Multifocal acquired demyelinating neuropathy masquerading as motor neuron disease

Immunosuppressant and immunomodulatory treatments for multifocal motor neuropathy

BACKGROUND

Multifocal motor neuropathy is characterised by progressive, predominantly distal, asymmetrical limb weakness and usually multiple partial motor nerve conduction blocks. Intravenous immunoglobulin is beneficial but the role of immunosuppressive agents is uncertain.

OBJECTIVES

To provide the best available evidence from randomised controlled trials on the role of immunosuppressive agents for the treatment of multifocal motor neuropathy.

SEARCH STRATEGY

For this update, we searched the Cochrane Neuromuscular Disease Group Trials Register (October 8 2008), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 4), MEDLINE (from January 1966 to October 8 2008), and EMBASE (from January 1980 to October 8 2008), for trials of multifocal motor neuropathy.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials were to be included and one was found. Prospective and retrospective case series and case reports were considered in the Discussion.

DATA COLLECTION AND ANALYSIS

Two review authors searched the titles and abstracts of the articles identified and extracted the data independently.

MAIN RESULTS

In this update, we found the first randomised controlled trial of multifocal motor neuropathy. This study, which randomised 28 patients, showed that mycophenolate mofetil did not significantly improve strength or function or reduce the need for intravenous immunoglobulin. We summarised the results of retrospective and prospective case series in the discussion.

AUTHORS' CONCLUSIONS

In the only randomised placebo-controlled trial of any immunosuppressive agent, mycophenolate mofetil did not produce significant benefit. Trials of other immunosuppressants should be undertaken.

Inflammatory demyelinating neuropathies and neuropathies associated with monoclonal gammopathies: treatment update

This review focuses on recent data regarding inflammatory demyelinating neuropathies and neuropathies associated with monoclonal gammopathies. We describe both acute and chronic inflammatory neuropathies, and we discuss conditions ranging from mostly cell-mediated to antibody-mediated disorders. These diseases are characterized by proximal and distal sensory motor involvement. Treatments are based on immune-modulation and/or immune-suppression. Work-up sequence and therapeutical modes are discussed in the light of recently published data, with a special interest on new treatment modalities.

Neuropathies associated with conduction block

PURPOSE OF REVIEW

Two disorders, Lewis-Sumner syndrome and multifocal motor neuropathy, are defined by the demonstration of conduction block. These two entities have been intertwined since their description but there are important distinctions between them. It is therefore timely to reconsider these disorders and the physiologic process that defines them.

RECENT FINDINGS

Understanding of the pathophysiology of conduction block has evolved with better understanding of the structure of the node of Ranvier and surrounding apparatus. Axonal excitability studies have begun to give insights into why multifocal motor neuropathy has only motor conduction block. The many published criteria for conduction block vary in sensitivity and specificity and the electromyographer must be aware of the difficulties in determining physiologic block. The distinctions between Lewis-Sumner syndrome and multifocal motor neuropathy have become increasingly clear. Evidence suggests that Lewis-Sumner syndrome is a multifocal variant of chronic inflammatory demyelinating polyneuropathy but that multifocal motor neuropathy is distinct.

SUMMARY

It is important to recognize the distinctions between these disorders, not only because there are important therapeutic issues, but also because a true understanding of the nature of these illnesses will only be accomplished if the overlaps and differences are carefully considered.

Abnormalities in cortical and peripheral excitability in flail arm variant amyotrophic lateral sclerosis

BACKGROUND

While some regard the flail arm syndrome as a variant of amyotrophic lateral sclerosis (ALS), others have argued that it is a distinct clinical entity. Consequently, the present study applied novel central and peripheral nerve excitability techniques to further explore disease pathophysiology in flail arm syndrome.

METHODS

Cortical and peripheral nerve excitability studies were undertaken in 11 flail arm patients, defined by muscle weakness limited to the proximal aspects of the upper limbs for at least 24 months.

RESULTS

Mean age at disease onset (60.3 years) was similar to other ALS phenotypes (58.3 years), with strong male predominance (male:female distribution: flail arm 10:1; ALS 1.5:1; p<0.05) and prolonged disease duration (flail arm 62.5 months; ALS 15.8 months; p<0.05). There was evidence of cortical hyperexcitability in flail arm patients, similar to findings in ALS, with reduction in short interval intracortical inhibition (flail arm 0.8 (0.6)%; ALS 4.1 (1.1)%; controls 8.5 (1.0)%; p<0.0001) and resting motor threshold (flail arm 53.4 (2.8)%; ALS 56.6 (1.8)%; controls 60.7 (1.5)%; p<0.05), along with an increase in motor evoked potential amplitude (flail arm 49.5 (9.0)%; ALS 44.4 (4.9)%; controls 25.8 (2.8)%; p<0.05). Peripheral nerve excitability studies demonstrated changes consistent with upregulation in persistent Na+ currents and reduction of slow K+ conductances, similar to findings in ALS.

CONCLUSION

This study has demonstrated the presence of cortical hyperexcitability in flail arm syndrome, along with abnormalities in peripheral nerve excitability, findings consistent with previous studies in other ALS phenotypes. By demonstrating the presence of upper motor neuron dysfunction, the present study suggests that the flail arm syndrome is an unusual variant of ALS.

[Long-term follow-up of multifocal motor neuropathy with conduction block under intravenous immunoglobulin]

INTRODUCTION

Multifocal motor neuropathy with conduction block is an immune-mediated motor neuropathy, which usually responds to intravenous immunoglobulin. However, efficacy of long-term intravenous immunoglobulin is controversial. Our aim was to establish the long-term effects of intravenous immunoglobulin therapy on clinical and neurophysiological outcome measures and to determine the criteria predicting a good response to long-term intravenous immunoglobulin treatment.

