Multifocal motor neuropathy: diagnosis, pathogenesis and treatment strategies

Comparison of the diagnostic accuracy of the 2010 European Federation of Neurological Societies/Peripheral Nerve Society and American Association of Electrodiagnostic Medicine diagnostic criteria for multifocal motor neuropathy

BACKGROUND AND PURPOSE

This study was undertaken to compare the sensitivity and specificity of the 2010 European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) diagnostic criteria for multifocal motor neuropathy (MMN) with those of the American Association of Electrodiagnostic Medicine (AAEM).

METHODS

Sensitivity and specificity of the two sets of criteria were retrospectively evaluated in 53 patients with MMN and 280 controls with axonal peripheral neuropathy, inflammatory demyelinating polyneuropathy, or amyotrophic lateral sclerosis. Comparison of the utility of nerve conduction studies with different numbers of nerves examined was also assessed.

RESULTS

The 2010 EFNS/PNS criteria had a sensitivity of 47% for definite MMN and 57% for probable/definite MMN, whereas the AAEM criteria had a sensitivity of 28% for definite MMN and 53% for probable/definite MMN. The sensitivity of the AAEM criteria was higher when utilizing area compared to amplitude reduction to define conduction block. Using supportive criteria, the sensitivity of the 2010 EFNS/PNS criteria for probable/definite MMN increased to 64%, and an additional 36% patients fulfilled the criteria (possible MMN). Specificity values for definite and probable/definite MMN were slightly higher with the AAEM criteria (100%) compared to the EFNS/PNS criteria (98.5% and 97%). Extended nerve conduction studies yielded slightly increased diagnostic sensitivity for both sets of criteria without significantly affecting specificity.

CONCLUSIONS

In our patient populations, the 2010 EFNS/PNS criteria demonstrated higher sensitivity but slightly lower specificity compared to the AAEM criteria. Extended nerve conduction studies are advised to achieve slightly higher sensitivity while maintaining very high specificity.

Neurofilaments in neurologic disease

Neurofilaments (NFs), major cytoskeletal constituents of neurons, have emerged as universal biomarkers of neuronal injury. Neuroaxonal damage underlies permanent disability in various neurological conditions. It is crucial to accurately quantify and longitudinally monitor this damage to evaluate disease progression, evaluate treatment effectiveness, contribute to novel treatment development, and offer prognostic insights. Neurofilaments show promise for this purpose, as their levels increase with neuroaxonal damage in both cerebrospinal fluid and blood, independent of specific causal pathways. New assays with high sensitivity allow reliable measurement of neurofilaments in body fluids and open avenues to investigate their role in neurological disorders. This book chapter will delve into the evolving landscape of neurofilaments, starting with their structure and cellular functions within neurons. It will then provide a comprehensive overview of their broad clinical value as biomarkers in diseases affecting the central or peripheral nervous system.

Prevention of axonal loss after immediate dosage titration of immunoglobulin in multifocal motor neuropathy

BACKGROUND

To evaluate whether ongoing axonal loss can be prevented in multifocal motor neuropathy (MMN) treated with immunoglobulin G (IgG), a group of patients with a median disease duration of 15.7 years (range: 8.3-37.8), treated with titrated dosages of immunoglobulins, was studied electrophysiologically at time of diagnosis and at follow-up.

RESULTS

At follow-up, the Z-score of the compound motor action potential amplitude of the median, fibular, and tibial nerves and the neurological performances were determined. In seven patients with a treatment-free period of 0.3 years (0.2-0.4), there was no progression of axonal loss (p = 0.2), whereas a trend toward further axonal loss by 1.3 Z-scores (0.9-17.0, p = 0.06) was observed in five patients with a treatment-free period of 4.0 years (0.9-9.0). The axonal loss in the group with a short treatment delay was significantly smaller than in the group with a longer treatment delay (p = 0.02). Also, there was an association between treatment delay and ongoing axonal loss (p = 0.004). The electrophysiological findings at follow-up were associated with the isokinetic strength performance, the neurological impairment score, and the disability, supporting the clinical relevance of the electrophysiological estimate of axonal loss.

CONCLUSION

Swift initiation of an immediately titrated IgG dosage can prevent further axonal loss and disability in continuously treated MMN patients.

Neuromuscular Ultrasound in Polyneuropathies

Neuromuscular ultrasound is a painless, radiation-free, high-resolution imaging technique for assessing the peripheral nervous system. It can accurately depict changes in the nerves and muscles of individuals with neuromuscular conditions, and it is therefore a robust diagnostic tool for the assessment of individuals with polyneuropathies. This review will outline the typical ultrasonographic changes found in a wide variety of polyneuropathies. In general, demyelinating conditions result in greater nerve enlargement than axonal conditions, and acquired conditions result in more patchy nerve enlargement compared to diffuse nerve enlargement in hereditary conditions. This review is data-driven, but more nuanced anecdotal findings are also described. The overall goal of this paper is to provide clinicians with an accessible review of the ultrasonographic approaches and findings in a wide variety of polyneuropathies.

A 21-bp deletion in the complement regulator CD55 promotor region is associated with multifocal motor neuropathy and its disease course

BACKGROUND AND AIMS

To further substantiate the role of antibody-mediated complement activation in multifocal motor neuropathy (MMN) immunopathology, we investigated the distribution of promotor polymorphisms of genes encoding the membrane-bound complement regulators CD46, CD55, and CD59 in patients with MMN and controls, and evaluated their association with disease course.

METHODS

We used Sanger sequencing to genotype five common polymorphisms in the promotor regions of CD46, CD55, and CD59 in 133 patients with MMN and 380 controls. We correlated each polymorphism to clinical parameters.

RESULTS

The genotype frequencies of rs28371582, a 21-bp deletion in the CD55 promotor region, were altered in patients with MMN as compared to controls (p .009; Del/Del genotype 16.8% vs. 7.7%, p .005, odds ratio: 2.43 [1.27-4.58]), and patients carrying this deletion had a more favorable disease course (mean difference 0.26 Medical Research Council [MRC] points/year; 95% confidence interval [CI]: 0.040-0.490, p .019). The presence of CD59 rs141385724 was associated with less severe pre-diagnostic disease course (mean difference 0.940 MRC point/year; 95% CI: 0.083-1.80, p .032).

INTERPRETATION

MMN susceptibility is associated with a 21-bp deletion in the CD55 promotor region (rs2871582), which is associated with lower CD55 expression. Patients carrying this deletion may have a more favorable long-term disease outcome. Taken together, these results point out the relevance of the pre-C5 level of the complement cascade in the inflammatory processes underlying MMN.

Amyotrophic lateral sclerosis; clinical features, differential diagnosis and pathology

Amyotrophic lateral sclerosis (ALS) is a late-onset syndrome characterized by the progressive degeneration of both upper motor neurons (UMN) and lower motor neurons (LMN). ALS forms a clinical continuum with frontotemporal dementia (FTD), in which there are progressive language deficits or behavioral changes. The genetics and pathology underlying both ALS and FTD overlap as well, with cytoplasmatic misvocalization of TDP-43 as the hallmark. ALS is diagnosed by exclusion. Over the years several diagnostic criteria have been proposed, which in essence all require a history of slowly progressive motor symptoms, with UMN and LMN signs on neurological examination, clear spread of symptoms through the body, the exclusion of other disorder that cause similar symptoms and an EMG that it is compatible with LMN loss. ALS is heterogeneous disorder that may present in multitude ways, which makes the diagnosis challenging. Therefore, a systematic approach in the diagnostic process is required in line with the most common presentations. Subsequently, assessing whether there are cognitive and/or behavioral changes within the spectrum of FTD and lastly determining the cause is genetic. This chapter, an outline on how to navigate this 3 step process.

