Acute motor conduction block neuropathy Another Guillain-Barré syndrome variant

Acute Motor Conduction Block Neuropathy After Initiation of Omalizumab: Case Report and Literature Review for Possible Causality

Background

Omalizumab is an established therapy for allergic conditions, yet its neurological effects remain underexplored compared to other biological agents.

Case description

A 45-year-old male with asthma developed acute quadriparesis one week after receiving the first dose of omalizumab. Electrophysiological studies have shown partial motor conduction block in multiple nerves, with reduced CMAP amplitudes and absent F-waves in others. CSF showed cyto-albuminous dissociation. The diagnosis was a variant of Guillain-Barré syndrome. Despite intravenous immunoglobulin (IVIG) therapy, the patient experienced persistent neuropathic symptoms.

Discussion

The patient presented with acute quadriparesis devoid of sensory or cranial nerve involvement, suggestive of a variant of Guillain-Barré syndrome (GBS) known as acute motor conduction block neuropathy (AMCBN). Electrophysiological studies have indicated conduction block without demyelination, implicating axonal degeneration. Despite negative findings for common etiologies, the temporal association between omalizumab administration and symptom onset suggests a potential link, supported by criteria for drug-induced illness. Conflicting evidence exists regarding omalizumab's neurological effects, with proposed mechanisms including autoimmune reactions and mast cell dysfunction. Comparisons to TNF-α antagonists highlight similar neuropathy patterns, indicating a need for further research to clarify omalizumab's neurotoxicity.

Conclusion

In conclusion, while omalizumab holds promise for allergic conditions, including chronic urticaria, its potential impact on peripheral nerves necessitates vigilance among clinicians. Further studies are imperative to ascertain the risk-benefit profile and elucidate underlying mechanisms and risk factors of neurological complications associated with omalizumab therapy.

Acute-Onset Quadriplegia Presenting With Hyperreflexia: A Dilemma in Diagnosis

An autoimmune polyradiculoneuropathy, Guillain-Barré syndrome (GBS) is an acute, rapidly progressive, and fulminant one. Rapidly developing motor weakness along with absent reflexes, with or without sensory impairment, is the hallmark of GBS. GBS is never a hereditary entity; it is always acquired by the individual. Here, we present an interesting case of GBS in a 37-year-old male patient presenting with lower limb weakness for one day which had progressed to upper limb weakness in a day. There was a history of fever and loose stools four days back. On examination, vitals were within normal limits including single breath count. Central nervous system (CNS) examination revealed as follows: bicep jerk, tricep jerk, and supinator jerk were National Institute of Neurological Disorders and Stroke (NINDS) scale grade 2 in bilateral upper limbs. Knee jerk was NINDS scale grade 3 in bilateral lower limbs, which was unusual considering that GBS presents with areflexia or reduced reflexes. Ankle jerk was absent in bilateral lower limbs. Plantars were mute bilaterally. Nerve conduction study was suggestive of axonal and demyelinating motor neuropathy involving all four limbs. The patient was planned for intravenous immunoglobulin at a dose of 2 g/kg/day for five days but developed an allergic reaction to the first dose; hence, the therapy was discontinued, and the option of plasmapheresis was given to which the patient refused. This is a report of a case of GBS with hyperreflexia which is an uncommon entity in the Indian subcontinent.

Electrodiagnostic methods to verify Guillain-Barré syndrome subtypes in Istanbul: A prospective multicenter study

BACKGROUND AND AIMS

This study aimed to identify the clinical characteristics and electrodiagnostic subtypes of Guillain-Barré syndrome (GBS) in Istanbul.

METHODS

Patients with GBS were prospectively recruited between April 2019 and March 2022 and two electrodiagnostic examinations were performed on each patient. The criteria of Ho et al., Hadden et al., Rajabally et al., and Uncini et al. were compared for the differentiation of demyelinating and axonal subtypes, and their relations with anti-ganglioside antibodies were analyzed.

RESULTS

One hundred seventy-seven patients were included, 69 before the coronavirus disease 2019 pandemic (April 2019-February 2020) and 108 during the pandemic (March 2020-March 2022), without substantial changes in monthly frequencies. As compared with the criteria of Uncini et al., demyelinating GBS subtype diagnosis was more frequent according to the Ho et al. and Hadden et al. criteria (95/162, 58.6% vs. 110/174, 63.2% and 121/174, 69.5%, respectively), and less frequent according to Rajabally et al.'s criteria (76/174, 43.7%). Fourteen patients' diagnoses made using Rajabally et al.'s criteria were shifted to the other subtype with the second electrodiagnostic examination. Of the 106 analyzed patients, 22 had immunoglobulin G anti-ganglioside antibodies (14 with the axonal subtype). They had less frequent sensory symptoms (54.5% vs. 83.1%, p = 0.009), a more frequent history of previous gastroenteritis (54.5% vs. 22.9%, p = 0.007), and a more severe disease as compared with those without antibodies.

INTERPRETATION

Serial electrodiagnostic examinations are more helpful for accurate subtype diagnosis of GBS because of the dynamic pathophysiology of the disease. We observed no significant increase in GBS frequency during the pandemic in this metropolis.

