Effect of intravenous immunoglobulin and plasmapheresis on nerve conduction parameters compared to the natural course of Guillain-Barré syndrome

BACKGROUND

Intravenous immunoglobulin (IVIg) and plasmapheresis (PLEX) are recommended in moderate to severe Guillain-Barré Syndrome (GBS), but there is paucity of studies evaluating its effect on nerve conduction studies (NCS). We report the effect of IVIg and PLEX on the NCS parameters and clinical outcomes compared to natural course (NC) of GBS patients.

METHOD

Moderate to severe GBS patients were included based on clinical, cerebrospinal fluid, and NCS finding. Six motor and sensory nerves were evaluated at admission, one month and 3 months, and NCS subtyping was done. Axonal and demyelination burden in motor nerves and early reversible conduction block (ERCB) were noted. Patients receiving IVIg, PLEX or on NC were noted. Outcome was defined at 3 months into complete, partial and poor using a 0-6 GBS Disability Scale (GBSDS).

RESULT

Seventy-two patients were included, whose median age was 36 years and 22(30.6 %) were females. 44 patients received IVIg, 9 PLEX and 19 were in NC, and they had comparable peak disability. AIDP was the dominant subtype at admission (58.3 %), which remained so at 3 months (50 %). The shift of subtypes was the highest from the equivocal group followed by AMAN and the least from AIDP. IVIg and PLEX group had more reduction in axonal burden and had ERCB compared to NC. 33(44 %) patients had complete recovery, and 40(55.5 %) patients had concordance in clinical and neurophysiological outcome.

CONCLUSION

Transition of GBS subtype may occur at follow-up from all the subtypes, the highest from the equivocal and the lowest from the AIDP group. IVIg/PLEX treatment may help in reducing conduction block and axonal burden.

Guidelines for Neuroprognostication in Adults with Guillain-Barré Syndrome

BACKGROUND

Guillain-Barré syndrome (GBS) often carries a favorable prognosis. Of adult patients with GBS, 10-30% require mechanical ventilation during the acute phase of the disease. After the acute phase, the focus shifts to restoration of motor strength, ambulation, and neurological function, with variable speed and degree of recovery. The objective of these guidelines is to provide recommendations on the reliability of select clinical predictors that serve as the basis of neuroprognostication and provide guidance to clinicians counseling adult patients with GBS and/or their surrogates.

METHODS

A narrative systematic review was completed using Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology. Candidate predictors, including clinical variables and prediction models, were selected based on clinical relevance and presence of appropriate body of evidence. The Population/Intervention/Comparator/Outcome/Time frame/Setting (PICOTS) question was framed as follows: "When counseling patients or surrogates of critically ill patients with Guillain-Barré syndrome, should [predictor, with time of assessment if appropriate] be considered a reliable predictor of [outcome, with time frame of assessment]?" Additional full-text screening criteria were used to exclude small and lower quality studies. Following construction of an evidence profile and summary of findings, recommendations were based on four GRADE criteria: quality of evidence, balance of desirable and undesirable consequences, values and preferences, and resource use. In addition, good practice recommendations addressed essential principles of neuroprognostication that could not be framed in PICOTS format.

RESULTS

Eight candidate clinical variables and six prediction models were selected. A total of 45 articles met our eligibility criteria to guide recommendations. We recommend bulbar weakness (the degree of motor weakness at disease nadir) and the Erasmus GBS Respiratory Insufficiency Score as moderately reliable for prediction of the need for mechanical ventilation. The Erasmus GBS Outcome Score (EGOS) and modified EGOS were identified as moderately reliable predictors of independent ambulation at 3 months and beyond. Good practice recommendations include consideration of both acute and recovery phases of the disease during prognostication, discussion of the possible need for mechanical ventilation and enteral nutrition during counseling, and consideration of the complete clinical condition as opposed to a single variable during prognostication.

CONCLUSIONS

These guidelines provide recommendations on the reliability of predictors of the need for mechanical ventilation, poor functional outcome, and independent ambulation following GBS in the context of counseling patients and/or surrogates and suggest broad principles of neuroprognostication. Few predictors were considered moderately reliable based on the available body of evidence, and higher quality data are needed.

