Predicting a positive response to intravenous immunoglobulin in isolated lower motor neuron syndromes

Immunology of amyotrophic lateral sclerosis - role of the innate and adaptive immunity

This review aims to summarize the latest evidence about the role of innate and adaptive immunity in Amyotrophic Lateral Sclerosis (ALS). ALS is a devastating neurodegenerative disease affecting upper and lower motor neurons, which involves essential cells of the immune system that play a basic role in innate or adaptive immunity, that can be neurotoxic or neuroprotective for neurons. However, distinguishing between the sole neurotoxic or neuroprotective function of certain cells such as astrocytes can be challenging due to intricate nature of these cells, the complexity of the microenvironment and the contextual factors. In this review, in regard to innate immunity we focus on the involvement of monocytes/macrophages, microglia, the complement, NK cells, neutrophils, mast cells, and astrocytes, while regarding adaptive immunity, in addition to humoral immunity the most important features and roles of T and B cells are highlighted, specifically different subsets of CD4+ as well as CD8+ T cells. The role of autoantibodies and cytokines is also discussed in distinct sections of this review.

Immunoglobulin for multifocal motor neuropathy

BACKGROUND

Multifocal motor neuropathy (MMN) is a rare, probably immune-mediated disorder characterised by slowly progressive, asymmetric, distal weakness of one or more limbs with no objective loss of sensation. It may cause prolonged periods of disability. Treatment options for MMN are few. People with MMN do not usually respond to steroids or plasma exchange. Uncontrolled studies have suggested a beneficial effect of intravenous immunoglobulin (IVIg). This is an update of a Cochrane Review first published in 2005, with an amendment in 2007. We updated the review to incorporate new evidence.

OBJECTIVES

To assess the efficacy and safety of intravenous and subcutaneous immunoglobulin in people with MMN.

SEARCH METHODS

We searched the following databases on 20 April 2021: the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, ClinicalTrials.gov, and WHO ICTRP for randomised controlled trials (RCTs) and quasi-RCTs, and checked the reference lists of included studies.

SELECTION CRITERIA

We considered RCTs and quasi-RCTs examining the effects of any dose of IVIg and subcutaneous immunoglobulin (SCIg) in people with definite or probable MMN for inclusion in the review. Eligible studies had to have measured at least one of the following outcomes: disability, muscle strength, or electrophysiological conduction block. We used studies that reported the frequency of adverse effects to assess safety.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed the literature searches to identify potentially relevant trials, assessed risk of bias of included studies, and extracted data. We followed standard Cochrane methodology.

MAIN RESULTS

Six cross-over RCTs including a total of 90 participants were suitable for inclusion in the review. Five RCTs compared IVIg to placebo, and one compared IVIg to SCIg. Four of the trials comparing IVIg versus placebo involved IVIg-naive participants (induction treatment). In the other two trials, participants were known IVIg responders receiving maintencance IVIg at baseline and were then randomised to maintenance treatment with IVIg or placebo in one trial, and IVIg or SCIg in the other. Risk of bias was variable in the included studies, with three studies at high risk of bias in at least one risk of bias domain. IVIg versus placebo (induction treatment): three RCTs including IVIg-naive participants reported a disability measure. Disability improved in seven out of 18 (39%) participants after IVIg treatment and in two out of 18 (11%) participants after placebo (risk ratio (RR) 3.00, 95% confidence interval (CI) 0.89 to 10.12; 3 RCTs, 18 participants; low-certainty evidence). The proportion of participants with an improvement in disability at 12 months was not reported. Strength improved in 21 out of 27 (78%) IVIg-naive participants treated with IVIg and one out of 27 (4%) participants who received placebo (RR 11.00, 95% CI 2.86 to 42.25; 3 RCTs, 27 participants; low-certainty evidence). IVIg treatment may increase the proportion of people with resolution of at least one conduction block; however, the results were also consistent with no effect (RR 7.00, 95% CI 0.95 to 51.70; 4 RCTs, 28 participants; low-certainty evidence). IVIg versus placebo (maintenance treatment): a trial that included participants on maintenance IVIg treatment reported an increase in disability in 17 out of 42 (40%) people switching to placebo and seven out of 42 (17%) remaining on IVIg (RR 2.43, 95% CI 1.13 to 5.24; 1 RCT, 42 participants; moderate-certainty evidence) and a decrease in grip strength in 20 out of 42 (48%) participants after a switch to placebo treatment compared to four out of 42 (10%) remaining on IVIg (RR 0.20, 95% CI 0.07 to 0.54; 1 RCT, 42 participants; moderate-certainty evidence). Adverse events, IVIg versus placebo (induction or maintenance): four trials comparing IVIg and placebo reported adverse events, of which data from two studies could be meta-analysed. Transient side effects were reported in 71% of IVIg-treated participants versus 4.8% of placebo-treated participants in these studies. The pooled RR for the development of side effects was 10.33 (95% CI 2.15 to 49.77; 2 RCTs, 21 participants; very low-certainty evidence). There was only one serious side effect (pulmonary embolism) during IVIg treatment. IVIg versus SCIg (maintenance treatment): the trial that compared continuation of IVIg maintenance versus SCIg maintenance did not measure disability. The evidence was very uncertain for muscle strength (standardised mean difference 0.08, 95% CI -0.84 to 1.00; 1 RCT, 9 participants; very low-certainty evidence). The evidence was very uncertain for the number of people with side effects attributable to treatment (RR 0.50, 95% CI 0.18 to 1.40; 1 RCT, 9 participants; very low-certainty evidence).