Nodal Conduction Block and Internodal Conduction Block in Nodopathy

OBJECTIVES

In 2015, a new term "nodopathy" was introduced to represent a group of neuropathy because of autoantibodies at the node of Ranvier and paranodal area. This review was conducted to highlight the electrophysiologic characteristics of acute and chronic nodopathies by the newly introduced term: "nodal conduction block (CB); CB without temporal dispersion or slow nerve conduction velocity" and by introducing a new term: "internodal CB; CB with temporal dispersion or/and slow nerve conduction velocity".

METHODS

Through PubMed searches, 23 cases of acute (<4 weeks of neuropathy) nodopathy and 12 cases of chronic (>4 weeks of neuropathy) nodopathy are identified. Two other required inclusion criteria are positive nodal antibody test and detailed nerve conduction data with or without figure. All existing data were analyzed to see whether these cases had nodal or internodal CB.

RESULTS

Among 23 cases of acute nodopathy, 11 had nodal CB, 9 internodal CB, and 3 mixed CB. Thus, nodal CB was observed in 61% of acute nodopathy cases and internodal CB in 52% of acute nodopathy cases. Among 12 cases of chronic nodopathy, all 12 had internodal CB.

CONCLUSIONS

Nodal CB is the nerve conduction characteristic of acute nodopathy, but internodal CB does not rule out acute nodopathy. Internodal CB is the nerve conduction characteristic of chronic nodopathy.

Serial Nerve Conduction Studies in Guillain-Barré Syndrome: Its Usefulness and Precise Timing

PURPOSE

Nerve conduction study (NCS) is essential for subclassifying Guillain-Barré syndrome (GBS). It is well known that the GBS subclassification can change through serial NCSs. However, the usefulness of serial NCSs is debatable, especially in patients with early stage GBS.

METHODS

Follow-up NCS data within 3 weeks (early followed NCS, EFN) and within 3 to 10 weeks (late-followed NCS, LFN) were collected from 60 patients with GBS who underwent their first NCS (FN) within 10 days after symptom onset. Each NCS was classified into five subtypes (normal, demyelinating, axonal, inexcitable, and equivocal), according to Hadden's and Rajabally's criteria. We analyzed the frequency of significant changes in classification (SCCs) comprising electrodiagnostic aggravation and subtype shifts between demyelinating and axonal types according to follow-up timing.

RESULTS

Between FN and EFN, 33.3% of patients with Hadden's criteria and 18.3% with Rajabally's criteria showed SCCs. Between FN and LFN, 23.3% of patients with Hadden's criteria and 21.7% with Rajabally's criteria showed SCCs, of which 71.4% (Hadden's criteria) and 46.2% (Rajabally's criteria) already showed SCCs from the EFN. The conditions of delayed SCCs between EFN and LFN were very early FN, mild symptoms at the FN, or persistent electrophysiological deterioration 3 weeks after symptom onset.

CONCLUSIONS

A substantial proportion of patients with GBS showed significant changes in neurophysiological classification at the early stage. Serial NCS may be helpful for precise neurophysiological classification. This study suggests that follow-up NCSs should be performed within 3 weeks of symptom onset in patients with GBS in whom FN was performed within 10 days of symptom onset.

Critical illness-associated weakness and related motor disorders

Weakness of limb and respiratory muscles that occurs in the course of critical illness has become an increasingly common and serious complication of adult and pediatric intensive care unit patients and a cause of prolonged ventilatory support, morbidity, and prolonged hospitalization. Two motor disorders that occur singly or together, namely critical illness polyneuropathy and critical illness myopathy, cause weakness of limb and of breathing muscles, making it difficult to be weaned from ventilatory support, commencing rehabilitation, and extending the length of stay in the intensive care unit, with higher rates of morbidity and mortality. Recovery can take weeks or months and in severe cases, and may be incomplete or absent. Recent findings suggest an improved prognosis of critical illness myopathy compared to polyneuropathy. Prevention and treatment are therefore very important. Its management requires an integrated team approach commencing with neurologic consultation, creatine kinase (CK) measurement, detailed electrodiagnostic, respiratory and neuroimaging studies, and potentially muscle biopsy to elucidate the etiopathogenesis of the weakness in the peripheral and/or central nervous system, for which there may be a variety of causes. These tenets of care are being applied to new cases and survivors of the coronavirus-2 disease pandemic of 2019. This chapter provides an update to the understanding and approach to critical illness motor disorders.

Electrophysiology of Guillain-Barré syndrome in Bangladesh: A prospective study of 312 patients

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Classification of neurophysiologic subtypes of Guillain-Barré syndrome largely depended on the applied criteria.

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Anti-GM1 antibodies were not exclusively associated with axonal Guillain-Barré syndrome.

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Conduction block was not exclusively associated with demyelinating Guillain-Barré syndrome.

Objective

To describe the electrophysiological features in relation to clinical and serological findings of Guillain-Barré syndrome (GBS) in the national neuroscience hospital in Bangladesh. This is one of the few studies that investigated GBS patients using standardized electrophysiology in low-income countries.

