CIDP - the relevance of recent advances in Schwann cell/axonal neurobiology

How I Treat Chronic Inflammatory Demyelinating Polyneuropathy Podcast

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired immune-mediated neuropathy that typically presents with progressive or relapsing, symmetric, proximal, and distal weakness of upper and lower limbs, sensory involvement of at least two limbs, and decreased or absent deep tendon reflexes. The symptoms of CIDP can be similar to those of other neuropathies, making diagnosis difficult, which can often lead to delays in correct diagnosis and treatment. The updated European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) 2021 guideline outlines a set of diagnostic criteria that help to identify CIDP with high accuracy and provides recommendations for the treatment of CIDP. The aim of this podcast, featuring Dr. Urvi Desai (Professor of Neurology, Wake Forest School of Medicine and Atrium Health Neurosciences Institute Wake Forest Baptist, Charlotte), is to discuss how the new guideline impacts diagnosis and treatment decisions in her everyday clinical practice. Using a patient case study example, the updated guideline recommends assessing a patient for clinical, electrophysiological, and supportive criteria for CIDP, enabling a more straightforward diagnosis of either typical CIDP, a CIDP variant, or an autoimmune nodopathy. A second patient case study highlights how the new guideline no longer considers autoimmune nodopathies as CIDP, as patients with these disorders do not meet hallmark CIDP criteria. This leaves an unmet need in terms of guidance on how to treat this subset of patients. Although the new guideline has not necessarily changed treatment preference in clinical practice, the addition of subcutaneous immunoglobulin (SCIG) into the guideline now better reflects clinical practice. The guideline helps to define and categorize CIDP more simply and consistently, allowing quicker and more accurate diagnosis, leading to a positive impact on treatment response and prognosis. These real-world insights into the diagnosis and management of patients with CIDP could help guide best clinical practice and help facilitate optimization of patient outcomes.

Glial cells and neurologic autoimmune disorders

Neurologic autoimmune disorders affect people's physical and mental health seriously. Glial cells, as an important part of the nervous system, play a vital role in the occurrence of neurologic autoimmune disorders. Glial cells can be hyperactivated in the presence of autoantibodies or pathological changes, to influence neurologic autoimmune disorders. This review is mainly focused on the roles of glial cells in neurologic autoimmune disorders and the influence of autoantibodies produced by autoimmune disorders on glial cells. We speculate that the possibility of glial cells might be a novel way for the investigation and therapy of neurologic autoimmune disorders.

Peripheral nerve electrophysiology studies in relation to fatigue in patients with chronic inflammatory demyelinating polyneuropathy

OBJECTIVE

To explore the relationship between fatigue, standard electrophysiological parameters and number and size of functioning motor units in patients with chronic inflammatory demyelinating polyneuropathy (CIDP).

METHODS

Experienced fatigue was assessed using the linearly-weighted, modified Rasch-built fatigue severity scale (R-FSS) and the multidimensional Checklist of Individual Strength (CIS). Averaged electrophysiology values were calculated from multiple nerves. Motor Unit Number Index (MUNIX) technique was utilised to assess motor unit function. Assessments were repeated in 15 patients receiving regular intravenous immunoglobulin therapy, with changes in parameters calculated.

RESULTS

R-FSS and CIS scores did not correlate MUNIX or MUSIX sum scores from 3 different muscles. Inverse correlation was observed only between distal CMAP area and R-FSS but not CIS scores. However, changes in distal CMAP area and R-FSS scores on repeat assessment were not correlated.

CONCLUSIONS

Experienced fatigue does not appear to correlate with loss of functioning motor units in patients with CIDP. Changes in experienced fatigue on repeat assessment did not correlate with changes in any of the electrophysiological parameters, suggesting fatigue experienced in CIDP is not strongly correlated with peripheral nerve dysfunction.

SIGNIFICANCE

Nerve conduction studies and MUNIX values do not appear to be useful surrogate markers for fatigue in CIDP.

Immunomodulatory and anti-oxidative effect of the direct TRPV1 receptor agonist capsaicin on Schwann cells

Background

Only few studies describe the impact of nutritive factors on chronic inflammatory demyelinating polyneuropathy (CIDP), an inflammatory disease of the peripheral nervous system. The active component of chili pepper, capsaicin, is the direct agonist of the transient receptor potential channel vanilloid subfamily member 1. Its anti-inflammatory effect in the animal model experimental autoimmune neuritis (EAN) has been previously demonstrated.

Methods

In the present study, we describe the anti-inflammatory and anti-oxidative influence of capsaicin on Schwann cells (SCs) in an in vitro setting. Hereby, we analyze the effect of capsaicin on Schwann cells’ gene expression pattern, major histocompatibility complex class II (MHC-II) presentation, and H₂O₂-induced oxidative stress. Furthermore, the effect of capsaicin on myelination was examined in a SC-dorsal root ganglia (DRG) coculture by myelin basic protein staining. Finally, in order to investigate the isolated effect of capsaicin on SCs in EAN pathology, we transplant naïve and capsaicin pre-treated SCs intrathecally in EAN immunized rats and analyzed clinical presentation, electrophysiological parameters, and cytokine expression in the sciatic nerve.