Sex differences in Guillain Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy and experimental autoimmune neuritis

Guillain Barré syndrome (GBS) and its variants, and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP and its variants, are regarded as immune mediated neuropathies. Unlike in many autoimmune disorders, GBS and CIDP are more common in males than females. Sex is not a clear predictor of outcome. Experimental autoimmune neuritis (EAN) is an animal model of these diseases, but there are no studies of the effects of sex in EAN. The pathogenesis of GBS and CIDP involves immune response to non-protein antigens, antigen presentation through non-conventional T cells and, in CIDP with nodopathy, IgG4 antibody responses to antigens. There are some reported sex differences in some of these elements of the immune system and we speculate that these sex differences could contribute to the male predominance of these diseases, and suggest that sex differences in peripheral nerves is a topic worthy of further study.

Reversible conduction failure in acute inflammatory demyelinating polyneuropathy

Reversible conduction failure (RCF) has been documented in acute motor axonal neuropathy (AMAN) and is considered a sign of nodopathy. Several reports of RCF in acute inflammatory demyelinating polyneuropathy (AIDP) have suggested that it could be a manifestation of nodopathy. We conducted this study to determine the frequency of RCF in AMAN and AIDP and to compare the clinical features between the two groups with or without RCF. RCF was observed in 38.9% and 18.5% patients in the AMAN and AIDP groups in our study, respectively. AIDP patients with anti-ganglioside antibodies represented 29.4% of the cohort. The clinical features of AIDP with RCF were more similar to those of AMAN with RCF than to those of typical AIDP. However, there were no significant differences in the frequency of anti-ganglioside antibody status between the groups. AIDP with RCF may be a manifestation of nodopathy. The current dichotomous electrodiagnostic criteria, classifying demyelinating and axonal neuropathy, are insufficient to define nodopathy. Further studies are required to revise the electrodiagnostic criteria for Guillain-Barré syndrome.

New classification of autoimmune neuropathies based on target antigens and involved domains of myelinated fibres

Autoimmune neuropathies are named by eponyms, by descriptive terminology or because of the presence of specific antibodies and are traditionally classified, on the basis of pathology and electrophysiology, as primary demyelinating or axonal. However, autoimmune disorders targeting specific molecules of the nodal region, although not showing pathological evidence of demyelination, can exhibit all the electrophysiological changes considered characteristic of a demyelinating neuropathy and acute neuropathies with antiganglioside antibodies, classified as axonal and due to nodal dysfunction, can present with reversible conduction failure and prompt recovery that appear contradictory with the common view of an axonal neuropathy. These observations bring into question the concepts of demyelinating and axonal nerve conduction changes and the groundwork of the classical dichotomous classification.We propose a classification of autoimmune neuropathies based on the involved domains of the myelinated fibre and, when known, on the antigen. This classification, in our opinion, helps to better systematise autoimmune neuropathies because points to the site and molecular target of the autoimmune attack, reconciles some contrasting pathological and electrophysiological findings, circumvents the apparent paradox that neuropathies labelled as axonal may be promptly reversible and finally avoids taxonomic confusion and possible misdiagnosis.

Prediction models for mechanical ventilation and outcome in Guillain-Barré syndrome

Various prediction models have been formulated to predict the need for mechanical ventilation (MV). In this study, we compare the sensitivity and specificity of Erasmus GBS Respiratory Insufficiency Score (EGRIS) and Sharshar score with single breath count (SBC) at 2 Hz to assess their usefulness in predicting MV and functional outcome. The primary outcome was prediction of MV and relative usefulness of all three models based on sensitivity and specificity. The secondary outcome was functional recovery at 6 months using the cut off points for MV and functional outcome at 6months was assessed using Hughes scale and categorized as good (<2) and poor (≥2). The median age was 30 years, and 64 (69.6%) were males. The sensitivity and specificity of EGRIS score was 78.1% and 67.2%, Sharshar score was 75.0% and 64.1%, and SBC at 2 Hz was 78.1% and 75.0%. The area under the receiver operating curves was maximum for SBC at 2 Hz (0.86) compared to other models, although insignificant. EGRIS score < 5 had better functional recovery compared to those with score ≥ 5 (66% vs 34%, p = 0.001). Similarly, in Sharshar score, 23/59 (39%) with score ≥ 4 had good recovery compared to 36 (61%) with score < 4 (p = 0.01). All the three models have comparable predictive values for MV. Outcome prediction is the best with EGRIS.