Methods

In a prospective and observational study, we investigated 312 GBS patients by standardized clinical, serological and electrophysiological methods. Unilateral motor and sensory nerve conduction studies (NCS) were performed within two weeks of onset of weakness. Follow up NCS were performed in 189 patients and classified according to eight sets of established GBS criteria. Serology included assessment of anti-GM1 antibodies and anti-campylobacter jejuni lipo-oligosaccharide (LOS) antibodies.

Results

Depending on the criteria used, 44–59% patients had axonal GBS with anti-GM1 antibodies being present in 55–58% and 9–42% patients had demyelinating GBS with anti-GM1 antibodies being present in 7–35%. Conduction block (CB) with demyelinative slowing in the same nerve segment was found in 24% (74/312) patients, and CB without demyelinative slowing in the same nerve segment was found in 18% (56/312) patients, of whom anti-GM1 antibodies were found in 27% and 57% patients respectively. Follow-up NCS showed a change in GBS classification in 11–26% of patients, mainly from demyelinating to axonal GBS.

Conclusions

The predominant subtype of GBS in Bangladesh is axonal but demyelinating GBS also occurs with classification being strongly dependent on the applied criteria.

Significance

The present study demonstrates the importance of reaching international agreement on GBS criteria that should be based on the best evidence.

Acute Axonal Motor Neuropathy With Completely Reversible Conduction Failure-Is It Really Axonal?

ABSTRACT

We present the case of a 24-year-old man with a 3-day history of limb weakness and flaccid tetraparesis, hyporreflexia, and gait difficulties (Hughes grade 3) in the examination. Electromyography at presentation revealed severe amplitude reduction in distal compound muscle action potentials of several nerves without features of demyelination, fulfilling electrodiagnostic criteria for acute axonal motor neuropathy. The patient was treated with immunoglobulin and recovered completely 21 days after symptom onset. Electromyography at this timepoint showed normalization of compound muscle action potentials without increased temporal dispersion. The electroclinical recovery profile in this patient is consistent with reversible conduction failure in distal nerve segments in detriment of axonal degeneration. Thus, it is an "axonal motor neuropathy" where axonopathy is unlikely, giving strength to the concept of "nodopathies/paranodopathies."

Clinical features of Guillain-Barré syndrome patients with elevated serum creatine kinase levels

Background

It is not well defined whether Guillain–Barré syndrome (GBS) patients with elevated serum creatine kinase (CK) levels have characteristic clinical features and are related to the subgroups of GBS.

Methods

We retrospectively studied 51 consecutive patients with GBS, who visited our hospital, and compared clinical, laboratory and electrophysiological findings between patients with and without elevated CK levels.

Results

Of 51 patients, 14 patients (27%) showed an elevation of serum CK levels. When compared with patients with the normal CK levels, the ratios of male, antecedent infections, and anti-GM1 antibody positivity were significantly higher in patients with elevated CK levels. The ratios of hypoesthesia, cranial nerve involvement, and urinary retention were significantly less in patients with elevated CK levels. There were no significant differences in disability at peak between two groups. In the electrophysiological examination, sensory nerve abnormalities were not observed. Although some patients with elevated CK levels showed prolongation of distal motor latencies (DMLs) and increase of durations in the initial examination, development of the prolongation of DMLs and increase of durations was not observed in the follow-up examinations. The findings were consistent with acute motor axonal neuropathy (AMAN) with reversible conduction failure (RCF) but not acute inflammatory demyelinating polyneuropathy (AIDP).

Conclusions

The results suggest that the GBS patients with elevated CK levels represent not a group of AIDP but a group of AMAN with axonal degeneration or RCF even though the initial electrophysiological examination shows AIDP pattern.

Rapid Recovery With Plasma Exchange in Acute Motor Axonal Neuropathy With Reversible Conduction Failure

Characterization of Guillain-Barré syndrome (GBS) subtypes has become increasingly complicated with the recognition of paranodal dysfunction and reversible conduction failure (RCF) in acute motor axonal neuropathy. We describe 2 cases of seronegative acute motor axonal neuropathy with RCF with a rapid onset of severe quadriplegia. Treatment with plasma exchange was associated with rapid clinical and electrophysiological response on serial examinations. Increased recognition of RCF may lead to improved characterization of GBS subtypes and may play a role in determining future treatment options in GBS.

Anti-ganglioside antibodies profile in Guillain-Barré syndrome: Correlation with clinical features, electrophysiological pattern, and outcome

BACKGROUND

Guillain-Barré syndrome (GBS) and its subtypes are associated with distinct anti-ganglioside antibodies. Hence, we aimed to determine the frequency of anti-ganglioside antibodies and its correlation with clinical features, electrophysiological patterns, and outcome in patients with GBS.

MATERIAL AND METHODS

The data regarding clinical features, electrophysiological patterns, and outcome at 6 months were collected and analyzed from the case records of patients diagnosed with GBS during 2008-2013 at a tertiary care hospital in south India.