Assessment of diagnostic criteria for multifocal motor neuropathy in patients included in the Italian database

BACKGROUND AND PURPOSE

This study aimed to assess the diagnostic criteria, ancillary investigations and treatment response using real-life data in multifocal motor neuropathy (MMN) patients.

METHODS

Clinical and laboratory data were collected from 110 patients enrolled in the Italian MMN database through a structured questionnaire. Twenty-six patients were excluded due to the unavailability of nerve conduction studies or the presence of clinical signs and symptoms and electrodiagnostic abnormalities inconsistent with the MMN diagnosis. Analyses were conducted on 73 patients with a confirmed MMN diagnosis and 11 patients who did not meet the diagnostic criteria.

RESULTS

The European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) diagnostic criteria were variably applied.

AUTHOR

When applying the American Association of Electrodiagnostic Medicine criteria, an additional 17% of patients fulfilled the criteria for probable/definite diagnosis whilst a further 9.5% missed the diagnosis. In 17% of the patients only compound muscle action potential amplitude, but not area, was measured and subsequently recorded in the database by the treating physician. Additional investigations, including anti-GM1 immunoglobulin M antibodies, cerebrospinal fluid analysis, nerve ultrasound and magnetic resonance imaging, supported the diagnosis in 46%-83% of the patients. Anti-GM1 immunoglobulin M antibodies and nerve ultrasound demonstrated the highest sensitivity. Additional tests were frequently performed outside the EFNS/PNS guideline recommendations.

CONCLUSIONS

This study provides insights into the real-world diagnostic and management strategies for MMN, highlighting the challenges in applying diagnostic criteria.

IgM anti-GM2 antibodies in patients with multifocal motor neuropathy target Schwann cells and are associated with early onset

BACKGROUND

Multifocal motor neuropathy (MMN) is a rare, chronic immune-mediated polyneuropathy characterized by asymmetric distal limb weakness. An important feature of MMN is the presence of IgM antibodies against gangliosides, in particular GM1 and less often GM2. Antibodies against GM1 bind to motor neurons (MNs) and cause damage through complement activation. The involvement of Schwann cells (SCs), expressing GM1 and GM2, in the pathogenesis of MMN is unknown.

METHODS

Combining the data of our 2007 and 2015 combined cross-sectional and follow-up studies in Dutch patients with MMN, we evaluated the presence of IgM antibodies against GM1 and GM2 in serum from 124 patients with MMN and investigated their binding to SCs and complement-activating properties. We also assessed the relation of IgM binding and complement deposition with clinical characteristics.

RESULTS

Thirteen out of 124 patients (10%) had a positive ELISA titer for IgM anti-GM2. Age at onset of symptoms was significantly lower in MMN patients with anti-GM2 IgM. IgM binding to SCs correlated with IgM anti-GM2 titers. We found no correlation between IgM anti-GM2 titers and MN binding or with IgM anti-GM1 titers. IgM binding to SCs decreased upon pre-incubation of serum with soluble GM2, but not with soluble GM1. IgM anti-GM2 binding to SCs correlated with complement activation, as reflected by increased C3 fixation on SCs and C5a formation in the supernatant.

CONCLUSION

Circulating IgM anti-GM2 antibodies define a subgroup of patients with MMN that has an earlier onset of disease. These antibodies probably target SCs specifically and activate complement, similarly as IgM anti-GM1 on MNs. Our data indicate that complement activation by IgM antibodies bound to SCs and MNs underlies MMN pathology.

Neuromuscular ultrasound in combination with nerve conduction studies helps identify inflammatory motor neuropathies from lower motor neuron syndromes

BACKGROUND AND PURPOSE

Identifying patients with inflammatory motor neuropathies (IMNs) is warranted since effective treatments are available and the prognosis of these patients differs from that of amyotrophic lateral sclerosis patients.

METHODS

Between January 2019 and May 2022, 102 consecutive treatment-naïve lower motor neuron syndrome (LMNS) patients were recruited; these patients were suspected of having multifocal motor neuropathy, pure motor chronic inflammatory demyelinating polyneuropathy or amyotrophic lateral sclerosis with initial lower motor neuron presentation. Neuromuscular ultrasound (US) and nerve conduction studies (NCSs) were conducted at baseline. Relevant diagnostic investigations were performed if clinically warranted. The proposed US evidence of IMN was as follows: (i) nerve enlargement at ≥1 of the predetermined sites or (ii) absence of high intensity fasciculations in predefined muscle groups. Final diagnoses were made by experienced physicians after a prolonged follow-up period (≥12 months). IMN patients were defined as LMNS patients who experienced convincing improvements in response to immunotherapies. IMN patients without electrodiagnostic demyelinating features were diagnosed with treatment-responsive LMNS (TR-LMNS).

RESULTS

In total, 16 patients were classified as IMN, including nine chronic inflammatory demyelinating polyneuropathy/multifocal motor neuropathy patients and seven TR-LMNS patients. Six TR-LMNS patients were identified by neuromuscular US. The sensitivity and specificity of NCSs, nerve US and muscle US were 56.3% and 100%, 43.8% and 90.7% and 68.8% and 97.7%, respectively. When these three modalities were combined, the sensitivity and specificity were 93.8% and 88.4%, respectively.

CONCLUSION

Neuromuscular US studies are supplementary modalities to NCSs, and the combined use of these techniques might improve the identification of IMNs in LMNS patients.

The diagnostic value of quantitative assessment of MR neurography in chronic inflammatory demyelinating polyradiculoneuropathy: a systematic review and meta-analysis

OBJECTIVES

The purpose of this study was to evaluate the diagnostic value of quantitative magnetic resonance neurography (MRN) in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We also compared various MRN parameters and determined the best performing one.

METHODS

Through literature searches in PubMed, Embase, Cochrane, Ovid MEDLINE and ClinicalTtrials.gov until March 1, 2023, we selected studies with the diagnostic performance of MRN in CIDP patients. The pooled estimated sensitivity and specificity of quantitative MRN parameters were determined by a bivariate random-effects model. Subgroup analysis was performed to evaluate the proper quantitative parameters and nerve sites.

RESULTS

A total of 14 quantitative MRN studies with 23 results gave a pooled sensitivity of 0.73 (95% CI 0.66-0.79) and a pooled specificity of 0.89 (95% CI 0.84-0.92). The area under the curve (AUC) was 0.89 (95%CI 0.86-0.92). Subgroup analysis of quantitative parameters showed the fractional anisotropy (FA) with the highest sensitivity of 0.85 (95% CI 0.77-0.90) and cross-sectional area (CSA) with the highest specificity of 0.95 (95% CI 0.85-0.99). The pooled correlation coefficient for interobserver agreements was 0.90 (95%CI 0.82-0.95).

CONCLUSION

Quantitative MRN has considerable diagnostic value in CIDP patients with accuracy and reliability. FA and CSA can be promising parameters in the future diagnosis of CIDP patients.

ADVANCES IN KNOWLEDGE

This is the first meta-analysis of quantitative MRN in the diagnosis of CIDP.We have selected reliable parameters with cut-off value and provided new insights for subsequent diagnosis of CIDP.

Multifocal motor neuropathy is not associated with altered innate immune responses to endotoxin

OBJECTIVE

Antibody- and complement-mediated peripheral nerve inflammation are central in the pathogenesis of MMN. Here, we studied innate immune responses to endotoxin in patients with MMN and controls to further our understanding of MMN risk factors and disease modifiers.

METHODS

We stimulated whole blood of 52 patients with MMN and 24 controls with endotoxin and collected plasma. With a multiplex assay, we determined levels of the immunoregulating proteins IL-1RA, IL-1β, IL-6, IL-10, IL-21, TNF-α, IL-8 and CD40L in unstimulated and LPS-stimulated plasma. We compared baseline and stimulated protein levels between patients and controls and correlated concentrations to clinical parameters.