METHODS

We retrospectively included all multifocal motor neuropathy with conduction blocks patients followed for at least 4 years who received intravenous immunoglobulin therapy. We compared clinical data, MRC sumscores and electrophysiological data between the first and the last examination in the department.

RESULTS

Seventeen patients were followed for an average of 8 years (range 4 to 18 years). At last examination, weakness remained asymmetric, predominant in the upper limbs, with a peripheral nerve distribution. At last examination, 3 patterns of evolution was seen: 6/17 patients had muscle strength improvement and need no more intravenous immunoglobulin therapy, 6/17 had initial improvement but became intravenous immunoglobulin dependent and 5/17 did not respond to intravenous immunoglobulin. MRC sumscores, number of conduction blocks and distal compound muscle action potential amplitudes were comparable between the first and the last examination (p>0.05). Improvement of MRC sumscores was not correlated with the clinical, biological and electrophysiological data that we analysed: age, gender, duration of disease, time from onset to intravenous immunoglobulin therapy, number of involved nerves, number of affected limbs, presence of muscle atrophy, MRC sumscores at diagnosis, number of conduction blocks, mean amplitude of the motor evoked potentials, presence of anti-GM1 antibodies, titers and IgM or IgG type of anti-GM1 antibodies.

CONCLUSIONS

In this study, one third of multifocal motor neuropathy with conduction blocks patients have clinical improvement at last examination and need no more treatment, one third are intravenous immunoglobulin dependent and one third have never responded to intravenous immunoglobulin. Electrophysiological data are comparable between the first and the last examination. No predictive factor has been disclosed for long-term response to intravenous immunoglobulin.

European Federation of Neurological Societies/Peripheral Nerve Society guideline on management of multifocal motor neuropathy

Several diagnostic criteria for multifocal motor neuropathy have been proposed in recent years and a beneficial effect of intravenous immunoglobulin (IVIg) and various other immunomodulatory drugs has been suggested in several trials and uncontrolled studies. The objectives were to prepare consensus guidelines on the definition, investigation and treatment of multifocal motor neuropathy. Disease experts and a patient representative considered references retrieved from MEDLINE and the Cochrane Library in July 2004 and prepared statements which were agreed in an iterative fashion. The Task Force agreed good practice points to define clinical and electrophysiological diagnostic criteria for multifocal motor neuropathy and investigations to be considered. The principal recommendations and good practice points were: (i) IVIg (2 g/kg given over 2-5 days) should be considered as the first line treatment (level A recommendation) when disability is sufficiently severe to warrant treatment. (ii) Corticosteroids are not recommended (good practice point). (iii) If initial treatment with IVIg is effective, repeated IVIg treatment should be considered (level C recommendation). The frequency of IVIg maintenance therapy should be guided by the individual response (good practice point). Typical treatment regimens are 1 g/kg every 2-4 weeks or 2 g/kg every 4-8 weeks (good practice point). (iv) If IVIg is not or not sufficiently effective then immunosuppressive treatment may be considered. Cyclophosphamide, ciclosporin, azathioprine, interferon beta1a, or rituximab are possible agents (good practice point). (v) Toxicity makes cyclophosphamide a less desirable option (good practice point).

European Federation of Neurological Societies/Peripheral Nerve Society Guideline on management of multifocal motor neuropathy. Report of a joint task force of the European Federation of Neurological Societies and the Peripheral Nerve Society

BACKGROUND

Several diagnostic criteria for multifocal motor neuropathy (MMN) have been proposed in recent years, and a beneficial effect of intravenous immunoglobulin (IVIg) and various other immunomodulatory drugs has been suggested in several trials and uncontrolled studies.

OBJECTIVES

The aim of this guideline was to prepare consensus guidelines on the definition, investigation, and treatment of MMN.

METHODS

Disease experts and a representative of patients considered references retrieved from MEDLINE and the Cochrane Library in July 2004 and prepared statements that were agreed in an iterative fashion.

RECOMMENDATIONS

The Task Force agreed on good practice points to define clinical and electrophysiological diagnostic criteria for MMN and investigations to be considered. The principal recommendations and good practice points were as follows: (1) IVIg (2 g/kg given over 2-5 days) should be considered as the first line of treatment (level A recommendation) when disability is sufficiently severe to warrant treatment; (2) corticosteroids are not recommended (good practice point); (3) if initial treatment with IVIg is effective, repeated IVIg treatment should be considered (level C recommendation). The frequency of IVIg maintenance therapy should be guided by the individual response (good practice point). Typical treatment regimens are 1 g/kg every 2-4 weeks or 2 g/kg every 4-8 weeks (good practice point); (4) if IVIg is not (or not sufficiently) effective, then immunosuppressive treatment may be considered. Cyclophosphamide, cyclosporine, azathioprine, interferon-beta1a, or rituximab are possible agents (good practice point); and (5) toxicity makes cyclophosphamide a less desirable option (good practice point).

Prediction of response to IVIg treatment in patients with lower motor neurone disorders

The distinction between multifocal motor neuropathy, treatable by intravenous immunoglobulins (IVIg), and degenerative motor neurone disorders is often difficult. To find predictive factors for the response to IVIg treatment, 40 consecutive patients with pure lower motor neurone disorders (LMND) were prospectively examined. They all received at least two times IVIg (2 g/kg bodyweight). Prior to the first and before all the following treatments a standardized evaluation was performed including clinical examination, neurophysiological and laboratory evaluation. According to changes in the neurological examination and the Neuromuscular Symptom Score, the patients were divided into responders and non-responders after the second course of treatment. In our study, no single clinical, neurophysiological, or laboratory parameter was sensitive enough to predict response. The only single parameter that highly correlated with a positive response to treatment was an elevated GM1 antibody titre. Lack of response to IVIg treatment is likely in patients with generalization of electromyographic signs of denervation beyond the clinically involved site, proximal localization of the weakness, and an elevated level of the creatinekinase. Conduction blocks do not distinguish between both groups. We propose a scoring system combining clinical, serological and neurophysiological data in order to decide which patients with LMND may receive IVIg.

