Invited review: motor neuropathies, motor neuron disorders, and antiglycolipid antibodies

Small Fibre Involvement in Multifocal Motor Neuropathy Explored with Sudoscan: A Single-Centre Experience

Objective: Multifocal motor neuropathy (MMN) is a rare inflammatory neuropathy, clinically characterized by exclusive motor involvement. We wished to evaluate the possible presence of sensory dysfunction, including the evaluation of small fibres, after a long-term disease course. Patients and methods: seven MMN patients, regularly followed in our Neurology Department, underwent clinical evaluation, neurophysiological examination by nerve conduction studies (NCSs), and Sudoscan. We compared neurophysiological data with a group of patients with other disorders of the peripheral nervous system. Results: NCSs showed a reduction of sensory nerve action potential amplitude in 2/7 MMN patients. Sudoscan showed borderline electrochemical skin conductance (ESC) values in 3/7 MMN patients (two of them with abnormal sensory NCSs). Conclusions: Our results confirm that sensory involvement may be found in some MMN after a long-term disease course, and it could also involve the small fibres.

Anti-sulfatide reactivity in patients with celiac disease

OBJECTIVE

To explore a possible significance of the presence of anti-ganglioside and anti-sulfatide antibodies in sera of adult patients with celiac disease (CD) in different clinical scenario.

METHODS

We selected 22 adult patients with newly diagnosed CD and 20 age-sex matched non-CD controls. Patients' serum was tested - before and after at least 6 months on a gluten-free diet (GFD) - for anti-GM1, GM2, GM3, GD1a, GD1b, GD3, GT1a, GT1b, GQ1b and sulfatide IgM, IgG and IgA auto-antibodies, by means of a dot blot technique and enzyme-linked immunosorbent assay (ELISA).

RESULTS

We found the presence of auto-antibodies in untreated patients. In particular, anti-sulfatide IgG antibodies were present in 8 (36%) patients independently of the presence of neurological symptoms. Anti-sulfatide IgA antibodies were present in 3 (19%) patients. During GFD, anti-sulfatide IgG disappeared in all the patients, whereas IgA were observed in 2 patients. Anti-sulfatide, anti-GM1 and anti-GM2 IgM antibodies were also observed in 2 patients on a GFD. All the other auto-antibodies were absent and no demographic or clinical parameters were associated. Non-CD controls did not present any auto-antibody.

CONCLUSIONS

We found anti-sulfatide IgG antibodies in CD patients on a gluten-containing diet. Anti-sulfatide IgA antibodies persisted during GFD together with the occurrence of other IgM auto-antibodies. These data suggest a possible link between gluten and IgG auto-antibodies.

Brain energy metabolism spurns fatty acids as fuel due to their inherent mitotoxicity and potential capacity to unleash neurodegeneration

The brain uses long-chain fatty acids (LCFAs) to a negligible extent as fuel for the mitochondrial energy generation, in contrast to other tissues that also demand high energy. Besides this generally accepted view, some studies using cultured neural cells or whole brain indicate a moderately active mitochondrial β-oxidation. Here, we corroborate the conclusion that brain mitochondria are unable to oxidize fatty acids. In contrast, the combustion of liver-derived ketone bodies by neural cells is long-known. Furthermore, new insights indicate the use of odd-numbered medium-chain fatty acids as valuable source for maintaining the level of intermediates of the citric acid cycle in brain mitochondria. Non-esterified LCFAs or their activated forms exert a large variety of harmful side-effects on mitochondria, such as enhancing the mitochondrial ROS generation in distinct steps of the β-oxidation and therefore potentially increasing oxidative stress. Hence, the question arises: Why do in brain energy metabolism mitochondria selectively spurn LCFAs as energy source? The most likely answer are the relatively higher content of peroxidation-sensitive polyunsaturated fatty acids and the low antioxidative defense in brain tissue. There are two remarkable peroxisomal defects, one relating to α-oxidation of phytanic acid and the other to uptake of very long-chain fatty acids (VLCFAs) which lead to pathologically high tissue levels of such fatty acids. Both, the accumulation of phytanic acid and that of VLCFAs give an enlightening insight into harmful activities of fatty acids on neural cells, which possibly explain why evolution has prevented brain mitochondria from the equipment with significant β-oxidation enzymatic capacity.

Individual Restriction Of Fine Specificity Variability In Anti-GM1 IgG Antibodies Associated With Guillain-Barré Syndrome

Elevated titers of serum antibodies against GM1 ganglioside are associated with a variety of autoimmune neuropathies. Much evidence indicates these autoantibodies play a primary role in the disease processes, but the mechanism for their appearance is unclear. We studied the fine specificity of anti-GM1 antibodies of the IgG isotype present in sera from patients with Guillain-Barré syndrome (GBS), using thin-layer chromatogram-immunostaining of GM1, asialo-GM1 (GA1), GD1b and GM1-derivatives with small modifications on the oligosaccharide moiety. We were able to distinguish populations of antibodies with different fine specificity. Remarkably, individual patients presented only one or two of them, and different patients had different populations. This restriction in the variability of antibody populations suggests that the appearance of the anti-GM1 antibodies is a random process involving restricted populations of lymphocytes. With the origin of disease-associated anti-GM1 antibodies as a context, this finding could provide explanation for the “host susceptibility factor” observed in GBS following enteritis with GM1 oligosaccharide-carrying strains of Campylobacter jejuni.

Anti-Glutamate Therapy in Amyotrophic Lateral Sclerosis: A Trial Using Lamotrigine

Glutamate excitotoxicity is implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). We report the results of a double blind, placebo controlled, trial using 100 mg of oral daily lamotrigine (3,5-diamino-6-(2,3 dichlorophenyl)-l,2,4-triazine) which inhibits glutamate release. 67 patients were entered and at trial termination of 1.5 years 15 had withdrawn (9 active and 6 placebo) and 12 had died (6 active and 6 placebo). Mean age at entry was 57.5 years for the active and 58.6 years for the placebo groups. Patients were seen at 3 monthly intervals and scored according to neurological deficit based upon age of onset, bulbar and respiratory involvement, ambulation and functional disability. The mean change in clinical scores for the active versus placebo groups over the trial period was 7.1 ± 3.3 and 9.0 ± 3.3 respectively (0.05 < p < 0.10). Changes in cortical threshold and MEP/CMAP ratios to magnetic stimulation also did not differ significantly between the two groups. We conclude that lamotrigine in the doses administered does not alter the course of ALS.

