Pathogenesis of axonal Guillain-Barré syndrome: hypothesis

Axonal pathology in early stages of Guillain-Barré syndrome

INTRODUCTION

Guillain-Barré syndrome (GBS) is an acute-onset, immune-mediated disease of the peripheral nervous system. It may be classified into 2 main subtypes: demyelinating (AIDP) and axonal (AMAN). This study aims to analyse the mechanisms of axonal damage in the early stages of GBS (within 10 days of onset).

DEVELOPMENT

We analysed histological, electrophysiological, and imaging findings from patients with AIDP and AMAN, and compared them to those of an animal model of myelin P2 protein-induced experimental allergic neuritis. Inflammatory oedema of the spinal nerve roots and spinal nerves is the initial lesion in GBS. The spinal nerves of patients with fatal AIDP may show ischaemic lesions in the endoneurium, which suggests that endoneurial inflammation may increase endoneurial fluid pressure, reducing transperineurial blood flow, potentially leading to conduction failure and eventually to axonal degeneration. In patients with AMAN associated with anti-ganglioside antibodies, nerve conduction block secondary to nodal sodium channel dysfunction may affect the proximal, intermediate, and distal nerve trunks. In addition to the mechanisms involved in AIDP, active axonal degeneration in AMAN may be associated with nodal axolemma disruption caused by anti-ganglioside antibodies.

CONCLUSION

Inflammatory oedema of the proximal nerve trunks can be observed in early stages of GBS, and it may cause nerve conduction failure and active axonal degeneration.

Axonal pathology in early stages of Guillain-Barré syndrome

INTRODUCTION

Guillain-Barré syndrome (GBS) is an acute-onset, immune-mediated disease of the peripheral nervous system. It may be classified into 2 main subtypes: demyelinating (AIDP) and axonal (AMAN). This study aims to analyse the mechanisms of axonal damage in the early stages of GBS (within 10days of onset).

DEVELOPMENT

We analysed histological, electrophysiological, and imaging findings from patients with AIDP and AMAN, and compared them to those of an animal model of myelin P2 protein-induced experimental allergic neuritis. Inflammatory oedema of the spinal nerve roots and spinal nerves is the initial lesion in GBS. The spinal nerves of patients with fatal AIDP may show ischaemic lesions in the endoneurium, which suggests that endoneurial inflammation may increase endoneurial fluid pressure, reducing transperineurial blood flow, potentially leading to conduction failure and eventually to axonal degeneration. In patients with AMAN associated with anti-ganglioside antibodies, nerve conduction block secondary to nodal sodium channel dysfunction may affect the proximal, intermediate, and distal nerve trunks. In addition to the mechanisms involved in AIDP, active axonal degeneration in AMAN may be associated with nodal axolemma disruption caused by anti-ganglioside antibodies.

CONCLUSION

Inflammatory oedema of the proximal nerve trunks can be observed in early stages of GBS, and it may cause nerve conduction failure and active axonal degeneration.

Axonal degeneration in Guillain-Barré syndrome: a reappraisal

The aim of this review was to analyse the pathophysiology of axonal degeneration in Guillain-Barré syndrome (GBS) with emphasis on early stages (≤ 10 days after onset). An overview of experimental autoimmune neuritis (EAN) models is provided. Originally GBS and acute inflammatory demyelinating polyneuropathy were equated, presence of axonal degeneration being attributed to a "bystander" effect. Afterwards, primary axonal GBS forms were reported, designated as acute motor axonal neuropathy/acute motor-sensory axonal neuropathy. Revision of the first pathological description of axonal GBS indicates the coexistence of active axonal degeneration and demyelination in spinal roots, and pure Wallerian-like degeneration in peripheral nerve trunks. Nerve conduction studies are essential for syndrome subtyping, though their sensitivity is scanty in early GBS. Serum markers of axonal degeneration include increased levels of neurofilament light chain and presence of anti-ganglioside reactivity. According to nerve ultrasonographic features and autopsy studies, ventral rami of spinal nerves are a hotspot in early GBS. In P₂-induced EAN models, the initial pathogenic change is inflammatory oedema of spinal roots and sciatic nerve, which is followed by demyelination, and Wallerian-like degeneration in nerve trunks possessing epi-perineurium; a critical elevation of endoneurial fluid pressure is a pre-requisite for inducing ischemic axonal degeneration. Similar lesion topography may occur in GBS. The repairing role of adaxonal Schwann cytoplasm in axonal degeneration is analysed. A novel pathophysiological mechanism for nerve trunk pain in GBS, including pure motor forms, is provided. The potential therapeutic role of intravenous boluses of methylprednisolone for early severe GBS and intractable pain is argued.

