This review charts the progress of anti-glycolipid antibodies in neuropathy, from their original discovery 20 years ago in immunoglobulin M paraproteinaemic neuropathy through to current discoveries mapping their relationship to subtypes of Guillain-Barre syndrome. Antibodies to >20 different glycolipids have now been associated with a wide range of clinically identifiable acute and chronic neuropathy syndromes. Particular progress has been achieved in understanding the link between acute motor axonal neuropathy and antibodies to GM1, GD1a, GM1b and GalNAc-GD1a, and between the cranial, bulbar and sensory variants of GBS and antibodies to the disialylated gangliosides GQ1b, GT1a, GD1b and GD3. In addition to clinical and serological studies, the origins and measurement of anti-glycolipid antibodies and their relationships to similar carbohydrate structures on infectious organisms, particularly Campylobacter jejuni, are discussed in the context of a molecular mimicry hypothesis. The structure and nomenclature of relevant glycolipids are outlined, along with information on their localization in nerve, and the influence this has on clinical phenotypes. Major advances have been made in animal modelling of anti-glycolipid antibody-associated diseases, both in vitro and in vivo. This has advanced our understanding of the role of anti-GQ1b antibodies in Miller Fisher syndrome with particular respect to the motor nerve terminal as a potential site of injury, and led to the creation of rabbit models of anti-GD1b and anti-GM1 antibody-mediated sensory and motor neuropathy, respectively. With such information in place, it will now be possible to determine the precise mechanisms by which antibodies injure the different compartments of peripheral nerve and establish how a range of immunomodulating therapies, including current treatments, exert their therapeutic effects. Despite these very significant advances, considerable gaps in our knowledge persist, and it is likely that other pathogenic pathways operate in inflammatory neuropathy that are unrelated to glycolipid antibodies, although these are outside the scope of this review.

Peripheral neuropathies and anti-glycolipid antibodies.

We report 2 patients with a treatable, immune-mediated motor polyneuropathy associated with antibodies to defined neural antigens. In these patients asymmetrical weakness developed in one arm and progressed over 2 to 3 years to involve the other arm, legs, and trunk. Both patients were initially diagnosed as having lower motor neuron forms of amyotrophic lateral sclerosis. However, repeated electrophysiological testing eventually showed multifocal conduction blocks in motor but not sensory fibers compatible with patchy selective demyelination. Serum testing by thin-layer chromatography and enzyme-linked immunosorbent assay revealed that both patients had high titers of antibody directed against GM1 and other gangliosides. Initial therapeutic trials of prednisone (100 mg daily for 4 to 6 months) and plasmapheresis were unsuccessful. Treatment with cyclophosphamide, however, was followed by Marchked improvement in strength in both patients.

A treatable multifocal motor neuropathy with antibodies to GM1 ganglioside.

A European Federation of Neurological Societies/Peripheral Nerve Society consensus guideline on the definition, investigation, and treatment of multifocal motor neuropathy (MMN) was published in 2006. The aim is to revise this guideline. Disease experts considered references retrieved from MEDLINE and Cochrane Systematic Reviews published between August 2004 and July 2009 and prepared statements that were agreed to in an iterative fashion. The Task Force agreed on Good Practice Points to define clinical and electrophysiological diagnostic criteria for MMN, investigations to be considered, and principal recommendations for treatment

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 - first revision

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.

Clinical spectrum of chronic acquired demyelinating polyneuropathies.

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.

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

We report five patients with pure motor neuropathy characterized by multifocal weakness, muscle atrophy that was sometimes profound, cramps, and fasciculations with relatively preserved reflexes. The clinical picture led to an initial diagnosis of motor neuron disease in all cases, but nerve conduction studies revealed multifocal conduction block confined to motor axons and predominantly involving proximal nerve segments. Routine sensory nerve conduction studies, ascending compound nerve action potentials, and somatosensory evoked potentials were all normal even through nerve segments in which motor conduction was severely blocked. Onset of symptoms was insidious, and progression was indolent. In two cases, after many years of neuropathy, sensory abnormalities developed but remained clinically trivial. These unusual cases probably have the same pathogenesis as previously described patients with persistent multifocal conduction block. Distinction from motor neuron disease is critical, since chronic demyelinating neuropathy may respond to treatment.

Stephen Clarke

Papers

Multifocal acquired demyelinating neuropathy masqurading as motor neuron disease