Multifocal motor neuropathy

Multifocal motor neuropathy (MMN) was first described in 1988 as a purely motor neuropathy affecting multiple motor nerves. The diagnosis was based entirely on demonstrating electrophysiological evidence of a conduction block (CB) that selectively affected motor axons, with sparing of sensory axons even through the site of motor CB. Subsequently, a similar disorder was reported but with absence of demonstrable CB on routine nerve conduction studies and there is still some debate as to whether MMN without CB is related to MMN. MMN is thought to be an inflammatory neuropathy related to an immune attack on motor nerves. The conventional hypothesis is that the primary pathology is segmental demyelination, but recent research raises the possibility of a primary axonopathy. Anti-GM1 antibodies can be found in some patients but it is unclear whether these antibodies are pathogenic. Intravenous immunoglobulin is the mainstay of treatment but other immunosuppressive treatments can also be effective.

Antibodies to heteromeric glycolipid complexes in multifocal motor neuropathy

BACKGROUND

Measurement of anti-GM1 IgM antibodies in multifocal motor neuropathy (MMN) sera is confounded by relatively low sensitivity that limits clinical usefulness. Combinatorial assay methods, in which antibodies react to heteromeric complexes of two or more glycolipids, are being increasingly applied to this area of diagnostic testing.

METHODS

A newly developed combinatorial glycoarray able to identify antibodies to 45 different heteromeric glycolipid complexes and their 10 individual glycolipid components was applied to a randomly selected population of 33 MMN cases and 57 normal or disease controls. Comparison with an enzyme-linked immunosorbent assay (ELISA) was conducted for selected single glycolipids and their complexes.

RESULTS

By ELISA, 22/33 MMN cases had detectable anti-GM1 IgM antibodies, whereas 19/33 MMN samples were positive for anti-GM1 antibodies by glycoarray. Analysis of variance (anova) revealed that of the 55 possible single glycolipids and their 1:1 complexes, antibodies to the GM1:galactocerebroside (GM1:GalC) complex were most significantly associated with MMN, returning 33/33 MMN samples as positive by glycoarray and 29/33 positive by ELISA. Regression analysis revealed a high correlation in absolute values between ELISA and glycoarray. Receiver operator characteristic analysis revealed insignificantly different diagnostic performance between the two methods. However, the glycoarray appeared to offer slightly improved sensitivity by identifying antibodies in four ELISA-negative samples.

CONCLUSIONS

The use of combinatorial glycoarray or ELISA increased the diagnostic sensitivity of anti-glycolipid antibody testing in this cohort of MMN cases, without significantly affecting specificity, and may be a useful assay modification for routine clinical screening.

Biochemical aspects of X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is the most common peroxisomal disorder. The disease is characterized by the accumulation of very long-chain fatty acids (VLCFA; >C22) in plasma and tissues. X-ALD is caused by mutations in the ABCD1 gene encoding ALDP, an adenosine triphosphate (ATP)-binding-cassette (ABC) transporter located in the peroxisomal membrane. In this paper, we describe the current knowledge on the function of ALDP, its role in peroxisomal VLCFA beta-oxidation and the consequences of a defect in ALDP on VLCFA metabolism. Furthermore, we pay special attention to the role of the VLCFA elongation system in VLCFA homeostasis, with elongation of very long-chain fatty acids like-1 (ELOVL1) as key player, and its relevance to X-ALD.

Pathomechanisms underlying X-adrenoleukodystrophy: a three-hit hypothesis

X-adrenoleukodystrophy (X-ALD) is a complex disease where inactivation of ABCD1 gene results in clinically diverse phenotypes, the fatal disorder of cerebral ALD (cALD) or a milder disorder of adrenomyeloneuropathy (AMN). Loss of ABCD1 function results in defective beta oxidation of very long chain fatty acids (VLCFA) resulting in excessive accumulation of VLCFA, the biochemical "hall mark" of X-ALD. At present, the ABCD1-mediated mechanisms that determine the different phenotype of X-ALD are not well understood. The studies reviewed here suggest for a "three-hit hypothesis" for neuropathology of cALD. An improved understanding of the molecular mechanisms associated with these three phases of cALD disease should facilitate the development of effective pharmacological therapeutics for X-ALD.

Anti-GM1 antibodies as a model of the immune response to self-glycans

Glycans are a class of molecules with high structural variability, frequently found in the plasma membrane facing the extracellular space. Because of these characteristics, glycans are often considered as recognition molecules involved in cell social functions, and as targets of pathogenic factors. Induction of anti-glycan antibodies is one of the early events in immunological defense against bacteria that colonize the body. Because of this natural infection, antibodies recognizing a variety of bacterial glycans are found in sera of adult humans and animals. The immune response to glycans is restricted by self-tolerance, and no antibodies to self-glycans should exist in normal subjects. However, antibodies recognizing structures closely related to self-glycans do exist, and can lead to production of harmful anti-self antibodies. Normal human sera contain low-affinity anti-GM1 IgM-antibodies. Similar antibodies with higher affinity or different isotype are found in some neuropathy patients. Two hypotheses have been developed to explain the origin of disease-associated anti-GM1 antibodies. According to the "molecular mimicry" hypothesis, similarity between GM1 and Campylobacter jejuni lipopolysaccharide carrying a GM1-like glycan is the cause of Guillain-Barré syndrome associated with anti-GM1 IgG-antibodies. According to the "binding site drift" hypothesis, IgM-antibodies associated with disease originate through changes in the binding site of normally occurring anti-GM1 antibodies. We now present an "integrated" hypothesis, combining the "mimicry" and "drift" concepts, which satisfactorily explains most of the published data on anti-GM1 antibodies.

