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

Management of chronic inflammatory demyelinating polyradiculoneuropathy

This review briefly describes current concepts concerning the nosological status, pathogenesis and management of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). CIDP is an uncommon variable disorder of unknown but probably autoimmune aetiology. The commonest form of CIDP causes more or less symmetrical progressive or relapsing weakness affecting proximal and distal muscles. Against this background the review describes the short-term responses to corticosteroids, intravenous immunoglobulin (IVIg) and plasma exchange that have been confirmed in randomised trials. In the absence of better evidence about long-term efficacy, corticosteroids or IVIg are usually favoured because of convenience. Benefit following introduction of azathioprine, cyclophosphamide, cyclosporin, other immunosuppressive agents, and interferon-beta and -alpha has been reported but randomised trials are needed to confirm these benefits. In patients with pure motor CIDP and multifocal motor neuropathy, corticosteroids may cause worsening and IVIg is more likely to be effective. General measures to rehabilitate patients and manage symptoms, including foot drop, weak hands, fatigue and pain, are important.

Treatment of IgM antibody associated polyneuropathies using rituximab

OBJECTIVES

Polyneuropathies with associated serum IgM antibodies are often difficult to treat. Rituximab is a monoclonal antibody directed against the B cell surface membrane marker CD20. Rituximab eliminates B cells from the circulation, and, over time, could reduce cells producing autoantibodies. This study tested the ability of rituximab to produce changes in serum antibody titres, and improvement in strength, in patients with neuromuscular disorders and IgM autoantibodies.

METHODS

Over a period of two years, the authors evaluated changes in strength, measured by quantitative dynamometry, and concentrations of several types of serum antibodies in patients with polyneuropathies and serum IgM autoantibodies. Twenty one patients treated with rituximab were compared with 13 untreated controls.

RESULTS

Treatment with rituximab was followed by improved strength (an increase of mean (SEM) 23% (2%)of normal levels of strength), a reduction in serum IgM autoantibodies (to 43% (4%) of initial values), and a reduction in total levels of IgM (to 55% (4%) of initial values). There was no change in levels of serum IgG antibodies. There were no major side effects, even though B cells were virtually eliminated from the circulation for periods up to two years.

CONCLUSIONS

In patients with IgM autoantibody associated peripheral neuropathies, rituximab treatment is followed by reduced serum concentrations of IgM, but not IgG, antibodies, and by improvement in strength. Additional studies, with placebo controls and blinded outcome measures, are warranted to further test the efficacy of rituximab treatment of IgM associated polyneuropathies.

Demyelination and axonal loss in multifocal motor neuropathy: distribution and relation to weakness

Multifocal motor neuropathy (MMN) is characterized by a slowly progressive, asymmetric weakness of the limbs without sensory loss. The arms are usually affected to a greater extent than the legs, and distal muscles more than proximal muscles. The distribution of electrophysiological abnormalities and its correlation with weak muscle groups in MMN have not been investigated systematically. The aim of the present study was to assess whether electrophysiological abnormalities have a preferential or random distribution, whether electrophysiological abnormalities in a nerve correlate with weakness in the innervated muscles, and whether these results are relevant for the development of optimal electrodiagnostic protocols. We compared the pattern of weakness and electrophysiological abnormalities in 39 patients with a lower motoneuron syndrome and a positive response to intravenous immunoglobulins. All patients underwent an extensive standardized electrophysiological examination. Electrophysiological evidence of demyelination was found more often in the nerves of the arms and was distributed randomly over lower arm, upper arm and shoulder segments. Electrophysiological evidence of axonal loss presented more frequently in longer nerves, occurring most often in the leg nerves. For the arm nerves, it is possible that the length dependence of axonal loss is due to the random distribution of demyelinating lesions that lead to axonal degeneration. Weakness was associated with features of demyelination and axonal loss in the nerves of the arm, and with features of axonal loss in leg nerves. However, a substantial number (approximately one-third) of electrophysiological abnormalities were found in nerves innervating non-weakened muscles. These results imply that in MMN, conduction block is most likely to be found in long arm nerves innervating weakened muscles, but if conduction block cannot be detected in these nerves, the electrophysiological examination should be extended to other arm nerves including those innervating non-weakened muscles.

Anterior interosseous nerve and multifocal motor neuropathy

We report the case of a 47-year-old woman with a left anterior interosseous nerve palsy. Surgical release of the anterior interosseous nerve was initially proposed, but electrodiagnostic evaluation demonstrated that the neuropathy was due not to compression or to neuralgic amyotrophy but to a proximal conduction block. At that time, the conduction block could be defined only by indirect electrodiagnostic criteria. A multifocal motor neuropathy with persistent conduction block was subsequently diagnosed, and the patient was treated with intravenous immunoglobulins. The efficacy of this treatment and the subsequent disclosure of conduction block in the right posterior interosseous and peroneal nerves definitively confirmed the multifocal motor neuropathy.

Treatment of immune neuropathies

PURPOSE OF THE REVIEW

Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating poly(radiculo)neuropathy (CIDP) and multifocal motor neuropathy (MMN) are potentially treatable disorders. The use of appropriate assessment scales to evaluate the effects of treatment is essential. Recent therapeutic trials and the question of whether patients with mild disease or other variants of these disorders need to be treated are discussed.