RESULTS

A total of 204 patients with GBS were studied, and 73 patients (mean age: 37.6 ± 17.5 years) who underwent anti-ganglioside antibody testing were analyzed. Male-to-female ratio was 2.5:1. IgG anti-ganglioside antibodies were positive in 41/73 patients. The most common IgG anti-ganglioside antibody observed in the acute demyelinating variant was anti-GT1b (n = 13; 17.8%), and, those in the acute axonal variant were anti-GM1, anti-GM2, anti-GD1b, and anti-GT1b antibodies (n = 9;12.3% each). Three patients died and 5 patients were unable to walk independently at the end of 6 months.

CONCLUSIONS

The frequency of anti-ganglioside antibodies in our cohort with GBS was 56%, with IgG anti-GT1b antibody being the most common. The anti-ganglioside antibodies were significantly positive in acute motor axonal neuropathy (AMAN) subtype of GBS. The presence of anti-ganglioside antibodies was not found to be of significant use in predicting the outcome. Although it was observed that the absence, and not the presence, of anti-ganglioside antibodies was associated with antecedent infection, dysautonomia, and requirement of ventilator support, the overall disease severity was not antibody dependant.

Clinical electrophysiology of axonal polyneuropathies

Axonal neuropathies encompass a wide range of acquired and inherited disorders with electrophysiologic characteristics that arise from the unique neurophysiology of the axon. Accurate interpretation of nerve conduction studies and electromyography requires an in-depth understanding of the pathophysiology of the axon. Here we review the unique neurophysiologic properties of the axon and how they relate to clinical electrodiagnostic features. We review the length-dependent Wallerian or "dying-back" processes as well as the emerging body of literature from acquired axonal neuropathies that highlights the importance of axonal disease at the nodes of Ranvier. Neurophysiologic features of individual inherited and acquired axonal diseases, including primary nerve disease as well as systemic immune mediated, metabolic, and toxic diseases involving the peripheral nerve, are reviewed. This comprehensive review of electrodiagnostic findings coupled with the current understanding of pathophysiology will aid the clinician in the evaluation of axonal polyneuropathies.

Autoimmune nodo-paranodopathies of peripheral nerve: the concept is gaining ground

Peripheral neuropathies are classified as primarily demyelinating or axonal. Microstructural alterations of the nodal region are the key to understand the pathophysiology of neuropathies with antibodies to gangliosides and the new category of nodo-paranodopathy has been proposed to better characterise these disorders and overcome some inadequacies of the dichotomous classification. Recently, the research in autoimmune neuropathies has been boosted by reports of patients carrying immunoglobulin G4 antibodies against paranodal axo-glial proteins with distinct phenotypes and showing loss of transverse bands, terminal myelin loop detachment, nodal widening and axonal loss. These patients have been classified up to now as chronic inflammatory demyelinating polyradiculoneuropathy but, in our opinion, better fit into the nodo-paranodopathy category because nerve injury is due to dismantling of the paranode, segmental de-remyelination is absent and the pathogenic mechanism is not inflammatory. Evidence from nerve conductions and electron microscopy studies in patients and mutant animal models can reconcile the apparent contrast between the electrophysiological 'demyelinating' features, explainable just by the paranodal involvement and the axonal pathology. These patients broaden the autoimmune nodo-paranodopathy category and re-emphasise the usage of the term that pointing to the site of nerve injury reminds specific pathophysiological mechanisms, reconciles contrasting electrophysiological and pathological findings, and avoids misdiagnosis and taxonomic confusion. In our opinion, the nodo-paranodopathy term more adequately classifies the peripheral nerve disorders due to an autoimmune attack directed and limited to the nodal region integrating the traditional classification of peripheral neuropathies.

Atypical Electrophysiological Findings in a Patient with Acute Motor and Sensory Axonal Neuropathy

Guillain–Barré syndrome (GBS) is an immune-mediated polyradiculoneuropathy with acute onset and rapid clinical worsening; early diagnosis and immunomodulating therapy can ameliorate the course of disease. During the first days, however, nerve conduction studies (NCSs) are not always conclusive. Here, we describe a 73-year-old man presenting with progressive muscular weakness of the lower limbs, ascending to the upper limbs, accompanied by distal sensory disturbances. Neuroimaging of brain and spine and NCSs were unremarkable; cerebrospinal fluid analysis revealed no albuminocytologic dissociation. Based on typical clinical features, and on positivity for serum GD1b-IgM antibodies, GBS with proximal conduction failure at multiple radicular levels was postulated, and a standard regime of intravenous immunoglobulin was administered. Four weeks later, the patient presented with flaccid tetraparesis, areflexia, and reduction of position sense, tingling paresthesias, and initial respiratory distress. Repeat NCS still revealed almost normal findings, except for the disappearance of right ulnar nerve F-waves. A few days thereafter, the patient developed severe respiratory insufficiency requiring mechanical ventilation for 2 weeks. On day 50, NCS revealed for the first time markedly reduced compound muscle action potentials and sensory nerve action potentials in all tested nerves, without signs of demyelination; needle electromyography documented widespread denervation. The diagnosis of acute motor and sensory axonal neuropathy was made. After 3 months of intensive rehabilitation, the patient regained the ability to walk with little assistance and was discharged home. In conclusion, normal NCS findings up to several weeks do not exclude the diagnosis of GBS. Very proximal axonal conduction failure with late distal axonal degeneration should be taken into consideration, and electrodiagnostic follow-up examinations, even employing unusual techniques, are recommended over several weeks after disease onset.

