of post-IVIg IL-11 levels overlapped with those of VWF and platelets. These data may explain thrombotic events following IVIg and open perspectives to monitor post-IVIg IL-11/thrombopoietin ratios, and to assess rIL-11 use with or without TPO-RA as megakaryopoiesis co-stimulating factors to overcome the relative hypoproduction of platelets or VWF in corresponding autoimmune diseases, besides immunosuppressant.

Antibody- and macrophage-mediated segmental demyelination in chronic inflammatory demyelinating polyneuropathy: clinical, electrophysiological, immunological and pathological correlates.

BACKGROUND AND PURPOSE: Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a heterogeneous autoimmune disorder critically lacking diagnostic biomarkers. Autoantibodies to nodal and paranodal components have recently been described in a small subset of patients. Here, the diagnostic value of immune reactivity toward the myelin compartment was investigated. METHODS: Ninety-four French CIDP patients were retrospectively studied. The reactivity toward the peripheral nerve was investigated. Sural nerve biopsies were examined by electron microscopy and immunofluorescence. RESULTS: Twenty-one patients (22%) and three patients (3%) presented with a strong immunoglobulin G or immunoglobulin M reactivity respectively against the myelin compartment. The clinical, electrophysiological and morphological features were examined in nine of these patients for whom sural nerve biopsies were available. Seven patients were electrodiagnosed with definite CIDP, one with possible CIDP and one was unclassifiable but sural nerve biopsy argued for CIDP diagnosis. Electron microscopy of sural nerve biopsies demonstrated the presence of macrophage-mediated demyelination restricted to the internode in all nine patients. Immunolabelling for voltage-gated sodium channels, myelin and axonal markers confirmed the presence of segmental demyelination and of remyelination. The nodal and paranodal regions, however, were unaffected in these patients. Nerve conduction studies corroborated the multifocal and segmental profile, and seven patients showed increased duration of proximal (1.5-5.1 times) and/or distal (1.2-3.4 times) compound muscle action potential in at least two nerves. CONCLUSION: Antibody- and macrophage-mediated demyelination appears responsible for conduction alterations in CIDP patients and nerve immunostaining assays may serve as a supportive diagnostic biomarker.

Classifications of neurogenetic diseases: An increasingly complex problem.

Neurodegenerative disorders represent a wide group of diseases affecting the central and/or peripheral nervous system. Many of these disorders were described in the 19th century, but our genetic knowledge of them is recent (over the past 25 years). However, the continual discovery of disease-causing gene mutations has led to difficulties in the classification of these diseases. For this reason, our present proposals for updating and simplifying the classification of some of these conditions (Charcot-Marie-Tooth diseases, distal hereditary motor neuropathies, hereditary sensory and autonomic neuropathies, hereditary spastic ataxias, hereditary spastic paraplegias and hereditary spastic ataxias) are expounded here.

Peripheral nervous system neuroimmunology seen by a neuro-pathologist.

In most dysimmune neuropathies, historically the microscopical lesions were described prior to immunological studies. The latter along with neuropathological studies have found some immune, albeit incomplete, explanations of the mechanisms of these lesions which we will describe in two main syndromes: the primitive auto-immune inflammatory peripheral polyneuropathies (GBS and CIDP) and polyneuropathies induced by a monoclonal dysglobulinemia. In some patients who have to be discussed case by case pathology (nerve biopsy) will confirm the diagnosis, may help to delineate the molecular anomalies and identify lesional mechanisms. We will review the high variability of nerve lesions which is characteristic of dysimmune neuropathies. Pathological studies confirm that both humoral and cellular immune reactions against Schwann cell and/or axonal antigens are implicated in primitive dysimmune neuropathies due to a dysfunction or failure of immune tolerance mechanisms. In case of a polyneuropathy associated to a monoclonal dysglobulinemia, pathological and immunological studies have shown that in many patients, the dysglobulinemia did harm the peripheral nerve; knowledge of the pathological lesions and their mechanisms is of major interest for orienting specific treatments.