Lymphome T révélé par une mononeuropathie multiple : étude d’un cas avec revue de la littérature

INTRODUCTION

Lymphoma occasionally affects the peripheral nervous system. Neuropathy usually appears in patients with known lymphoma but rarely represents the initial manifestation of underlying malignancy. We report a case in which mononeuritis multiplex (MM) was the dominant feature in the clinical presentation of a peripheral T-cell non-Hodgkin lymphoma (NHL).

OBSERVATION

A 32-year-old man suffered from an asymmetric progressive sensory-motor peripheral neuropathy. The left peroneal nerve was affected first, then the left median nerve after one month, followed by the left trigeminal nerve ten months later. The electrophysiological study confirmed the diagnosis of axonal sensory-motor MM. Mediastinal adenopathies, splenomegaly, pancytopenia and inflammatory syndrome were also found. An osteo-medullary biopsy showed a T-cell NHL. Nerve biopsy study found an inflammatory lymphoid infiltration without malignant cell supporting the hypothesis of an inflammatory pathogenic process. Chemotherapy including cyclophosphamide, hydralazine, vincristine and prednisone were administered monthly during 8 months. No improvement was obtained.

DISCUSSION

It must be emphasised that this case is an uncommon one. On the one hand, NHL is rarely associated with MM and on the other hand, it can exceptionally be revealed by a MM. We were able to find 30 reported cases of distal neuropathy revealing a NHL including, 8 mononeuritis simplex, 9 MM and 13 polyneuropathies. Polyradiculoneuritis cases were excluded from this study because the neuropathy is usually caused by a meningeal infiltration. The neuropathy was in the majority of the cases chronic and axonal. The lymphoma was more often B-cell than T-cell. The B-cell lymphoma was frequently associated with a poor prognosis. All mechanisms were present with a predominance of neurolymphomatosis.

Long-term evolution of anti-ganglioside antibody levels in patient with chronic dysimmune neuropathy under IVIg therapy

The authors retrospectively examined the anti-ganglioside antibody (AGA) IgM level changes from 14 patients with chronic dysimmune neuropathy (5 with multifocal motor neuropathy and 9 with chronic inflammatory demyelinating polyneuropathy) treated with maintenance doses of intravenous immunoglobulins (IVIg). The median follow-up was 5 years. At last follow-up, 93% of the patients had an increment of AGA levels, and five patients with initial AGA values within normal range became positive during follow-up. Overall, median AGA titers significantly increased from the first to the last samples, despite a substantial clinical stability after the initial improvement with IVIg. The AGA increment rate was inversely correlated with IVIg infusions interval necessary to maintain therapeutic efficacy. Thus, antibody testing in the follow-up of patients with dysimmune neuropathies may be helpful to predict the decline of IVIg efficacy and to identify those patients who eventually take advantage from an increase in infusion frequency.

Relapsing sensorimotor neuropathy with ophthalmoplegia, antidisialosyl antibodies, and extramembranous glomerulonephritis

A 72-year-old man presented with oculomotor dysfunction, subacute relapsing sensorimotor neuropathy, elevated erythrocyte sedimentation rate, IgM monoclonal paraprotein, cold agglutinins, and antidisialosyl IgM antibodies, features previously described by the acronym CANOMAD (chronic ataxic neuropathy with ophthalmoplegia, M protein, agglutination, and disialosyl antibodies). The patient also had extramembranous glomerulopathy associated with this syndrome. Treatment with corticosteroids improved both the neuropathy and glomerulopathy. This case suggests that the spectrum of neuropathy associated with monoclonal gammopathy may be broader than originally believed.

A new type of anti-ganglioside antibodies present in neurological patients

High titers of anti-GA1 antibodies have been associated with neurological syndromes. In most cases, these antibodies cross-react with the structurally related glycolipids GM1 and GD1b, although specific anti-GA1 antibodies have also been reported. The role of specific anti-GA1 antibodies is uncertain since the presence of GA1 in the human nervous system has not been clarified. A rabbit was immunized with GD1a and its sera were screened for antibody reactivity by standard immunoassay methods (HPTLC-immunostaining and ELISA). Anti-GD1a antibodies were not detected but, unexpectedly, anti-GA1 IgG-antibodies were found. Antibody binding to GA1 was inhibited by soluble GA1 but also by GD1a. These results indicate that the rabbit produced antibodies that recognize epitopes present on the glycolipids, that are absent or not exposed on solid phase adsorbed GD1a. We investigated the presence of these unusual anti-ganglioside antibodies in normal and neurological patient sera. Approximately, 10% of normal human sera contained low titer of specific anti-GA1 IgG-antibodies but none of them recognized soluble GD1a. High titers of IgG-antibodies reacting only with GA1 were detected in 12 patient sera out of 325 analyzed. Of these, 6 sera showed binding that was inhibited by soluble GD1a and four of them also by GM1. This new type of anti-ganglioside antibodies should be considered important elements for understanding of the pathogenesis of these diseases as well as their diagnosis.

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.

Transcranial magnetic stimulation in lower motor neuron diseases

OBJECTIVE

To study the diagnostic value of transcranial magnetic stimulation (TMS) in a group of patients with lower motor neuron disease (LMND). Among LMND, several chronic immune mediate motor neuropathies may simulate amyotrophic lateral sclerosis (ALS).

METHODS

Forty patients with LMND were included TMS was performed at the first visit. The patients were seen prospectively every 3 months for a period of 1-4 years.

RESULTS

Three different groups were distinguished at the end of follow-up: (1) ALS group with 7 patients, (2) Pure motor neuropathy with 14 patients and (3) Other LMND including 12 patients with hereditary spinal amyotrophy, 3 patients with Kennedy's disease and 4 patients with post-poliomyelitis. On the basis of the results of TMS variables, 6 out of 7 ALS patients had abnormality of silent period (SP) associated or not with abnormality of excitatory threshold or amplitude ratio. Patients with pure motor neuropathy had normal SP and amplitude ratio. Four out of 14 patients had increased central motor conduction time (CMCT), one had increased CMCT and excitatory threshold, and one patient had a slightly increased excitatory threshold. Considering the abnormality of TMS variables in the groups, SP, excitatory threshold, and amplitude ratio were chosen in a post-hoc attempt to select variables yielding high sensitivity and specificity. The overall sensitivity of TMS for diagnosis of ALS among LMND was 85.7%, its specificity was 93.9%. When only the abnormality of SP was taken into account, the sensitivity was unchanged. But the specificity was improved to 100%.