Results

In SC monoculture, incubation with capsaicin significantly reduces interferon gamma-induced MHC-II production as well as toll-like receptor 4 and intercellular adhesion molecule 1 mRNA expression. Calcitonin gene-related peptide mRNA production is significantly upregulated after capsaicin treatment. Capsaicin reduces H₂O₂-induced oxidative stress in SC in a preventive, but not therapeutic setting. In a SC-DRG coculture, capsaicin does not affect myelination rate. After intrathecal transplantation of naïve and capsaicin pre-treated SCs in EAN-immunized rats, naïve, but not capsaicin pre-treated intrathecal SCs, ameliorated EAN pathology in rats.

Conclusions

In conclusion, we were able to demonstrate a direct immunomodulatory and anti-oxidative effect of capsaicin in a SC culture by reduced antigen presentation and expression of an anti-inflammatory profile. Furthermore, capsaicin increases the resistance of SCs against oxidative stress. A primary effect of capsaicin on myelination was not proven. These results are in concordance with previous data showing an anti-inflammatory effect of capsaicin, which might be highly relevant for CIDP patients.

Lysosomes as a therapeutic target

Lysosomes are membrane-bound organelles with roles in processes involved in degrading and recycling cellular waste, cellular signalling and energy metabolism. Defects in genes encoding lysosomal proteins cause lysosomal storage disorders, in which enzyme replacement therapy has proved successful. Growing evidence also implicates roles for lysosomal dysfunction in more common diseases including inflammatory and autoimmune disorders, neurodegenerative diseases, cancer and metabolic disorders. With a focus on lysosomal dysfunction in autoimmune disorders and neurodegenerative diseases - including lupus, rheumatoid arthritis, multiple sclerosis, Alzheimer disease and Parkinson disease - this Review critically analyses progress and opportunities for therapeutically targeting lysosomal proteins and processes, particularly with small molecules and peptide drugs.

IgPro20, the Polyneuropathy and Treatment with Hizentra® study (PATH), and the treatment of chronic inflammatory demyelinating polyradiculoneuropathy with subcutaneous IgG

Subcutaneous IgG (SCIG) administration may be preferred over the intravenous route (IVIG) in chronic inflammatory demyelinating polyneuropathy (CIDP) because it minimizes ‘end of cycle’ treatment-related fluctuations, reduces systemic adverse effects, improves convenience/quality of life and potentially lowers overall costs. Early reports of the use of highly concentrated SCIG preparations suggested they were effective and well-tolerated in chronic inflammatory demyelinating polyneuropathy. This was confirmed in the Polyneuropathy and Treatment with Hizentra® study of 172 subjects randomized to receive maintenance therapy with placebo or one of two doses of IgPro20 (20% IgG stabilized with L-Proline) for 6 months. Risk of relapse was reduced by SCIG in a dose-related manner as compared with placebo. A total of 88% of polyneuropathy and treatment with hizentra subjects felt the subcutaneous method was ‘easy to learn’. Local adverse events were mostly mild or moderate, and systemic adverse events were infrequent. Some patients may prefer maintenance therapy with SCIG over IVIG.

Electro-Physiology of Coupling Model and Its Impact on Naja Kaouthia Venom Treated Sciatic Nerves of Toad

Demyelination in peripheral nerves causes dysfunction of slowing down and stoppage of nerve impulses causing many neurological diseases, such as chronic inflammatory demyelinating polyneuropathy, Guillain-Barre syndrome, etc. This paper aims to develop a recovery model having interaction of a demyelinated nerve with a normal myelinated nerve. We validated the model by coupling between peripheral nerve of toad (demyelinated with Naja kaouthia venom) and a normal nerve of toad. An increase in both nerve conduction velocity as well as compound action potential amplitude is observed in the repetition of the experiments indicating gradual recovery of the patients. The significance behind this work is to suppress the malfunctioning of the demyelinated nerve by the normal electro-physiological activity of the normal nerve for speedy recovery using coupling model. The recovery model will be used in the treatment of neurological disorders with the influence of normal neuro physiological properties of a normal adjacent nerve.

Individualized immunoglobulin therapy in chronic immune-mediated peripheral neuropathies

Despite the well-recognized importance of immunoglobulin therapy individualization during the treatment of chronic inflammatory demyelinating polyneuropathy (CIDP), the pathway to best achieve optimization is unknown. There are many pharmacokinetic and immunobiologic variables that can potentially influence the appropriateness of any individual therapy. Although identification of specific autoantibodies and their targets has only been accomplished in a minority of patients with CIDP, already the diagnostic and treatment implications of specific autoantibody detection are being realized. Individual variability in IgG pharmacokinetic properties including IgG catabolic rates and distribution, as well as the IgG level necessary for disease control also require consideration during the optimization process. For optimization to be successful there must be a measure of treatment response that has a clinically meaningful interpretation. There are currently available well-defined and validated clinical assessment tools and outcome measures that are well suited for this purpose. While there remains much to learn on how best to manipulate immunopathology and immunoglobulin pharmacokinetics in the most favorable way, there currently exists an understanding of these principles to a degree sufficient to begin to develop rational and evidence-based treatment optimization strategies.