RESULTS

Protein level changes after stimulation were comparable between groups (p > 0.05). IL-1RA, IL-1β, IL-6 and IL-21 baseline concentrations showed a positive correlation with monthly IVIg dosage (all corrected p-values < 0.016). Patients with anti-GM1 IgM antibodies showed a more pronounced IL-21 increase after stimulation (p 0.048).

CONCLUSIONS

Altered endotoxin-induced innate immune responses are unlikely to be a susceptibility factor for MMN.

Immune-Mediated Neuropathies: Pathophysiology and Management

Dysfunction of the immune system can result in damage of the peripheral nervous system. The immunological mechanisms, which include macrophage infiltration, inflammation and proliferation of Schwann cells, result in variable degrees of demyelination and axonal degeneration. Aetiology is diverse and, in some cases, may be precipitated by infection. Various animal models have contributed and helped to elucidate the pathophysiological mechanisms in acute and chronic inflammatory polyradiculoneuropathies (Guillain-Barre Syndrome and chronic inflammatory demyelinating polyradiculoneuropathy, respectively). The presence of specific anti-glycoconjugate antibodies indicates an underlying process of molecular mimicry and sometimes assists in the classification of these disorders, which often merely supports the clinical diagnosis. Now, the electrophysiological presence of conduction blocks is another important factor in characterizing another subgroup of treatable motor neuropathies (multifocal motor neuropathy with conduction block), which is distinct from Lewis-Sumner syndrome (multifocal acquired demyelinating sensory and motor neuropathy) in its response to treatment modalities as well as electrophysiological features. Furthermore, paraneoplastic neuropathies are also immune-mediated and are the result of an immune reaction to tumour cells that express onconeural antigens and mimic molecules expressed on the surface of neurons. The detection of specific paraneoplastic antibodies often assists the clinician in the investigation of an underlying, sometimes specific, malignancy. This review aims to discuss the immunological and pathophysiological mechanisms that are thought to be crucial in the aetiology of dysimmune neuropathies as well as their individual electrophysiological characteristics, their laboratory features and existing treatment options. Here, we aim to present a balance of discussion from these diverse angles that may be helpful in categorizing disease and establishing prognosis.

Value of Antibody Determinations in Chronic Dysimmune Neuropathies

Chronic dysimmune neuropathies encompass a group of neuropathies that share immune-mediated pathomechanism. Chronic dysimmune antibody-related neuropathies include anti-MAG neuropathy, multifocal motor neuropathy, and neuropathies related to immune attack against paranodal antigens. Such neuropathies exhibit distinguishing pathomechanism, clinical and response to therapy features with respect to chronic inflammatory demyelinating polyradiculoneuropathy and its variants, which represent the most frequent form of chronic dysimmune neuropathy. This narrative review provides an overview of pathomechanism; clinical, electrophysiological, and biochemical features; and treatment response of the antibody-mediated neuropathies, aiming to establish when and why to look for antibodies in chronic dysimmune neuropathies.

Application and Research Progress of High Frequency Ultrasound in the Diagnosis of Chronic Inflammatory Neuropathies

In recent years, clinicians have gradually improved their understanding of multiple neuropathy and have done some studies about chronic inflammatory neuropathies, for example, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy, and Lewis-Sumne syndrome. The early diagnosis is very important for the next step treatment and long-term prognosis. At present, the disease mainly depends on clinical and neural electrophysiological examination, but imaging studies are few. In recent years, with the rapid development of high frequency ultrasound, it could clearly show the morphology of the nerve, and it has been an emerging diagnosis tool of polyneuropathies. This article mainly reviews the application and the latest research progress of high frequency ultrasound in these diseases.

Clinical Utility of Repetitive Nerve Stimulation Test in Differentiating Multifocal Motor Neuropathy From Progressive Muscular Atrophy

OBJECTIVES

To evaluate the utility of repetitive nerve stimulation test (RNS) for differentiating multifocal motor neuropathy (MMN) and progressive muscular atrophy (PMA).

METHODS

We retrospectively enrolled 20 patients with MMN or PMA. We extracted the results of the initial 3-Hz RNS in the ulnar and accessory nerves and compared the percentage and frequency of abnormal decremental responses between both groups.

RESULTS

RNS was performed in 8 ulnar and 9 accessory nerves in patients with MMN, and in 8 ulnar and 10 accessory nerves in patients with PMA. Patients with MMN had a significantly lower decrement percentage (0.6 ± 4.0% in MMN vs. 10.3 ± 6.5% in PMA, P < 0.01) and frequency of abnormal decremental response (0 of 9 in MMN vs. 6 of 10 in PMA, P = 0.01) than patients with PMA in the accessory nerve.

CONCLUSIONS

The RNS has clinical utility for differentiating MMN from PMA.

Classical Complement Pathway Inhibition in a "Human-On-A-Chip" Model of Autoimmune Demyelinating Neuropathies

Chronic autoimmune demyelinating neuropathies are a group of rare neuromuscular disorders with complex, poorly characterized etiology. Here we describe a phenotypic, human-on-a-chip (HoaC) electrical conduction model of two rare autoimmune demyelinating neuropathies, chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN), and explore the efficacy of TNT005, a monoclonal antibody inhibitor of the classical complement pathway. Patient sera was shown to contain anti-GM1 IgM and IgG antibodies capable of binding to human primary Schwann cells and induced pluripotent stem cell derived motoneurons. Patient autoantibody binding was sufficient to activate the classical complement pathway resulting in detection of C3b and C5b-9 deposits. A HoaC model, using a microelectrode array with directed axonal outgrowth over the electrodes treated with patient sera, exhibited reductions in motoneuron action potential frequency and conduction velocity. TNT005 rescued the serum-induced complement deposition and functional deficits while treatment with an isotype control antibody had no rescue effect. These data indicate that complement activation by CIDP and MMN patient serum is sufficient to mimic neurophysiological features of each disease and that complement inhibition with TNT005 was sufficient to rescue these pathological effects and provide efficacy data included in an investigational new drug application, demonstrating the model's translational potential.

Amyotrophic lateral sclerosis mimics

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset motor neuron disorder characterized by progressive degeneration of cortical, bulbar, and spinal motor neurons. When a patient presents with a progressive upper and/or lower motor syndrome, clinicians must pay particular attention to any atypical features in the history and/or clinical examination suggesting an alternate diagnosis, as up to 10% percent of patients initially diagnosed with ALS have a mimic of ALS. ALS is a clinical diagnosis and requires the exclusion of other disorders that may have similar presentations but a more favorable prognosis or an effective therapy. Because there is currently no specific diagnostic biomarker that is sensitive or specific for ALS, understanding the spectrum of clinical presentations of ALS and its mimics is paramount. While true mimics of ALS are rare, the clinician must correctly identify these disorders to avoid the misdiagnosis of ALS and to initiate effective treatment where available.

Multifocal Motor Neuropathy With Cranial Nerve Involvement and Vocal Cord Paralysis: A Case Report

Multifocal motor neuropathy (MMN) is a progressive, multifocal weakness, which typically begins and predominates in the upper extremities with the absence of a sensory deficit and a hallmark electrophysiologic finding of conduction block. We describe a case of an adult male with MMN who developed both cranial nerve involvement and vocal cord paralysis. The patient presented with left shoulder weakness without sensory loss followed by hoarseness of voice and later developed tongue deviation and wasting of the left sternocleidomastoid and left trapezius muscle. Laryngeal electromyography (EMG) showed findings evident for a focal mononeuropathy involving the left recurrent laryngeal nerve. EMG and nerve conduction studies (EMG NCV) of the upper extremities showed evidence for a multifocal mainly motor neuropathy involving the left spinal accessory and hypoglossal nerves, combined with the presence of median and ulnar proximal conduction blocks bilaterally. Given the clinical presentation and electrophysiologic findings of conduction block, the patient was managed as a case of MMN and received the standard treatment with Intravenous Immunoglobulin (IVIg). Upon follow-up, there was an improvement in symptoms and no recurrence of motor weakness and hoarseness of voice. There are a few case reports about MMN but none with multiple lower cranial nerve involvement.