The value of sensory nerve conduction studies in the diagnosis of Guillain-Barré syndrome

Electrophysiology plays a determinant role in Guillain-Barré syndrome (GBS) diagnosis, classification, and prognostication. However, traditional electrodiagnostic (EDX) criteria for GBS rely on motor nerve conduction studies (NCS) and are suboptimal early in the course of the disease or in the setting of GBS variants. Sensory nerve conduction studies, including the sural-sparing pattern and the sensory ratio are not yet included in EDX criteria despite their well-established role in GBS diagnosis. The aim of this review is to discuss the diagnostic value of sensory NCS in GBS, their role in establishing the diagnosis and predicting the outcome according to the various subtypes of the disease.

Non-COVID Neurological Emergencies: A Silent Killer Going Unnoticed during COVID-19 Pandemic

Objective  This study assesses the impact of coronavirus disease 2019 (COVID-19) on the pattern of neurological emergencies reaching a tertiary care center.

Materials and Methods  This is a retrospective and single center study involving 295 patients with neurological emergencies mainly including acute stroke, status epilepticus (SE), and tubercular meningitis visiting emergency department (ED) from January 1 to April 30, 2020 and divided into pre- and during lockdown, the latter starting from March 25 onward. The primary outcome was number of neurological emergencies visiting ED per week in both periods. Secondary outcomes included disease severity at admission, need for mechanical ventilation (MV), delay in hospitalization, in-hospital mortality, and reasons for poor compliance to ongoing treatment multivariate binary logistic regression was used to find independent predictors of in-hospital mortality which included variables with p <0.1 on univariate analysis. Structural break in the time series analysis was done by using Chow test.

Results  There was 53.8% reduction in number of neurological emergencies visiting ED during lockdown (22.1 visits vs. 10.2 visits per week, p = 0.001), significantly affecting rural population ( p = 0.004). Presenting patients had comparatively severe illness with increased requirement of MV ( p < 0.001) and significant delay in hospitalization during lockdown ( p < 0.001). Poor compliance to ongoing therapy increased from 34.4% in pre-lockdown to 64.7% patients during lockdown ( p < 0.001), mostly due to nonavailability of drugs ( p < 0.001). Overall, 35 deaths were recorded, with 20 (8.2%) in pre-lockdown and 15 (29.4%) during lockdown ( p = 0.001). Lockdown, nonavailability of local health care, delay in hospitalization, severity at admission, and need for MV emerged as independent predictors of poor outcome in stroke and delay in hospitalization in SE.

Conclusion  COVID-19 pandemic and associated lockdown resulted in marked decline in non-COVID neurological emergencies reporting to ED, with more severe presentations and significant delay from onset of symptoms to hospitalization.

[Association of motor nerve conduction block with different subtypes of childhood Guillain-Barré syndrome]

OBJECTIVE

To study the association of motor nerve conduction block (CB) with different subtypes of childhood Guillain-Barré syndrome (GBS).

METHODS

A retrospective analysis was performed on the clinical and nerve electrophysiological data of 50 children with GBS. According to the results of nerve electrophysiology, the children were divided into an acute inflammatory demyelinating polyneuropathy (AIDP) group with 29 children and an acute motor axonal neuropathy (AMAN) group with 21 children. According to the presence or absence of motor nerve CB, the children with AMAN or AIDP were further divided into subgroups: group AMAN with or without motor nerve CB (n=10 and 11 respectively) and group AIDP with or without motor nerve CB group (n=19 and 10 respectively). The subgroups were compared in terms of age of onset, sex, Hughes Functional Grading Scale (HFGS) at nadir for the most severe involvement of motor function, and short-term prognosis based on HFGS score at 1 month after disease onset.

