Multifocal motor neuropathy

Role of tubulin post-translational modifications in peripheral neuropathy

Peripheral neuropathy is a common disorder that results from nerve damage in the periphery. The degeneration of sensory axon terminals leads to changes or loss of sensory functions, often manifesting as debilitating pain, weakness, numbness, tingling, and disability. The pathogenesis of most peripheral neuropathies remains to be fully elucidated. Cumulative evidence from both early and recent studies indicates that tubulin damage may provide a common underlying mechanism of axonal injury in various peripheral neuropathies. In particular, tubulin post-translational modifications have been recently implicated in both toxic and inherited forms of peripheral neuropathy through regulation of axonal transport and mitochondria dynamics. This knowledge forms a new area of investigation with the potential for developing therapeutic strategies to prevent or delay peripheral neuropathy by restoring tubulin homeostasis.

Study on the Diagnostic Value of Neuroelectrophysiological Examination in Patients with Amyotrophic Lateral Sclerosis

Objective

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease with unknown causes involving upper and lower motor neurons. Our study aimed to explore the diagnostic value of neuroelectrophysiological examination in patients with amyotrophic lateral sclerosis.

Methods

A total of 64 patients admitted to our hospital from January 2014 to December 2020 were selected as ALS group. Additionally, 64 normal healthy people in the same period were selected as the control group. Electrophysiological tests were performed on all personnel involved in the study, and the results and parameter changes of different personnel were compared and analyzed.

Results

There was a statistical difference between the EMG data of clinically confirmed ALS and the proposed ALS and possible ALS (p < 0.05). The abnormality of confirmed ALS was particularly obvious, and the overall abnormal rate of EMG in ALS was 85%. The CMCT of the upper and lower limbs of clinically diagnosed ALS, suspected ALS, and possible ALS were longer than that of the normal group (p < 0.05). There was no significant statistical difference between clinically diagnosed ALS and suspected ALS (p > 0.05), and there was a difference between clinically diagnosed ALS and possible ALS (p < 0.05). In ALS group, the frequency of F wave decreased, which may be related to the involvement of F wave conduction pathway and the degree of lower motor neuron involvement (p < 0.05). In addition, the amplitudes of F and H waves increased, which was related to the involvement of upper motor neurons (p < 0.05). In ALS group, SCV was hardly involved, and CMAP decreased significantly, which was positively correlated with the degree of muscular atrophy and muscle strength decline (p < 0.05). The sensitivity of electrophysiological detection was 76.56%, the specificity was 78.33%, and the AUC was 0.8578.

Conclusion

Patients with clinically suspected ALS should undergo electrophysiological testing as soon as possible, which is conducive to the early diagnosis and differential diagnosis of ALS. This trial is registered with ChiCTR2100046535.

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.

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.

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.

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.

Advances in imaging technologies for the assessment of peripheral neuropathies in rheumatoid arthritis

Peripheral neuropathy in patients with rheumatoid arthritis is associated with a maladaptive autoimmune response that may cause chronic pain and disability. Nerve conduction studies are the routine method performed when rheumatologists presume its presence. However, this approach is invasive, may not reveal subtle malfunctions in the early stages of the disease, and does not expose abnormalities in structures surrounding the nerves and muscles, limiting the possibility of a timely diagnosis. This work aims to present a narrative review of new technologies for the clinical assessment of peripheral neuropathy in Rheumatoid Arthritis. Through a bibliographic search carried out in five repositories, from 1990 to 2020, we identified three technologies that could detect peripheral nerve lesions and perform quantitative evaluations: (1) magnetic resonance neurography, (2) functional magnetic resonance imaging, and (3) high-resolution ultrasonography of peripheral nerves. We found these tools can overcome the main constraints imposed by the previous electrophysiologic methods, enabling early diagnosis.

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.

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.

Nerve ultrasound improves detection of treatment-responsive chronic inflammatory neuropathies

OBJECTIVE

To examine the diagnostic accuracy of nerve ultrasound in a prospective cohort of consecutive patients with a clinical suspicion of chronic inflammatory neuropathies, including chronic inflammatory demyelinating polyneuropathy, Lewis-Sumner syndrome, and multifocal motor neuropathy, and to determine the added value in the detection of treatment-responsive patients.