High-dose cyclophosphamide without stem cell rescue for refractory multifocal motor neuropathy

Patients with multifocal motor neuropathy (MMN) respond to intravenous immune globulin (IVIg) and cyclophosphamide, although the benefit is not sustained. High-dose cyclophosphamide can induce a remission in patients with autoimmune diseases, including chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We describe a patient with refractory MMN who improved with high-dose cyclophosphamide (50 mg/kg for 4 days) without stem cell rescue. Following treatment she discontinued IVIg. At a 6-month examination, her strength had improved and she had regained the ability to write. High-dose cyclophosphamide may be a successful treatment for patients with MMN refractory to other therapies.

Multifocal motor neuropathy

PURPOSE OF THIS REVIEW

To conduct a critical review of recent studies on the clinical and therapeutic aspects of multifocal motor neuropathy, and to analyse their implications for patient management.

RECENT FINDINGS

Recent studies have contributed to defining the specific position of multifocal motor neuropathy within the spectrum of chronic immune-mediated polyneuropathies. One study compared features of this condition with multifocal acquired demyelinating sensory and motor neuropathy, while others have focused on pathological alterations at the site of conduction blocks. A further study described six new cases of multifocal acquired motor neuropathy, which should be considered as a variant of multifocal motor neuropathy. Several Cochrane reviews and review articles have shown evidence of the efficacy of intravenous immunoglobulins in the treatment of multifocal motor neuropathy. The issue of long-term intravenous immunoglobulins in multifocal motor neuropathy, however, has yielded controversial results. Two studies have shown progressive motor deterioration in most patients, correlated with electrophysiological signs indicative of axonal degeneration, while a third study found signs of sustained clinical and electrophysiological improvement after a mean follow up of 7.25 years.

SUMMARY

Multifocal motor neuropathy is a distinct clinical entity that differs from chronic inflammatory demyelinating polyradiculoneuropathy and multifocal acquired demyelinating sensory and motor neuropathy, although they share some electrophysiological characteristics. Although the aetiology remains unsolved, frequent association with high-titer antibodies against ganglioside GM1, together with an often positive response to intravenous immunoglobulins further support an autoimmune mechanism. New therapeutic strategies are required, however, that focus on the effects and the costs of treatment over long-term follow up.

A practical definition of conduction block in IvIg responsive multifocal motor neuropathy

BACKGROUND

Multifocal motor neuropathy with conduction block (MMN) can be mistaken for motor neurone disease or other lower motor neurone syndromes, but is treatable with intravenous immunoglobulin (IvIg). Formal electrophysiological criteria for conduction block (CB) are so stringent that substantial numbers of patients may miss out on appropriate treatment.

METHODS

Electrophysiological data were collected from 10 healthy volunteers and compared to data from 10 patients who satisfied the clinical criteria for MMN and who responded to IvIg. This produced a definition of CB in MMN patients which was compared with existing definitions to assess "miss rates".

RESULTS

Mean values for compound muscle action potential area, amplitude, and duration were calculated in normal subjects. Results beyond 3 SD of their respective means were considered abnormal. Using these criteria, CB in the context of MMN was defined as a reduction in negative peak area >23% along a distal nerve segment or >29% across a proximal segment; or a reduction in amplitude >32% across a distal segment or >33% across a proximal segment. All IvIg responsive patients had at least one nerve segment showing such CB. Employing some criteria from the literature would have denied treatment to over 30% of responsive patients.

CONCLUSION

In the clinical setting of suspected MMN, less stringent criteria for CB can improve the diagnosis of this treatable disorder. Exclusions on grounds of temporal dispersion may be over-restrictive. A little over one third of CBs occur proximally.

Immunosuppressant and immunomodulatory treatments for multifocal motor neuropathy

BACKGROUND

Multifocal motor neuropathy is a distinct clinical entity characterised by progressive, predominantly distal, asymmetrical limb weakness and minimal sensory abnormality. The diagnostic feature of this condition is the presence of multiple partial motor nerve conduction blocks. Controlled trials have demonstrated the efficacy of regular intravenous immunoglobulin infusions. Immunosuppressive agents have been used as primary, second-line or adjunctive agents for its treatment. This review was undertaken to identify and review systematically randomised controlled trials of immunosuppressive agents. The use of intravenous immunoglobulin will be the subject of a separate review.

OBJECTIVES

To provide the best available evidence from randomised controlled trials on the role of immunosuppressive agents for the treatment of multifocal motor neuropathy.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group trials register for all trials of multifocal motor neuropathy published, using 'multifocal motor neuropathy' OR 'chronic inflammatory demyelinating polyradiculoneuropathy' OR ' conduction block' OR ' motor neuropathy' AND 'immunosuppressive agents', 'immunosuppressants', 'corticosteroids', 'plasma exchange', 'azathioprine', 'cyclophosphamide', 'cyclosporin', 'ciclosporin', 'methotrexate', and 'mycophenolate', 'immunomodulatory agents', 'interferon', 'total lymphoid irradiation' or 'bone marrow transplantation' as search terms. In addition we searched MEDLINE, EMBASE for 2000 and 2001 and CINAHL, LILACS for all years. We updated the register search in February 2004 and searched MEDLINE (January 1966 to end May 2004) and EMBASE (January 1980 to end May 2004).