Anti-ganglioside Complex IgM Antibodies in Multifocal Motor Neuropathy Post-influenza Vaccination

Multifocal motor neuropathy (MMN) is a peripheral nerve disorder characterized by progressive, predominantly distal, asymmetric limb weakness with minimal or no sensory impairment, and characterized by the presence of antibodies (30-80% cases), mostly IgM, to the gangliosides, mainly ganglioside monosialic acid (GM1). We describe a case of MMN in a patient who developed symptoms of paresthesia and extremity weakness a few days after receiving the influenza vaccine and was found to have high titers of anti-GM1 IgM antibody levels. He was initially treated with intravenous immune globulin (IVIG) which is one of the mainstays of treatment but relapsed and was then successfully treated with plasma exchange.

Evidence base for investigative and therapeutic modalities in chronic inflammatory demyelinating polyneuropathy and multifocal motor neuropathy

Chronic inflammatory demyelinating polyneuropathy, its variants and multifocal motor neuropathy belong to a spectrum of peripheral nerve disorders with complex dysimmune disease mechanisms. Awareness of the unique clinical phenotypes but also heterogeneity between patients is vital to arrive at early suspicion and ordering appropriate tests. This includes requirements for optimal electrodiagnostic protocol, aimed to capture sufficient electrophysiologic evidence for relevant abnormalities, a case-based approach on the eventual need to further expand the diagnostic armamentarium and correct reading of their results. Considerable phenotypical variation, diverse combinations of abnormalities found on diagnostic tests and heterogeneity in disease course and treatment response, all contribute to widespread differences in success rates on timely diagnosis and optimal treatment. We aim to provide a practical overview and guidance on relevant diagnostic and management strategies, including pitfalls and present a summary of the relevant novel developments in this field.

MRI of the intraspinal nerve roots in patients with chronic inflammatory neuropathies: abnormalities correlate with clinical phenotypes

OBJECTIVE

Chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN) are caused by inflammatory changes of peripheral nerves. It is unknown if the intra-spinal roots are also affected. This MRI study systematically visualized intra-spinal nerve roots, i.e., the ventral and dorsal roots, in patients with CIDP, MMN and motor neuron disease (MND).

METHODS

We performed a cross-sectional study in 40 patients with CIDP, 27 with MMN and 34 with MND. All patients underwent an MRI scan of the cervical intra-spinal roots. We systematically measured intra-spinal nerve root sizes bilaterally in the transversal plane at C5, C6 and C7 level. We calculated mean nerve root sizes and compared them between study groups and between different clinical phenotypes using a univariate general linear model.

RESULTS

Patients with MMN and CIDP with a motor phenotype had thicker ventral roots compared to patients with CIDP with a sensorimotor phenotype (p = 0.012), while patients with CIDP with a sensory phenotype had thicker dorsal roots compared to patients with a sensorimotor phenotype (p = 0.001) and with MND (p = 0.004).

CONCLUSION

We here show changes in the morphology of intra-spinal nerve roots in patients with chronic inflammatory neuropathies, compatible with their clinical phenotype.

Motor unit integrity in multifocal motor neuropathy: A systematic evaluation with CMAP scans

Introduction/Aims

Progressive axonal loss in multifocal motor neuropathy (MMN) is often assessed with nerve conduction studies (NCS), by recording maximum compound muscle action potentials (CMAPs). However, reinnervation maintains the CMAP amplitude until a significant portion of the motor unit (MU) pool is lost. Therefore, we performed more informative CMAP scans to study MU characteristics in a large cohort of patients with MMN.

Methods

We derived the maximum CMAP amplitude (CMAP_max), an MU number estimate (MUNE), and the largest MU amplitude stimulus current required to elicit 5%, 50%, and 95% of CMAP_max (S5, S50, S95) and relative ranges ([S95 − S5] × 100 / S50) from the scans. These metrics were compared with clinical, laboratory, and NCS results.

Results

Forty MMN patients and 24 healthy controls were included in the study. CMAP_max and MUNE were reduced in MMN patients (both P < .001). Largest MU amplitude as a percentage of CMAP_max was increased in MMN patients (P < .001). Disease duration and treatment duration were not associated with MUNE. Relative range was larger in patients with anti‐GM1 antibodies than in those without anti‐GM1 antibodies (P = .016) and controls (P < .001). The largest MU amplitudes were larger in patients without anti‐GM1 antibodies than in patients with anti‐GM1 antibodies (P = .037) and controls (P = .044).

Discussion

We found that MU loss is common in MMN and accompanied by enlarged MUs. Presence of anti‐GM1 antibodies was associated with increased relative range of MU thresholds and reduction in largest MU amplitude. Our findings indicate that CMAP scans complement routine NCS, and may have potential for practical monitoring of treatment efficacy and disease progression.

Immunoglobulin shortage: Practice modifications and clinical outcomes in a reference centre

BACKGROUND

Growing numbers of indications for intravenous immunoglobulins (IVIg) in recent years has resulted in an increase in the consumption of these products. A lack of raw material has led to IVIg shortage. The objective of this work was to evaluate the impact of this situation on patient care in one French referral centre considering practice modifications and clinical impact.

METHODS

All patients treated with IVIg for chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy and myasthenia gravis from October 2017 to October 2018 were included.

RESULTS

Out of 142 patients, 111 (78%) had a modification of their IVIg treatment. We noted that 75 (68%) patients had a delay in IVIg treatment, 41 (37%) patients had a decrease in IVIg doses and 31 (28%) experienced IVIg treatment interruption. Thirty percent of patients for whom IVIg treatment was discontinued were switched to other treatments mainly plasma exchange (16%) or corticosteroids (13%). Switches to plasma exchange or corticosteroids were carried out in order to save immunoglobulins for patients who had no other alternatives. Fifty-eight (52%) patients presented a deterioration of their clinical score after IVIg treatment changes including 31 (28%) patients who had a moderate or a clinically significant deterioration. Concerning practice modifications, we noted a substantial though not significant decrease in median IVIg dose for myasthenia gravis and a significant increase in the delay between IVIg courses for chronic inflammatory demyelinating polyneuropathy and multifocal motor neuropathy (P=0.011 and P=0.018 respectively).

CONCLUSION

Our study showed a rather important number of changes in IVIg treatment related to IVIg shortage during the period considered. These changes had a negative impact on the clinical status of some patients.

Childhood-Onset Multifocal Motor Neuropathy with IgM Antibodies to Gangliosides GM1: A Case Report with Poor Outcome

BACKGROUND

Multifocal motor neuropathy (MMN) is a slowly progressive motor neuropathy characterized by asymmetric muscle weakness without sensory involvement. Typically, MMN respond completely to treatment with intravenous immunoglobulin (IVIg). MMN is even rarer in the pediatric population, where only five patients have been reported up to now.

CASE REPORT

We discuss the 3-year follow-up of a 13-year-old girl with MMN who was positive for IgM antibodies to gangliosides GM1. She was diagnosed with MMN in accordance with the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) criteria. Serological studies revealed that she tested positive for IgM antibodies to GM1. She underwent intravenous methylprednisolone followed by an oral prednisone taper, intravenous immunoglobulin (IVIg), plasma exchange followed by IVIG and prednisone and Rituximab. No improvement was referred. At the present, she shows flaccid tetraplegia, facial diplegia, and bulbar cranial nerve palsy.