RESULTS

Motor nerve CB was reversible in children with AMAN. AMAN children with motor nerve CB had a significantly lower HFGS score than those without motor nerve CB at 1 month after onset (P<0.05). AIDP children with motor nerve CB had a significantly higher HFGS score than those with motor nerve CB at 1 month after onset (P<0.05).

CONCLUSIONS

AMAN with reversible motor nerve CB suggests mild nerve fiber lesion and has better recovery than AMAN and AIDP without motor nerve CB in short term.

A unicenter, prospective study of Guillain-Barré syndrome in Spain

OBJECTIVE

We report a prospective study analysing clinical characteristics, subtyping and prognosis in Guillain-Barré syndrome (GBS).

METHOD

The study was based on consecutive GBS patients admitted between 2009 and 2017. Disability was serially assessed using the GBS disability scale.

RESULTS

Fifty-six GBS patients were identified with an average age of 55 years (range, 5-86 years) and a male/female ratio of 2.1. The interval to nadir was <7 days in 59% of cases, and 7 to 28 days in the remainder; at nadir, 35.5% of patients were able to walk unaided, and 64.5% did not. Mechanical ventilation was needed in 20% of cases. There were two fatal cases. Clinical variants included paraparetic GBS seven cases, Miller Fisher syndrome one case, and acute sensory ataxic neuropathy (ASAN) one case. Serial electrophysiology showed a demyelinating pattern in 62.5% of cases, axonal in 28.5%, inexcitable in 1.8%, equivocal in 1.8%, and normal in 5.4%. Very early (1 to 4 days after onset) electrophysiology was done in 18 patients; equivocal or normal features in six of them evolved into an axonal pattern in four. Reversible conduction failure of sensitive nerves occurred in ASAN. Antiganglioside antibodies were only detected in axonal GBS. At 24-month follow-up, functional outcome did not differ between demyelinating and axonal GBS. Clinico-pathological correlation in an early fatal case is reported.

CONCLUSIONS

This GBS study demonstrates comparable clinical features to previous investigations from well-defined populations. There was a relatively high prevalence of axonal GBS. We provide new pathophysiological insights on nerve conduction alterations.

Motor Nerve Conduction Block Predicting Outcome of Guillain-Barre Syndrome

Introduction: Motor nerve conduction blocks (CBs) could be detected in both acute inflammatory demyelinating polyradiculoneuropathy (AIDP) and acute motor axonal neuropathy (AMAN). We aimed to identify the correlation between CBs and functional outcome in the two subtypes of GBS. Methods: Motor nerve conduction studies were performed in 17 patients with AIDP and 23 with AMAN. All patients were treated with intravenous immunoglobulin, and their disabilities were evaluated with Hughes functional grading scale before treatment, 1 month and 6 months after onset. Results: AMAN with CBs had higher reduction of Hughes grade (indicating more improved outcomes) at 1 month (1.71 ± 0.83 vs. 1 ± 0.67, p = 0.034) than AIDP with CBs. AMAN with CBs had higher reduction of Hughes grade at 1 month (1.71 ± 0.83 vs. 0.56 ± 0.73, p = 0.002) than AMAN without CBs. The reduction of Hughes grade at 1 month showed no significant difference between AIDP with and without CBs. Discussion: Motor nerve CBs in AMAN indicated better prognosis than in AIDP.

Age may contribute to the increased frequency of axonal Guillain-Barré syndrome

INTRODUCTION

The frequency of axonal Guillain-Barré syndrome (GBS) varies among countries. Previous studies supporting the high frequency of axonal GBS in South America have been carried out with pediatric populations. We seek to determine the frequency of axonal GBS in both children and adults in South America.

METHODS

This is a retrospective cohort analysis of patients who were diagnosed with GBS between January 2006 and December 2013 in a neurological center in Buenos Aires, Argentina. Adults and children with a diagnosis of GBS were included and classified by applying Ho and colleagues' criteria¹ for axonal GBS.