CONCLUSIONS

TMS helped to distinguish suspected ALS from pure motor neuropathy.

Peripheral nervous system and central nervous system pathology in rapidly progressive lower motor neuron syndrome with immunoglobulin M anti-GM1 ganglioside antibody

Pathological studies, including novel teased peripheral nerve fiber studies, were performed in a patient who presented with a rapidly progressive, lower motor neuron syndrome and high titer of immunoglobulin M anti-GM1 ganglioside antibody. In the central nervous system, there was a severe loss of motor neurons and central chromatolysis with ubiquitin immunopositive cytoplasmic inclusions in residual motor neurons. In the peripheral nervous system, axonal degeneration of myelinated fibers in the anterior nerve roots was evident. Pathologic evidence of sensory nerve involvement was also found despite the absence of clinical or electrophysiological sensory abnormalities. Sectional studies of single myelinated nerve fibers from an antemortem sural nerve biopsy showed remyelination and globular paranodal swellings due to focal complex myelin folding and degeneration in 13% of fibers. Postmortem studies of the sural nerves 4 weeks later showed paranodal demyelination (90% of fibers), but no paranodal swellings and similar findings were present in samples of the ulnar, radial, median, tibial, and common peroneal nerves. Paranodal abnormalities of enlargement of the adaxonal space, myelin degeneration, and axonal compaction were found on cross-sectional studies of individual teased fibers, which on conventional light microscopic assessment appeared normal. These changes suggest a disturbance of paranodal axonal-myelin adhesion due to binding of the anti-GM1 ganglioside antibody to the common epitope known to be present on the myelin sheath and nodal axolemma in the paranodal region of both motor and sensory nerves.

Normally occurring human anti-GM1 immunoglobulin M antibodies and the immune response to bacteria

Anti-GM(1) antibodies of the immunoglobulin M (IgM) isotype are normal components of the antibody repertoire of adult human serum. Using a sensitive high-performance thin-layer chromatography (HPTLC) immunostaining assay, we found that these antibodies were absent in the umbilical vein and children <1 month of age but could be detected after 1 month of age. Although most of the children older than 6 months of age were positive, there were still a few negative children. The appearance of anti-GM(1) IgM antibodies showed a perfect concordance with two well-characterized antibacterial antibodies, anti-Forssman and anti-blood group A, which indicates a similar origin. We also studied IgM reactivity with lipopolysaccharides (LPSs) from gram-negative bacteria isolated from stool samples from healthy babies and from Escherichia coli HB101 in serum from individuals of different ages. We found a positive reaction with both LPSs in all the children more than 1 month of age analyzed, even in those that were negative for anti-GM(1) antibodies. Anti-GM(1) IgM antibodies were purified from adult serum by affinity chromatography and tested for the ability to bind LPSs from different bacteria. This highly specific preparation showed reactivity only with LPS from a strain of Campylobacter jejuni isolated from a patient with diarrhea. We conclude that normally occurring IgM antibodies are generated after birth, probably during the immune defense against specific bacterial strains.

Serum IgM anti-GM1 ganglioside antibodies in lower motor neuron syndromes

Lower motor neuron syndromes (LMNS) are heterogenous conditions, which include patients with progressive lower motor neuron disease (LMND) and cases with the clinical phenotype of motor neuropathy (MN). The aim of this study was to estimate the IgM anti-GM1 ganglioside antibodies titer and the ratio of the light chains in order to define the presence of autoimmunity process in particular cases with LMNS. Twenty-eight patients were diagnosed with LMND and 15 patients were diagnosed with MN (10 patients with multifocal motor neuropathy with conduction block, five patients with MN without conduction block). Total of 103 patients with classical amyotrophic lateral sclerosis (ALS) and 50 healthy, age-matched persons were also tested. The IgM anti-GM1 ganglioside titer and the ratio of lambda/kappa light chains in serum were determined using the ELISA technique. High titer of IgM anti-GM1 antibodies were detected in serum of 46% LMND patients, 80% of MN patients, and 18% of the classical ALS cases. An elevated ratio of lambda/kappa light chains appeared in 18% of LMND patients, and in 67% of the MN cases. The lambda/kappa light chains ratio was normal in all ALS patients. The presence of elevated titer of IgM anti-GM1 ganglioside antibodies and the changed ratio of the light chains supports the presence of autoimmune process in LMNS and may provide clues for their management.

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.

The origin of anti-GM1 antibodies in neuropathies: the "binding site drift" hypothesis

Elevated titers of serum antibodies against GM1-ganglioside are associated with a variety of autoimmune neuropathies. The origin of these autoantibodies is still unknown, although there is evidence that they are produced by CD5+ B-lymphocytes and that antigen mimicry is involved. Anti-GM, IgM-antibodies in the normal human immunological repertoire are low affinity antibodies that cross-react with other glycoconjugates carrying Gal beta1-3GalNAc and probably do not have GM1-mediated biological activity. Other anti-GM1 IgM-antibodies with higher affinity and/or different fine specificity are present in patients with motor syndromes. Based on our studies of structural requirement for binding, we hypothesize that disease-associated anti-GM1 antibodies originate at random by mutations affecting the binding site of naturally-occurring ones. The hypothesis is conceptually similar to the established phenomenon of "genetic drift" in species evolutionary biology and is therefore termed "binding site drift".