Review: Molecular mimicry of host structures by lipopolysaccharides of Campylobacter and Helicobacter spp.: implications in pathogenesis

Molecular mimicry of host structures by the saccharide portion of lipopolysaccharide (LPS) contributes to the virulence of certain strains of mucosal pathogens. Mimicry by the low molecular weight (low-Mr) LPSs of Neisseria and Haemophilus spp. have been the most extensively studied. However, studies within the last decade have revealed other types of mimicry within the saccharide moieties of LPSs of the enteric pathogen Campylobacter jejuni and the gastroduodenal pathogen Helicobacter pylori. The core oligosaccharides of low-Mr LPSs of C. jejuni serotypes which are associated with the development of Guillain-Barré syndrome (GBS), a neurological disorder, exhibit mimicry of gangliosides. Cross-reactive antibodies between LPSs and gangliosides which are induced during antecedent C. jejuni infection are considered to play an important role in GBS pathogenesis. The O-polysaccharide chains of high-Mr LPSs of a number of H. pylori strains mimic Lewisx and/or Lewisy blood group antigens. This mimicry may camouflage the bacterium in the gastric mucosa upon initial infection. With the progression of infection, the mimicry may play a role in immune response regulation and the induction of autoantibodies against the gastric proton pump, a glycoprotein that also expresses Lewis antigens.

Antibody cross-reactivities between gangliosides and lipopolysaccharides of Campylobacter jejuni serotypes associated with Guillain-Barré syndrome

Ganglioside-antibodies produced subsequent to Campylobacter jejuni infection may play a role in the pathogenesis of the neurological disorder Guillain-Barré syndrome (GBS). Since lipopolysaccharides (LPS) of certain C. jejuni serotypes associated with GBS (O:2, O:4, O:19) exhibit structural mimicry of gangliosides in their core oligosaccharides, we investigated antibody and ligand cross-reactivities between gangliosides and LPS of these C. jejuni serotypes. GM1-antibody reacted with O:19 LPS reflecting GM1 mimicry by the O:19 core oligosaccharide. On the other hand, asialoGM1-antibody bound to O:2 and O:19 LPS indicating a shared epitope not dependent on ganglioside mimicry. Serum IgA from GBS patients after C. jejuni infection reacted with gangliosides, predominantly GM1, and LPS of all three serotypes. Cholera toxin (GM1 ligand) recognized O:4 and O:19 LPS, whereas peanut agglutinin (Galβ1-3GalNAc ligand) recognized LPS of all three serotypes, thereby confirming structural mimicry. These results suggest that LPS from certain C. jejuni strains may function as cross-reactive antigens for anti-ganglioside B cells.

Association of NOD1 and NOD2 polymorphisms with Guillain-Barré syndrome in Northern Indian population

BACKGROUND

Nucleotide oligomerization domain (NOD) proteins are cytosolic pattern recognition receptors that respond to bacterial substrate and induce NF-κB activation in host. Association of NOD polymorphisms have been studied in many autoimmune disorders, however its role in Guillain-Barré syndrome (GBS) remains unknown. We have investigated NOD1 Glu266Lys and NOD2 (Arg702Trp and Gly908Arg) gene polymorphisms among patients with GBS.

MATERIALS AND METHOD

Polymorphisms in NOD-1 (Glu266Lys) and NOD-2 (Arg702Trp and Gly908Arg) genes were studied using polymerase chain reaction-restriction fragment length polymorphism in 105 patients with GBS and 100 healthy controls.