SELECTION CRITERIA

All randomised controlled trials and quasi-randomised clinical trials in which allocation was not random but was intended to be unbiased (e.g. alternate allocation) were to have been selected. Since no such trials were discovered, all prospective and retrospective case series were included in the 'background' or 'discussion' sections of the review.

DATA COLLECTION AND ANALYSIS

All studies on multifocal motor neuropathy or lower motor neuron weakness with conduction block and no sensory abnormality were scrutinised for data on patients treated with any form of immunosuppressive agents besides intravenous immunoglobulin. The information on the outcome of treatment was then collated and summarised.

MAIN RESULTS

We found no randomised controlled trials of any immunosuppressive agents for multifocal motor neuropathy. We summarised the results of retrospective and prospective case series in the discussion of the review.

AUTHORS' CONCLUSIONS

There are no randomised controlled trials to indicate whether immunosuppressive agents are beneficial in multifocal motor neuropathy.

Multifocal motor neuropathy: current concepts and controversies

Multifocal motor neuropathy (MMN) is now a well-defined purely motor multineuropathy characterized by the presence of multifocal partial motor conduction blocks (CB), frequent association with anti-GM1 IgM antibodies, and usually a good response to high-dose intravenous immunoglobulin (IVIg) therapy. However, several issues remain to be clarified in the diagnosis, pathogenesis, and therapy of this condition including its nosological position and its relation to other chronic dysimmune neuropathies; the degree of CB necessary for the diagnosis of MMN; the existence of an axonal form of MMN; the pathophysiological basis of CB; the pathogenetic role of antiganglioside antibodies; the mechanism of action of IVIg treatments in MMN and the most effective regimen; and the treatment to be used in unresponsive patients. These issues are addressed in this review of the main clinical, electrophysiological, immunological, and therapeutic features of this neuropathy.

Multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is an immune-mediated disorder characterised by slowly progressive, asymmetrical weakness of limbs without sensory loss. The clinical presentation of MMN mimics that of lower-motor-neuron disease, but in nerve-conduction studies of patients with MMN motor-conduction block has been found. By contrast with chronic inflammatory demyelinating polyneuropathy, treatment with prednisolone and plasma exchange is generally ineffective in MMN and even associated with clinical worsening in some patients. Of the immunosuppressants, cyclophosphamide has been reported as effective but only anecdotally. Various open trials and four placebo-controlled trials have shown that treatment with high-dose intravenous immunoglobulin leads to improvement of muscle strength in patients with MMN. Although clinical, pathological, imaging, immunological, and electrophysiological studies have improved our understanding of MMN over the past 15 years, further research is needed to elucidate pathogenetic disease mechanisms in the disorder.

Assessment of disease progression in motor neuron disease

Motor neuron disease (MND) is characterised by progressive deterioration of the corticospinal tract, brainstem, and anterior horn cells of the spinal cord. There is no pathognomonic test for the diagnosis of MND, and physicians rely on clinical criteria-upper and lower motor neuron signs-for diagnosis. The presentations, clinical phenotypes, and outcomes of MND are diverse and have not been combined into a marker of disease progression. No single algorithm combines the findings of functional assessments and rating scales, such as those that assess quality of life, with biological markers of disease activity and findings from imaging and neurophysiological assessments. Here, we critically appraise developments in each of these areas and discuss the potential of such measures to be included in the future assessment of disease progression in patients with MND.

Intravenous immunoglobulin for multifocal motor neuropathy

BACKGROUND

Multifocal motor neuropathy 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. The treatment options for multifocal motor neuropathy are sparse. Patients with multifocal motor neuropathy do not usually respond to steroids or plasma exchange, and may even worsen with these treatments. Many uncontrolled studies have suggested a beneficial effect of intravenous immunoglobulin.

OBJECTIVES

To review systematically the evidence from randomised controlled trials concerning the efficacy and safety of intravenous immunoglobulin in multifocal motor neuropathy.

SEARCH STRATEGY

We used the search strategy of the Cochrane Neuromuscular Disease Review Group to search the Disease Group register (searched September 2003), MEDLINE (January 1990 to September 2003), EMBASE (January 1990 to September 2003) and ISI (January 1990 to September 2003) databases for randomised controlled trials.

SELECTION CRITERIA

Randomised controlled studies examining the effects of any dose of intravenous immunoglobulin versus placebo in patients with definite or probable multifocal motor neuropathy. Outcome measures had to include one of the following: disability, strength, or conduction block. Studies which reported the frequency of adverse effects were used to assess safety.

DATA COLLECTION AND ANALYSIS

Two authors reviewed literature searches to identify potentially relevant trials, scored their quality and extracted data independently. For dichotomous data, we calculated relative risks, and for continuous data, effect sizes and weighted pooled effect sizes. Statistical uncertainty was expressed with 95% confidence intervals.

MAIN RESULTS

Four randomised controlled trials including a total of 34 patients were suitable for this systematic review. Strength improved in 78% of patients treated with intravenous immunoglobulin and only 4% of placebo-treated patients. Disability improved in 39% of patients after intravenous immunoglobulin treatment and in 11% after placebo (statistically not significantly different). Mild, transient side effects were reported in 71% of intravenous immunoglobulin treated patients. Serious side effects were not encountered.

AUTHORS' CONCLUSIONS

Limited evidence from randomised controlled trials shows that intravenous immunoglobulin has a beneficial effect on strength. There was a non-significant trend towards improvement in disability. More research is needed to discover whether intravenous immunoglobulin improves disability and is cost-effective.