METHODS

Between February 2015 and July 2018, we included 100 consecutive incident patients with a clinical suspicion of chronic inflammatory neuropathy. All patients underwent nerve ultrasound, extensive standardized nerve conduction studies (NCS), and other relevant diagnostic investigations. We evaluated treatment response using predefined criteria. A diagnosis of chronic inflammatory neuropathy was established when NCS were abnormal (fulfilling criteria of demyelination of the European Federation of Neurological Societies/Peripheral Nerve Society) or when the degree of nerve enlargement detected by sonography was compatible with chronic inflammatory neuropathy and there was response to treatment.

RESULTS

A diagnosis of chronic inflammatory neuropathy was established in 38 patients. Sensitivity and specificity of nerve ultrasound and NCS were 97.4% and 69.4% and 78.9% and 93.5%, respectively. The added value of nerve ultrasound in detection of treatment-responsive chronic inflammatory neuropathy was 21.1% compared to NCS alone.

CONCLUSIONS

Nerve ultrasound and NCS are complementary techniques with superior sensitivity in the former and specificity in the latter. Addition of nerve ultrasound significantly improves the detection of chronic inflammatory neuropathies. Therefore, it deserves a prominent place in the diagnostic workup of chronic inflammatory neuropathies.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that nerve ultrasound is an accurate diagnostic tool to detect chronic inflammatory neuropathies.

Childhood-onset multifocal motor neuropathy with IgM antibodies to GM2 and GalNac-GD1a

BACKGROUND

Multifocal motor neuropathy (MMN) is an acquired immune-mediated form of neuropathy characterized by upper and asymmetric limb weakness without sensory loss. The mean age of onset is 40 years (range, 20-70 years), and childhood-onset MMN is extremely rare. In the present report, we discuss a case of childhood-onset MMN in a patient who tested positive for anti-GM2 and anti-GalNac-GD1a immunoglobulin M (IgM) antibodies.

CASE REPORT

A 12-year-old girl presented with progressive weakness of the upper extremities without sensory loss. Electrophysiological assessments revealed definite conduction blocks in the left median and bilateral radial nerves. 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 GM2 and GalNac-GD1a. Partial improvements in both muscle weakness and electrophysiological assessments were achieved after 8 months of high-dose intravenous immunoglobulin (IVIg) treatment.

CONCLUSION

Although childhood-onset MMN is rare, most patients respond to IVIg treatment. This is the first case of childhood-onset MMN in a patient who tested positive for anti-GM2 and anti-GalNac-GD1a IgM antibodies. Although half of the adult patients with MMN test positive for anti-GM1 IgM antibodies, they were not detected in our patient. Comprehensive testing for serum anti-glycolipid antibodies in addition to GM1 may aid in the diagnosis of childhood-onset MMN.

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.

Risk of osteoporosis in patients with chronic inflammatory neuropathy- a population-based cohort study

The risk of osteoporosis in patients with chronic inflammatory neuropathy (CIN) has not been evaluated in detail. We conducted a population-based case-control study nested in a retrospective cohort to analyze osteoporosis risk among patients with CIN using a nationwide database. Patients with CIN based on the Korean Classification of Disease diagnostic code were included and were matched to controls. A Cox proportional hazards regression model was used to evaluate the effect of CIN on osteoporosis. After propensity score matching, 585 CIN patients and 585 controls were selected. Patients with CIN had an increased osteoporosis risk (hazard ratio [HR] = 2.293, 95% confidence interval [CI] 1.460-3.601) compared with controls. The osteoporosis risk was higher among male patients with CIN than among male controls (HR = 5.404, 95% CI 2.252-12.969), while there were no significant differences among women. Among the CIN patients, the average daily dose of corticosteroids was higher in those who developed osteoporosis (19.6 mg [10.8-49.3]) than those who did not (16.2 mg [7.2-29.1], p = 0.001). The osteoporosis risk among CIN patients is higher than among controls. High risk of osteoporosis in male patients may indicate that osteoporosis in CIN patients results from the disease itself or related treatments.

Thoracal arachnoiditis ossificans associated with multifocal motor neuropathy: a case report

The association of arachnoiditis ossificans with acquired peripheral nerve disease is rare. We report a case who presented with progressive myelopathy due to arachnoiditis ossificans from prior trauma, complicated with multifocal motor neuropathy. Intradural bone was removed at surgery.