RESULTS

Homozygous genotype (Lys/Lys) of NOD1 was significantly associated with GBS (p=0.013); and its subtypes viz. acute motor axonal neuropathy (AMAN) and acute inflammatory demyelinating polyneuropathy (AIDP) (p=0.008 and p=0.024 respectively) than controls. In NOD2 (Arg702Trp and Gly908Arg) polymorphisms, only heterozygous genotype (Arg/Trp and Gly/Arg) showed significant association with GBS (p=0.001 and p=0.01 respectively); subtypes AMAN, acute motor-sensory axonal neuropathy (AMSAN) and AIDP showed association with heterozygote Arg702Trp (p=0.001; p=0.029 and p=0.001 respectively) whereas only AIDP was associated with heterozygote genotype Gly908Arg (p=0.003).

CONCLUSION

NOD1 (Glu266Lys) and NOD2 (Arg702Trp and Gly908Arg) polymorphisms were associated with an increased susceptibility to GBS. These polymorphisms could be genetic marker to GBS susceptibility.

Role of Campylobacter jejuni infection in the pathogenesis of Guillain-Barré syndrome: an update

Our current knowledge on Campylobacter jejuni infections in humans has progressively increased over the past few decades. Infection with C. jejuni is the most common cause of bacterial gastroenteritis, sometimes surpassing other infections due to Salmonella, Shigella, and Escherichia coli. Most infections are acquired due to consumption of raw or undercooked poultry, unpasteurized milk, and contaminated water. After developing the diagnostic methods to detect C. jejuni, the possibility to identify the association of its infection with new diseases has been increased. After the successful isolation of C. jejuni, reports have been published citing the occurrence of GBS following C. jejuni infection. Thus, C. jejuni is now considered as a major triggering agent of GBS. Molecular mimicry between sialylated lipooligosaccharide structures on the cell envelope of these bacteria and ganglioside epitopes on the human nerves that generates cross-reactive immune response results in autoimmune-driven nerve damage. Though C. jejuni is associated with several pathologic forms of GBS, axonal subtypes following C. jejuni infection may be more severe. Ample amount of existing data covers a large spectrum of GBS; however, the studies on C. jejuni-associated GBS are still inconclusive. Therefore, this review provides an update on the C. jejuni infections engaged in the pathogenesis of GBS.

Immunoreactivity of glycoproteins isolated from human peripheral nerve and Campylobacter jejuni (O:19)

Objective:

Antibodies to ganglioside GM1 are associated with Guillain-Barré Syndrome (GBS) in patients with serologic evidence of a preceding infection with Campylobacter jejuni. Molecular mimicry between C. jejuni Lipopolysaccharide (LPS) and ganglioside GM1 has been proven to be the immunopathogenic mechanism of the disease in the axonal variant of GBS. GM1-positive sera cross-react with several Gal-GalNAc-bearing glycoproteins from the human peripheral nerve and C. jejuni (O:19). This study aimed to examine the immunoreactivity of the digested cross-reactive glycoproteins isolated from the human peripheral nerve and C. jejuni (O:19) with Peanut Agglutinin (PNA) as a marker for the Gal-GalNAc determinant, and with sera from patients with GBS.

Materials and Methods:

For this purpose, the cross-reactive glycoproteins from peripheral nerve and C. jejuni (O:19) were enzymatically digested with trypsin and the obtained peptides were incubated with PNA and GBS sera.

Results:

Western blot analysis of the separated peptides revealed several bands showing positive reactivity to PNA and to sera from patients with GBS, present in both digests from peripheral nerve and C. jejuni (O:19).

Conclusions:

These data indicate the possible molecular mimicry between the cross-reactive glycoproteins present in C. jejuni and human peripheral nerve and its potential role in the development of GBS following infection with C. jejuni (O:19).

Improved serological diagnosis stresses the major role of Campylobacter jejuni in triggering Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is a postinfectious autoimmune polyradiculoneuropathy. The most frequent antecedent pathogen is Campylobacter jejuni, followed by cytomegalovirus. However, more than 40% of GBS cases currently cannot be attributed to triggering events. This might be due to the shortcomings of the serological assays used for diagnosing infections, in particular for C. jejuni. In our study investigating 36 patients with acute GBS, standard serological methods identified the triggering viral or bacterial etiology in only 25% of cases. However, using a highly specific enzyme-linked immunosorbent assay based on two recombinant outer antigens encoded by C. jejuni genes Cj0017 (P39) and Cj0113 (P18), we found serological evidence of a preceding C. jejuni infection in 80.6% of the patients but in only 3.5% of the controls. We conclude that the role of C. jejuni in triggering GBS has been greatly underestimated.