Neuropathies motrices multifocales avec blocs de conduction persistants : 18 ans après

Multifocal motor neuropathy with persistent conduction blocks was firstly reported in 1986 and outlined from the group of purely motor diseases of the peripheral nervous system. The main criterion is the presence of conduction blocks located only on the motor nerves; additionally 30 percent of patients have IgM subclass serum antibodies directed against GM1 ganglioside. The clinical picture is a multifocal, asymmetrical, neuropathy, starting and predominant in the upper limbs, occurring in males aged 50 years and more, and having a progressive course. There is no biological sign besides elevated anti-GM1 antibodies. CSF analysis discloses mild increased protein count. The course is unpredictable, the neuropathy may be strictly limited to one or two motor nerves, or spread to other motor nerves in the four limbs. There is no involvement of the sensory and the cranial nerves, no involvement of the autonomic and the central nervous system. The pathophysiology is unknown, animal models do not allow to confirm the role of humoral immunity, and the role of anti-GM1 antibodies is controversial. Randomized controlled trials have assessed the efficacy of intravenous immunoglobulins which dramatically improve strength in 70-80 percent of patients in the short term, but remain unable to prevent motor deterioration in most patients, together with the occurrence of new conduction blocks. Corticosteroids and plasma exchanges do not improve the patients and may be followed by transient worsening. Long-term efficacy of immunosuppressive agents is not known.

Pure motor mononeuropathy with distal conduction block: an unusual presentation of multifocal motor neuropathy with conduction blocks

OBJECTIVE

To report an hitherto undescribed presentation of Motor Neuropathy with Multifocal Conduction Block (MMNCB).

METHODS

Description of two patients presenting with complete paralysis of the 3 heads of the trapezius muscle (case one) and progressive weakness of finger extension (case 2).

RESULTS

Nerve conduction studies (NCS) established that the corresponding nerves were distally inexcitable. In the affected muscles, no voluntary activity was elicited in both patients with spontaneous activity noted in patient 2. Systematic NCSs documented an asymptomatic, partial conduction block (CB) in a median nerve forearm segment in both patients. Neurophysiological follow-up after a dramatic response to intravenous immunoglobulins demonstrated recovery of the initially unobtainable motor responses.

CONCLUSIONS

This indicates that a complete, distal CB of the motor fibers destined to the trapezius muscle in patient 1, and to the extensor indicis proprius in patient 2, had caused the heralding deficits.

SIGNIFICANCE

These findings underscore the possibility of distal CB in this disorder and the need for extensive NCSs, including asymptomatic nerves, for an accurate diagnosis.

Plasma exchange for chronic inflammatory demyelinating polyradiculoneuropathy

BACKGROUND

Chronic inflammatory demyelinating polyradiculoneuropathy is an uncommon progressive or relapsing paralysing disease caused by inflammation of the peripheral nerves. If the hypothesis that it is due to autoimmunity is correct, removal of autoantibodies in the blood by plasma exchange should be beneficial.

OBJECTIVES

To evaluate the efficacy of plasma exchange in chronic inflammatory demyelinating polyradiculoneuropathy.

SEARCH STRATEGY

We searched the Neuromuscular Disease Group Register (December 2003), and MEDLINE (January 1966 to January 2003), EMBASE (January 1980 to January 2003), CINAHL (January 1982 to December 2002) and LILACS (January 1982 to January 2003). We also scrutinised the bibliographies of the trials, and contacted the trial authors and other disease experts.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials in participants of any age comparing plasma exchange with sham treatment or no treatment. A trial showing no significant difference in the benefit from plasma exchange with intravenous immunoglobulin has been included in a separate Cochrane review.

DATA COLLECTION AND ANALYSIS

Two authors selected the trials, extracted the data and assessed methodological quality independently. Where possible data were combined according to the methods of the Cochrane Neuromuscular Disease Review Group.

PRIMARY OUTCOME MEASURE

one crossover trial including 18 participants showed 2 (95% confidence interval (CI) 0.8 to 3.0) points more improvement after four weeks in an 11-point disability scale with plasma exchange (10 exchanges over four weeks) than with sham exchange. Rapid deterioration after plasma exchange occurred in eight of 12 who had improved.

SECONDARY OUTCOME MEASURES

when the results of this trial and another with 29 participants treated in a parallel group design trial were combined, there were 31 points (95% CI 16 to 45) more improvement in an impairment scale after plasma exchange (six exchanges over three weeks) than after sham exchange. There were significant improvements in both trials in an electrophysiological measure, the proximally evoked compound muscle action potential, after three or four weeks. Non-randomised evidence indicates that plasma exchange induces adverse events in 3% to 17% of procedures. These are sometimes serious.

REVIEWERS' CONCLUSIONS

Evidence from two small trials showed that plasma exchange provides significant short-term benefit in about two-thirds of patients with chronic inflammatory demyelinating polyradiculoneuropathy but rapid deterioration may occur afterwards. Adverse events related to difficulty with venous access, use of citrate and haemodynamic changes are not uncommon. More research is needed to identify agents which will prolong the beneficial action of plasma exchange.

Autoimmune neuropathies

Autoimmune neuropathies are common and treatable disorders of the peripheral nerves, which should be properly recognized. This article discusses their diagnosis, differential diagnosis and proper treatment.

A variant of multifocal motor neuropathy with acute, generalised presentation and persistent conduction blocks

OBJECTIVE

Multifocal motor neuropathy with persistent conduction blocks is classically described as a chronic neuropathy with progressive onset, and acute forms have not previously been characterised. We report four cases of severe motor impairment with acute and generalised onset and with persistent motor conduction blocks.