Acute axonal neuropathy subtype of Guillain Barré syndrome in a French pediatric series: Adequate follow-up may require repetitive electrophysiological studies

Different subtypes of Guillain Barré Syndromes (GBSs) are defined by their electrophysiological characteristics, acute inflammatory demyelinating neuropathy (AIDP), and acute motor/motor-sensory axonal forms (AMAN/AMSAN) with either reversible nerve conduction failure (RCF) or axonal degeneration. Our aim was to describe initial clinical and electrophysiological characteristics of axonal forms of GBS in a pediatric population and their short- and long-term evolution. Electroneuromyogram (ENMG) results were collected at diagnosis and at two months of evolution and interpreted using the recently proposed pattern of RCF vs axonal degeneration. Clinical evaluation was standardized using the GBS disability scale ("GBSds") at diagnosis, and then at 3, 6, and 12 months of evolution. Outcome was compared to those of patients with AIDP diagnosed within the same period. Eleven patients were included, among whom eight patients presenting with AMAN and three with AMSAN. Two subgroups were identified according to severity. Three patients had a severe form (GBSds ≥2 at 12 months), two of them presenting an axonal degeneration on ENMG studies. Seven patients had a less severe form (GBSds ≤1 at 12 months), five of them with RCF on ENMG studies. Axonal forms had a more severe evolution than demyelinating forms (n = 17) at 3 months (median GBSds 3 and 2, respectively), 6 months (2 and 0), and 12 months (1 and 0), (p < 0,05). Axonal forms of GBS in children have a more severe global outcome than demyelinating forms. Axonal degeneration in two successive early ENMGs may be a prognostic factor of poor outcome.

Optimizing the electrodiagnostic accuracy in Guillain-Barré syndrome subtypes: Criteria sets and sparse linear discriminant analysis

OBJECTIVE

To optimize the electrodiagnosis of Guillain-Barré syndrome (GBS) subtypes at first study.

METHODS

The reference electrodiagnosis was obtained in 53 demyelinating and 45 axonal GBS patients on the basis of two serial studies and results of anti-ganglioside antibodies assay. We retrospectively employed sparse linear discriminant analysis (LDA), two existing electrodiagnostic criteria sets (Hadden et al., 1998; Rajabally et al., 2015) and one we propose that additionally evaluates duration of motor responses, sural sparing pattern and defines reversible conduction failure (RCF) in motor and sensory nerves at second study.

RESULTS

At first study the misclassification error rates, compared to reference diagnoses, were: 15.3% for sparse LDA, 30% for our criteria, 45% for Rajabally's and 48% for Hadden's. Sparse LDA identified seven most powerful electrophysiological variables differentiating demyelinating and axonal subtypes and assigned to each patient the diagnostic probability of belonging to either subtype. At second study 46.6% of axonal GBS patients showed RCF in two motor and 8.8% in two sensory nerves.

CONCLUSIONS

Based on a single study, sparse LDA showed the highest diagnostic accuracy. RCF is present in a considerable percentage of axonal patients.

SIGNIFICANCE

Sparse LDA, a supervised statistical method of classification, should be introduced in the electrodiagnostic practice.

Guillain-Barré syndrome: What have we learnt during one century? A personal historical perspective

We are approaching the centenary of the first description of Guillain-Barré syndrome. The past 30 years had witnessed an amazing progress in the understanding of the immunological and pathological mechanisms of this disorder. We now recognize that Guillain-Barré syndrome is remarkably heterogeneous and under this umbrella term are several variants and subtypes with distinct clinical, electrophysiological and immunopathological features. This review is a historical journey, through a personal perspective, following the milestones that led to the current substantial knowledge of Guillain-Barré syndrome.

Auto-antibodies to contactin-associated protein 1 (Caspr) in two patients with painful inflammatory neuropathy

Auto-antibodies against the paranodal proteins neurofascin-155 and contactin-1 have recently been described in patients with chronic inflammatory demyelinating polyradiculoneuropathy and are associated with a distinct clinical phenotype and response to treatment. Contactin-associated protein 1 (Caspr, encoded by CNTNAP1) is a paranodal protein that is attached to neurofascin-155 and contactin-1 (CNTN1) but has not yet been identified as a sole antigen in patients with inflammatory neuropathies. In the present study, we screened a cohort of 35 patients with chronic inflammatory demyelinating polyradiculoneuropathy (age range 20-80, 10 female, 25 male) and 22 patients with Guillain-Barré syndrome (age range 17-86, eight female, 14 male) for autoantibodies against paranodal antigens. We identified two patients, one with chronic inflammatory demyelinating polyradiculoneuropathy and one with Guillain-Barré syndrome, with autoantibodies against Caspr by binding assays using Caspr transfected human embryonic kidney cells and murine teased fibres. IgG3 was the predominant autoantibody subclass in the patient with Guillain-Barré syndrome, IgG4 was predominant in the patient with chronic inflammatory demyelinating polyradiculoneuropathy. Accordingly, complement deposition after binding to HEK293 cells was detectable in the patient with IgG3 autoantibodies only, not in the patient with IgG4. Severe disruption of the paranodal and nodal architecture was detectable in teased fibres of the sural nerve biopsy and in dermal myelinated fibres, supporting the notion of the paranodes being the site of pathology. Deposition of IgG at the paranodes was detected in teased fibre preparations of the sural nerve, further supporting the pathogenicity of anti-Caspr autoantibodies. Pain was one of the predominant findings in both patients, possibly reflected by binding of patients' IgG to TRPV1 immunoreactive dorsal root ganglia neurons. Our results demonstrate that the paranodal protein Caspr constitutes a new antigen that leads to autoantibody generation as part of the novel entity of neuropathies associated with autoantibodies against paranodal proteins.