An idiopathic thrombocytopenic purpura with polyneuropathy

Concurrent association of idiopathic thrombocytopenic purpura (ITP) and peripheral neuropathy is a rare condition. There are only few case reports published concerning peripheral neuropathy with ITP. One of the etiopathogenetic mechanisms proposed is intraneural hemorrhage, but the pathogenesis is not fully understood. Autoimmune nature with common antibodies to the platelets and the nerve´s myelin sheath should also be considered. Here we describe a 47-year-old woman, with a family history of autoimmune diseases. She was diagnosed 2 years ago with ITP and later developed a chronic combined inflammatory demyelinating polyneuropathy. Treatment with high-dose steroids was initiated with a poor response. The patient showed a clear improvement in platelet count and in the peripheral neuropathy symptoms when treatment with intravenous immunoglobulin was administered. Common etiologic mechanism of the two diseases should be considered, both, because of the simultaneous time of development and a similar response to intravenous immunoglobulin treatment.

Novel pathomechanisms in inflammatory neuropathies

Inflammatory neuropathies are rare autoimmune-mediated disorders affecting the peripheral nervous system. Considerable progress has recently been made in understanding pathomechanisms of these disorders which will be essential for developing novel diagnostic and therapeutic strategies in the future. Here, we summarize our current understanding of antigenic targets and the relevance of new immunological concepts for inflammatory neuropathies. In addition, we provide an overview of available animal models of acute and chronic variants and how new diagnostic tools such as magnetic resonance imaging and novel therapeutic candidates will benefit patients with inflammatory neuropathies in the future. This review thus illustrates the gap between pre-clinical and clinical findings and aims to outline future directions of development.

Maintenance IV immunoglobulin treatment in chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) patients treated with intravenous immunoglobulin (IVIg) usually start with a standard dosage of 2 g/kg bodyweight. Only a minority of patients has a sustained improvement, and most require ongoing maintenance treatment. Preferred IVIg regimens, however, vary considerably between doctors and at present it is unknown which is optimal. As there are also large differences in IVIg dosage and interval requirements between patients, optimal IVIg maintenance treatment of CIDP is even more complex. The lack of evidence-based guidelines on how IVIg maintenance treatment should be administered may potentially lead to under- or overtreatment of this expensive therapy. We provide an overview of published practical IVIg maintenance treatment regimens, IVIg maintenance schedules used in randomized controlled trials and one based upon our own long-term experience on how this treatment could be given in CIDP.

A Brain-Derived Neurotrophic Factor-Based p75NTR Peptide Mimetic Ameliorates Experimental Autoimmune Neuritis Induced Axonal Pathology and Demyelination

Axonal damage and demyelination are major determinants of disability in patients with peripheral demyelinating neuropathies. The neurotrophin family of growth factors are essential for the normal development and myelination of the peripheral nervous system (PNS), and as such are potential therapeutic candidates for ameliorating axonal and myelin damage. In particular, BDNF promotes peripheral nerve myelination via p75 neurotrophin receptor (p75NTR) receptors. Here, we investigated the therapeutic efficacy of a small structural mimetic of the region of BDNF that binds to p75NTR (cyclo-dPAKKR) in experimental autoimmune neuritis (EAN), an established animal model of peripheral demyelinating neuropathy. Examination of rodents induced with EAN revealed that p75NTR is abundantly expressed in affected peripheral nerves. We found that systemic administration of cyclo-dPAKKR ameliorates EAN disease severity and accelerates recovery. Animals treated with cyclo-dPAKKR displayed significantly better motor performance compared to control animals. Histological assessment revealed that cyclo-dPAKKR administration limits the extent of inflammatory demyelination and axonal damage, and protects against the disruption of nodal architecture in affected peripheral nerves. In contrast, a structural control peptide of cyclo-dPAKKR exerted no influence. Moreover, all the beneficial effects of cyclo-dPAKKR in EAN are abrogated in p75NTR heterozygous mice, strongly suggesting a p75NTR-dependent effect. Taken together, our data demonstrate that cyclo-dPAKKR ameliorates functional and pathological defects of EAN in a p75NTR-dependant manner, suggesting that p75NTR is a therapeutic target to consider for future treatment of peripheral demyelinating diseases and targeting of p75NTR is a strategy worthy of further investigation.

Two years' long-term follow up in chronic inflammatory demyelinating polyradiculoneuropathy: efficacy of intravenous immunoglobulin treatment

BACKGROUND

Administration of intravenous immunoglobulins (IVIgs) is established for long-term treatment of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Prevention of secondary axonal loss going along with permanent clinical disability and muscular atrophy is a major aim in CIDP therapy. To assess long-term clinical efficacy of IVIg treatment despite heterogenous disease course and variable complaints reported by the patients, long-term electrophysiological monitoring was performed for systematic evaluation of therapeutic efficacy of IVIg.

METHODS

A total of 21 patients with CIDP treated with IVIg 1 g/kg bodyweight every 3-6 weeks were examined electrophysiologically every 12 months over a period of 2 years.

RESULTS

Assessment of clinical symptoms, using the Inflammatory Neuropathy Cause and Treatment (INCAT) and Hughes functional grading score (F-score) revealed improvement of motor and sensory symptoms over a period of 2 years. As electrophysiological results remained stable, IVIg treatment seems to be suitable to prevent axonal loss in CIDP.