CONCLUSION

Although childhood onset MMN is rare, most patients reported in literature respond to IVIg treatment. In a few cases, however, IVIg can be ineffective. In our patient, IVIg as well as treatment with prednisolone, plasma exchange and rituximab have failed.

Quantitative magnetic resonance imaging of the brachial plexus shows specific changes in nerve architecture in chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy and motor neuron disease

BACKGROUND

The immunological pathophysiologies of chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN) differ considerably, but neither has been elucidated completely. Quantitative magnetic resonance imaging (MRI) techniques such as diffusion tensor imaging, T2 mapping, and fat fraction analysis may indicate in vivo pathophysiological changes in nerve architecture. Our study aimed to systematically study nerve architecture of the brachial plexus in patients with CIDP, MMN, motor neuron disease (MND) and healthy controls using these quantitative MRI techniques.

METHODS

We enrolled patients with CIDP (n = 47), MMN (n = 29), MND (n = 40) and healthy controls (n = 10). All patients underwent MRI of the brachial plexus and we obtained diffusion parameters, T2 relaxation times and fat fraction using an automated processing pipeline. We compared these parameters between groups using a univariate general linear model.

RESULTS

Fractional anisotropy was lower in patients with CIDP compared to healthy controls (p < 0.001), patients with MND (p = 0.010) and MMN (p < 0.001). Radial diffusivity was higher in patients with CIDP compared to healthy controls (p = 0.015) and patients with MND (p = 0.001) and MMN (p < 0.001). T2 relaxation time was elevated in patients with CIDP compared to patients with MND (p = 0.023). Fat fraction was lower in patients with CIDP and MMN compared to patients with MND (both p < 0.001).

CONCLUSION

Our results show that quantitative MRI parameters differ between CIDP, MMN and MND, which may reflect differences in underlying pathophysiological mechanisms.

SMN1 Duplications Are Associated With Progressive Muscular Atrophy, but Not With Multifocal Motor Neuropathy and Primary Lateral Sclerosis

Objective

To assess the association between copy number (CN) variation in the survival motor neuron (SMN) locus and multifocal motor neuropathy (MMN), progressive muscular atrophy (PMA), and primary lateral sclerosis (PLS) susceptibility and to determine the association of SMN1 and SMN2 CN with MMN, PMA, and PLS disease course.

Methods

In this monocenter study, we used multiplex ligation-dependent probe amplification to determine SMN1 and SMN2 CN in Dutch patients with MMN, PMA, and PLS and controls. We stratified clinical parameters for SMN1 and SMN2 CN. We analyzed SMN1 and SMN2 exons 1–6, intron 6, and exon 8 CN to study the genetic architecture of SMN1 duplications.

Results

SMN1 and SMN2 CN were determined in 132 patients with MMN, 150 patients with PMA, 104 patients with PLS, and 956 control subjects. MMN and PLS were not associated with CN variation in SMN1 or SMN2. By contrast, patients with PMA more often than controls carried SMN1 duplications (≥3 SMN1 copies, 12.0% vs 5.0%, odds ratio 2.69 (1.43–4.91), p 0.0020). SMN1 and SMN2 CN status was not associated with MMN, PLS, or PMA disease course. In case of SMN1 exon 7 duplications, exons 1–6, exon 8, and introns 6 and 7 were also duplicated, suggesting full SMN1 duplications.

Conclusions

SMN1 duplications are associated with PMA, but not with PLS and MMN. SMN1 duplications in PMA are balanced duplications. The results of this study highlight the primary effect of altered SMN CN on lower motor neurons.

Long-term treatment with subcutaneous immunoglobulin in multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is a rare disease with a prevalence of less than 1 per 100,000 people. Intravenous immunoglobulin (IVIG) therapy, performed for a long-term period, has been demonstrated able to improve the clinical picture of MMN patients, ameliorating motor symptoms and/or preventing disease progression. Treatment with subcutaneous immunoglobulin (SCIg) has been shown to be as effective as IVIG. However, previously published data showed that follow-up of MMN patients in treatment with SCIg lasted no more than 56 months. We report herein the results of a long-term SCIg treatment follow up (up to 96 months) in a group of 8 MMN patients (6 M; 2F), previously stabilized with IVIG therapy. Clinical follow-up included the administration of Medical Research Council (MRC) sum-score, the Overall Neuropathy Limitation Scale (ONLS) and the Life Quality Index questionnaire (LQI) at baseline and then every 6 months. Once converted to SCIg, patients’ responsiveness was quite good. Strength and motor functions remained stable or even improved during this long-term follow-up with benefits on walking capability, resistance to physical efforts and ability in hand fine movements.

Chronic Immune-Mediated Polyneuropathies

This article discusses the chronic immune-mediated polyneuropathies, a broad category of acquired polyneuropathies that encompasses chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), the most common immune-mediated neuropathy, the CIDP variants, and the vasculitic neuropathies. Polyneuropathies associated with rheumatological diseases and systemic inflammatory diseases, such as sarcoidosis, will also be briefly covered. These patients' history, examination, serum studies, and electrodiagnostic studies, as well as histopathological findings in the case of vasculitis, confirm the diagnosis and differentiate them from the more common length-dependent polyneuropathies. Prompt identification and initiation of treatment is imperative for these chronic immune-mediated polyneuropathies to prevent disability and even death.

Ultrasound scanning in the diagnosis of peripheral neuropathies

Nerve ultrasound scanning has become a valuable diagnostic tool in the routine workup of peripheral nerve disorders, effectively complementing conventional electrodiagnostic studies. The most relevant sonographic features are nerve size and structural integrity. Several peripheral neuropathies show characteristic and distinct patterns of nerve enlargement, allowing their early and accurate identification, and reducing test-burden and diagnostic delay for patients. In mononeuropathies such as carpal tunnel syndrome and ulnar neuropathy at the elbow, nerve enlargement develops only at specific sites of entrapment, while in polyneuropathy the nerve enlargement may be multifocal, regional or even diffuse. Nerve ultrasound scanning can reliably identify chronic inflammatory neuropathies, even when extensive electrodiagnostic studies fail, and it should therefore be embedded in routine diagnostic workup of peripheral neuropathies. In this paper we describe a potential diagnostic strategy to achieve this.

Nerve Ultrasound as Helpful Tool in Polyneuropathies

Background: Polyneuropathies (PNP) are a broad field of diseases affecting millions of people. While the symptoms presented are mostly similar, underlying causes are abundant. Thus, early identification of treatable causes is often difficult. Besides clinical data and basic laboratory findings, nerve conduction studies are crucial for etiological classification, yet limited. Besides Magnetic Resonance Imaging (MRI), high-resolution nerve ultrasound (HRUS) has become a noninvasive, fast, economic and available tool to help distinguish different types of nerve alterations in neuropathies. Methods: We aim to describe typical ultrasound findings in PNP and patterns of morphological changes in hereditary, immune-mediated, diabetic, metabolic and neurodegenerative PNP. Literature research was performed in PubMed using the terms ‘nerve ultrasound’, neuromuscular ultrasound, high-resolution nerve ultrasound, peripheral nerves, nerve enlargement, demyelinating, hereditary, polyneuropathies, hypertrophy’. Results: Plenty of studies over the past 20 years investigated the value of nerve ultrasound in different neuropathies. Next to nerve enlargement, patterns of nerve enlargement, echointensity, vascularization and elastography have been evaluated for diagnostic terms. Furthermore, different scores have been developed to distinguish different etiologies of PNP. Conclusions: Where morphological alterations of the nerves reflect underlying pathologies, early nerve ultrasound might enable a timely start of available treatment and also facilitate follow up of therapy success.

High-resolution mapping identifies HLA class II associations with multifocal motor neuropathy

OBJECTIVE

To gain further insight in the immunopathology underlying multifocal motor neuropathy (MMN) by exploring the association between MMN and the human leukocyte antigen (HLA) class II DRB1, DQB1, and DQA loci in depth and by correlating associated haplotypes to detailed clinical and anti-ganglioside antibody data.