Detection of preceding Campylobacter jejuni infection by polymerase chain reaction in patients with Guillain-Barré syndrome

Based on culture and serological evidence, a strong association between Campylobacter jejuni infection and Gullain-Barré syndrome (GBS) has been established. However, culture underestimates C. jejuni infection in GBS and the specificity of serology remains uncertain. Thus, a direct sensitive detection method for recent C. jejuni infection is required. We used the PCR technique in GBS patients to assess its role in the diagnosis of C. jejuni infection. From June 2001 to March 2003, stool specimens from 42 patients with GBS and an equal number of age- and gender-matched healthy controls were analysed for C. jejuni infection by culture and PCR. Gullain-Barré syndrome subtypes were classified by clinical and electrophysiological studies. Of the GBS patients, two (4.8%) and eight (19%) were positive by culture and PCR, respectively, and the difference was significant (P < 0.05). None of the controls were positive for C. jejuni by culture or PCR. All C. jejuni-positive GBS patients had axonal degeneration with or without sensory involvement. The incidence of C. jejuni-associated GBS cases was more frequent during summer than winter (7/19, 36.8% vs. 1/23, 4.3%, P < 0.01). Polymerase chain reaction appears to be a sensitive tool to detect preceding C. jejuni infection in GBS patients.

Axonal Guillain-Barré syndrome: a critical review

Axonal Guillain-Barré Syndrome (GBS) was first described by Feasby et al. in 1986, challenging the existent notion of GBS being a primarily demyelinating disease. The severe course and slow recovery commonly seen in these patients was ascribed to axonal degeneration. Other authors challenged this claim on several grounds. Amidst these controversies, epidemics of a similar illness were reported from China, which were given the acronym AMAN, having exclusive motor involvement in contrast to the cases already described in which both motor and sensory involvement were present (AMSAN). Pathologically, Wallerian degeneration, minimal lymphocytic response, absent demyelination or inflammation and periaxonal macrophages are prominent features. Ultrastructural studies have revealed node of Ranvier to be the prime target of immune attack. A frequent occurrence of antecedent Campylobacter jejuni infection and a strong association between elevated titres of IgG GM1 and axonal GBS on a background of preceding C. jejunii infection has been observed and molecular mimicry between lipopolysaccharides of C. jejuni and neural epitopes has been proposed as a mechanism of injury. Clinically axonal variant is similar to AIDP, but a more severe course, with frequent respiratory involvement, ventilator dependence and significant residue may be seen. Diagnosis is essentially electrophysiological. Treatment is similar to AIDP, preferential benefit of either IVIG or plasmapheresis needs to be further evaluated. A critical review of existing literature in axonal GBS is presented.

Development of an immunoassay for rapid detection of ganglioside GM(1) mimicry in Campylobacter jejuni strains

Mimicry of peripheral nerve gangliosides by Campylobacter jejuni lipopolysaccharides (LPSs) has been proposed to induce cross-reacting antiganglioside antibodies in Guillain-Barré syndrome (GBS). Because current methods for LPS characterization are labor-intensive and inhibit the screening of large numbers of strains, a rapid GM(1) epitope screening assay was developed. Biomass from two agar plates of confluent growth yielded sufficient LPS using a novel phenol-water and ether extraction procedure. Extracts of LPS were reacted with cholera toxin (GM(1) ligand), peanut agglutinin (Gal beta1-->3GalNAc ligand), and anti-GM(1) antibodies. After the assay was validated, 12 of 59 (20%) C. jejuni serostrains, including four serotypes that have not previously been associated with GBS, reacted with two or more anti-GM(1) ganglioside reagents. Subsequently, LPS extracts from 5 of 7 (71%) C. jejuni isolates and 2 of 3 (67%) C. jejuni culture collection strains bore GM(1) structures. Overall, the assay system was reliable, efficient, and reproducible and may be adapted for large-scale epidemiological studies.