Serial electrophysiological findings in Guillain-Barré syndrome not fulfilling AIDP or AMAN criteria

Guillain-Barré syndrome (GBS) is categorized into two major subtypes: acute inflammatory demyelinating polyneuropathy (AIDP) and acute motor axonal neuropathy (AMAN). However, a proportion of patients are electrophysiologically unclassified because of electrophysiological findings that do not fulfil AIDP or AMAN criteria, and underlying pathophysiological mechanisms and lesion distributions of unclassified patients are not well defined. The aims of this study are to elucidate disease pathophysiology and lesion distribution in unclassified patients. We retrospectively studied 48 consecutive GBS patients. Patients were classified on the basis of initial electrophysiological findings according to Ho's criteria. Clinical and serial electrophysiological examinations of unclassified patients were conducted. Twelve (25 %) GBS patients were unclassified. All unclassified patients were able to walk independently at 21 days after onset. No unclassified patients, except one patient with diabetes mellitus, had sensory nerve involvement. Eight patients underwent a follow-up study within 15 days of the initial study. Distal motor latencies (DMLs) of the left median motor nerve were found to be significantly and uniformly decreased compared with initial studies (p = 0.008). DMLs (p < 0.0001) and distal compound action potential (CMAP) durations (p = 0.002) of all nerves were significantly decreased, and distal CMAP amplitudes (p = 0.026) significantly increased compared with initial studies. In unclassified GBS patients, DML values during initial electrophysiological studies would be prolonged compared with expected values in the same patient unaffected by GBS and later improve rapidly with increased distal CMAP amplitudes without the development of excessive temporal dispersions. Lesions are also present in distal nerve segments caused by reversible conduction failure.

Demyelinating Guillain-Barré syndrome recurs more frequently than axonal subtypes

Guillain-Barré syndrome (GBS) is considered a monophasic disorder yet recurrences occur in up to 6% of patients. We retrospectively studied an Italian-Japanese population of 236 GBS and 73 Miller Fisher syndrome (MFS) patients and searched for factors which may be associated with recurrence. A recurrent patient was defined as having at least two episodes that fulfilled the diagnostic criteria for GBS and MFS with an identifiable recovery after each episode and a minimum of 2months between episodes. Preceding Campylobacter jejuni (C. jejuni) infection and antiganglioside antibodies were also assessed. Seven (3%) recurrent GBS and one (1.4%) recurrent MFS patients were identified. In the individual patient the clinical features during episodes were usually similar varying in severity whereas the preceding infection differed. None of the patients had GBS in one episode and MFS in the recurrence or vice versa. Recurrent GBS patients, compared with monophasic GBS, did not have preceding diarrhea at the first episode and considering the electrophysiological subtypes, acute inflammatory demyelinating polyneuropathies recurred more frequently than axonal GBS (6.5% vs 0.9%, p=0.04). In conclusion in a GBS population with a balanced number of demyelinating and axonal subtypes less frequent diarrhea and demyelination at electrophysiology were associated with recurrence.

Nodopathies of the peripheral nerve: an emerging concept

Peripheral nerve diseases are traditionally classified as demyelinating or axonal. It has been recently proposed that microstructural changes restricted to the nodal/paranodal region may be the key to understanding the pathophysiology of antiganglioside antibody mediated neuropathies. We reviewed neuropathies with different aetiologies (dysimmune, inflammatory, ischaemic, nutritional, toxic) in which evidence from nerve conductions, excitability studies, pathology and animal models, indicate the involvement of the nodal region in the pathogenesis. For these neuropathies, the classification in demyelinating and axonal is inadequate or even misleading, we therefore propose a new category of nodopathy that has the following features: (1) it is characterised by a pathophysiological continuum from transitory nerve conduction block to axonal degeneration; (2) the conduction block may be due to paranodal myelin detachment, node lengthening, dysfunction or disruption of Na(+) channels, altered homeostasis of water and ions, or abnormal polarisation of the axolemma; (3) the conduction block may be promptly reversible without development of excessive temporal dispersion; (4) axonal degeneration, depending on the specific disorder and its severity, eventually follows the conduction block. The term nodopathy focuses to the site of primary nerve injury, avoids confusion with segmental demyelinating neuropathies and circumvents the apparent paradox that something axonal may be reversible and have a good prognosis.