Nerve ultrasound in polyneuropathies

Ultrasound can be used to visualize pathology in the peripheral nerves of patients with polyneuropathy. Nerve enlargement is the most frequent pathology, but other abnormalities, including abnormal nerve echogenicity and vascularity, are also encountered. This monograph presents an overview of the role of nerve ultrasound in the evaluation and management of both inherited and acquired polyneuropathies. A description of the sonographic techniques and common abnormalities is provided, followed by a presentation of typical findings in different neuropathies. Scoring systems for characterizing the presence and pattern of nerve abnormalities as they relate to different polyneuropathies are presented. Muscle Nerve 57: 716-728, 2018.

Childhood-Onset Multifocal Motor Neuropathy With Immunoglobulin M Antibodies to Gangliosides GM1 and GM2: A Case Report and Review of the Literature

Multifocal motor neuropathy is a rare immune-mediated neuropathy characterized by progressive asymmetric weakness and atrophy without sensory abnormalities. Although disease onset is usually in adulthood, a few childhood-onset cases have been reported. Here, we report the case of an 8-year-old boy with multifocal motor neuropathy who presented with a slowly progressive left and distal upper limb weakness without sensory loss. The initial high-dose intravenous immunoglobulin treatment significantly improved left upper limb muscle weakness. Continued monthly intravenous immunoglobulin treatment gradually improved muscle strength for several months initially. While the muscle strength decreased slightly after 8 months of therapy, it was better than that before intravenous immunoglobulin treatment. One year and eight months after the initiation of treatment, serum testing for IgM antibodies to gangliosides, GM1 and GM2, was negative. This is the first pediatric report of the serum IgM autoantibodies positive to GM1 and GM2. The clinical course is similar to that of partial intravenous immunoglobulin responders among patients with adulthood-onset multifocal motor neuropathy. Since the symptoms plateaued after the initial intravenous immunoglobulin therapy, prognosis appears to be determined by the patient's initial response to intravenous immunoglobulin treatment.

Outcome measures in MMN revisited: further improvement needed

The objectives of this study were to provide an overview of the outcome measures (OMs) applied in clinical trials in multifocal motor neuropathy (MMN) and to determine the responsiveness of a core set of selected OMs as part of the peripheral neuropathy outcome measures standardization (PeriNomS) study. The following OMs were serially applied in 26 patients with newly diagnosed or relapsing MMN, receiving intravenous immunoglobulin (assessments: T0/T3/T12 months): 14 muscle pairs MRC (Medical Research Council) scale, the Neuropathy Impairment Scale motor-subset, a self-evaluation scale, grip strength, and MMN-RODS© (Rasch-built overall disability scale). All data, except the grip strength, were subjected to Rasch analyses before determining responsiveness. For grip strength, responsiveness was examined using a combined anchor- (SF-36 question-2) and distribution-based (½ × SD) minimum clinically important difference (MCID) techniques, determining the proportion of patients exceeding both the identified cut-offs. For the remaining scales, the magnitude of change for each patient on each scale was determined using the MCID related to the individual SE (responder definition: MCID-SE ≥ 1.96). Overall, a great assortment of measures has been used in MMN trials with different responsiveness definitions. For the selected OMs, responsiveness was poor and only seen in one fourth to one third of the patients, the grip strength being more responsive. Despite the efforts taken to standardize outcome assessment, further clinimetric responsiveness studies are needed in MMN.

Peripheral neuropathies

Peripheral neuropathies are diseases of the peripheral nervous system that can be divided into mononeuropathies, multifocal neuropathies, and polyneuropathies. Symptoms usually include numbness and paresthesia. These symptoms are often accompanied by weakness and can be painful. Polyneuropathies can be divided into axonal and demyelinating forms, which is important for diagnostic reasons. Most peripheral neuropathies develop over months or years, but some are rapidly progressive. Some patients only suffer from mild, unilateral, slowly progressive tingling in the fingers due to median nerve compression in the wrist (carpal tunnel syndrome), while other patients can be tetraplegic, with respiratory insufficiency within 1-2 days due to Guillain-Barré syndrome. Carpal tunnel syndrome, with a prevalence of 5% and incidence of 1-2 per 1000 person-years, is the most common mononeuropathy. Population-based data for chronic polyneuropathy are relatively scarce. Prevalence is estimated at 1% and increases to 7% in persons over 65 years of age. Incidence is approximately 1 per 1000 person-years. Immune-mediated polyneuropathies like Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy are rare diseases, with an annual incidence of approximately 1-2 and 0.2-0.5 per 100 000 persons respectively. Most peripheral neuropathies are more prevalent in older adults and in men, except for carpal tunnel syndrome, which is more common in women. Diabetes is a common cause of peripheral neuropathy and is associated with both mono- and polyneuropathies. Among the group of chronic polyneuropathies, in about 20-25% no direct cause can be found. These are slowly progressive axonal polyneuropathies.