Guillain-Barré syndrome

The concepts of Guillain-Barré syndrome have changed substantially over the last 10 years, and the last 2 years have been no exception. Guillain-Barré syndrome is now recognized as a heterogeneous disorder with many clinical manifestations. Most current investigations are centered on the hypothesis of molecular mimicry. The major challenge now is to identify the precise mechanisms of nerve fiber injury and to determine how to prevent immune injury.

Lipopolysaccharides from Campylobacter jejuni O:41 strains associated with Guillain-Barré syndrome exhibit mimicry of GM1 ganglioside

Three Campylobacter jejuni, biotype 2, serotype O:41 strains that were isolated from patients who developed Guillain-Barré syndrome (GBS) and one C. jejuni isolate from a patient who developed enteritis only were examined. The aim of the study was to determine the structure of the core oligosaccharide (OS) of the lipopolysaccharide (LPS) of C. jejuni serotype O:41, a serotype rarely associated with the development of GBS, and to determine if the LPS shares similar epitopes with any of the major human gangliosides. Electrophoretic analysis with silver staining or immunoblotting demonstrated that the strains had LPS profiles characteristic of low-molecular-weight LPS. Colorimetric analysis detected N-acetylneuraminic (sialic) acid in the core OSs of all the strains. Thin-layer chromatography with immunostaining showed that antisera raised against the GBS strains reacted with the GM1 ganglioside, suggesting that C. jejuni serotype O:41 LPSs and the GM1 ganglioside have similar epitopes. Furthermore, polyclonal anti-GM1 and anti-asialoGM1 antibodies cross-reacted with each C. jejuni O:41 LPS tested, suggesting that the serotype O:41 core OS has a GM1- and asialoGM1-like structure. LPSs extracted from C. jejuni serostrains O:2, O:3, and O:19 were also used in the study. Cholera toxin (a GM1 ligand) and peanut agglutinin (a Galbeta1-3GalNAc ligand) recognized all serotype O:41 LPSs and the serostrain O:2 LPS. Immunoadsorption results confirmed GM1 relatedness. Moreover, the core OS was isolated from a GBS-associated C. jejuni O:41 LPS by gel permeation chromatography. An analysis by gas-liquid chromatography (GLC), GLC-mass spectrometry, and nuclear magnetic resonance showed the core OS of one of the C. jejuni O:41 GBS isolates to have a tetrasaccharide structure consistent with GM1 mimicry.

Microtiter assay for detecting Campylobacter spp. and Helicobacter pylori with surface gangliosides which bind cholera toxin

Campylobacter jejuni with Gm1 ganglioside in the core of its lipopolysaccharide has been associated with Guillain-Barré syndrome. Since this epitope may be of considerable pathophysiologic importance and since this ganglioside binds cholera toxin, a rapid screening assay to detect bacteria that bind cholera toxin as an indication of Gm1 on their surfaces was developed. In the assay, bacterial lawns were grown on agar plates, harvested with phosphate-buffered saline, boiled, and incubated with a standard concentration of cholera B subunit. Preparations from strains with Gm1 were observed to inhibit the binding of cholera B subunit to Gm1 in a microtiter enzyme-linked immunosorbent assay. By using this assay with two groups of strains, 37 positive strains were detected among the 197 tested. Species with positive isolates included C. jejuni, Campylobacter coli, and Helicobacter pylori. The assay is capable of testing large numbers of isolates and should prove useful in future clinical and epidemiological studies of bacteria with this epitope.

Campylobacter species and Guillain-Barré syndrome

Since the eradication of polio in most parts of the world, Guillain-Barré syndrome (GBS) has become the most common cause of acute flaccid paralysis. GBS is an autoimmune disorder of the peripheral nervous system characterized by weakness, usually symmetrical, evolving over a period of several days or more. Since laboratories began to isolate Campylobacter species from stool specimens some 20 years ago, there have been many reports of GBS following Campylobacter infection. Only during the past few years has strong evidence supporting this association developed. Campylobacter infection is now known as the single most identifiable antecedent infection associated with the development of GBS. Campylobacter is thought to cause this autoimmune disease through a mechanism called molecular mimicry, whereby Campylobacter contains ganglioside-like epitopes in the lipopolysaccharide moiety that elicit autoantibodies reacting with peripheral nerve targets. Campylobacter is associated with several pathologic forms of GBS, including the demyelinating (acute inflammatory demyelinating polyneuropathy) and axonal (acute motor axonal neuropathy) forms. Different strains of Campylobacter as well as host factors likely play an important role in determining who develops GBS as well as the nerve targets for the host immune attack of peripheral nerves. The purpose of this review is to summarize our current knowledge about the clinical, epidemiological, pathogenetic, and laboratory aspects of campylobacter-associated GBS.