Multifocal motor neuropathy and asymptomatic Hashimoto's thyroiditis: first report of an association

Motor neuropathy with multifocal conduction blocks represents a recently identified autoimmune disorder of the peripheral nerve myelin. Association of motor neuropathies or neuronopathies with thyroid disorders, such as hyperthyroidism, hypothyroidism or thyroid neoplasms has been rarely described. We studied a 61-year-old man with a 2-year-history of slowly progressive weakness of the left limbs with atrophy and fasciculations. Nerve conduction velocity studies revealed multifocal motor conduction blocks. Serum IgM titer of antibodies against GM1 was elevated (1:1280; n.v. up to 1:640). Thyroid studies were compatible with Hashimoto's thyroiditis. Therapy with high dose intravenous immunoglobulins was followed by a prompt clinical recovery. Then the disease assumed an intravenous immunoglobulins dependent course with a full clinical, but transient, recovery. This is the first observation of an association of multifocal motor neuropathy with high titers of GM1 and Hashimoto's thyroiditis and reinforces the multifocal motor neuropathy autoimmune origin as well as the repeated clinical recoveries after intravenous immunoglobulins. This case also suggests to deeply investigate the thyroid function in patients with multifocal motor neuropathy.

High affinity as a disease determinant factor in anti-GM(1) antibodies: comparative characterization of experimentally induced vs. disease-associated antibodies

Elevated titers of serum anti-GM(1) antibodies of IgG isotype are found frequently in patients with Guillain-Barré syndrome. Much evidence indicates that these autoantibodies are involved in disease progression, but their exact function and the mechanism of their appearance are still unclear. In an attempt to reproduce "ganglioside syndrome", the experimental model of neuropathy developed by Nagai et al. (Neurosci. Lett. 2 (1976) 107), rabbits were intensively immunized with GM(1) in complete Freund adjuvant (CFA). High titers of anti-GM(1) antibodies were produced, with class switch and affinity maturation indicating an elaborate immune response. Unexpectedly, the rabbits did not show any clinical symptoms of neuropathy. Relatively affinities of both IgM and IgG antibodies were significantly lower than those of similar antibodies from neuropathy patients. These results suggest the existence of a threshold value above which affinity of anti-GM(1) antibodies becomes an important factor in disease induction. The absence of neuropathy symptoms in rabbits may be explained by absence of these high-affinity anti-GM(1) antibodies.

Elevated serum titers of proinflammatory cytokines and CNS autoantibodies in patients with chronic spinal cord injury

This study characterized the proinflammatory cytokines, interleukin-2 (IL-2) and tumor necrosis factor alpha (TNFalpha), the antiinflammatory cytokines, IL-4 and IL-10, autoantibodies specific for GM1 ganglioside (anti-GM1), IgG and IgM, and myelin-associated glycoprotein (anti-MAG), in the sera of infection-free, chronic (>12 months), traumatically injured SCI patients (n = 24). Healthy able-bodied subjects (n = 26) served as controls. The proinflammatory cytokines and anti-GM1 antibodies were of particular interest as they have been implicated in an autoimmune "channelopathy" component to central and peripheral conduction deficits in various chronic neuroinflammatory diseases. Antibody and cytokine titers were established using enzyme-linked immunosorbent assays (ELISA). The mean anti-GM(1) (IgM) titer value for the SCI group was significantly higher (p < 0.05) than controls. The SCI group also demonstrated significantly higher titers (p < 0.05) of IL-2 and TNF alpha than controls. No differences were found between the SCI group and control group mean levels of IL-4 or IL-10. Overall, the serum of 57% of SCI patients contained increased levels of autoantibodies or proinflammatory cytokines relative to control values. These results provide preliminary support for the hypothesis that chronic immunological activation in the periphery occurs in a subpopulation of chronic SCI patients. It remains to be established whether elevated serum titers of proinflammatory cytokines and autoantibodies against GM1 are beneficial to the patients or whether they are surrogate markers of a channelopathy that compounds the neurological impairment associated with traumatic axonopathy or myelinopathy.

Electrodiagnostic approach to the patient with suspected motor neuron disease

The diagnosis of amyotrophic lateral sclerosis (ALS) per se may be challenging since there is no single diagnostic test for ALS (with the exception of finding a mutation in the SOD1 gene). Additionally, the disease may begin focally and resemble a variety of other neurologic disorders that share clinical features with ALS. This latter point emphasizes an important imperative for the clinician--the need to consider a broad range of peripheral and central nervous system disorders in the process of differential diagnosis of ALS, especially when the disease is in its early stages. The authors review the diagnostic criteria for ALS and discuss which features to consider in determining the degree of certainty or level of confidence in the diagnosis. The authors then enumerate the important differential diagnostic possibilities that emerge from a careful consideration of the clinical features and comment on neuroimaging studies and laboratory tests employed in the diagnostic process. Next, the authors turn their attention to the important role played by electrophysiologic studies in the diagnostic evaluation of the patient with suspected ALS. The authors then return to a focused consideration of selected disorders in the differential diagnosis of ALS and conclude with a summary of their diagnostic approach for this disease.

Anti-LM1 antibodies in the sera of patients with Guillain-Barré syndrome, Miller Fisher syndrome, and motor neuron disease

This study is designed to establish whether sialosylneolactotetraosylceramide (LM1), a major component of human peripheral nerve ganglioside, is a potential target antigen for the development of peripheral autoimmune neuropathies such as Guillain-Barré syndrome (GBS) and Miller Fisher syndrome (MFS). Serum antibodies against LM1 in 116 patients with GBS, 56 patients with MFS, 88 patients with motor neuron disease (MND) and 60 normal control subjects were quantified using enzyme-linked immunosorbent assay (ELISA). The presence of anti-LM1 antibodies were confirmed using an immunostaining method on high-performance thin-layer chromatographic plates (HPTLC). Anti-LM1 IgG antibodies were detected in 22% (25/116) of patients with GBS. The ratio of the demyelination type to the axonal type of GBS was approximately 3:1. Among the 25 anti-LM1-positive GBS patients, additional anti-GM1 IgG antibodies were detected in 7 patients, 4 of whom possessed the axonal form of GBS. Anti-LM1 antibodies were also detected in a significant portion of patients with MFS (20%, 11/56). In contrast, anti-LM1 antibodies were detected in only 2% (2/88) of patients with MND, and 7% (4/60) of normal control subjects. The results of this study suggest that serum antibodies against LM1 may have a pathogenic role in the development of GBS and MFS.