Motor neuronopathy in Chediak-Higashi syndrome.

Chediak-Higashi syndrome is a rare autosomal recessive disease characterized by partial oculocutaneous albinism, recurrent pyogenic infections and the presence of giant granules in many cells such as leucocytes (hallmark of the disease). Neurological symptoms are rare. We describe two sisters who presented the same phenotype of slowly progressive motor neuronopathy (with Babinski sign in one patient); biopsy of the sural nerve showed an abnormal endoneurial accumulation of lipofuscin granules. We discuss these two observations and compare them with the few case reports of neuropathy in Chediak-Higashi syndrome.

POEMS syndrome with prominent acute axonal lesions.

Polyneuropathy is a common presenting component of POEMS syndrome whose symptoms are attributed to an overproduction of vascular endothelial growth factor (VEGF). We report two female patients with POEMS syndrome presenting as a severe predominantly axonal neuropathy. A nerve biopsy was performed for these patients; pathological data confirmed unusual numerous acute axonal lesions associated with other classical signs of POEMS syndrome. POEMS syndrome is usually associated with demyelinating neuropathy (and secondary axonal loss); however, prominent axonal neuropathy (with acute axonal lesions on nerve biopsy) can also be observed in this disease. These observations illustrate the heterogeneity of peripheral nervous system involvement in POEMS syndrome.

Krox20 inactivation in the PNS leads to CNS/PNS boundary transgression by central glia.

CNS/PNS interfaces constitute cell boundaries, since they delimit territories with different neuronal and glial contents. Despite their potential interest in regenerative medicine, the mechanisms restricting oligodendrocytes and astrocytes to the CNS, and Schwann cells to the PNS in mammals are not known. To investigate the involvement of peripheral glia and myelin in the maintenance of the CNS/PNS boundary, we have first made use of different mouse mutants. We show that inactivation of Krox20/Egr2, a master regulatory gene for myelination in Schwann cells, results in transgression of the CNS/PNS boundary by astrocytes and oligodendrocytes and in myelination of nerve root axons by oligodendrocytes. In contrast, such migration does not occur with the Trembler(J) mutation, which prevents PNS myelination without affecting Krox20 expression. Altogether these data suggest that maintenance of the CNS/PNS boundary requires a new Krox20 function separable from myelination control. Finally, we have analyzed a human patient affected by a congenital amyelinating neuropathy, associated with the absence of the KROX20 protein in Schwann cells. In this case, the nerve roots were also invaded by oligodendrocytes and astrocytes. This indicates that transgression of the CNS/PNS boundary by central glia can occur in pathological situations in humans and suggests that the underlying mechanisms are common with the mouse.

[Small fibre neuropathy in primary Sjögren syndrome]. / Neuropathie des petites fibres au cours du syndrome de Sjögren primitif.

PURPOSE: About forty percent of the patients with primary Sjögren's syndrome (pSS) experience chronic neuropathic pain with normal electrodiagnostic studies. Two previous studies suggest that chronic neuropathic pain in pSS is due to small fiber neuropathy (SFN). Quantification of epidermal nerve fiber density after skin biopsy has been validated to diagnose small fiber neuropathy. METHODS: Skin biopsy was performed in 14 consecutive pSS patients (satisfying the american-european classification criteria) with chronic neuropathic pain and normal electrodiagnostic studies suggesting SFN. RESULTS: Fourteen female pSS patients exhibited chronic neuropathic pain [burning sensation (n=14), prickling (n=4), dysesthesia (n=8)] with paroxystic exacerbations (n=10) and allodynia (n=13), for a mean period of 18.4±12.4 months. Neuropathic pain involved mostly hands and feet (n=13), with a distal (n=9) and leg (n=4) predominant distribution. Neurological examination disclosed normal deep tendon responses and absence of motor weakness (n=14). Small fiber neuropathy was confirmed by skin biopsy in 13 cases. Epidermal nerve fiber density was decreased in distal [(n=12), mean 3.5±1.7 fibers/mm (N>6.9)] and proximal site of biopsy [(n=9), mean 7.04±2.63 fibers/mm (N>9.3)]. CONCLUSION: Small fiber neuropathy is commonly responsible of chronic neuropathic pain in pSS. Prevalence, physiopathology and neurological evolution of such neuropathies still remain unknown.