RESULTS

The study included 105 patients with GBS. Among 58 adults, only 5 individuals were classified as axonal GBS compared with 16 of 47 children. The frequency of axonal GBS was significantly higher in children than in adults (34% vs. 8.6%, P = 0.0001).

DISCUSSION

As shown in a cohort of South American patients, age may impact the frequency of axonal GBS. Muscle Nerve 56: 1311-1313, 2017.

Nodo-paranodopathy, internodopathy and cleftopathy: Target-based reclassification of Guillain-Barré-like immune-mediated polyradiculoneuropathies in dogs and cats

Recent views on Guillain-Barré syndrome (GBS) question the accuracy of classification into axonal and demyelinating subtypes that represent convergent neurophysiological phenotypes rather than immunological targets. Instead it has been proposed to clarify the primarily affected fibre subunit in nerve biopsies. As nerve biopsies rarely are part of routine work-up in human patients we evaluated tissues taken from companion animals affected by GBS-like polyradiculoneuropathy to screen for distribution of immune cells, targeted fibre components and segregating non-inflammatory lesions. We identified that immune responses were directed either at Schmidt-Lanterman clefts, the paranode-node complex or both. Based on infiltrative and non-inflammatory changes, four subtypes and/or stages were distinguished, some of which indicate localisation of primary target antigens while others represent convergent late stage pictures, as a consequence to epitope spreading. The impact of histological subtyping onto clinical management and prognosis remains to be evaluated in future clinical trials. Natural development and clinical manifestation of large animal dysimmune neuropathy may reflect human Guillain-Barré syndrome more accurately than experimental models and therefore provide complementary clues for translational research.

Outcome of Guillain-Barre syndrome patients with respiratory paralysis

BACKGROUND AND AIMS

To evaluate the outcome of patients with Guillain -: Barre syndrome (GBS) having respiratory failure treated with modified intubation policy.

DESIGN AND METHODS

Consecutive patients with GBS having single breath count below 12 and respiratory rate >30/min were included and their clinical details noted. The patients were intubated and mechanically ventilated (MV) if their PaO2 was <60 mmHg on venturi mask, PaCo2 > 50 mmHg or pH < 7.3. Their electrophysiological subtypes and complications were noted. The hospital mortality and 3 months outcome were compared in MV and those could be managed without MV even with respiratory compromise.

RESULTS

Out of 369 patients, 102 (27.6%) patients had respiratory compromise who were included in this study. Of the patients with respiratory compromise, 44 (43.1%) were intubated and mechanically ventilated after a median of 4 days of hospitalization. The median duration of MV was 21 (range 1-88) days. The patients with autonomic dysfunction (56.8% vs. 19%), facial weakness (78% vs. 36.2%), bulbar weakness (81.8% vs. 31%), severe weakness (63.8% vs. 31%) and high transaminase level (47.7% vs. 25.9%) needed MV more frequently. In our study, 6.8% patients died and 26.6% had poor outcome which was similar between MV and non-MV patients. The MV patients had longer hospitalization and more complications compared with non-MV group.

CONCLUSION

In GBS patients with respiratory compromise, conservative intubation does not increase mortality and disability.

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.

Guillain-Barré syndrome: subtypes and predictors of outcome from India

There is a paucity of large studies evaluating the subtypes of Guillain-Barré syndrome (GBS) and their outcome from Southeast Asia. We report cliniconeurophysiological subtypes of GBS and their correlation with triggering events and 3-month outcome from northern India. Three hundred and twenty eight consecutive patients with GBS were clinically evaluated, including their triggers, severity, autonomic involvement, cranial nerve palsy, and respiratory paralysis. Nerve conduction study (NCS) was repeated at 3 weeks if the initial study was normal. They were categorized into acute inflammatory demyelinating polyradiculoneuropathy (AIDP), acute motor axonal neuropathy (AMAN), acute motor sensory axonal neuropathy (AMSAN), inexcitable motor nerve, and equivocal. Clinically, 204 (62.2%) patients had pure motor, 106 (32.3%) motor sensory, 16 (4.9%) Miller Fisher syndrome, and 2 (0.6%) pure sensory GBS. Based on NCS, 242 (73.8%) had AIDP, 44 (13.4%) AMAN, 15 (4.6%) AMSAN, 8 (2.4%) inexcitable motor nerves, and 27 (8.2%) equivocal GBS. AIDP patients were older, more common in summer, had lesser peak disability, and better outcome compared to those with AMAN. Eleven (3.4%) patients died and 48 (14.6%) had poor outcome at 3 months. The poor outcome was related to severity, dysautonomia, and inexcitable motor nerves. AIDP is the commonest variant of GBS in our study and has better outcome compared to AMAN.