Variable patterns of anti-GM(1) IgM-antibody populations defined by affinity and fine specificity in patients with motor syndromes: evidence for their random origin

Elevated titers of serum antibodies against GM(1)-ganglioside are associated with a variety of autoimmune neuropathies. Although much evidence indicates that these autoantibodies play a primary role in the disease processes, the mechanism of their appearance is unclear. Low-affinity anti-GM(1) antibodies of the IgM isotype are part of the normal human immunological repertoire. In patients with motor syndromes, we found that in addition to the usual anti-GM(1) antibodies, the sera contain IgM-antibodies that recognize GM(1) with higher affinity and/or different specificity. This latter type of antibodies was not detected in other autoimmune diseases. We studied the fine specificity of both normal and motor disease-associated antibodies using HPTLC-immunostaining of GM(1) and structurally related glycolipids, soluble antigen binding inhibition, and GM(1) affinity columns. Normal low-affinity anti-GM(1) antibodies cross-react with GA(1) and/or GD(1b). In the motor syndrome patients, different populations of antibodies characterized by their affinity and cross-reactivity were detected. Although one population is relatively common (low affinity, not cross-reacting with GA(1) and GD(1b)), there are remarkably few sera having the same set of populations. These results suggest that the appearance of the new antibody populations is a random process. When the different antibody populations were analyzed in relation to the three-dimensional structure of GM(1), a restricted area of the GM(1) oligosaccharide (the terminal Galbeta1-3GalNAc) was found to be involved in binding of normal anti-GM(1) antibodies. Patient antibodies recognize slightly different areas, including additional regions of the GM(1) molecule such as the NeuNAc residue. We hypothesize that disease-associated antibodies may originate by spontaneous mutation of normal occurring antibodies.

A surface plasmon resonance biosensor assay for measurement of anti-GM(1) antibodies in neuropathy

OBJECTIVE

To develop a rapid assay for the detection and measurement of anti-GM(1) ganglioside antibodies in patients with neuropathy, using a surface plasmon resonance-based biosensor.

BACKGROUND

Elevated levels of anti-GM(1) ganglioside antibodies are observed in patients with acute and chronic motor neuropathies. Assays for detecting anti-GM(1) antibodies in serum are increasingly being used to help the physician in the evaluation of these patients.

METHODS

Antigens were immobilized by adsorption of GM(1) (active) and GM(2) (control) gangliosides onto a dextran-based sensor chip which is in contact with a flow cell carrying the sample. Interaction of specific antibodies directed against GM(1) with the ganglioside-coated sensor chip caused a change in refractive index at the surface of the chip, which was detected by an optical sensor, using the phenomenon of surface plasmon resonance. Sera from patients and healthy individuals were analyzed by the new assay and results were compared with those from ELISA. Anti-GM(1) antibody isotype was identified by using a secondary antibody.

RESULTS

The binding of anti-GM(1) antibodies to the immobilized GM(1) was observed in real time after reference subtraction of the response from GM(2) control. The response was proportional to antibody concentration. The assay exhibited high specificity for sera from patients with multifocal motor neuropathy and Guillain-Barré syndrome with antibodies against GM(1).

CONCLUSIONS

The surface plasmon resonance biosensor assay offers a rapid system for directly measuring antibody levels in serum without the use of any labels, while comparing favorably with the ELISA system in sensitivity and specificity.

Coupling of nerve growth factor to its receptor: inhibition by anti-GM3 ganglioside antibody

1. Normal differentiation of PC 12 cells and dorsal root ganglionic neurons in culture need nerve growth factor (NGF) for their neurite outgrowth. 2. An antibody against GM3 ganglioside was found to inhibit the nerve growth factor mediated neurite formation of both the cells in vitro significantly. 3. Further analysis revealed that the binding of 125I-NGF to live PC 12 cells could be markedly inhibited by anti-GM3 antibody in a dose dependent manner. 4. Scatchard analysis revealed that in the presence of anti-GM3 antibody only some low affinity binding sites were available for NGF-high affinity binding sites were totally blocked. 5. These results further strengthen the hypothesis that anti-GM3 antibody affects neuronal cell growth by interfering with the coupling of growth factors to their cell surface receptors.

Ganglioside agglutination immunoassay for rapid detection of autoantibodies in immune-mediated neuropathy

Elevated levels of serum autoantibodies directed against gangliosides are closely associated with acute and chronic autoimmune neuropathies. An agglutination immunoassay using polystyrene microparticles coated with a total extract of brain gangliosides was used to test patient sera for the presence of anti-ganglioside antibodies. Results were compared with those obtained by ELISA for anti-GM1 and anti-GQ1b ganglioside antibodies. Eight of the twelve sera from patients with multifocal motor neuropathy and seven of the thirteen sera from patients with Guillain-Barré syndrome were positive for the presence of anti-ganglioside antibodies by the ganglioside agglutination immunoassay. The assay compared favorably with the ELISA system in sensitivity and specificity, while requiring a fraction of the time and cost to perform. The new assay can serve as a rapid and effective method for detecting or screening for anti-ganglioside antibodies in patients with acute or chronic immune-mediated neuropathies. It would be particularly useful for detecting antibodies that react with multiple gangliosides, or with minor or as yet uncharacterized gangliosides.