PATIENTS AND RESULTS

An acute tetraparesis with diffuse areflexia but little or no sensory disturbance was the clinical picture. Serial electrophysiological tests showed persistent multifocal motor conduction blocks with absent F waves in most tested motor nerves. No or minor abnormalities of the sensory nerve action potentials were observed. Cerebrospinal fluid contained normal or mildly increased protein levels (<1 g/l) without cells. Campylobacter jejuni serology was negative in three patients and consistent with past infection in one patient. Anti-ganglioside antibodies were positive in three patients. A five day course of intravenous immunoglobulins produced nearly complete symptom resolution in three patients and was ineffective in one patient.

CONCLUSION

Because of the persistence of multifocal motor conduction blocks for several weeks or months as the isolated electrophysiological feature, these cases could not be consistent with Guillain-Barré syndrome or chronic inflammatory demyelinating polyneuropathy. They suggest an original variant of multifocal motor neuropathy with an acute and generalised initial presentation and persistent motor conduction blocks affecting all four limbs.

Demyelinating focal motor neuropathy of the ulnar nerve masquerading as compression in Guyon's canal: a case report

Ulnar nerve-innervated intrinsic muscle weakness, in the absence of sensory complaints or deficits, usually is the result of compression at the ulnar nerve in zone II of Guyon's canal. In rare instances the problem is not caused by a compressive neuropathy but by a demyelinating focal motor neuropathy. Demyelinating neuropathies have been well documented in the neurologic literature but they have received little attention in the hand surgery literature. We report on one such case and the importance of differentiating the 2 neuropathies. Although surgery often is necessary for a compressive neuropathy it is contraindicated for a demyelinating neuropathy.

Consensus criteria for the diagnosis of multifocal motor neuropathy

At this time, there are no widely accepted criteria for the diagnosis of multifocal motor neuropathy. Furthermore, there is insufficient empirical data to define clinical and laboratory features that may reliably separate certain lower motor neuron syndromes with overlapping features as distinct. The AAEM therefore developed five criteria through a formal consensus process that are described in this document to act as a guide for diagnosing multifocal motor neuropathy with a high level of confidence (definite multifocal motor neuropathy) or with a moderate level of confidence (probable motor neuropathy). In brief, the diagnosis requires clinical weakness without objective sensory loss or upper motor neuron signs in the distribution of two or more named nerves that is due to conduction block in two or more motor nerves outside of common entrapment sites. Furthermore, normal results are required for sensory nerve conduction studies.

Multifocal motor neuropathy: clinical and immunological features and response to IVIg in relation to the presence and degree of motor conduction block

OBJECTIVE

To determine whether patients with clinically typical multifocal motor neuropathy (MMN) with or without definite or probable conduction block (CB) differ in terms of clinical presentation, immunological findings, or response to treatment with intravenous immunoglobulin (IVIg).

METHODS

23 consecutive patients were studied with the typical clinical features of MMN, consisting of a progressive multineuropathic motor impairment with minimal or no sensory loss. In 14 patients, electrophysiological studies disclosed the presence of a definite or probable CB according to the criteria proposed by the American Association of Electrodiagnostic Medicine (AAEM) in at least one motor nerve. Six patients had possible CB, defined as a degree of CB 10% less than that required by the AAEM for probable CB, while no CB was detected in three patients.

RESULTS

Patients with possible CB did not differ from those with a definite or probable CB in terms of age at disease onset (mean 38.8 v 38.2 years, respectively), distribution and severity of limb weakness, clinical impairment (mean Rankin score 2.2 in both), and frequency of antiganglioside antibodies (33% v 29%). Patients with possible CB had a longer mean disease duration (9 v 5.9 years, p < 0.05) and a less frequent consistent response to IVIg (67% v 86%) than those with a definite or probable CB. Patients without a detectable CB had a similar frequency of antiganglioside antibodies (33%) but had a longer disease duration (20.3 years), greater impairment (Rankin score 2.7), and more frequent signs of axonal degeneration (41% of examined motor nerves) than patients with CB (13-15%, p < 0.005). Only one patient without detectable CB (33%) consistently improved with IVIg.

CONCLUSIONS

Patients with possible CB were clinically and immunologically indistinguishable from those with definite or probable CB, albeit with a slightly less frequent response to IVIg. This finding suggests that failure to fulfil AAEM criteria for CB in patients with otherwise clinically typical MMN should not preclude this diagnosis and consequently a treatment trial with IVIg. Whether the longer duration and greater severity of the disease and more frequent axonal impairment in patients without detectable CB than in those with CB explain their lower response to IVIg remains to be established.

Evidence for axonal membrane hyperpolarization in multifocal motor neuropathy with conduction block

Multiple nerve excitability measurements were used to investigate axonal membrane properties of patients diagnosed with multifocal motor neuropathy (MMN). Six patients were selected, all with evidence of distal focal motor conduction block involving the median nerve in the forearm. In all patients, the median nerve was stimulated at the wrist, just distal to the site of block, and the resulting compound muscle action potentials were recorded from abductor pollicis brevis. Stimulus-response behaviour, the strength--duration time constant, threshold electrotonus to 100 ms polarizing currents, a current-threshold relationship and the recovery of excitability following supramaximal activation were recorded using a protocol described recently. When compared with control values, patients demonstrated significantly greater superexcitability, a 'fanning out' of threshold electrotonus recordings, and a significant change in the slope of the current--threshold relationship. These abnormalities in axonal membrane excitability parameters closely resembled those in normal axons hyperpolarized following release from ischaemia. To test for axonal hyperpolarization, DC depolarizing currents were applied to the nerves of three patients, and all the excitability parameters were normalized by depolarization. Attempts to trace excitability measures proximally towards the site of block were unsuccessful, as the nerve became inexcitable in all cases. It is suggested that the distal hyperpolarization is probably linked to focal depolarization and that the clinical features of MMN are consistent with a depolarizing/hyperpolarizing lesion.