Spinal nerve involvement in early Guillain-Barré syndrome: a clinico-electrophysiological, ultrasonographic and pathological study

OBJECTIVE

Although prevailing spinal nerve involvement has been recognized in a few detailed Guillain-Barré syndrome (GBS) autopsy reports, imaging studies addressing this question in cervical nerves are lacking.

METHODS

We describe clinical, electrophysiological, ultrasonographic (US) and pathological findings in six consecutive early GBS patients, evaluated within 10 days of onset.

RESULTS

Patients' ages ranged from 37 to 80 years. Five patients required mechanical ventilation, two of them having died 9 and 28 days after onset. Upper- and lower-limb nerve US showed abnormal findings in just 8.8% of scanned peripheral nerves. In comparison with 46 aged-matched control subjects, US of the fifth to seventh cervical nerves showed changes in four cases, which consisted of significant nerve enlargement, blurred boundaries of the corresponding ventral rami, or both. Autopsy study in one case demonstrated that pathology, consisting of demyelination and endoneurial inflammatory oedema, mainly involved cervical and lumbar nerves.

CONCLUSIONS

In early GBS inflammatory oedema of spinal nerves is a pathogenically relevant feature to understanding the mechanism of ascending paralysis, particularly when conventional electrophysiological studies are normal or not diagnostic.

SIGNIFICANCE

Findings advocate the use of cervical nerve US in early GBS.

A new approach to ELISA-based anti-glycolipid antibody evaluation of highly adhesive serum samples

The enzyme-linked immunosorbent assay (ELISA) is a standard immunoassay used in measuring antibody reactivity (expressed as titers) for glycosphingolipids (GSLs) such as gangliosides and sulfoglycolipids in the sera of patients with Guillain-Barré syndrome (GBS), variants of GBS, and chronic inflammatory demyelinating polyneuropathy (CIDP). In the present study, anti-GSL antibodies were evaluated using a new formula of affinity parametric complex (APC), calculated from limiting-dilution serum assay data, followed by affinity parametric complex criterion (APCC). Using assay results based on APCC, we analyzed serum samples categorized into acute inflammatory demyelinating polyneuropathy (AIDP), acute motor-sensory axonal neuropathy (AMSAN), CIDP, CIDP with myasthenia gravis (MG), and amyotrophic lateral sclerosis (ALS). We were able to determine the affinity strength of antibodies otherwise hidden in the non-specific background activity in highly adhesive serum samples. The thin-layer chromatography (TLC)-immuno-overlay method assured us that this new method is an accurate and reliable way for evaluating anti-GSL antibodies using ELISA serum sample data.

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.

Electrodiagnostic criteria for Guillain-Barrè syndrome: a critical revision and the need for an update