Identification of Gal(beta 1-3)GalNAc bearing glycoproteins in cerebrospinal fluid of amyotrophic lateral sclerosis (ALS) patients

Glycoproteins in cerebrospinal fluid of 55 patients with amyotrophic lateral sclerosis (ALS), six disease controls (multifocal motor neuropathy, sensorimotor neuropathy, Guillain-Barré syndrome, spinal muscular atrophy type II, motor neuropathy with monoclonal gammopathy) and 20 healthy controls were separated by PAGE electrophoresis and then detected immunochemically with peanut agglutinin (PNA). In 36 amyotrophic lateral sclerosis patients the 262 kDa glycoprotein was significantly increased (over the normal mean +/- SD x 2), which was associated with a decrease in the 114 kDa fraction. In the remaining patients, both fractions were either equal in concentration or the 114 kDa glycoprotein predominated. In normal cerebrospinal fluid, the 114 kDa glycoprotein predominated over the other glycoproteins. The total amount of separated glycoproteins was increased in 15 amyotrophic lateral sclerosis patients. In 12 of them it was followed by an increase in the percentage of the 262 kDa glycoprotein. There was no correlation between the content of the peanut agglutinin-labelled glycoproteins and the patients' age, duration and severity of the disease. There was a correlation between the 262 kDa glycoprotein being increased in cerebrospinal fluid and the electrophysiological pattern of denervation seen in electromyographic study. The glycoproteins change, similar to that occurring in amyotrophic lateral sclerosis patients, was also observed in one case of multifocal motor neuropathy (MMN). We suggest that in amyotrophic lateral sclerosis and multifocal motor neuropathy, the peanut agglutinin-labelled glycoproteins are released in excess from the nervous tissues into the cerebrospinal fluid as a result of neuronal degeneration. The question to be answered is, whether the released glycoproteins are becoming targets for auto-antibodies.

Normal human plasma contains antibodies that specifically block neuropathy-associated human anti-GM1 IgG-antibodies

Intravenous immunoglobulin (IVIg) is used in the treatment of a variety of autoimmune diseases. The blocking of disease-associated antibodies by anti-idiotype antibodies present in IVIg has been proposed as an action mechanism. Anti-GM1 antibodies have been implicated in motor neuropathies. Although IVIg is frequently applied for these diseases, the presence in IVIg or in human plasma of anti-idiotype antibodies that recognize anti-GM1 antibodies has not been clearly demonstrated. Here we present evidence that normal human plasma contains antibodies that inhibit the binding of anti-GM1 IgG-antibodies from neuropathy patients but do not inhibit anti-GM1 IgG-antibodies of rabbit origin with the same fine specificity. The significance of these findings in the course of acute and chronic neuropathies is discussed.

Bilateral phrenic neuropathy as a presenting feature of multifocal motor neuropathy with conduction block

Diaphragmatic paralysis has previously been reported as a result of diverse pathologic processes involving the peripheral nervous system. We report the clinical history, physical findings, and antibody profile of an atypical case of multifocal motor neuropathy with conduction block initially presenting with respiratory failure secondary to bilateral phrenic neuropathy.

Immunochemical quantification of glycoconjugates in serum and cerebrospinal fluid of amyotrophic lateral sclerosis patients

Glycoconjugates in the serum of 73 patients with amyotrophic lateral sclerosis (ALS), 21 cases of other motor neuron diseases and 20 healthy controls were determined. Cerebrospinal fluid (CSF) was studied in 64, 7 and 10 of these subjects, respectively. The level of sialic acid containing glycoconjugates, detected by Maakia amurensis agglutinin (MAA), was decreased in the serum of 61.6% of the ALS patients, while in the CSF it was decreased, on average, in 75% of these cases. Only in single ALS cases was the concentration of these glycoconjugates increased. There was no correlation between the content of MAA-labelled glycoconjugates both in serum and CSF and the titre of sialic acid containing anti-GM1 gangliosides. The glycoconjugates, detected by peanut agglutinin (PNA) which recognizes the disaccharide galactose beta(1-3)N- acetylgalactosamine (GGN), were decreased in the serum of 78.1% of ALS patients, while in CSF they were increased in 54.7% of these cases. There was no correlation between the concentration of PNA-labelled glycoconjugates both in serum and CSF as well as the titre of antibodies against GGN-containing anti-GM1 and anti- AGM1 gangliosides. Changes in the level of the MAA- and PNA- labelled glycoconjugates, as well as the titre of anti-GM1 and anti-AGM1 gangliosides antibodies were not specific for ALS. They were also observed in some cases of other motor neuron diseases. The low level of the lectin-labelled glycoconjugates in serum and partly in CSF of the majority of ALS patients is possibly the consequence of their accelerated clearance and/or specific inactivation by the formation of immune complexes or epitope binding. Degeneration of neurons and muscle cells could also be responsible. The relatively low incidence of high anti- glycolipids antibodies titre may be, at least partly, connected with the low concentration of the appropriate antigens. The increased content of PNA-labelled glycoconjugates in the CSF of the majority of ALS patients, together with the low incidence of high titre of antibodies against the appropriate glycolipids, could indicate that in CSF this lectin binds to the GGN epitope of glycoproteins rather than to the GGN epitope of glycolipids.

Rabbit experimental sensory ataxic neuropathy: anti-GD1b antibody-mediated trkC downregulation of dorsal root ganglia neurons

We previously reported experimental sensory neuropathy in rabbit induced by the immunization of ganglioside GD1b. The major pathological change in diseased rabbits was degeneration of primary sensory neurons with central axons extending to the dorsal column of the spinal cord. The loss of primary sensory neurons that mediate proprioceptive sensation prompted us to investigate the expression of trkC in dorsal root ganglia (DRG) because this type of neuron is thought depend mainly on neurotrophin-3-mediated trkC signaling. Northern blotting analysis revealed markedly reduced expression of trkC in DRG of diseased rabbits in acute phase. This result together with the absence of lymphocytic infiltration in DRG of diseased rabbits at any stage suggests the anti-GD1b antibody-mediated downregulation of trkC expression could be one of the pathogenesis of this experimental sensory ataxic neuropathy.

Chronic motor axonal neuropathy: pathological evidence of inflammatory polyradiculoneuropathy

Chronic immune and inflammatory motor neuropathies may resemble motor neuron disease, and the distinction may be particularly difficult if conduction block or GM1 antibodies are absent. The pathology of this axonal type of chronic motor neuropathy has not been characterized except in a few cases associated with paraproteinemia. We describe the clinical, electrophysiological, and pathological findings in a patient with a chronic motor axonal neuropathy, normal immunoelectrophoresis, and no GM1 antibodies. At autopsy the spinal cord was normal with the exception of chromatolytic motor neurons. All the ventral roots were greatly thinned. Of 10 mixed nerves and numerous spinal roots sampled, five showed areas of perineurial, perivascular lymphocytic infiltration. There was severe axonal loss in the motor roots that was not as evident in mixed nerves, and the sensory nerves and roots were virtually unaffected. Our findings suggest that a chronic motor axonal neuropathy without paraproteinemia or GM1 antibodies may, in some cases, result from an inflammatory process.