CSF cytokine profile distinguishes multifocal motor neuropathy from progressive muscular atrophy

Objective:

We aimed to compare the cytokine and chemokine profiles of patients with multifocal motor neuropathy (MMN) with those of patients with progressive muscular atrophy (PMA) and amyotrophic lateral sclerosis (ALS) to investigate immunologic differences in the CNS.

Methods:

CSF from 12 patients with MMN, 8 with PMA, 26 with sporadic ALS, and 10 with other noninflammatory neurologic disorders was analyzed for 27 cytokines and chemokines using the multiplex bead array assay. Cytokine titers of the 4 groups were compared, and correlations between the titers of relevant cytokines and clinical parameters were evaluated.

Results:

There were no obvious intrathecal changes except for interleukin (IL)-1 receptor antagonist in patients with MMN. In contrast, IL-4, IL-7, IL-17, eotaxin/CCL11, fibroblast growth factor-2 (FGF-2), granulocyte colony-stimulating factor (G-CSF), and platelet-derived growth factor BB titers were significantly elevated in patients with PMA and ALS; of these, FGF-2 and G-CSF titers were elevated compared with those in patients with MMN. IL-4 and IL-10 titers were high in patients with ALS, particularly patients with possible ALS presenting with a slowly progressive course or mild symptoms.

Conclusions:

The CSF cytokine profile of patients with MMN is distinct from that of patients with PMA and ALS. The similarity of the cytokine profiles between patients with PMA and ALS suggests that PMA shares common immunologic features with ALS in the CNS, even without clinical evidence of upper motor neuron involvement.

Clonality of anti-GM1 IgM antibodies in multifocal motor neuropathy and the Guillain-Barré syndrome

OBJECTIVE

Multifocal motor neuropathy (MMN) and the Guillain-Barré syndrome (GBS) are immune-mediated motor neuropathies with antibodies against the ganglioside GM1. In GBS, these antibodies are induced by molecular mimicry, but in MMN their origin is elusive.

METHODS

We compared the light-chain use of anti-GM1 IgM antibodies in serum from 42 patients with MMN and 23 patients with GBS by ELISA.

RESULTS

Exclusive use of either κ or λ light chains was found in 38 (90%) patients with MMN and 9 (39%) with GBS (p<0.001).

CONCLUSIONS

Anti-GM1 IgM antibodies in most patients with MMN are produced by only a single or very limited number of B-cell clones, whereas in most patients with GBS, anti-GM1 IgM antibodies are most likely polyclonal.

[MR neurography for lesion localization in the peripheral nervous system. Why, when and how?]

Peripheral neuropathies are frequent disorders which are often challenging in the diagnostic work-up. Diagnostic difficulties first and foremost arise with regard to lesion localization and the precise definition of spatial lesion patterns. Magnetic resonance (MR) neurography as a diagnostic imaging tool directly visualizes nerve lesions thereby facilitating lesion localization not only in traumatic nerve lesions but also in the large and heterogeneous group of intrinsic, spontaneously occurring non-focal neuropathies. The major diagnostic sign for lesion detection and localization is the T2 lesion which can be evaluated with high spatial resolution at the anatomical level of nerve fascicles. Lesion detection at the fascicular level by MR neurography advances the diagnostic work-up in the peripheral nervous system (PNS), because fascicular and partial nerve lesions of spontaneously occurring intrinsic neuropathies and polyneuropathies present a classical diagnostic pitfall for traditional localization by means of physical findings and electrophysiology. With the appropriate techniques and strategies MR neurography can now cover large anatomical areas of the PNS in a single examination session.

Sera from patients with multifocal motor neuropathy disrupt the blood-nerve barrier

OBJECTIVE

In multifocal motor neuropathy (MMN), the destruction of the blood-nerve barrier (BNB) has been considered to be the key step in the disease process. The purpose of the present study was to ascertain whether sera from patients with MMN can open the BNB, and which component of patient sera is the most important for this disruption.