Electrophysiology plays a determinant role in Guillain-Barré syndrome (GBS) diagnosis, classification of the subtypes and in establishing prognosis. In the last three decades, different electrodiagnostic criteria sets have been proposed for acute inflammatory demyelinating neuropathy (AIDP), acute motor axonal neuropathy (AMAN) and acute motor and sensory axonal neuropathy (AMSAN). Criteria sets for AIDP varied for the parameters indicative of demyelination considered, for the cut-off limits and the number of required abnormalities (all a priori established) showing different sensitivities. Criteria sets for AMAN and AMSAN were proposed on the initial assumption that these subtypes were pathologically characterised by simple axonal degeneration. However, some AMAN patients show transient conduction block/slowing in intermediate and distal nerve segments, mimicking demyelination but without the development of abnormal temporal dispersion, named reversible conduction failure (RCF). The lack of distinction between RCF and demyelinating conduction block leads to fallaciously classify AMAN patients with RCF as AIDP or AMAN with axonal degeneration. Serial electrophysiological studies are mandatory for proper diagnosis of GBS subtypes, identification of pathophysiological mechanisms and prognosis. More reliable electrodiagnostic criteria should be devised to distinguish axonal and demyelinating subtypes of GBS, taking into consideration the RCF pattern and focussing on temporal dispersion.

Clinical and pharmacological aspects of inflammatory demyelinating diseases in childhood: an update

Inflammatory demyelinating diseases comprise a spectrum of disorders affecting the myelin of the central and peripheral nervous system. These diseases can usually be differentiated on the basis of clinical, radiological, laboratory and pathological findings.

Recent studies have contributed to current awareness that inflammatory demyelinating diseases are not restricted to the adult age group, but are more common in pediatric age than previously believed. Some of pediatric inflammatory demyelinating diseases carry an unfavorable long-term prognosis but appropriate treatments can improve the outcome. The possibility of physical and cognitive disability resulting from these diseases, highlights the urgent need for therapeutic strategies for neurorehabilitation, neuroregeneration, and neurorepair.

This review discusses characteristics of primary demyelinating diseases more frequently observed in childhood, focusing on epidemiology, clinical aspects and treatments.

Evaluation of lumbosacral nerve root conduction in chickens by electrophysiological testing including high-resolution spinal magnetic stimulation

The value of avian models in peripheral nerve research recently became substantiated by the immunobiological similarity of avian inflammatory demyelinating polyradiculoneuropathy to human Guillain-Barré syndrome providing an alternative animal model for experimental autoimmune neuritis. As electrophysiologic evaluation of nerve roots is essential part of the diagnosis of polyradiculoneuropathies in humans, it would be favourable to have similar research methods available for juvenile chickens. Hence, this study was performed (1) to establish a tool-set that allows for reproducible evaluation of the tibial/sciatic nerve and its nerve roots, (2) to achieve age-matched reference values, and (3) to trace the kinetics of peripheral nerve maturation within chickens. Nine chickens underwent serial electrodiagnostic examinations between the age of 6 and 15 weeks. Several methods of sensory and motor nerve fiber stimulation of the tibial/sciatic nerve were tested and modified or established. Ultimately, scalp-recorded somatosensory evoked potentials, compound muscle action potentials elicited by tibial/sciatic nerve electrical as well as spinal magnetic stimulation and motor nerve conduction velocity were available for tibial/sciatic nerve and nerve root evaluation in chickens. Base values were obtained for all investigations and parameters. Results indicated that the maturation of the nerve fibers is incomplete up to the age of 15 weeks. The methods tested here provide an excellent tool-set for quantitative tibial/sciatic nerve and nerve root assessment in avian polyradiculoneuropathies, especially within the scope of longitudinal monitoring of the disease course.

Transient immunosuppression: a bridge between infection and the atypical autoimmunity of Guillain-Barré syndrome?

Guillain-Barré syndrome (GBS) is an acute, usually monophasic, disorder of the peripheral nervous system that is assumed to be of immune-mediated pathogenesis. However, several clinical features and experimental findings of GBS are uncharacteristic for an immune-mediated disorder and set this condition apart from other disorders with a putative immune-mediated pathogenesis. These features include, among others, the monophasic nature of GBS, the lack of response to immunosuppressive (unlike immunomodulatory) therapy, the absence of a typical association with immunogenetic background and the inability to establish a valid and relevant animal model. We suggest a comprehensive hypothesis for the pathogenesis of GBS that is based on the assumption that the condition is due to a transient (or occasionally chronic) immune deficiency, as in most cases GBS follows an infection with pathogens known to induce immunosuppression. Such infections may be followed by breakdown of immune tolerance and induction of an immune attack on peripheral nerves. Mounting of the immune-mediated assault might be triggered either by the same infective pathogen or by secondary infection. Clearance of the infection and resumption of a normal immune response and tolerance eventually terminate the immune-mediated damage to the peripheral nerves and enable recovery. This hypothesis assumes that the entire sequence of events that culminates in GBS is due to transient exogenous factors and excludes a significant role for inherent host susceptibility, which explains the monophasic nature of the disorder.