CONCLUSIONS

This study confirms efficacy of IVIg as firstline therapy in CIDP. Doses and frequency of IVIg application should be adapted based on clinical evaluation and analysis of long-term electrophysiological findings.

Subcutaneous immunoglobulins in the treatment of chronic immune-mediated neuropathies

Intravenous immunoglobulins represent an established therapy for the treatment of chronic immune-mediated neuropathies, specifically chronic inflammatory demyelinating polyradiculoneuropathies (CIDPs) as well as multifocal motor neuropathies (MMNs). For the treatment of antibody deficiency syndromes, subcutaneous immunoglobulins (SCIgs) have represented a mainstay for decades. An emerging body of evidence suggests that SCIg might also exhibit clinical efficacy in CIDP and MMN. This article reviews the current evidence for clinical effectiveness, as well as safety of SCIg for the treatment of immune-mediated neuropathies, and addresses remaining open questions in this context. We conclude that despite the need for controlled long-term studies to demonstrate long-term efficacy of SCIg in immune-mediated neuropathies, SCIg may already represent a potential therapeutic alternative for selected patients.

Guillain-Barré syndrome associated with CASPR2 antibodies: two paediatric cases

The pathogenesis of Guillain-Barré syndrome (GBS) is considered to be, at least in part, mediated by autoantibodies directed against neuronal antigens. Antibodies to contactin-associated protein-like 2 (CASPR2), part of the voltage-gated potassium channel complex (VGKC-complex), are associated with neurological disease predominantly affecting the peripheral nervous system but are not known to be associated with GBS. We report two cases of ganglioside antibody-negative paediatric GBS associated with CASPR2 antibodies. Both patients made a complete clinical recovery. The tissue distribution and function of CASPR2 make it a biologically plausible autoimmune target in GBS and its clinical relevance in GBS should be determined in further studies.

Dimethyl Fumarate Ameliorates Lewis Rat Experimental Autoimmune Neuritis and Mediates Axonal Protection

BACKGROUND

Dimethyl fumarate is an immunomodulatory and neuroprotective drug, approved recently for the treatment of relapsing-remitting multiple sclerosis. In view of the limited therapeutic options for human acute and chronic polyneuritis, we used the animal model of experimental autoimmune neuritis in the Lewis rat to study the effects of dimethyl fumarate on autoimmune inflammation and neuroprotection in the peripheral nervous system.

METHODS AND FINDINGS

Experimental autoimmune neuritis was induced by immunization with the neuritogenic peptide (amino acids 53-78) of P2 myelin protein. Preventive treatment with dimethyl fumarate given at 45 mg/kg twice daily by oral gavage significantly ameliorated clinical neuritis by reducing demyelination and axonal degeneration in the nerve conduction studies. Histology revealed a significantly lower degree of inflammatory infiltrates in the sciatic nerves. In addition, we detected a reduction of early signs of axonal degeneration through a reduction of amyloid precursor protein expressed in axons of the peripheral nerves. This reduction correlated with an increase of nuclear factor (erythroid derived 2)-related factor 2 positive axons, supporting the neuroprotective potential of dimethyl fumarate. Furthermore, nuclear factor (erythroid derived 2)-related factor 2 expression in Schwann cells was only rarely detected and there was no increase of Schwann cells death during EAN.

CONCLUSIONS

We conclude that immunomodulatory and neuroprotective dimethyl fumarate may represent an innovative therapeutic option in human autoimmune neuropathies.

Optimizing IgG therapy in chronic autoimmune neuropathies: a hypothesis driven approach

Prolonged intravenous immunoglobulin (IVIG) therapy is used for the chronic autoimmune neuropathies chronic idiopathic demyelinating polyneuropathy and multifocal motor neuropathy, but the doses and treatment intervals are usually chosen empirically due to a paucity of data from dose-response studies. Recent studies of the electrophysiology and immunology of these diseases suggest that antibody-induced reversible dysfunction of nodes of Ranvier may play a role in conduction block and disability which responds to immunotherapy more rapidly than would be expected for demyelination or axonal damage per se. Clinical reports suggest that in some cases, the effects of each dose of IVIG may be transient, wearing-off before the next dose is due. These observations lead us to hypothesize that that therapeutic IgG acts by competing with pathologic autoantibodies and that individual patients may require different IgG levels for optimal therapeutic effects. Frequent IVIG dosing and weekly subcutaneous IgG have been tried as ways of continuously maintaining high serum IgG levels, resulting in stabilization of neuromuscular function in small case series. Frequent grip strength and disability measurements, performed by the patient at home and reported electronically, can be used to assess the extent and duration of responses to IgG doses. Individualization of IgG treatment regimens may optimize efficacy, minimize disability, and identify nonresponders.

Somatosensory evoked potentials in chronic inflammatory demyelinating polyradiculoneuropathy

PURPOSE

Somatosensory evoked potentials (SEPs) offer complementary results to those of nerve conduction studies and contribute to the electrodiagnostic criteria of chronic inflammatory demyelinating polyradiculoneuropathy.