Guillain-Barré syndrome and Fisher's syndrome following Campylobacter jejuni infection

The patients with Guillain-Barré Syndrome (GBS) subsequent to Campylobacter jejuni enteritis showed axonal degeneration and had IgG anti-GM1 antibody. The most frequently isolated C. jejuni from the patients was specific serotype of Penner's 19 in Japan. In the lipopolysaccharide (LPS) in C. jejuni of this serotype, the same oligosaccharide structure as GM1 ganglioside existed, suggesting the molecular mimicry between GM1 in nervous tissue and C. jejuni LPS. IgG anti-GM1 antibody may bind the nodes of Ranvier and axon terminals and causes degeneration of the motor axon. Some patients develop Fisher's syndrome following C. jejuni infection. C. jejuni strains from the patients who had IgG anti-GQ1b antibody in the acute phase had GQ1b epitope in their LPS, and the molecular mimicry between GQ1b in nervous tissue and an antecedent infectious agent was clarified.

Human autoimmune neuropathies

Peripheral nerve diseases are among the most prevalent disorders of the nervous system. Because of the accessibility of the peripheral nervous system (PNS) to direct physiological and pathological study, neuropathies have traditionally played a unique role in developing our understanding of basic mechanism of nervous system injury and repair. At present they are providing new insight into the mechanisms of immune injury to the nervous system. A rapidly growing catalogue of PNS disorders are now suspected to be immune-mediated, and in the best understood of these disorders, the molecular and cellular targets of immune attack are known, and the pathophysiology follows directly from the specific immune injury. This review summarizes the immunologically relevant features of the PNS, then considers selected immune-mediated neuropathies, focusing on pathogenetic mechanisms. Finally, the PNS is providing a testing ground for new immunotherapies and approaches to protection and regeneration, including the use of trophic factors. The current status of treatment and implications for future approaches is reviewed.

Guillain-Barré syndrome. A severe case calling for intensive treatment

Guillain-Barré syndrome is a relatively common disease with a low mortality rate. Early recognition and institution of treatment lead to a more favorable outcome, especially in more severe cases. Because the patient's condition may deteriorate rapidly, it is crucial to keep the patient in the hospital until his or her condition is confirmed to be stable. Plasmapheresis improves symptoms when instituted within 2 weeks of symptom onset. Treatment with high-dose intravenous immune globulin produces similar results. Speed of recovery varies, but often occurs in a few weeks or months.

Molecular mimicry of host structures by bacterial lipopolysaccharides and its contribution to disease

The core oligosaccharides of low-molecular-weight lipopolysaccharide (LPS), also termed lipooligosaccharide (LOS), of pathogenic Neisseria spp. mimic the carbohydrate moieties of glycosphingolipids present on human cells. Such mimicry may serve to camouflage the bacterial surface from the host. The LOS component is antigenically and/or chemically identical to lactoneoseries glycosphingolipids and can become sialylated in Neisseria gonorrhoeae when the bacterium is grown in the presence of cytidine 5'-monophospho-N-acetylneuraminic acid, the nucleotide sugar of sialic acid. Strains of Neisseria meningitidis and Haemophilus influenzae also express similarly sialylated LPS. Sialylation of the LOS influences susceptibility to bactericidal antibody, may decrease or prevent phagocytosis, cause down-regulation of complement activation, and decrease adherence to neutrophils and the subsequent oxidative burst response. The core oligosaccharides of LPS of Campylobacter jejuni serotypes which are associated with the development of the neurological disorder, Guillain-Barré syndrome (GBS), exhibit mimicry of gangliosides. Cross-reactive antibodies between C. jejuni LPS and gangliosides are considered to play an important role in GBS pathogenesis. In contrast, the O-chain of a number of Helicobacter pylori strains exhibit mimicry of Lewis(x) and Lewis(y) blood group antigens. The role of this mimicry remains to be investigated, but may play a role in bacterial camouflage, the induction of autoimmunity and immune suppression in H. pylori-associated disease.