METHODS

We performed high-resolution HLA-class II typing for the DRB1, DQB1, and DQA1 loci in 126 well-characterized MMN patients and assessed disease associations with haplotypes. We used a cohort of 1305 random individuals as a reference for haplotype distribution in the Dutch population.

RESULTS

The DRB1*15:01-DQB1*06:02 haplotype (OR 1.6 [95% CI 1.1-2.2], p < 0.05) and the DRB1*12:01-DQB1*03:01 haplotype (OR 2.7 [95% CI 1.2-5.5], p < 0.05) were more frequent in patients with MMN than in controls. These haplotypes were not associated with disease course, response to treatment or anti-ganglioside antibodies.

CONCLUSIONS

MMN is associated with the DRB1*15:01-DQB1*06:02 and DRB1*12:01-DQB1*03:01 haplotypes. These HLA molecules or gene variants in their immediate vicinity may promote the specific inflammatory processes underlying MMN.

Small Fibre Involvement in Multifocal Motor Neuropathy Explored with Sudoscan: A Single-Centre Experience

Objective: Multifocal motor neuropathy (MMN) is a rare inflammatory neuropathy, clinically characterized by exclusive motor involvement. We wished to evaluate the possible presence of sensory dysfunction, including the evaluation of small fibres, after a long-term disease course. Patients and methods: seven MMN patients, regularly followed in our Neurology Department, underwent clinical evaluation, neurophysiological examination by nerve conduction studies (NCSs), and Sudoscan. We compared neurophysiological data with a group of patients with other disorders of the peripheral nervous system. Results: NCSs showed a reduction of sensory nerve action potential amplitude in 2/7 MMN patients. Sudoscan showed borderline electrochemical skin conductance (ESC) values in 3/7 MMN patients (two of them with abnormal sensory NCSs). Conclusions: Our results confirm that sensory involvement may be found in some MMN after a long-term disease course, and it could also involve the small fibres.

Quantitative assessment of brachial plexus MRI for the diagnosis of chronic inflammatory neuropathies

Objective

This study aimed at developing a quantitative approach to assess abnormalities on MRI of the brachial plexus and the cervical roots in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN) and to evaluate interrater reliability and its diagnostic value.

Methods

We performed a cross-sectional study in 50 patients with CIDP, 31 with MMN and 42 disease controls. We systematically measured cervical nerve root sizes on MRI bilaterally (C5, C6, C7) in the coronal [diameter (mm)] and sagittal planes [area (mm²)], next to the ganglion (G₀) and 1 cm distal from the ganglion (G₁). We determined their diagnostic value using a multivariate binary logistic model and ROC analysis. In addition, we evaluated intra- and interrater reliability.

Results

Nerve root size was larger in patients with CIDP and MMN compared to controls at all predetermined anatomical sites. We found that nerve root diameters in the coronal plane had optimal reliability (intrarater ICC 0.55–0.87; interrater ICC 0.65–0.90). AUC was 0.78 (95% CI 0.69–0.87) for measurements at G₀ and 0.81 (95% CI 0.72–0.91) for measurements at G₁. Importantly, our quantitative assessment of brachial plexus MRI identified an additional 10% of patients that showed response to treatment, but were missed by nerve conduction (NCS) and nerve ultrasound studies.

Conclusion

Our study showed that a quantitative assessment of brachial plexus MRI is reliable. MRI can serve as an important additional diagnostic tool to identify treatment-responsive patients, complementary to NCS and nerve ultrasound.

Electronic supplementary material

The online version of this article (10.1007/s00415-020-10232-8) contains supplementary material, which is available to authorized users.

Excitability of motor and sensory axons in multifocal motor neuropathy

OBJECTIVE

To assess excitability differences between motor and sensory axons of affected nerves in patients with multifocal motor neuropathy (MMN).

METHODS

We performed motor and sensory excitability tests in affected median nerves of 20 MMN patients and in 20 age-matched normal subjects. CMAPs were recorded from the thenar and SNAPs from the 3rd digit. Clinical tests included assessment of muscle strength, two-point discrimination and joint position.

RESULTS

All MMN patients had weakness of the thenar muscle and normal sensory tests. Motor excitability testing in MMN showed an increased threshold for a 50% CMAP, increased rheobase, decreased stimulus-response slope, fanning-out of threshold electrotonus, decreased resting I/V slope, shortened refractory period, and more pronounced superexcitability. Sensory excitability testing in MMN revealed decreased accommodation half-time and S2-accommodation and less pronounced subexcitability. Mathematical modeling indicated increased Barrett-Barrett conductance for motor fibers and increase in internodal fast potassium conductance for sensory fibers.

CONCLUSIONS

Excitability findings in MMN suggest myelin sheath or paranodal seal involvement in motor fibers and, possibly, paranodal detachment in sensory fibers.

SIGNIFICANCE

Excitability properties of affected nerves in MMN differ between motor and sensory nerve fibers.

Dramatic clinical response to ultra-high dose IVIg in otherwise treatment resistant inflammatory neuropathies

BACKGROUND

Intravenous immunoglobulin (IVIg) has short and long-term efficacy in both chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy with conduction block (MMNCB). There is potential for under and over-treatment if trial regimens are strictly adhered to in clinical practice where titrating dose to clinical response is recommended.

METHODS

We report the response to high-dose IVIg (>2 g/kg/6 weeks) in a subgroup of patients with definite CIDP or MMNCB who were unresponsive to 'usual' dosing. IVIg frequency and dosing was determined for each individual by subjective and objective outcome measures for impairment, grip strength, and activity and participation.

RESULTS

Six patients (three with chronic inflammatory demyelinating polyneuropathy (CIDP), three with MMN) were included. Two patients (one CIDP and one MMNCB) returned to full-time work on fractionated IVIg doses of 5 g/kg/month and 9 g/kg/month. Patient three (CIDP) failed numerous other immunosuppressants but responded to short-term fractionated 4 g/kg/month of IVIg. Patient four has severe, refractory, childhood-onset CIDP, remains stable but dependent currently on 6.9 g/kg/month of IVIg. Patients five and six, both with MMNCB, required short term 4.5-5 g/kg/month to recover significant bilateral hand strength. No IVIg-related adverse events occurred in any individual.

CONCLUSIONS

These six cases demonstrate the safety and effectiveness of a treatment approach that includes individualised but evidence-based clinical assessment and, when necessary, high-doses of IVIg to restore patients' strength and ability to participate in activities of daily activities. Careful patient selection is important.

Clinical outcomes in multifocal motor neuropathy: A combined cross-sectional and follow-up study

OBJECTIVE

To assess the clinical course of multifocal motor neuropathy (MMN) in a large cohort of patients and to identify predictive factors of a progressive disease course.

METHODS

Between May 2015 and February 2016, we collected clinical data from 100 patients with MMN, of whom 60 had participated in a nationwide cross-sectional cohort study in 2007. We documented clinical characteristics using standardized questionnaires and performed a standardized neurologic examination. We used multiple linear regression analysis to identify factors that correlated with worse outcome.

RESULTS

We found that age at diagnosis (45.2 vs 48.6 years, p < 0.02) was significantly increased between 2007 and 2015-2016, whereas diagnostic delay decreased by 15 months. Seven out of 10 outcome measures deteriorated over time (all p < 0.01). Patients who had a lower Medical Research Council (MRC) sumscore and absence of 1 or more reflexes at the baseline visit showed a greater functional loss at follow-up (p = 0.007 and p = 0.016).

CONCLUSIONS

Our study shows that MMN is a progressive disease. Although 87% of patients received maintenance treatment, muscle strength, reflexes, vibration sense, and the Self-Evaluation Scale score significantly deteriorated over time. Lower MRC sumscore and absence of reflexes predicted a more progressive disease course.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that lower MRC sumscore and the absence of reflexes predict a more progressive disease course in patients with MMN.