METHODS

We performed nerve conduction studies and SEPs in patients with symmetrical motor weakness, areflexia, and/or sensory disturbances lasting for at least 8 weeks. We determined two groups according to the electrodiagnostic criteria of the European Federation of Neurological Societies. Group 1 included patients who met the definite or probable electrodiagnostic criteria, and group 2 included patients who met the possible electrodiagnostic criteria. We also compared SEPs results with those of controls (group of healthy subjects).

RESULTS

Sixteen patients (14 men; mean age, 59 ± 17.3 years) were included in the study. The latencies of potentials N9, N13, N7, and N22 and the intervals N9-N13 and N7-N22 were significantly increased in patients compared with controls. The N9/iP14 amplitude ratio was significantly lower in patients. There was no significant difference in the latencies of SEPs between the two groups of patients.

CONCLUSIONS

We confirm the contribution of SEPs as complementary information to nerve conduction studies in chronic inflammatory demyelinating polyradiculoneuropathy diagnosis. In addition to the usual abnormalities, a decrease in the N9/iP14 amplitude ratio could potentially be used as an electrodiagnostic criterion.

Pathophysiology and biomarkers in chronic inflammatory demyelinating polyradiculoneuropathies

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an acquired dysimmune disorder characterized by strong heterogeneity in terms of clinical manifestations, prognostic and response to treatment. To date, its pathophysiology and potential target antigens are not totally identified despite substantial progress in the understanding of the involved molecular mechanisms. Recent researches in the field have underlined the importance of cell-mediated immunity (lymphocytesT CD4+, CD8+ and macrophages), the breakdown of blood-nerve barrier, a failure of T-cell regulation, and the disruption of nodal and paranodal organization at the node of Ranvier. This last point is possibly mediated by autoantibodies towards axoglial adhesion molecules which may disrupt sodium and potassium voltage-gated channels clustering leading to a failure of saltatory conduction and the apparition of conduction blocks. The purpose of this article is to overview the main pathophysiologic mechanisms and biomarkers identified in CIDP.

Rapid and reversible responses to IVIG in autoimmune neuromuscular diseases suggest mechanisms of action involving competition with functionally important autoantibodies

Intravenous immunoglobulin (IVIG) is widely used in autoimmune neuromuscular diseases whose pathogenesis is undefined. Many different effects of IVIG have been demonstrated in vitro, but few studies actually identify the mechanism(s) most important in vivo. Doses and treatment intervals are generally chosen empirically. Recent studies in Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy show that some effects of IVIG are readily reversible and highly dependent on the serum IgG level. This suggests that in some autoantibody-mediated neuromuscular diseases, IVIG directly competes with autoantibodies that reversibly interfere with nerve conduction. Mechanisms of action of IVIG which most likely involve direct competition with autoantibodies include: neutralization of autoantibodies by anti-idiotypes, inhibition of complement deposition, and increasing catabolism of pathologic antibodies by saturating FcRn. Indirect immunomodulatory effects are not as likely to involve competition and may not have the same reversibility and dose-dependency. Pharmacodynamic analyses should be informative regarding most relevant mechanism(s) of action of IVIG as well as the role of autoantibodies in the immunopathogenesis of each disease. Better understanding of the role of autoantibodies and of the target(s) of IVIG could lead to more efficient use of this therapy and better patient outcomes.

Chronic inflammatory demyelinating polyradiculoneuropathy and variants: where we are and where we should go

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a chronic and often disabling sensory motor neuropathy postulated as caused by an immune attack against peripheral nerve myelin. In addition to a classic sensory–motor polyneuropathy, other phenotypes of CIDP have been described including the Lewis- Sumner syndrome, distal acquired demyelinating symmetric (DADS) neuropathy, pure motor CIDP, pure sensory CIDP including chronic immune sensory polyradiculopathy (CISP), and focal CIDP. These phenotypes are currently considered to be variants of CIDP, even if the possibility that they represent different demyelinating neuropathies cannot be fully excluded considering differences in their response to therapy. Several data support the role of the immune system in the pathogenesis of CIDP even if the precise targets and actors (antibodies and lymphocytes) of this immune response remain uncertain. Recent studies have shown that the therapeutic response may differ in patients with peculiar clinical presentations supporting the hypothesis that different pathogenetic mechanisms may underlie the heterogeneity of CIDP. The majority of patients with CIDP show improvement after immune therapies including corticosteroids, plasma exchange, and high-dose intravenous immunoglobulin (IVIg). It remains unclear why none of the other immune therapies that were reported to be variably effective in other immune disorders proved to be effective also in CIDP.

Antibodies to neurofascin exacerbate adoptive transfer experimental autoimmune neuritis

Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy are autoimmune disorders of the peripheral nervous system in which autoantibodies are implicated in the disease pathogenesis. Recent work has focused on the nodal regions of the myelinated axon as potential autoantibody targets. Here we screened patient sera for autoantibodies to neurofascin and assessed the pathophysiological relevance of anti-neurofascin antibodies in vivo. Levels of anti-neurofascin antibodies were higher in sera from patients with Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy when compared with those of controls. Anti-neurofascin antibodies exacerbated and prolonged adoptive transfer experimental autoimmune neuritis and caused conduction defects when injected intraneurally.