[Albers-Schönberg's disease with ocular manifestation]. / Atteinte ophtalmologique au cours de la maladie d'Albers-Schönberg.

Albers-Schönberg's disease is a rare disease (one case in 100,000 inhabitants), asymptomatic in the majority of cases. It belongs to the four clearly individualized forms of human osteopetrosis and has an autosomal dominant transmission. It induces generalized osteosclerosis, and most symptoms result from complications such as fractures following mild injury, compression of cranial nerves, especially the optic nerve, by stenosis of extracranial ostia, but also osteomyelitis of the lower maxilla. The treatment of Albers-Schönberg's disease is disappointing and only symptomatic, although the responsible genetic anomaly was recently identified. We report here the case of a 54-year-old woman, whose diagnosis of the disease has been known since adolescence, who presented with unilateral loss of vision and perimetric deficit due to papilla edema resulting from stenosis of the optic canal and benign intracranial hypertension.

[Management of stroke in sub-Saharan Africa: current issues]. / Prise en charge des accidents vasculaires cérébraux en Afrique subsaharienne.

In sub-Saharan Africa, stroke is likely to present an increasingly important public health problem with a larger relative share of overall morbidity and mortality. Overall, sub-Saharan Health Care is characterized by a lack of human resources, lack of facilities for special investigations, and especially an absence of specific programs addressing the prevention of cardiovascular conditions. Current data on the epidemiology of stroke in sub-Saharan Africa, although sparse and fragmentary, indicate a comparatively high incidence of cerebral hemorrhage associated with high blood pressure, while ischemic stroke in black Africans still appears to be related primarily to small artery disease, HIV infection, and sickle cell disease. With urbanization, the role of large-vessel atherosclerosis is increasing. It is thus essential to coordinate government funding, health care professionals and development agencies to address this rising health problem. Access to health care needs to be better structured, and screening programs should be developed in order to identify and treat vascular risk factors. Improved training of health care professionals is also required in the areas of prevention, diagnosis and management of stroke. Implementation of best-practice recommendations for the management of stroke adapted to the specificities and resources of African countries would help rationalize the scarce resources currently available.

Intramuscular interferon beta-1a in chronic inflammatory demyelinating polyradiculoneuropathy.

OBJECTIVE: Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) shares immunologic features with multiple sclerosis (MS). Because IM interferon beta-1a (IM IFNbeta-1a) is an effective and safe treatment for MS, we conducted a dose-ranging efficacy study of IFNbeta-1a in patients with CIDP. METHODS: Adults with IV immunoglobulin (IVIg)-dependent CIDP (n = 67) were enrolled in this 32-week double-blind trial and randomized to IM IFNbeta-1a. Patients received 30 microg once weekly plus placebo (n = 12), IM IFNbeta-1a 60 microg once weekly plus placebo (n = 11), IM IFNbeta-1a 30 microg twice weekly (n = 11), IM IFNbeta-1a 60 microg twice weekly (n = 11), or placebo twice weekly (n = 22). Participants were maintained on IVIg through week 16, when IVIg was discontinued. Patients who worsened were restarted on IVIg. The primary outcome was total IVIg dose (g/kg) administered from week 16 to 32. RESULTS: There was no difference in total IVIg dose administered after week 16 for patients treated with IFNbeta-1a (1.20 g/kg) compared with placebo (1.34 g/kg; p = 0.75). However, exploratory analyses suggested IFNbeta-1a significantly reduced total dose of IVIg compared with placebo for participants who required either high-dose IVIg (>0.95 g/kg per month) or had greater weakness at baseline (Medical Research Council sum score <51). Adverse events included flu-like symptoms, headache, and fatigue in the IFNbeta-1a groups. CONCLUSIONS: Interferon beta-1a (IFNbeta-1a) therapy did not provide significant benefit over IV immunoglobulin (IVIg) therapy alone for patients with chronic inflammatory demyelinating polyradiculoneuropathy. However, IFNbeta-1a might be beneficial for patients with more severe disability or those needing high doses of IVIg. LEVEL OF EVIDENCE: This study was designed to provide Class I evidence for the safety and efficacy of IM IFNbeta-1a in the treatment of CIDP but has been subsequently classified as Class II due to a >20% patient dropout rate. Thus, this randomized, controlled clinical trial provides Class II evidence of no effect on primary and secondary endpoints of 4 dosage regimens of IM IFNbeta-1a added to IVIg in persons with CIDP.