The use of IVIg in the treatment of inflammatory polyneuropathies and myasthenia gravis at The Walton Centre

BACKGROUND

Immunoglobulin is a blood product used in a variety of medical disorders, usually delivered intravenously (IVIg). Neurology patients, particularly those with inflammatory polyneuropathy, utilise a lot of IVIg. There is a national shortage of immunoglobulin and, thus, pressing need to ensure minimum effective dosing as well as rigorous outcome assessments to assess benefit at treatment start and subsequently, as placebo effects can be strong.

METHODS

Serial audit of IVIg use at The Walton Centre against national guidelines was carried out through analysis of clinical notes of day unit patients. Review of the national immunoglobulin database and of neurology outpatient notes to benchmark our practice and provide some comparison with the wider nation was also performed.

RESULTS

Serial audit led to improved adherence to guidelines, and analysis of practice identified wide variation in IVIg use.

CONCLUSION

Local audit and benchmarking of practice can be used to promote quality and consistency of IVIg use across the NHS.

Guillain-Barré syndrome in a man presenting with upper extremity monoplegia

Outside academia, community and rural medical centers often rely on clinical signs and symptoms for early intervention, as means of gathering objective data may be unavailable, or the reliance of biological testing may take too long to return. Continued reporting of atypical presentations is therefore necessary for broadening clinical recognition of such cases.

Clinical characteristics of fibroblast growth factor receptor 3 antibody-related polyneuropathy: a retrospective study

BACKGROUND AND PURPOSE

Autoantibodies are increasingly being used as a diagnostic biomarker of chronic inflammatory neuropathies. However, their role and associated clinical syndrome are not well defined.

METHODS

This retrospective chart review evaluated the clinical presentation, diagnostic workup and therapeutic responses in fibroblast growth factor receptor 3 (FGFR3) antibody-associated neuropathy.

RESULTS

A total of 27 patients [14 men, aged 29-87 (65 ± 14) years] with positive FGFR3 antibody were included. Distal lower-extremity paresthesia (66%), unsteady gait (26%) and foot drop (11%) were common presenting symptoms. Symptom onset was acute in four (15%) cases. Distal lower-extremity weakness (mild in eight and severe in three patients) was the most frequent motor finding. Decreased distal sensation to pinprick (59%) and loss of vibration sensation (37%) were observed. Titer of FGFR3 ranged between 3100 and 30 000 (normal < 3000) with a mean of 10 688 ± 7284. Apart from the occasional association of other neuropathy-related autoantibodies, comprehensive neuropathy workup was otherwise unrevealing. Six patients had other autoimmune disease and seven patients had a history of cancer. Electromyography reflected sensorimotor neuropathy with mixed axonal and demyelinating features in 11 cases. Pure sensory neuropathy was noted in three patients. Demyelination was found in five of six nerve biopsies. Intravenous immunoglobulin response was observed in 8/10 treated patients.

CONCLUSIONS

The FGFR3 antibody appears not to be restricted to sensory neuropathy only. Its role in the pathogenicity of chronic inflammatory neuropathies is not yet well established and, although there may be a role for immunotherapy, larger studies are warranted.

Different distribution of demyelination in chronic inflammatory demyelinating polyneuropathy subtypes

In demyelinating polyneuropathies, distribution patterns of demyelination reflect underlying pathogenesis. Median and ulnar nerve conduction studies were reviewed in 85 typical chronic inflammatory demyelinating polyneuropathy (CIDP) patients and 29 multifocal acquired demyelinating sensory and motor neuropathy (MADSAM). Distal latencies were prolonged in typical CIDP and near normal in MADSAM. Abnormal amplitude reductions in the nerve trunks were more frequent in MADSAM than typical CIDP. Presumably because the blood-nerve barrier is anatomically deficient at the distal nerve terminals, antibody-mediated demyelination is a major pathophysiology in typical CIDP. In contrast, blood-nerve barrier breakdown is likely to be predominant in MADSAM.

Diagnostic accuracy of MRI and ultrasound in chronic immune-mediated neuropathies

OBJECTIVE

To assess and compare the diagnostic performance of qualitative and (semi-)quantitative MRI and ultrasound for distinguishing chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN) from segmental spinal muscular atrophy (sSMA).

METHODS

Patients with CIDP (n = 13), MMN (n = 10), or sSMA (n = 12) and healthy volunteers (n = 30) were included. MRI of the brachial plexus, using short tau inversion recovery (STIR), nerve-specific T2-weighted (magnetic resonance neurography [MRN]), and diffusion tensor imaging (DTI) sequences, was evaluated. Furthermore, with ultrasound, cross-sectional areas of the nerves were evaluated. Three radiologists blinded for diagnosis qualitatively scored hypertrophy and increased signal intensity (STIR and MRN), and intraobserver and interobserver agreement was assessed. For the (semi-)quantitative modalities, group differences and receiver operator characteristics were calculated.

RESULTS

Hypertrophy and increased signal intensity were found in all groups including healthy controls. Intraobserver and interobserver agreements varied considerably (intraclass correlation coefficients 0.00-0.811 and 0.101-0.491, respectively). DTI showed significant differences (p < 0.05) among CIDP, MMN, sSMA, and controls for fractional anisotropy, axial diffusivity, and radial diffusivity in the brachial plexus. Ultrasound showed significant differences in cross-sectional area (p < 0.05) among CIDP, MMN, and sSMA in upper arm and brachial plexus. For distinguishing immune-mediated neuropathies (CIDP and MMN) from sSMA, ultrasound yielded the highest area under the curve (0.870).

CONCLUSION

Qualitative assessment of hypertrophy and signal hyperintensity on STIR or MRN is of limited value. DTI measures may discriminate among CIDP, MMN, and sSMA. Currently, ultrasound may be the most appropriate diagnostic imaging aid in the clinical setting.

Polyneuropathies

BACKGROUND

Polyneuropathies (peripheral neuropathies) are the most common type of disorder of the peripheral nervous system in adults, and specifically in the elderly, with an estimated prevalence of 5-8%, depending on age. The options for treatment depend on the cause, which should therefore be identified as precisely as possible by an appropriate diagnostic evaluation.

METHODS

This review is based on the current guidelines and on large-scale cohort studies and randomized, controlled trials published from 2000 to 2017, with an emphasis on non-hereditary types of polyneuropathy, that were retrieved by a selective search in PubMed.

RESULTS

Diabetes is the most common cause of polyneuropathy in Europe and North America. Alcohol-associated polyneuropathy has a prevalence of 22-66% among persons with chronic alcoholism. Because of the increasing prevalence of malignant disease and the use of new chemotherapeutic drugs, chemotherapy-induced neuropathies (CIN) have gained in clinical importance; their prevalence is often stated to be 30-40%, with high variation depending on the drug(s) and treatment regimen used. Polyneuropathy can also arise from genetic causes or as a consequence of vitamin deficiency or overdose, exposure to toxic substances and drugs, and a variety of immunological processes. About half of all cases of polyneu - ropathy are associated with pain. Neuropathic pain can be treated symptomatically with medication. Exercise, physiotherapy, and ergotherapy can also be beneficial, depending on the patient's symptoms and functional deficits.

CONCLUSION

A timely diagnosis of the cause of polyneuropathy is a prerequisite for the initiation of appropriate specific treatment. Patients with severe neuropathy of unidentified cause should be referred to a specialized center for a thorough diagnostic evaluation.

Human immune globulin 10% with recombinant human hyaluronidase in multifocal motor neuropathy

Objective

The primary aim was to determine the safety of treatment with human immune globulin 10% with recombinant human hyaluronidase (fSCIg) compared to intravenous immunoglobulin (IVIg) in a prospective open-label study in patients with multifocal motor neuropathy (MMN).