Acute motor axonal neuropathy: an antibody-mediated attack on axolemma

The acute motor axonal neuropathy (AMAN) form of the Guillain-Barre syndrome is a paralytic disorder of abrupt onset characterized pathologically by motor nerve fiber degeneration of variable severity and by sparing of sensory fibers. There is little demyelination or lymphocytic inflammation. Most cases have antecedent infection with Campylobacter jejuni and many have antibodies directed toward GM1 ganglioside-like epitopes, but the mechanism of nerve-fiber injury has not been defined. In 7 fatal cases of AMAN, immunocytochemistry demonstrated the presence of IgG and the complement activation product C3d bound to the axolemma of motor fibers. The most frequently involved site was the nodal axolemma, but in more severe cases IgG and C3d were found within the periaxonal space of the myelinated internodes, bound to the outer surface of the motor axon. These results suggest that AMAN is a novel disorder caused by an antibody- and complement-mediated attack on the axolemma of motor fibers.

Chronic progressive steroid responsive axonal polyneuropathy: a CIDP vaariant or a primary axonal disorder?

Five patients presented with chronic,, progressive, predominantly motor polyneuropathy. CSF protein content was increased in 4 patients. Motor conduction velocities and EMG were consistent with axonal involvement. Sural nerve conductions were normal in all cases and sural nerve biopsy performed in 1 patient was normal. Serum antibodies to GM1, GD1a, GD1b, and GM2 were negative. All patients improved after steroid treatment and 3 completely recovered. Because of therapeutic implications it is important to differentiate these patients from those with chronic idiopathic axonal neuropathies. It is unclear whether this is a primary axonal, probably immune-mediated, polyneuropathy, or whether it represents one extreme of the chronic inflammatory demyelinating polyradiculoneuropathy spectrum characterized by severe axonal loss. We suggest that the term "chronic inflammatory polyneuropathy," encompassing cases from pure demyelinating to pure axonal neuropathies responsive to steroids, should be reinstated and that, like in Guillain-Barré syndrome, different subtypes should be individuated.

Anti-ganglioside GM1 antibodies in Guillain-Barré syndrome and their relationship to Campylobacter jejuni infection

To clarify the association between Campylobacter jejuni (Cj) infection and antibodies to ganglioside GM1 (anti-GM1) in Guillain-Barré syndrome (GBS), we have carried out a prospective case-control study of 96 patients with GBS. Cj infection occurred in 25 (26%) patients. IgG and/or IgM anti-GM1 were identified in 24 (25%) patients and in 1 of 71 (1.4%) household controls (p < 0.001). Thirteen of the 25 (52%) Cj-positive patients had anti-GM1 compared with 11 of the 71 (15%) Cj-negative patients (p < 0.001). Neither the peak overall disability nor the 1-year disability differed between the anti-GM1-positive and anti-GM1-negative patients. However, patients with the combination of Cj infection and anti-GM1 positivity recovered more slowly than Cj/anti-GM1-negative patients (p = 0.05), were more likely to have axonal degeneration, and were significantly more disabled at the end of 1 year (p = 0.02). The presence of Cj infection is more important than anti-GM1 positivity in determining the extent of axonal involvement and, hence, prognosis. Since the presence of anti-GM1 is not a significant poor-prognostic factor, a search should be made for other properties of Cj infection that would account for its relationship to axonal degeneration.

Critical illness neuropathy: diagnosis and management

Critical illness neuropathy is a distinct form of polyneuropathy that develops as part of a syndrome often observed in critical care units consisting of septicemia with encephalopathy, respiratory failure with difficulty in weaning and an axonal degenerative polyneuropathy. Critical illness neuropathy (CIN) has been discussed in the recent neurological and critical care literature, but has not been discussed, to the best of our knowledge, in the rehabilitation literature. This article acquaints rehabilitation personnel with the methods used to diagnose CIN and differentiate it from other neuropathies and the impact that multidisciplinary rehabilitation may have on the outcome of this disorder. We found that with an appropriate history, and compatible physical findings, electrodiagnostic testing helped diagnose CIN and that intensive rehabilitation was advantageous in improving our patients conditions.