Early identification of 'acute-onset' chronic inflammatory demyelinating polyneuropathy

Distinguishing patients with acute-onset chronic inflammatory demyelinating polyneuropathy from acute inflammatory demyelinating polyneuropathy prior to relapse is often challenging at the onset of their clinical presentation. In the present study, nerve excitability tests were used in conjunction with the clinical phenotype and disease staging, to differentiate between patients with acute-onset chronic inflammatory demyelinating polyneuropathy and patients with acute inflammatory demyelinating polyneuropathy at an early stage, with the aim to better guide treatment. Clinical assessment, staging and nerve excitability tests were undertaken on patients initially fulfilling the diagnostic criteria of acute inflammatory demyelinating polyneuropathy soon after symptom onset and their initial presentation. Patients were subsequently followed up for minimum of 12 months to determine if their clinical presentations were more consistent with acute-onset chronic inflammatory demyelinating polyneuropathy. Clinical severity as evaluated by Medical Research Council sum score and Hughes functional grading scale were not significantly different between the two cohorts. There was no difference between the time of onset of initial symptoms and nerve excitability test assessment between the two cohorts nor were there significant differences in conventional nerve conduction study parameters. However, nerve excitability test profiles obtained from patients with acute inflammatory demyelinating polyneuropathy demonstrated abnormalities in the recovery cycle of excitability, including significantly reduced superexcitability (P < 0.001) and prolonged relative refractory period (P < 0.01), without changes in threshold electrotonus. In contrast, in patients with acute-onset chronic inflammatory demyelinating polyneuropathy, a different pattern occurred with the recovery cycle shifted downward (increased superexcitability, P < 0.05; decreased subexcitability, P < 0.05) and increased threshold change in threshold electrotonus in both hyperpolarizing and depolarizing directions [depolarizing threshold electrotonus (90-100 ms) P < 0.005, hyperpolarizing threshold electrotonus (10-20 ms), P < 0.01, hyperpolarizing threshold electrotonus (90-100 ms), P < 0.05], perhaps suggesting early hyperpolarization. In addition, using excitability parameters superexcitability, subexcitability and hyperpolarizing threshold electrotonus (10-20 ms), the patients with acute inflammatory demyelinating polyneuropathy and acute-onset chronic inflammatory demyelinating polyneuropathy could be clearly separated into two non-overlapping groups. Studies of nerve excitability may be able to differentiate acute from acute-onset chronic inflammatory demyelinating polyneuropathy at an early stage. Characteristic nerve excitability parameter changes occur in early acute-onset chronic inflammatory demyelinating polyneuropathy, to match the clinical phenotype. Importantly, this pattern of change was strikingly different to that shown by patients with acute inflammatory demyelinating polyneuropathy, suggesting that nerve excitability techniques may be useful in distinguishing acute-onset chronic inflammatory demyelinating polyneuropathy from acute inflammatory demyelinating polyneuropathy at the initial stage.

Neurofascin IgG4 antibodies in CIDP associate with disabling tremor and poor response to IVIg

OBJECTIVE

To describe the frequency of antibodies against neurofascin in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and the associated clinical features.

METHODS

Immunocytochemistry was used to identify antibodies to neurofascin 155 (NF155) and 186. Serum reactivity with paranodes and brain tissue was tested with immunohistochemistry of teased-nerve fibers and rat brain. Antibody titers and immunoglobulin (Ig) G isotypes were determined using ELISA. Clinical information was obtained retrospectively.

RESULTS

Two of 53 patients, but none of 204 controls, had antibodies to NF155 (p = 0.041). The 2 patients with NF155 antibodies developed severe polyradiculoneuropathy with predominant distal weakness that was refractory to IVIg. Eight additional patients with IVIg-refractory CIDP were then identified from a national database; 2 of them with the same clinical features also had NF155 antibodies. Overall, 3 of the 4 patients with NF155 antibodies had a disabling and characteristic tremor (high amplitude, low frequency, postural, and intention). Patients' antibodies reacted with the paranodes in teased-nerve fibers and with the neuropil of rat cerebellum, brain, and brainstem. Anti-NF155 antibodies were predominantly of the IgG4 isotype in all patients.

CONCLUSION

Patients with CIDP positive for IgG4 NF155 antibodies constitute a specific subgroup with a severe phenotype, poor response to IVIg, and disabling tremor. Autoantibodies against paranodal structures associate with distinct clinical features in CIDP and their identification has diagnostic, prognostic, and therapeutic implications.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that autoantibodies to NF155 identify a CIDP subtype characterized by severe neuropathy, poor response to IVIg, and disabling tremor.

Subcutaneous IgG in neurologic diseases

Subcutaneous administration of IgG (SCIG) has become widely used in primary immune deficiency diseases but it has only recently been studied for maintenance therapy in autoimmune peripheral neuropathies, such as chronic idiopathic demyelinating polyneuropathy and multifocal motor neuropathy. Weekly self-administration of SCIG is safe and well-tolerated, and results in steady-state serum IgG levels, as contrasted with the peaks and troughs of monthly immune globulin (human) for intravenous use. Freedom from the need for venous access or medical personnel for infusions, flexibility in scheduling, convenience of home therapy, and improved clinical stability due to the steady-state IgG levels, lead many patients to prefer SCIG to immune globulin (human) for intravenous use. Long-term studies are needed to determine if the constant IgG levels and clinical stability translate into better long-term outcomes.