[Polyneuropathies in vitamin B1 deficiency in Reunion and Mayotte islands in 70 patients of Maori and Comorian descent]. / Polyneuropathies par hypovitaminose B1 aux îles de la Réunion et de Mayotte: à propos de 70 cas d'origine mahoraise et comorienne.

Beriberi is an uncommon disorder related to thiamine deficiency. It is mainly found in underdeveloped countries among populations with poorly diversified diet, consisting largely of milled white cereals, a poor source of thiamine. In industrialized countries, thiamine deficiency with cardiac failure is more frequently found than the dry beriberi in high risk groups like chronic alcoholics. Nevertheless our attention was drawn to an outbreak of 70 cases of dry beriberi which occurred from 1997 to 2005 in the French territories of Reunion and Mayotte islands. It was characterized by an acute or sub-acute sensorimotor polyneuropathy with axonal lesions, affecting the lower limbs and occasionally the upper limbs, sometimes associated with cardiac beriberi. It affected young, non alcoholic individuals from the Mahoran and Comorian community who were in apparent good health when the illness occurred. Our study highlighted the feeding habits which are partly responsible for the development of the disease due to a chronic lack of thiamine and which probably contributed together with multiple cofactors to trigger off the illness. But many elements and mainly biological ones, also lead us to think that there is a genetic predisposition to develop this neuropathy.

Ataxia with oculomotor apraxia type 2: a clinical and genetic study of 19 patients.

Ataxia with oculo-motor apraxia type 2 (AOA2) is a recently described autosomal recessive cerebellar ataxia (ARCA) caused by mutations in the senataxin gene (SETX). We analysed the phenotypic spectrum of 19 AOA2 patients with mutations in SETX, which seems to be the third most frequent form of ARCA in Algeria after Freidreich ataxia and Ataxia with vitamin E deficiency. In AOA2 patients, the mean age at onset for all families was in the second decade. Cerebellar ataxia was progressive, slowly leading to disability which was aggravated by axonal polyneuropathy present in almost all the patients. Mean disease duration until wheelchair was around 20 years. Oculo-motor apraxia (OMA) was present in 32% of the patients while convergent strabismus was present in 37%. Strabismus is therefore also very suggestive of AOA2 when associated with ataxia and polyneuropathy even in the absence of OMA. Cerebellar atrophy was more severe in the eldest patients; however it may also be an early sign since it was present in the youngest and paucisymptomatic patients. The initial sign was gait ataxia in all but two patients who presented with head tremor and writer cramp, respectively. Serum alpha-fetoprotein, which was elevated in all tested patients, was a good marker to suggest molecular studies of the SETX gene.

[Sensory-motor neuropathy: a slow and misleading case of leprosy]. / Neuropathie périphérique sensitivomotrice : une forme lente et trompeuse de maladie de Hansen.