AUTHORS' CONCLUSIONS

Low-certainty evidence from three small RCTs shows that IVIg may improve muscle strength in people with MMN, and low-certainty evidence indicates that it may improve disability; the estimate of the magnitude of improvement of disability has wide CIs and needs further studies to secure its significance. Based on moderate-certainty evidence, it is probable that most IVIg responders deteriorate in disability and muscle strength after IVIg withdrawal. SCIg might be an alternative treatment to IVIg, but the evidence is very uncertain. More research is needed to identify people in whom IVIg withdrawal is possible and to confirm efficacy of SCIg as an alternative maintenance treatment.

Increased muscle echointensity correlates with clinical disability and muscle strength in chronic inflammatory demyelinating polyneuropathy

BACKGROUND AND PURPOSE

We evaluated muscle echointensity as a marker for secondary axonal damage in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) using ultrasonography. Findings were correlated with clinical disability and muscular strength.

METHODS

Eighty patients with CIDP (40 with typical and 40 with atypical CIDP) were examined clinically, including assessment of Medical Research Council (MRC) sum score and Inflammatory Neuropathy Cause and Treatment Overall Disability Sum Score (INCAT-ODSS). Echointensity in eight proximal and distal muscles of the arms and legs was evaluated by muscle ultrasonography using the Heckmatt scale.

RESULTS

Alterations of echointensity occurred most frequently in the distal leg muscles, with a median (range) Heckmatt score of 1.5 (1-4). There were no differences between typical and atypical CIDP patients with regard to Heckmatt score. Alterations of echointensity correlated to disability and muscle strength. The arm score of the INCAT-ODSS correlated to Heckmatt score for the distal arm muscles (r = 0.23, p = 0.046) and the leg score of the INCAT-ODSS correlated to Heckmatt scores for the proximal (r = 0.34, p = 0.002) and distal leg muscles (r = 0.33, p = 0.004). MRC sum score, as well as individual MRC scores for arm and leg muscles, correlated to Heckmatt scores of the corresponding muscle groups (r = -0.25, p = 0.02 for MRC sum score).

CONCLUSION

Increased muscle echointensity, reflecting fibrosis and fatty infiltration due to secondary axonal damage, correlated to muscular strength and disability in a large cohort of CIDP patients. Alterations of echointensity occur in both typical and atypical CIDP patients and are pronounced in the distal leg muscles.

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.

Progressive Muscular Atrophy

Progressive muscular atrophy (PMA) is a rare, sporadic, adult-onset motor neuron disease, clinically characterized by isolated lower motor neuron features; however, clinically evident upper motor neuron signs may emerge in some patients. Subclinical upper motor neuron involvement is identified pathologically, radiologically, and neurophysiologically in a substantial number of patients with PMA. Patients with subclinical upper motor neuron involvement do not fulfill the revised El Escorial criteria to participate in amyotrophic lateral sclerosis clinical trials. Intravenous immunoglobulin therapy is only marginally beneficial in a small subgroup of patients with lower motor neuron syndrome without conduction block.

The clinical spectrum of isolated peripheral motor dysfunction

INTRODUCTION

Isolated peripheral motor dysfunction due to lower motor neuron or peripheral nerve disorders presents an interesting challenge to clinicians because of the diverse differential diagnosis with a broad range of prognoses.

METHODS

We retrospectively reviewed clinical data of adults who presented over 12 years with muscle weakness, atrophy, or fasciculations, but without hyperreflexia or sensory involvement.

RESULTS

In 119 patients, 52% had a motor neuron disease (MND), 13% had immune neuropathies, 11% had genetic neuronopathies, 10% had residual or post-polio syndrome, 5% had benign fasciculation, 1% had an infectious etiology, and 8% were not given a final diagnosis. Only MND patients had cognitive dysfunction or frontal release signs. Bulbar and respiratory symptoms virtually excluded consideration of immune neuropathy.

CONCLUSIONS

Only half of the patients were diagnosed with MND. A significant minority have treatable conditions. Cognitive involvement, frontal release signs, and bulbar or respiratory symptoms are strongly suggestive of MND.

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.

Is IVIg therapy warranted in progressive lower motor neuron syndromes without conduction block?

OBJECTIVE

To evaluate the likelihood of response to IV immunoglobulin (IVIg) by studying consecutive patients presenting with progressive, asymmetric, pure lower motor neuron (LMN) limb weakness, and to determine the clinical phenotype of those who respond.

METHODS

Thirty-one consecutive patients with progressive, focal-onset LMN limb weakness, without evidence of clinical upper motor neuron signs; sensory, respiratory, or bulbar involvement; or evidence of motor nerve conduction block on electrodiagnostic studies, were prospectively included in this study. Each patient underwent treatment with IVIg (2 g/kg) for a minimum of 3 months. Electrodiagnostic studies, a neuromuscular symptom score, and expanded Medical Research Council sum score were documented before and after IVIg treatment. The final diagnosis was determined after prolonged clinical follow-up.

RESULTS

Only 3 of 31 patients (10%) responded to IVIg. All responders demonstrated distal upper limb-onset weakness, EMG abnormalities confined to the clinically weak muscles, and a normal creatine kinase. This set of features was also identified in 31% of nonresponders presenting with distal upper limb weakness. Sex, age at onset, number of involved limb regions, and the duration of symptoms before treatment were not significantly different between groups.

CONCLUSION

The findings of the present study do not support uniform use of IVIg in patients presenting with progressive asymmetric LMN limb weakness. It is suggested that IVIg treatment be limited to patients who demonstrate clinical and laboratory features suggestive of multifocal motor neuropathy.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that IVIg will not improve muscle function in 90% of patients with progressive, asymmetric, pure LMN weakness.