Pathophysiology of immune-mediated demyelinating neuropathies--Part II: Neurology

In the second part of this review we deal with the clinical aspects of immune-mediated demyelinating neuropathies. We describe the relationship between pathophysiology and symptoms and discuss the pathophysiology of specific disease entities, including Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy, anti-myelin-associated glycoprotein neuropathy, and POEMS syndrome.

Variability in intravenous immunoglobulin G regimens for autoimmune neuromuscular disorders

AIMS

We reviewed the intravenous immunoglobulin G (IVIG) dispensing records of a specialty pharmacy to characterize the IVIG treatment regimens used for chronic inflammatory demyelinating polyneuropathy (CIDP) and myasthenia gravis (MG) in community practice.

METHODS

Anonymized records were selected based on International Classification of Diseases, Ninth Revision (ICD-9) codes and IVIG treatment for > 1 month. Each patient's immunoglobulin G (IgG) dose per infusion (mg/kg/dose) was multiplied by the number of doses per month (30.5 days divided by the dosing interval in days) to yield the total monthly dose (mg/kg/month). Data were analyzed and summarized using descriptive statistics.

RESULTS

Forty-six patients (median age, 56.5 years; range, 8-86 years) fulfilled the inclusion criteria. Thirty-one patients with CIDP received IgG at 7- to 92-day intervals (mean [standard deviation (SD)], 28 [16] days). The mean (SD) IgG dose was 75 (60) g/dose, equivalent to 866 (623) mg/kg/dose and 1145 (778) mg/kg/month. Six patients with stable MG received IVIG or subcutaneous IgG at 3.5- to 61-day intervals (28 [20] days) at a mean (SD) IgG dose of 39 (15) g/dose, equivalent to 405 (108) mg/kg/dose and 783 (680) mg/kg/month. Nine patients with MG with acute exacerbations received IgG at 7- to 42-day intervals (22 [12] days) at a mean (SD) dose of 40 (21) g/dose, equivalent to 403 (172) mg/kg/dose and 641 (288) mg/kg/month. One patient with CIDP and 4 patients with MG were treated with weekly subcutaneous IgG injections.

CONCLUSION

Although patients with CIDP and MG are treated with mean total monthly IgG doses similar to those approved by the US Food and Drug Administration, the individual doses and intervals vary considerably, suggesting that physicians may be adjusting IgG dosing according to each patient's clinical condition and treatment response. Further study is necessary to determine the criteria used to adjust IgG treatment regimens and whether these adjustments optimize clinical outcomes while limiting overall costs.

Optimization of intravenous immunoglobulin in chronic inflammatory demyelinating polyneuropathy evaluated by grip strength measurement

BACKGROUND

Optimal dose and timing of repeated intravenous immunoglobulin therapy (IVIg) for intractable chronic inflammatory demyelinating polyneuropathy (CIDP) patients have not been determined. The aim of this study was to optimize dose and timing of IVIg for CIDP patients who need frequent IVIg using daily grip strength measurement.

METHODS

Repeated IVIg were administered for two intractable CIDP patients. Grip strength was recorded at home every day to access the clinical change in symptoms, and dose and timing of IVIg were optimized based on the results.

RESULTS

The decrement on grip strength was a sensitive indicator of symptom exacerbation. 100 g of IVIg had a limited effect for each patient. In one patient, symptoms maintained after monthly 60 g of IVIg. In another, 100 g of IVIg every 7 weeks resulted in a marked improvement. After receiving 20 g of IVIg weekly, each patient showed further improvement.

CONCLUSION

Optimal dose and timing possibly vary in each individual patient. Dose titration of IVIg is necessary to avoid over- and undertreatment. The daily self-monitoring of grip strength is a helpful tool for clinical assessment in CIDP.

An update on Schwann cell biology--immunomodulation, neural regulation and other surprises

Schwann cells are primarily discussed in the context of their ability to form myelin. However there are many subtypes of these neural crest derived cells including satellite cells of the dorsal root ganglia and autonomic ganglia, the perisynaptic Schwann cells of the neuromuscular junction and the non-myelin forming Schwann cells which ensheathe the unmyelinated fibres of the peripheral nervous system which are about 80% of peripheral nerves. This review discusses the many functions of these Schwann cell subsets including their seminal role in axonal ensheathment, perineuronal organisation, maintenance of normal neural function, synapse formation, response to damage and repair and an increasingly recognised active role in pain syndromes.

Antibodies to contactin-1 in chronic inflammatory demyelinating polyneuropathy

OBJECTIVE

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a frequent autoimmune neuropathy with a heterogeneous clinical spectrum. Clinical and experimental evidence suggests that autoantibodies may be involved in its pathogenesis, but the target antigens are unknown. Axoglial junction proteins have been proposed as candidate antigens. We examined the reactivity of CIDP patients' sera against neuronal antigens and used immunoprecipitation for antigen unraveling.