Conduction block in acute motor axonal neuropathy

Guillain-Barré syndrome is divided into two major subtypes, acute inflammatory demyelinating polyneuropathy and acute motor axonal neuropathy. The characteristic electrophysiological features of acute motor axonal neuropathy are reduced amplitude or absence of distal compound muscle action potentials indicating axonal degeneration. In contrast, autopsy study results show early nodal changes in acute motor axonal neuropathy that may produce motor nerve conduction block. Because the presence of conduction block in acute motor axonal neuropathy has yet to be fully recognized, we reviewed how often conduction block occurred and how frequently it either reversed or was followed by axonal degeneration. Based on Ho's criteria, acute motor axonal neuropathy was electrodiagnosed in 18 patients, and repeated motor nerve conduction studies were carried out on their median and ulnar nerves. Forearm segments of these nerves and the across-elbow segments of the ulnar nerve were examined to evaluate conduction block based on the consensus criteria of the American Association of Electrodiagnostic Medicine. Twelve (67%) of the 18 patients with acute motor axonal neuropathy had definite (n=7) or probable (n=5) conduction blocks. Definite conduction block was detected for one patient (6%) in the forearm segments of both nerves and probable conduction block was detected for five patients (28%). Definite conduction block was present across the elbow segment of the ulnar nerve in seven patients (39%) and probable conduction block in two patients (11%). Conduction block was reversible in seven of 12 patients and was followed by axonal degeneration in six. All conduction blocks had disappeared or begun to resolve within three weeks with no electrophysiological evidence of remyelination. One patient showed both reversible conduction block and conduction block followed by axonal degeneration. Clinical features and anti-ganglioside antibody profiles were similar in the patients with (n=12) and without (n=6) conduction block as well as in those with (n=7) and without (n=5) reversible conduction block, indicating that both conditions form a continuum; a pathophysiological spectrum ranging from reversible conduction failure to axonal degeneration, possibly mediated by antibody attack on gangliosides at the axolemma of the nodes of Ranvier, indicating that reversible conduction block and conduction block followed by axonal degeneration and axonal degeneration without conduction block constitute continuous electrophysiological conditions in acute motor axonal neuropathy.

Long term clinical and electrophysiological assessment of Croatian children with corticospinal tract involvement in Guillain-Barré syndrome (GBS)

Guillain-Barré syndrome (GBS) is characterized by areflexia. Hyperreflexia is reported in acute motor axonal neuropathy (AMAN). We present 16 children with GBS at the age of 14 months to 13 years. All children studied fulfilled accepted diagnostic criteria for GBS. Hyperreflexia or positive Babinski sign were obtained in all children studied during follow up. Brain and spinal cord MR scans did not reveal any significant structural and morphological abnormalities of central nervous system. The children were examined clinically and electromyoneurographically 2-5 times successively during 1-8.5 years of follow-up. According to established electrodiagnostic criteria demyelinating form of GBS was most common (68%) compared to axonal (18,7%) or mixed form (12,5%). No children had antecendent Campylobacter jejuni infection. Antiganglioside antibodies were detected in 18,7% of patients associated with demyelinating or mixed (axonal/demyelinating) form. Time to nadir and recovery period of walking ability is prolonged more often in demyelinating GBS. Clinical improvement occur earlier compared to improvement of abnormal electrophysiological parameters.Outcome was excellent in 11 in the period 1 month-8.5 years. Hyperreflexia usually appeared in recovery period suggesting involvement of upper motor neurons or spinal interneurons occurring in Croatian children with both demyelinating and axonal form of GBS usually associated with milder course of disease.