Mechanisms of distal axonal degeneration in peripheral neuropathies

Peripheral neuropathy is a common complication of a variety of diseases and treatments, including diabetes, cancer chemotherapy, and infectious causes (HIV, hepatitis C, and Campylobacter jejuni). Despite the fundamental difference between these insults, peripheral neuropathy develops as a combination of just six primary mechanisms: altered metabolism, covalent modification, altered organelle function and reactive oxygen species formation, altered intracellular and inflammatory signaling, slowed axonal transport, and altered ion channel dynamics and expression. All of these pathways converge to lead to axon dysfunction and symptoms of neuropathy. The detailed mechanisms of axon degeneration itself have begun to be elucidated with studies of animal models with altered degeneration kinetics, including the slowed Wallerian degeneration (Wld(S)) and Sarm knockout animal models. These studies have shown axonal degeneration to occur through a programmed pathway of injury signaling and cytoskeletal degradation. Insights into the common disease insults that converge on the axonal degeneration pathway promise to facilitate the development of therapeutics that may be effective against other mechanisms of neurodegeneration.

Rapid and reversible responses to IVIG in autoimmune neuromuscular diseases suggest mechanisms of action involving competition with functionally important autoantibodies

Intravenous immunoglobulin (IVIG) is widely used in autoimmune neuromuscular diseases whose pathogenesis is undefined. Many different effects of IVIG have been demonstrated in vitro, but few studies actually identify the mechanism(s) most important in vivo. Doses and treatment intervals are generally chosen empirically. Recent studies in Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy show that some effects of IVIG are readily reversible and highly dependent on the serum IgG level. This suggests that in some autoantibody-mediated neuromuscular diseases, IVIG directly competes with autoantibodies that reversibly interfere with nerve conduction. Mechanisms of action of IVIG which most likely involve direct competition with autoantibodies include: neutralization of autoantibodies by anti-idiotypes, inhibition of complement deposition, and increasing catabolism of pathologic antibodies by saturating FcRn. Indirect immunomodulatory effects are not as likely to involve competition and may not have the same reversibility and dose-dependency. Pharmacodynamic analyses should be informative regarding most relevant mechanism(s) of action of IVIG as well as the role of autoantibodies in the immunopathogenesis of each disease. Better understanding of the role of autoantibodies and of the target(s) of IVIG could lead to more efficient use of this therapy and better patient outcomes.

Guillain-Barré syndrome in Asia

Over the past 20 years, the most notable advance in understanding Guillain-Barré syndrome (GBS) has been the identification of an axonal variant. This advance arose chiefly through studies undertaken in East Asian countries and comprised two major aspects: first, the immunopathogenesis of axonal GBS related to anti-ganglioside antibodies and molecular mimicry of Campylobacter jejuni; and second, the observation that distinct electrophysiological patterns of axonal GBS existed, reflecting reversible conduction failure (RCF). As a consequence, the pathophysiology of acute motor axonal neuropathy (AMAN) has perhaps become better understood than acute inflammatory demyelinating polyneuropathy. Despite these more recent advances, a critical issue remains largely unresolved: whether axonal GBS is more common in Asia than in Europe or North America. If it is more common in Asia, then causative factors must be more critically considered, including geographical differences, issues of genetic susceptibility, the role of antecedent infections and other potential triggering factors. It has become apparent that the optimal diagnosis of AMAN requires serial electrophysiological testing, to better delineate RCF, combined with assessment for the presence of anti-ganglioside antibodies. Recent collaborative approaches between Europe and Asia have suggested that both the electrophysiological pattern of AMAN and the seropositivity for anti-ganglioside antibodies develop similarly. Separately, however, current electrodiagnostic criteria for AMAN limited to a single assessment appear inadequate to identify the majority of cases. As such, diagnostic criteria will need to be revised to improve the diagnostic sensitivity for AMAN.

Antibodies to single glycolipids and glycolipid complexes in Guillain-Barré syndrome subtypes

OBJECTIVE

To comprehensively investigate the relationship between antibodies to single glycolipids and their complexes and Guillain-Barré syndrome subtypes and clinical features.

METHODS

In acute sera from 199 patients with Guillain-Barré syndrome, immunoglobulin G (IgG) antibodies to glycolipids and ganglioside complexes were tested using ELISA against individual antigens from single glycolipids including gangliosides (LM1, GM1, GM1b, GD1a, GalNAc-GD1a, GD1b, GT1a, GT1b, GQ1b) and a neutral glycolipid, asialo-GM1 (GA1), and antigens from the combination of 2 different glycolipids. Based on serial nerve conduction studies, the electrodiagnoses were as follows: 69 demyelinating subtype, 85 axonal subtypes, and 45 unclassified.

RESULTS

Significant associations were detected between acute motor axonal neuropathy subtype and IgG antibodies to GM1, GalNAc-GD1a, GA1, or LM1/GA1 complex. Reversible conduction failure was significantly associated with IgG antibodies to GM1, GalNAc-GD1a, GD1b, or complex of LM1/GA1. No significant association was demonstrated between acute inflammatory demyelinating polyneuropathy and any of the glycolipids or ganglioside complexes. Anti-ganglioside complex antibodies alone were detected in 7 patients (5 axonal subtype).