Antiglycosphingolipid immune responses in neurology. The Vienna experience with isotypes, subclasses, and disease

IgM, IgG, IgA, and IgG subclass anti-GM1, anti-GQ1b, and anti-asialo-GM1 (anti-GA1) antibodies, respectively, were investigated by ELISA in serum from neurological and other patients. Increased anti-GM1 occurred mostly in approximately 15-35% of the cases without statistical differences; high percentages were found in Guillain-Barré syndrome (GBS) preceded by gastrointestinal infection and multifocal motor neuropathy. Roughly, IgM anti-GM1 was most frequent; however, distinct IgG and IgA reactions were found i.a. in GBS. A particular IgM anti-mono- and disialoganglioside pattern occurred in a patient with sensorimotor neuropathy and paraproteinemia. Anti-GQ1b was elevated in all Miller-Fisher patients, with some prevalence of IgG2 among IgG subclasses. Cross-reactivity of anti-GQ1b was demonstrated with Campylobacter jejuni lipopolysaccharides. Increased anti-GM1 and/or anti-GA1 was more frequent in systemic lupus erythematosus with central nervous system involvement than without. Incidence of anti-GM1 and anti-GA1 in X-adrenoleukodystrophy was relatively high. Although anti-GSL antibodies seem to have limited diagnostic value, studies of isotypes, subclass patterns, and cross-reactivities may lead to further insight into the origin of (auto) immune responses and their immunepathogenetic role in disease.

Gangliosides and glycosphingolipids of peripheral nervous system myelins--a minireview

A summary is provided of the available data on the composition of gangliosides and glycosphingolipids in the peripheral nervous system (PNS) including myelins and their antigenic properties. The composition of gangliosides and glycosphingolipids in the PNS is very different from that in the central nervous system (CNS), both quantitatively and qualitatively. One major difference is the abundance of neolacto-series gangliosides in the PNS, with the backbone structure Gal beta 1-4GlcNAc beta1-3Gal beta 1-4Glc1-1'Cer. Their abundance contrasts with the abundance of ganglio-series gangliosides in the CNS. The neolacto-series gangliosides are localized mainly in the myelins of the PNS. In addition to gangliosides, other acidic and neutral glycosphingolipids in the neolactoseries are also characteristic of the myelins of the PNS. The ceramide (fatty acid and sphingosine base) compositions of gangliosides in the PNS are different from those in the CNS gangliosides, having greater percentages of long-chain fatty acids and dehydrosphingosines than found in the CNS gangliosides.

Chorea-acanthocytosis with polyclonal antibodies to ganglioside GM1

A patient with chorea-acanthocytosis presenting with axonal neuropathy showed an elevation in IgM polyclonal antibodies to the GM1 ganglioside, which were estimated by enzyme-linked immunosorbent assay and complement-mediated liposome immune lysis assay (LILA). This is the first demonstration of such antibodies in chorea-acanthocytosis. Anti-GM1 antibodies might have directly caused the axonal neuropathy by binding to GM1 or cross-reactive antigens in the nerves.

Antibody panels in idiopathic polyneuropathy and motor neuron disease

We prospectively evaluated patients with idiopathic polyneuropathy (PN) and motor neuron disease (MND) with commercial antibody (Ab) panels. Patients with sensorimotor PN received a "sensorimotor neuropathy profile" [3-sulfated glucuronyl paragloboside (SGPG)/myelin-associated glycoprotein (MAG), GM1, asialo-GM1, GD1b, Hu, sulfatide]. Motor neuropathy or MND patients underwent a "motor neuropathy profile" (SGPG/MAG, GM1, asialo-GM1). Seven of 78 patients (9.0%) with sensorimotor PN and 3 of 44 patients (6.8%) with MND had abnormal panels. None of 60 patients with axonal sensory or sensorimotor PN had antisulfatide Ab. Seven of 13 patients (54%) with multifocal motor neuropathy had abnormal panels, with 6 seropositive to GM1. We found abnormal Ab panels in fewer than 10% of patients with idiopathic sensorimotor PN and MND. Moreover, abnormal Ab tests often did not relate to the clinical context. Our data do not support the use of commercial Ab panels in the evaluation of patients with idiopathic PN or MND.

Isolation and culture of bovine endothelial cells of endoneurial origin

Penetration of immunoglobulins and/or migration of activated lymphocytes into peripheral nervous system (PNS) parenchyma are the initial key steps to develop immunological disorders of PNS including Guillain-Barré syndrome, IgM neuropathy and chronic inflammatory demyelinating polyradiculoneuropathy. Hence, it is important to know the cellular property of endothelial cells of endoneurial tissue origin (PnMEC) because these cells constitute the bulk of the blood-nerve barrier (BNB). For this purpose, we developed a method to isolate and culture pure populations of PnMECs from bovine cauda equina. PnMECs were identified by their cobblestone appearance, immunoreactivity against Factor VIII/von Willebrand factor (vWF) antigen, and positive uptake of DiI-Ac-LDL. The glucose transporter type 1 (GLUT1) expression of these cells was rapidly down-regulated in vitro. Other than GM3(NeuAc) and GM3(NeuGc) as major glycosphingolipids, PnMECs comprise GM1, GD1a, GD1b and GT1b, which are shared by PNS parenchyma, and sialyl lactosaminyl paragloboside (SLPG) as minor species. Because bovine PnMECs proliferate rapidly and a large mass of cells could be obtained, this method should contribute to the biochemical analysis of surface molecules in PnMECs that might play a key role in the formation of BNB as well as in pathological conditions involving the PNS.