The diagnostic process of sensory-motor neuropathies is difficult. Atypical variants and rare etiologies also contribute to delay the diagnosis. We report the case of a 70-year-old woman with slowly progressive asymmetric axonal sensory-motor neuropathy. Leprosy was identified after an eight-year delay. Nerve biopsy was required to establish the diagnosis: electron microscopy revealed debris of Hansen's bacillus in the nerve. Treatment was fully curative after several months. Leprosy is a rare cause of neuropathy in Europeans. Systematic inquiry about travel to endemic areas would be helpful in establishing the diagnosis. In such cases, nerve biopsy is crucial.

Recommendations on diagnostic strategies for chronic inflammatory demyelinating polyradiculoneuropathy.

BACKGROUND: Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an immune mediated treatable peripheral neuropathy, the diagnosis of which is straightforward in more than half of cases. Numerous sets of electrophysiological criteria have been published. However, in some cases, electrophysiological data are not sufficient and patients that may benefit from treatment escape accurate diagnosis. OBJECTIVE: To describe a step by step diagnostic procedure for neurologists facing a peripheral neuropathy of undetermined cause, to help make an accurate diagnosis of CIDP. METHODS: A group of French experts was established, neurologists and neurophysiologists being recruited on the basis of personal experience with patients suffering from CIDP and also on publications in the field. A full literature review was conducted on the topic of diagnostic criteria and procedures for the diagnosis of CIDP, and meetings were scheduled to reach a consensus on the best diagnostic workup in different clinical situations. RESULTS: Six meetings were conducted and a consensus was reached, based on the available literature and experience in the management of such patients. Discussions resulted in defining five clinical situations in which a diagnosis of CIDP may be considered, and procedures were detailed in each case, including the location of nerve biopsy and use of non-conventional electrophysiological testing and imaging procedures. CONCLUSION: The guidelines in the diagnostic procedure reported here result from a consensus of French experts in the field of peripheral neuropathy and allow a diagnosis of CIDP to be made in the most frequently encountered situations. These recommendations may be of value for physicians as they rely on the rational use of available techniques in typical clinical situations.

Severe early-onset axonal neuropathy with homozygous and compound heterozygous MFN2 mutations.

OBJECTIVE: Severe early-onset axonal neuropathy (SEOAN) is a heterogeneous phenotype first delineated by Ouvrier et al., characterized by progressive axonal degeneration with gait problems often progressing to wheelchair requirement and later respiratory involvement. Most cases are sporadic single cases. Some have heterozygous mitofusin 2 (MFN2) mutations, many of which are de novo dominant mutations. The aim of this study was to investigate the mode of inheritance in three individuals with severe early-onset axonal neuropathy and homozygous or compound heterozygous MFN2 mutations. METHODS: The clinical and molecular findings in the parents of three individuals with SEOAN with homozygous or compound heterozygous MFN2 mutations were examined. RESULTS: All parents were asymptomatic or mildly symptomatic with some signs of peripheral neuropathy indicating a minimal phenotype. Two had hearing problems. All parents carried the relevant single base (heterozygous) MFN2 variations. CONCLUSION: Severe early-onset axonal neuropathy due to MFN2 mutations can present as an apparently recessively inherited neuropathy but the minimal phenotype in the parents suggests a semi-dominant mechanism.

Contribution of electron microscopy to the study of neuropathies associated with an IgG monoclonal paraproteinemia.

A typical monoclonal IgG dysglobulinemia whether benign (monoclonal gammopathy of undetermined significance, MGUS) or malignant can give rise to peripheral neuropathy by damaging nerves. At first, neurotoxicity of the chemotherapy if the patient is treated must be ruled out in such cases. Indeed, a variety of other mechanisms have been described: endoneurial deposits of immunoglobulin, infiltration of the immunoglobulin within myelin sheaths, POEMS syndrome, deposits of amyloid, chronic inflammatory demyelinating polyradiculoneuropathy and infiltration of malignant cells. Ultrastructural examination of a nerve biopsy can be decisive in combination with routine histological and immunopathological examinations. Characterization of the mechanism of the neuropathy in a dysglobulinemic context is important as it governs therapeutic options, which in certain cases are particularly beneficial.