CONCLUSIONS

The current study demonstrates that antibodies to single glycolipids and ganglioside complexes are associated with acute motor axonal neuropathy or acute motor conduction block neuropathy but not acute inflammatory demyelinating polyneuropathy.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that antibodies to glycolipids are increased in patients with acute motor axonal neuropathy and acute motor conduction block neuropathy but not acute inflammatory demyelinating polyneuropathy.

Acute Motor Conduction Block Neuropathy: Another Distinct Variant of Guillain-Barre Syndrome

We describe a patient who developed progressive weakness in all limbs without sensory symptoms 4 weeks after upper respiratory system infection. Electrophysiological findings suggested a new variant of Guillain-Barré syndrome named "acute motor conduction block neuropathy". Electrophysiological studies were performed at admission, 12^th and 28^th weeks. At the 28^th week, the clinical examination and electrophysiological findings showed complete recovery.

Axonal Guillain-Barré syndrome: concepts and controversies

Acute motor axonal neuropathy (AMAN) is a pure motor axonal subtype of Guillain-Barré syndrome (GBS) that was identified in the late 1990s. In Asia and Central and South America, it is the major subtype of GBS, seen in 30-65% of patients. AMAN progresses more rapidly and has an earlier peak than demyelinating GBS; tendon reflexes are relatively preserved or even exaggerated, and autonomic dysfunction is rare. One of the main causes is molecular mimicry of human gangliosides by Campylobacter jejuni lipo-oligosaccharides. In addition to axonal degeneration, electrophysiology shows rapidly reversible nerve conduction blockade or slowing, presumably due to pathological changes at the nodes or paranodes. Autoantibodies that bind to GM1 or GD1a gangliosides at the nodes of Ranvier activate complement and disrupt sodium-channel clusters and axoglial junctions, which leads to nerve conduction failure and muscle weakness. Improved understanding of the disease mechanism and pathophysiology might lead to new treatment options and improve the outlook for patients with AMAN.

Pathophysiology of immune-mediated demyelinating neuropathies--Part II: Neurology

In the second part of this review we deal with the clinical aspects of immune-mediated demyelinating neuropathies. We describe the relationship between pathophysiology and symptoms and discuss the pathophysiology of specific disease entities, including Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy, anti-myelin-associated glycoprotein neuropathy, and POEMS syndrome.

Guillain-Barré syndrome and variants

Guillain-Barré syndrome (GBS) is characterized by rapidly evolving ascending weakness, mild sensory loss, and hyporeflexia or areflexia. Acute inflammatory demyelinating polyneuropathy was the first to be recognized over a century ago and is the most common form of GBS. Axonal motor and sensorimotor variants have been described in the last three decades and are mediated by molecular mimicry targeting peripheral nerve motor axons. Other rare phenotypic variants have been recently described with pure sensory variant, restricted autonomic manifestations, and the pharyngeal-cervical-brachial pattern. It is important to recognize GBS and its variants because of the availability of equally effective therapies in the form of plasmapheresis and intravenous immunoglobulins.

Two unusual variants of Guillain-Barre syndrome

Guillain-Barre syndrome (GBS) is a group of autoimmune diseases characterised by acute, acquired and immune-mediated polyneuroradiculopathy. A large number of clinical subtypes of GBS have been described over last 100 years since the first description of this syndrome. We report two such cases GBS variants--first, AMAN with brisk reflexes and second being acute motor axonal neuropathy with conduction block. Through this case report, we intend to make the treating physicians and neurologist aware of these rare variants so that such cases would be appropriately diagnosed and treated.

An antibody to the GM1/GalNAc-GD1a complex correlates with development of pure motor Guillain-Barré syndrome with reversible conduction failure

Antibodies to a ganglioside complex consisting of GM1 and GalNAc-GD1a (GM1/GalNAc-GD1a) are found in sera from patients with Guillain-Barré syndrome (GBS). To elucidate the clinical significance of anti-GM1/GalNAc-GD1a antibodies in GBS, clinical features of 58 GBS patients with IgG anti-GM1/GalNAc-GD1a antibodies confirmed by enzyme-linked immunosorbent assay and thin layer chromatography immunostaining were analyzed. Compared to GBS patients without anti-GM1/GalNAc-GD1a antibodies, anti-GM1/GalNAc-GD1a-positive patients more frequently had a preceding respiratory infection (n=38, 66%, p<0.01) and were characterized by infrequency of cranial nerve deficits (n=9, 16%, p<0.01) and sensory disturbances (n=26, 45%, p<0.01). Of the 28 anti-GM1/GalNAc-GD1a-positive patients for whom electrophysiological data were available, 14 had conduction blocks (CBs) at intermediate segments of motor nerves, which were not followed by evident remyelination. Eight of 10 bedridden cases were able to walk independently within one month after the nadir. These results show that the presence of anti-GM1/GalNAc-GD1a antibodies correlated with pure motor GBS characterized by antecedent respiratory infection, fewer cranial nerve deficits, and CBs at intermediate sites of motor nerves. The CB may be generated through alteration of the regulatory function of sodium channels in the nodal axolemma.