Corticosteroids for chronic inflammatory demyelinating polyradiculoneuropathy

BACKGROUND

Chronic inflammatory demyelinating polyradiculoneuropathy is a peripheral neuropathy caused by peripheral nerve inflammation probably due to autoimmunity and would be expected to benefit from corticosteroids. Non-randomised studies suggest that corticosteroids are often beneficial.

OBJECTIVES

To evaluate the efficacy of corticosteroids for treating chronic inflammatory demyelinating polyradiculoneuropathy.

SEARCH STRATEGY

Search of the Cochrane Neuromuscular Disease Group register for randomised trials of corticosteroids treatment for chronic inflammatory demyelinating polyradiculoneuropathy and enquiry from subject experts.

SELECTION CRITERIA

Types of studies: All randomised or quasi-randomised trials Types of Participants: All patients with chronic inflammatory demyelinating polyradiculoneuropathy who were diagnosed by an internationally accepted definition. Types of interventions: Treatment with any form of corticosteroids or adrenocorticotropic hormone. Types of outcome measures:

PRIMARY OUTCOME MEASURE

Change in disability 12 weeks after randomisation.

SECONDARY OUTCOME MEASURES

1. Change in impairment 12 weeks after randomisation. 2. Change in maximum motor nerve conduction velocity or compound muscle action potential amplitude after 12 weeks. 3. Side effects of corticosteroids.

DATA COLLECTION AND ANALYSIS

One author extracted the data and the other checked them.

MAIN RESULTS

We identified one randomised controlled trial, an open study in which 19 corticosteroids treated patients showed more improvement in impairment than 16 untreated controls after 12 weeks. Experience from large non-randomised studies suggests that steroids are beneficial.

REVIEWER'S CONCLUSIONS

A single randomised controlled trial with 35 participants provided weak evidence to support the conclusion from non-randomised studies that oral corticosteroids reduce impairment in chronic inflammatory demyelinating polyradiculoneuropathy. Corticosteroids are known to have serious long term side effects. The long term risk and benefits have not been adequately studied.

Secondary amyloidosis as a life-ending event in multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is a disorder of peripheral nerve often associated with a high monosialoganglioside (GM1) antibody and multifocal conduction block. It has a chronic, indolent course with involvement of predominantly peripheral motor nerves, usually in an asymmetric fashion. There have been few reported cases of progression to frank quadriplegia. Secondary amyloidosis refers to the deposition of amyloid in various tissues due to an underlying chronic inflammatory state. We report the first case, to our knowledge, of a patient with MMN associated with high titer of GM1 antibody who developed acute paraplegia with both cranial nerve and worsening sensory involvement associated with multiorgan compromise due to a secondary amyloidosis involving the myocardium.

Medical technology assessment. Electrodiagnosis in motor neuron diseases and amyotrophic lateral sclerosis

In motor neuron diseases/amyotrophic lateral sclerosis (MND-ALS), electrodiagnostic techniques are essential in supporting the diagnosis and excluding other conditions that clinically resemble MND-ALS. Electrodiagnostic techniques can also monitor disease progression and provide prognostic information. Electromyography has an important role in the diagnosis of MND-ALS, but some drawbacks should be borne in mind. Although internationally accepted electrophysiological criteria have been defined to support MND-ALS diagnosis, differences in different laboratories can raise unexpected difficulties in application of diagnosis criteria. Much work needs to be done to increase standardisation of the electrodiagnosis of MND-ALS in order to improve quality. Differential diagnosis with motor axonal neuropathies may be particularly difficult. EMG is an essential tool for the early diagnosis of MND-ALS, which increases potential benefit of therapeutic interventions. A wide discussion among neurophysiologists from different schools could create a sound consensus on early diagnosis of MND-ALS.

Diagnosis of motor neuropathy

Motor neuropathy is a clinical entity which leads to consideration of a wide spectrum of peripheral nerve disorders. Firstly, it may be distinguished from other causes of peripheral motor involvement such as muscle diseases and disorders of the neuromuscular junction. Secondly, it may be discussed in two different forms: acute and chronic. Acute chronic neuropathies are mainly observed in Guillain-Barré syndrome, in which electrophysiological studies allow us to recognize the classical demyelinating form and the axonal form. The other causes of acute motor neuropathy are mainly poliomyelitis and porphyrias. Chronic motor neuropathies are mainly observed in motor neuron diseases, mainly amyotrophic lateral sclerosis, but also Kennedy's disease and other lower motor neuron diseases which may be inherited or acquired. The other causes are multifocal motor neuropathy and the predominantly motor forms of chronic inflammatory demyelinating polyneuropathy. The characterization of these different types of chronic neuropathy is of major importance because of the therapeutic consequences which may lead to the proposal of specific treatments.

Multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is a recently identified peripheral nerve disorder characterized by progressive, predominantly distal, asymmetric limb weakness mostly affecting upper limbs, minimal or no sensory impairment, and by the presence on nerve conduction studies of multifocal persistent partial conduction blocks on motor but not sensory nerves. The etiopathogenesis of MMN is not known, but there is some evidence, based mostly on the clinical improvement after immunological therapies, that the disease has an immunological basis. Antibodies, mostly IgM, to the gangliosides GM1, and though less frequently, GM2 and GD1a, are frequently detected in patients' sera, helping in the diagnosis of this disease. Even if there is some experimental evidence that these antibodies may be pathogenic in vitro, their role in the neuropathy remains to be established. Patients with MMN do not usually respond to steroids or plasma exchange, which may occasionally worsen the symptoms, while the efficacy of cyclophosphamide is limited by its relevant side effects. More than 80% of MMN patients rapidly improve with high dose intravenous immunoglobulin therapy (IVIg). The effect of this therapy is, however, transient and improvement has to be maintained with periodic infusions. A positive response to interferon-beta has been recently reported in a minority of patients, some of whom were resistant to IVIg. Even if many progresses have been made on the diagnosis and therapy of MMN, there are still several issues on the nosological position, etiopathogenesis and long-term treatment of this neuropathy that need to be clarified.

Asymmetric Acquired Demyelinating Polyneuropathies: MMN and MADSAM

More than a half a century after Austin's initial description of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), the clinical spectrum of chronic acquired demyelinating polyneuropathies has expanded. Currently there are a number of entities that can be put under the heading of chronic acquired demyelinating neuropathy (CADP) based on differing clinical presentations. In this scheme, CIDP is used only to refer to patients with demyelinating neuropathies and generalized symmetric weakness. In contrast, multifocal motor neuropathy (MMN) and multifocal acquired demyelinating sensory and motor neuropathy (MADSAM) fall into the category of asymmetrical, multifocal forms of CADP. These are distinguished from each other only by the presence of sensory involvement. In our opinion, there are pragmatic reasons for splitting these clinical presentations into distinct entities. Although each of these clinical subtypes shares some basic similarities, there are important differences. MMN is usually considered resistant to corticosteroid therapy and the first line agent in this disorder is intravenous immunoglobulin (IVIg). MADSAM neuropathy can be responsive to prednisone or IVIg, and has a profile more analogous to classic CIDP with regards to its laboratory features and treatment response.

Intravenous immunoglobulin therapy in multifocal motor neuropathy: a double-blind, placebo-controlled study

We conducted a double-blind, placebo-controlled, study of 19 patients fulfilling eligibility criteria for multifocal motor neuropathy with persistent conduction block. They were enrolled and divided into two groups: those who had never been treated previously with intravenous immunoglobulins (IVIg) (Group 1: 10 patients) and those who presented recurrent symptoms after previously successful treatment with IVIg (Group 2: nine patients). They were randomized prospectively to receive either IVIg or placebo at a dose of 500 mg/kg/day for 5 consecutive days, once a month for 3 months. At month 4, patients found to be responders remained on the same treatment for the 3 following months, while non-responders were switched to the alternative study drug for the 3 following months. Clinical assessment was conducted with the MRC score in 28 muscles and a self-evaluation scale (five daily motor activities scored from 0 to 5). In Group 1, nine patients completed the study, of whom initially four received IVIg and five placebo; four patients responded to IVIg (two at months 4 and 7, and a further two at month 7 after switching treatment at month 4), two patients responded to placebo at months 4 and 7, and three patients did not respond to either treatment. In Group 2, nine patients completed the study. Five patients first received IVIg and all responded at months 4 and 7. Four patients first received placebo and none responded at month 4; all were then switched to IVIg and three responded at month 7. When the 18 patients were considered together, seven out of the nine patients who received IVIg first were responders at month 4, compared with two of the nine patients who received placebo first, a difference that was statistically significant (P = 0.03). On the other hand, there was no significant difference in MRC score but a significant difference in the self-evaluation score, at month 4, between IVIg patients and placebo patients. Electrophysiological studies did not show significant differences at month 4 in motor parameters between IVIg patients and placebo patients. IgM anti-GM1 titres did not change significantly in patients treated with IVIg compared with those who received placebo, between baseline, month 4 and month 7. However, of five patients who had significantly high anti-GM1 titres (>3200) at baseline, four responded to IVIg. This trial confirms that IVIg is a promising therapeutic option for multifocal motor neuropathy.

Clinical spectrum of chronic acquired demyelinating polyneuropathies

A number of presentations of chronic demyelinating polyneuropathy have been identified, each distinguished by its phenotypic pattern. In addition to classic chronic inflammatory demyelinating polyneuropathy (CIDP), which is characterized clinically by symmetric proximal and distal weakness and sensory loss, several regional variants can be recognized: multifocal motor neuropathy (MMN: asymmetric and pure motor), multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy (asymmetric, sensory, and motor), and distal acquired demyelinating symmetric (DADS) neuropathy (symmetric, distal, sensory, and motor). There are also temporal, pathological, and disease-associated variants. This review describes a clinical scheme for approaching the chronic acquired demyelinating polyneuropathies that leads to a rational use of supportive laboratory studies and treatment options. In addition, we propose new diagnostic criteria for CIDP that more accurately reflect current clinical practice.

Multifocal motor neuropathy presenting with respiratory failure

Multifocal motor neuropathy is a disorder characterized by slowly progressive asymmetrical limb weakness and multiple motor conduction blocks. We report a 56-year-old woman with this disorder who presented unusually with respiratory failure and who initially had absent responses to phrenic nerve stimulation bilaterally. The mechanism of the patient's respiratory failure may have been chronic conduction blocks in the phrenic nerves leading to diaphragmatic weakness.

Intravenous immunoglobulin treatment in peripheral nerve disorders--indications, mechanisms of action and side-effects

This review summarizes observations of clinical use of high dose intravenous immunoglobulin G (IVIg) in regards to administration, kinetics, known or postulated mechanisms of action, and adverse reactions. Indications and value of IVIg for the treatment of various neuropathies with presumed autoimmune aetiology are examined. New knowledge that advances the understanding of the pathogenesis of the neuropathies and of the mechanisms of action of IVIg is discussed.