METHODS

We evaluated the effects of sera from patients with MMN, patients with amyotrophic lateral sclerosis, and control subjects on the expression of tight junction proteins and vascular cell adhesion molecule-1 (VCAM-1), and on the transendothelial electrical resistance (TEER) in human peripheral nerve microvascular endothelial cells (PnMECs).

RESULTS

The sera from patients with MMN decreased the claudin-5 protein expression and the TEER in PnMECs. However, this effect was reversed after application of an anti-vascular endothelial growth factor (anti-VEGF) neutralising antibody. The VEGF secreted by PnMECs was significantly increased after exposure to the sera from patients with MMN. The sera from patients with MMN also increased the VCAM-1 protein expression by upregulating the nuclear factor kappa-B (NF-κB) signalling. The immunoglobulin G purified from MMN sera decreased the expression of claudin-5 and increased the VCAM-1 expression in PnMECs.

CONCLUSIONS

The sera from MMN patients may disrupt the BNB function via the autocrine secretion of VEGF in PnMECs, or the exposure to autoantibodies against PnMECs that are contained in the MMN sera. Autoantibodies against PnMECs in MMN sera may activate the BNB by upregulating the VCAM-1 expression, thereby allowing for the entry of a large number of circulating inflammatory cells into the peripheral nervous system.

Are multifocal motor neuropathy patients underdiagnosed? An epidemiological survey in Japan

INTRODUCTION

Our objective was to do an epidemiologic survey of patients with multifocal motor neuropathy (MMN) in comparison with those with amyotrophic lateral sclerosis (ALS) in Japan.

METHODS

In this retrospective study, we examined 46 patients with MMN and 1,051 patients with ALS from major neuromuscular centers in Japan from 2005 to 2009. Diagnosis was based on the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) and the revised El Escorial criteria. The efficacy of intravenous immunoglobulin (IVIg) was also taken into consideration in the diagnosis of MMN.

RESULTS

The ratio of MMN to ALS patients (0–0.10) varied among the centers, but mostly converged to 0.05. The prevalence was estimated to be 0.29 MMN patients and 6.63 ALS patients per 100,000 population.

CONCLUSIONS

The frequency of MMN patients was around 1 out of 20 ALS patients, and MMN was possibly underdiagnosed in some centers.

MMN: from immunological cross-talk to conduction block

Multifocal motor neuropathy (MMN) is a rare inflammatory neuropathy characterized by progressive, asymmetric distal limb weakness and conduction block (CB). Clinically MMN is a pure motor neuropathy, which as such can mimic motor neuron disease. GM1-specific IgM antibodies are present in the serum of approximately half of all MMN patients, and are thought to play a key role in the immune pathophysiology. Intravenous immunoglobulin (IVIg) treatment has been shown to be effective in MMN in five randomized placebo-controlled trials. Despite long-term treatment with intravenous immunoglobulin (IVIg), which is efficient in the majority of patients, slowly progressive axonal degeneration and subsequent muscle weakness cannot be fully prevented. In this review, we will discuss the current understanding of the immune pathogenesis underlying MMN and how this may cause CB, available treatment strategies and future therapeutic targets.

Anterior interosseous nerve syndrome: fascicular motor lesions of median nerve trunk

Objective:

We sought to determine lesion sites and spatial lesion patterns in spontaneous anterior interosseous nerve syndrome (AINS) with high-resolution magnetic resonance neurography (MRN).

Methods:

In 20 patients with AINS and 20 age- and sex-matched controls, MRN of median nerve fascicles was performed at 3T with large longitudinal anatomical coverage (upper arm/elbow/forearm): 135 contiguous axial slices (T2-weighted: echo time/repetition time 52/7,020 ms, time of acquisition: 15 minutes 48 seconds, in-plane resolution: 0.25 × 0.25 mm). Lesion classification was performed by visual inspection and by quantitative analysis of normalized T2 signal after segmentation of median nerve voxels.

Results:

In all patients and no controls, T2 lesions of individual fascicles were observed within upper arm median nerve trunk and strictly followed a somatotopic/internal topography: affected were those motor fascicles that will form the anterior interosseous nerve further distally while other fascicles were spared. Predominant lesion focus was at a mean distance of 14.6 ± 5.4 cm proximal to the humeroradial joint. Discriminative power of quantitative T2 signal analysis and of qualitative lesion rating was high, with 100% sensitivity and 100% specificity (p < 0.0001). Fascicular T2 lesion patterns were rated as multifocal (n = 17), monofocal (n = 2), or indeterminate (n = 1) by 2 independent observers with strong agreement (kappa = 0.83).