Methods

Our study consisted of two phases: the IVIg phase (visits 1–3; 12 weeks), in which patients remained on IVIg treatment, and the fSCIg phase (visits 4–7; 36 weeks), in which patients received fSCIg treatment. After visit 3, IVIg was switched to an equivalent dose and frequency of fSCIg. Outcome measures were safety, muscle strength, disability and treatment satisfaction.

Results

Eighteen patients were enrolled in this study. Switching to fSCIg reduced the number of systemic adverse events (IVIg 11.6 vs. fSCIg 5.0 adverse events/per person-year, p < 0.02), and increased the number of local reactions at the injection site (IVIg 0 vs. fSCIg 3.3 local reactions/per person-year, p < 0.01). Overall, no significant differences in muscle strength and disability between fSCIg and IVIg were found. Treatment with fSCIg was perceived as optimal treatment option by 8 of the 17 patients (47.1%) and they continued with fSCIg after study closure because of improved independence and flexibility to administer treatment.

Conclusion

Treatment with fSCIg can be considered a safe alternative for patients with MMN on IVIg treatment. fSCIg could be a favorable option in patients who prefer self-treatment and more independency, and in patients who experience systemic adverse events on IVIg or have difficult intravenous access.

Electronic supplementary material

The online version of this article (10.1007/s00415-019-09475-x) contains supplementary material, which is available to authorized users.

Complications of Immunoglobulin Therapy and Implications for Treatment of Inflammatory Neuropathy: A Review

BACKGROUND

Intravenous Immunoglobulin (IVIg) forms a cornerstone of effective treatment for acute and chronic inflammatory neuropathies, with a class I evidence base in Guillain-Barré Syndrome (GBS), Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). It is generally considered to be a safe therapy however there are several recognised complications which are reviewed in this article.

DISCUSSION AND CONCLUSION

Most adverse events are immediate and mild such as headache, fever and nausea although more serious immediate reactions such as anaphylaxis may rarely occur. Delayed complications are rare but may be serious, including thromboembolic events and acute kidney injury, and these and associated risk factors are also discussed. We emphasise the importance of safe IVIg administration and highlight practical measures to minimise complications of this therapy.

Nerve ultrasound and magnetic resonance imaging in the diagnosis of neuropathy

PURPOSE OF REVIEW

This review summarizes the most relevant developments in the fields of nerve ultrasound and MRI in the diagnosis of treatable inflammatory neuropathies over the last 18 months.

RECENT FINDINGS

MRI and nerve ultrasound can accurately identify potentially treatable neuropathies and thereby help to improve diagnosis. Advanced MRI techniques also show potential to dissect pathophysiology. The apparent mismatch between nerve function and morphology is not surprising and reflects different dimensions of the disease process in neuropathies.

SUMMARY

MRI and nerve ultrasound have become useful tools in the diagnosis of inflammatory neuropathies. VIDEO ABSTRACT.

Conduction block in immune-mediated neuropathy: paranodopathy versus axonopathy

BACKGROUND AND PURPOSE

Conduction block is a pathognomonic feature of immune-mediated neuropathies. The aim of this study was to advance understanding of pathophysiology and conduction block in chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN).

METHODS

A multimodal approach was used, incorporating clinical phenotyping, neurophysiology, immunohistochemistry and structural assessments.

RESULTS

Of 49 CIDP and 14 MMN patients, 25% and 79% had median nerve forearm block, respectively. Clinical scores were similar in CIDP patients with and without block. CIDP patients with median nerve block demonstrated markedly elevated thresholds and greater threshold changes in threshold electrotonus, whilst those without did not differ from healthy controls in electrotonus parameters. In contrast, MMN patients exhibited marked increases in superexcitability. Nerve size was similar in both CIDP groups at the site of axonal excitability. However, CIDP patients with block demonstrated more frequent paranodal serum binding to teased rat nerve fibres. In keeping with these findings, mathematical modelling of nerve excitability recordings in CIDP patients with block support the role of paranodal dysfunction and enhanced leakage of current between the node and internode. In contrast, changes in MMN probably resulted from a reduction in ion channel density along axons.

CONCLUSIONS

The underlying pathologies in CIDP and MMN are distinct. Conduction block in CIDP is associated with paranodal dysfunction which may be antibody-mediated in a subset of patients. In contrast, MMN is characterized by channel dysfunction downstream from the site of block.

Slowly progressive distal muscle weakness: neuropathy or myopathy?

Nonaka myopathy is an autosomal recessive and slowly progressive distal myopathy. It is part of a rare group of myopathies predominantly affecting the distal limb musculature. Over 150 cases have been reported across the Middle East, Japan and Europe. We report the case of a 33-year-old woman presenting with symmetrical upper and lower limb weakness, most severely affecting the distal muscle groups. After extensive neurological investigation including neurophysiology, muscle biopsy and genetic analysis, she was finally diagnosed with Nonaka myopathy and treated conservatively with physiotherapy.

Incidence and Prevalence of Chronic Inflammatory Demyelinating Polyradiculoneuropathy: A Systematic Review and Meta-Analysis

BACKGROUND

Prevalence and incidence rates of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) are required to determine the impact of CIDP on society. We aimed to estimate the prevalence and incidence of CIDP worldwide and to determine the effect of diagnostic criteria on prevalence and incidence.

METHOD

A systematic review was conducted for all published incidence and prevalence studies on CIDP until May 18, 2017. Methodological quality was assessed using the Methodological Evaluation of Observational Research checklist. We performed a random effect meta-analysis to estimate pooled prevalence and incidence rates.

RESULTS

Of the 907 studies, 11 were included in the systematic review, 5 in the meta-analysis of incidence (818 cases; 220,513,514 person-years) and 9 in the meta-analysis of prevalence (3,160 cases; 160,765,325 population). These studies had a moderate quality. The pooled crude incidence rate was 0.33 per 100,000 person-years (95% CI 0.21-0.53; I2 = 95.7%) and the pooled prevalence rate was 2.81 per 100,000 (95% CI 1.58-4.39; I2 = 99.1%). Substantial heterogeneity in incidence and prevalence across studies seems to be partly explained by using different diagnostic criteria.

CONCLUSION

These findings provide a starting point to estimate the social burden of CIDP and demonstrate the need to reach consensus on diagnostic criteria for CIDP.

Intravenous immunoglobulin for treatment of chronic inflammatory demyelinating polyneuropathy and multifocal motor neuropathy in France: are daily practices in accordance with guidelines?

BACKGROUND AND PURPOSE

Chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN) are rare autoimmune diseases. Guidelines were published in 2010 for their diagnosis and treatment. In France, intravenous immunoglobulins (IVIGs) are mainly used for the first-line treatment. The burden of healthcare costs is often underlined but rarely studied. The aim of this survey was to compare to guidelines, the daily practice of French neurologists with IVIGs for CIDP and MMN treatment.

METHODS

This was a retrospective observational study consisting of an online questionnaire performed between March and May 2014. A total of 49 questionnaires were included, a quarter of which were from neurologists working in neuromuscular reference centers (NRCs).

RESULTS

A total of 182 patient case reports were studied. Patients were referred to an NRC for initial diagnosis in approximately 30% of cases in CIDP and 50% of cases in MMN. The initial management of IVIG (frequency, dose and duration) was not different between NRCs and non-NRCs. Guidelines were followed and neurologists were relatively at ease in diagnosing and treating patients.

CONCLUSIONS

This was the first national study to describe the implementation of the European Federation of Neurological Sciences/Peripheral Nerve Society guidelines in the daily management of IVIGs in patients with MMN and CIDP in France. Efforts are needed to improve long-term tailored treatment and home treatment to reduce economic costs.