RECENT FINDINGS

Recent clinical trials and Cochrane reviews give new information on the effect of various treatments in patients with GBS, CIDP and MMN. Intravenous immunoglobulin remains the only treatment proven to be effective in MMN. Combinations of treatment may be even more effective in GBS. Studies on prognostic factors related to improvement have been reported. Whether patients with Miller-Fisher syndrome or those with mild GBS should also be treated is still debated. New assessment scales at the disability and handicap level have now been evaluated for GBS and CIDP, and are ready for use. Results of studies in experimental models contribute to our understanding of the mechanism of action of intravenous immunoglobulin.

SUMMARY

Recent new information on the use of intravenous immunoglobulin and steroids indicates that the former should remain the cornerstone of treatment for GBS and MMN, and probably also for CIDP. Whether steroids not only suppress disease activity in CIDP but also eradicate the disease remains to be established. Some GBS patients have secondary deterioration or finally turn out to have CIDP; additional information in this group of patients may lead to more appropriate disease management. Most patients with CIDP and those with MMN need long-term treatment. New treatment strategies should now focus also on the effect and the costs of treatment over long-term follow up.

Multifocal motor neuropathy: long-term clinical and electrophysiological assessment of intravenous immunoglobulin maintenance treatment

We performed a long-term follow-up study of 11 patients with multifocal motor neuropathy (MMN) who received maintenance treatment with intravenous immunoglobulins (IVIg). Patients were treated initially with one full course of IVIg (0.4 g/kg for 5 days) followed by one IVIg infusion (0.4 g/kg) every week. During follow-up, the frequency and dosage of IVIg infusions were determined for each patient and ranged from one infusion every 1 to 7 weeks and an average dose of 7 to 48 g per week. During the 4- to 8-year follow-up period, muscle strength was assessed by measuring the MRC (Medical Research Council) sumscore of 20 muscle groups and by performing hand-held dynamometry on a selection of weak muscle groups. Systematic electrophysiological studies were performed before treatment and each year during IVIg maintenance treatment. Disability was assessed with the upper limb and lower limb subscales of the Guy's Neurological Disability Scale before treatment, after the first full course of IVIg and at the last follow-up examination. Muscle strength improved significantly within 3 weeks of the start of IVIg treatment and was still significantly better at the last follow-up examination than before treatment, even though it decreased slightly and significantly during the follow-up period. Upper limb disability was significantly better after the first full course of IVIg than before treatment. Conduction block disappeared in six nerve segments but new conduction block appeared in eight nerve segments during the follow-up period. Changes consistent with improvement (remyelination or reinnervation) occurred in 13 nerves during follow-up and changes consistent with worsening (demyelination or axon loss) occurred in 14 nerves. Electrophysiological changes consistent with improvement were significantly associated with the presence of conduction block before IVIg treatment. In conclusion, IVIg maintenance treatment has a beneficial long-term effect on muscle strength and upper limb disability but may not prevent a slight decrease in muscle strength. The electrophysiological findings imply that IVIg treatment favourably influences the mechanisms of remyelination or reinnervation but that axon loss cannot be prevented.

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.

Monofocal motor neuropathy: Improvement with intravenous immunoglobulin

Multifocal motor neuropathy (MMN) is a chronic, immune-mediate, peripheral myelinopathy. Inherent in its name, MMN implies involvement of two or more motor nerves. We report three patients with weakness and partial motor conduction block restricted to a single nerve and localized to sites that are not at risk for entrapment or compression injury. None of the patients had sensory involvement and all showed a favorable response to intravenous immunoglobulin therapy. Based on these observations and reports of three additional patients, we believe that monofocal motor neuropathy is a partial form of MMN and should be treated as such.

Intravenous immunoglobulin in neurological disease: a specialist review

Treatment of neurological disorders with intravenous immunoglobulin (IVIg) is an increasing feature of our practice for an expanding range of indications. For some there is evidence of benefit from randomised controlled trials, whereas for others evidence is anecdotal. The relative rarity of some of the disorders means that good randomised control trials will be difficult to deliver. Meanwhile, the treatment is costly and pressure to "do something" in often distressing disorders considerable. This review follows a 1 day meeting of the authors in November 2000 and examines current evidence for the use of IVIg in neurological conditions and comments on mechanisms of action, delivery, safety and tolerability, and health economic issues. Evidence of efficacy has been classified into levels for healthcare interventions (tables 1 and 2).

Systematic reviews of treatment for inflammatory demyelinating neuropathy

This review describes the progress made in preparing Cochrane systematic reviews of randomized controlled trials for Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), multifocal motor neuropathy (MMN) and the demyelinating neuropathies associated with paraproteins. The discovery of antibodies against myelin and axolemmal glycolipids and proteins has not yet replaced the clinicopathological classification on which treatment trials have been based. Systematic reviews have endorsed the equivalence of plasma exchange (PE) and intravenous immunoglobulin (IVIg) and the lack of efficacy of steroids in GBS. Systematic reviews have also endorsed the value of steroids, PE and IVIg in CIDP but randomized controlled trials have only shown benefit from IVIg in MMN. There is a paucity of evidence concerning the efficacy of treatments in paraproteinaemic demyelinating neuropathy apartment from small trials showing short-term benefit from PE or IVIg. There is a lack of good quality controlled trials of immunosuppressive agents in any of these conditions. As the number of treatment trials increases, Cochrane systematic reviews will be an increasingly valuable resource for summarizing the evidence from randomised controlled trials on which to base clinical practice. They already demonstrate major deficiencies in the existing evidence base.

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.