METHODS

Primary cultures of hippocampal neurons were used to select patients' sera that showed robust reactivity with the cell surface of neurons. The identity of the antigens was established by immunoprecipitation and mass spectrometry, and subsequently confirmed with cell-based assays, immunohistochemistry with teased rat sciatic nerve, and immunoabsorption experiments.

RESULTS

Four of 46 sera from patients with CIDP reacted strongly against hippocampal neurons (8.6%) and paranodal structures on peripheral nerve. Two patients' sera precipitated contactin-1 (CNTN1), and 1 precipitated both CNTN1 and contactin-associated protein 1 (CASPR1). Reactivity against CNTN1 was confirmed in 2 cases, whereas the third reacted only when CNTN1 and CASPR1 were cotransfected. No other CIDP patient or any of the 104 controls with other neurological diseases tested positive. All 3 patients shared common clinical features, including advanced age, predominantly motor involvement, aggressive symptom onset, early axonal involvement, and poor response to intravenous immunoglobulin.

INTERPRETATION

Antibodies against the CNTN1/CASPR1 complex occur in a subset of patients with CIDP who share common clinical features. The finding of this biomarker may help to explain the symptoms of these patients and the heterogeneous response to therapy in CIDP.

Chronic inflammatory demyelinating polyneuropathy (CIDP)

BACKGROUND

Chronic immune-mediated demyelinating polyneuropathies can often lead to severe neurologic disability.

MATERIALS AND METHODS

Literature review and personal experience with these types of neuropathies.

CONCLUSIONS

It is important to recognize these immune-mediated neuropathies as they respond to treatment.

Erythropoietin enhances nerve repair in anti-ganglioside antibody-mediated models of immune neuropathy

Guillain-Barré syndrome (GBS) is a monophasic immune neuropathic disorder in which a significant proportion of patients have incomplete recovery. The patients with incomplete recovery almost always have some degree of failure of axon regeneration and target reinnervation. Anti-ganglioside antibodies (Abs) are the most commonly recognized autoimmune markers in all forms of GBS and specific Abs are associated with the slow/poor recovery. We recently demonstrated that specific anti-ganglioside Abs inhibit axonal regeneration and nerve repair in preclinical models by activation of small GTPase RhoA and its downstream effectors. The objective of this study was to determine whether erythropoietin (EPO), a pleiotropic cytokine with neuroprotective and neurotrophic properties, enhances nerve regeneration in preclinical cell culture and animal models of autoimmune neuropathy/nerve repair generated with monoclonal and patient derived Abs. Primary neuronal cultures and a standardized sciatic crush nerve model were used to assess the efficacy of EPO in reversing inhibitory effects of anti-ganglioside Abs on nerve repair. We found that EPO completely reversed the inhibitory effects of anti-ganglioside Abs on axon regeneration in cell culture models and significantly improved nerve regeneration/repair in an animal model. Moreover, EPO-induced proregenerative effects in nerve cells are through EPO receptors and Janus kinase 2/Signal transducer and activator of transcription 5 pathway and not via early direct modulation of small GTPase RhoA. These preclinical studies indicate that EPO is a viable candidate drug to develop further for neuroprotection and enhancing nerve repair in patients with GBS.

Advances in the diagnosis, pathogenesis and treatment of CIDP

Chronic inflammatory demyelinating polyneuropathy (CIDP) is the most common chronic autoimmune neuropathy. Despite clinical challenges in diagnosis-owing in part to the existence of disease variants, and different views on how many electrophysiological abnormalities are needed to document demyelination-consensus criteria seem to have been reached for research or clinical practice. Current standard of care involves corticosteroids, intravenous immunoglobulin (IVIg) and/or plasmapheresis, which provide short-term benefits. Maintenance therapy with IVIg can induce sustained remission, increase quality of life and prevent further axonal loss, but caution is needed to avoid overtreatment. Commonly used immunosuppressive drugs offer minimal benefit, necessitating the development of new therapies for treatment-refractory patients. Advances in our understanding of the underlying immunopathology in CIDP have identified new targets for future therapeutic efforts, including T cells, B cells, and transmigration and transduction molecules. New biomarkers and scoring systems represent emerging tools with the potential to predict therapeutic responses and identify patients with active disease for enrollment into clinical trials. This Review highlights the recent advances in diagnosing CIDP, provides an update on the immunopathology including new target antigens, and discusses current treatments, ongoing challenges and future therapeutic directions.

From the periphery to the brain: Wiring the olfactory system

The olfactory system represents a perfect model to study the interactions between the central and peripheral nervous systems in order to establish a neural circuit during early embryonic development. In addition, another important feature of this system is the capability to integrate new cells generated in two neurogenic zones: the olfactory epithelium in the periphery and the wall of the lateral ventricles in the CNS, both during development and adulthood. In all these processes the combination and sequence of specific molecular signals plays a critical role in the wiring of the olfactory axons, as well as the precise location of the incoming cell populations to the olfactory bulb. The purpose of this review is to summarize recent insights into the cellular and molecular events that dictate cell settling position and axonal trajectories from their origin in the olfactory placode to the formation of synapses in the olfactory bulb to ensure rapid and reliable transmission of olfactory information from the nose to the brain.