Conclusion:

It has been difficult to prove the existence of fascicular/partial nerve lesions in spontaneous neuropathies using clinical and electrophysiologic findings. With MRN, fascicular lesions with strict somatotopic organization were observed in upper arm median nerve trunks of patients with AINS. Our data strongly support that AINS in the majority of cases is not a surgically treatable entrapment neuropathy but a multifocal mononeuropathy selectively involving, within the main trunk of the median nerve, the motor fascicles that continue distally to form the anterior interosseous nerve.

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.

Acute motor neuropathy with pure distal involvement--a case report of multifocal motor neuropathy

Multifocal motor neuropathy is an acquired pure motor neuropathy seen principally in adults and usually responds to treatment with intravenous immunoglobulin. We report a 12 year old boy with marked distal weakness in both upper and lower limbs with no proximal involvement. These clinical features appear to be distinct from more common inflammatory childhood neuropathies and are in keeping with a diagnosis of Multifocal Motor Neuropathy. Confirming the diagnosis, serial nerve conduction studies showed a pattern of pure motor conduction block with normal sensory potentials. To our knowledge this is only the second case report of this condition occurring in childhood.

Electrodiagnosis in neuromuscular disease

Electromyography (EMG) is an important diagnostic tool for the assessment of individuals with various neuromuscular diseases. It should be an extension of a thorough history and physical examination. Some prototypical characteristics and findings of EMG and nerve conduction studies are discussed; however, a more thorough discussion can be found in the textbooks and resources sited in the article. With an increase in molecular genetic diagnostics, EMG continues to play an important role in the diagnosis and management of patients with neuromuscular diseases and also provides a cost-effective diagnostic workup before ordering a battery of costly genetic tests.

Multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is a rare disorder in which the symptoms are caused by persistent conduction block lesions. The mononeuropathy multiplex progresses over time with increasing axonal loss. The cause of the conduction blocks and axonal loss are not completely understood but immune mechanisms are involved and response to intravenous immunoglobulin has been established. The importance of MMN goes beyond its clinical incidence as the increasing understanding of the pathogenesis of this disorder has implications for other peripheral nerve diseases and for our knowledge of peripheral nerve biology.

MRI neurography findings in patients with idiopathic brachial plexopathy: correlations with clinical-neurophysiological data in eight consecutive cases

OBJECTIVE

Idiopathic brachial plexopathy is a non-progressive disorder characterized by the sudden onset of shoulder pain associated with weakness and sometimes paraesthesia of the arm. Clinical and electrophysiological examinations are the primary diagnostic tools and allow physicians to localize the site of damage. MRI neurography is rarely performed in this setting.

METHODS

We herein describe the cases of eight consecutive patients suffering from idiopathic brachial plexopathy. All patients underwent clinical visits, neurophysiological evaluations and MRI neurography.

RESULTS

We confirmed the primary role of clinical and neurophysiological evaluations in the diagnosis of idiopathic brachial plexopathy and demonstrate the usefulness of brachial plexus MRI neurography for confirming the presence of inflammatory changes.

CONCLUSION

In patients with idiopathic brachial plexopathy, MR neurography is a helpful tool for excluding different aetiologies, such as compression or tumour formation, and/or confirming inflammatory changes.

Diagnosis, epidemiology and treatment of inflammatory neuropathies

This article reviews the main diagnostic, epidemiological and therapeutic issues relating to the three main inflammatory neuropathies: Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy and multifocal motor neuropathy. The current knowledge base and recent developments are described.

Autoimmune neuromuscular disorders

Autoimmune neuromuscular disorders affecting peripheral nerves, neuromuscular junction or muscle have a wide clinical spectrum with diverse pathogenetic mechanisms. Peripheral nervous system may be targeted in the context of complex immune reactions involving different cytokines, antigen-presenting cells, B cells and different types of T cells. Various immunomodulating and cytotoxic treatments block proliferation or activation of immune cells by different mechanisms attempting to control the response of the immune system and limit target organ injury. Most treatment protocols for autoimmune neuromuscular disorders are based on the use of corticosteroids, intravenous immunoglobulins and plasmapheresis, with cytotoxic agents mostly used as steroid-sparing medications. More recently, development of specific monoclonal antibodies targeting individual cell types allowed a different approach targeting specific immune pathways, but these new treatments are also associated with various adverse effects and their long-term efficacy is still unknown.