BACKGROUND AND AIMS:Subcutaneous immunoglobulin (SCIg) is an alternative maintenance therapy to intravenous immunoglobulin (IVIg) in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The CIDP guideline considers switching from IVIg to SCIg at an equivalent dosage reasonable; however, the optimal dosing strategy is unknown. This case series examines whether a 1:1 IVIg-to-SCIg switch maintains clinical stability. METHODS:IVIg-dependent, clinically stable CIDP patients who switched from IVIg to SCIg in the Erasmus Medical Center were retrospectively evaluated. Clinical deterioration was defined as a decline in grip strength or muscle strength, or an increase in disability based on minimal clinically important difference criteria within 4 months after the switch. RESULTS:A total of 10 consecutive CIDP patients on stable IVIg regimens switched to an equivalent (1:1) SCIg dose. One patient remained clinically stable, while nine patients deteriorated. Three of these became clinically stable after increasing the SCIg dose to 1:1.3 or 1:1.5, whereas three patients did not regain stability despite a dose increase to 1:1.3. Clinical stability was maintained in the patient receiving a low dose (0.4 g/kg every 3 weeks), whereas patients receiving higher doses (≥ 1 g/kg every 3 weeks) deteriorated. Five patients switched back to IVIg, while five remained on SCIg throughout follow-up. INTERPRETATION:A 1:1 IVIg-to-SCIg switch was insufficient to maintain clinical stability in most CIDP patients, including those on higher IVIg maintenance doses. Some but not all patients regained stability after increasing the SCIg dose. Optimal dose adjustment strategies, including whether temporary higher dosing is required, remain to be determined in future studies.

BACKGROUND:Tremor can be a disabling symptom of chronic inflammatory demyelinating polyneuropathy (CIDP). Studies on tremor in CIDP are limited and generally include small populations. We aim to determine the prevalence, clinical characteristics and treatment response of tremor in a large cohort of patients with CIDP. METHODS:We conducted a multicentre cross-sectional study in patients with CIDP. Tremor was assessed using the Fahn-Tolosa-Marin Clinical Rating Scale for Tremor (FTM-TRS) and electromyography tremor recording. CIDP and additional tremor characteristics were assessed with validated scales and specific questionnaires. RESULTS:Of the 124 included CIDP patients, 86 patients (69%, 95% CI 61 to 77%) currently had clinically tremulous movements (CTM), mainly consisting of tremor but also of myoclonus or both. Lifetime prevalence was 76% (95% CI 68 to 83%). CTM were present in the upper extremities in all (median FTM-TRS part A (FTM-TRS-A) upper extremity score 4, range 1-16), and in the lower extremities in 20% (median FTM-TRS-A lower extremity score 0, range 0-9). Tremor and myoclonus were most prevalent during action/intention. CTM were associated with CIDP-related and tremor-related disability and upper arm sensory impairment. Complete or partial improvement of CTM following immune therapy was reported by 22 out of 48 patients (46%; 95% CI 31 to 61%), while 8 out of 10 patients (80%, 95% CI 44 to 98%) reported partial improvement with beta-blocker use. CONCLUSIONS:CTM are common in CIDP. They are generally mild, although it does impact disability. Immune therapy reportedly improved CTM in a proportion of patients, while beta-blockers seemed effective in a small subgroup of patients.

Background and Objectives This study describes the human leukocyte antigen (HLA) Class II allele frequencies in patients with anti-CNTN1+ and anti-Caspr1+ autoimmune nodopathy (AN).Methods Forty-four AN patients and 50 seronegative CIDP patients from 19 different European hospitals were included in the study. Thirty AN patients had anti-contactin 1 (CNTN1) antibodies, 11 anti-contactin-associated protein 1 (Caspr1) antibodies, and 3 had antibodies against both proteins. HLA-DRB1 was genotyped at the 4-digit allele levels, and the percentage of individuals carrying each allele was compared with that of the general population, obtained from the Allele frequencies database.Results HLA-DRB1*11 alleles appeared in higher proportions in anti-CNTN1+ patients than in seronegative CIDP patients and in the general population (46.7% vs 18% vs 28.4%), with an odds ratio of 3.99 (CI = 1.44 to 11.03, p = 0.01) and 2.2 (CI = 1.07 to 4.53, p = 0.04), respectively. HLA-DRB1*03:01 alleles appeared in significantly higher proportions in anti-Caspr1+ patients than in CIDP patients and in the general population (64.3% vs 22% vs 24.2%), with an odds ratio of 6.38 (CI = 1.77 to 22.99, p = 0.007) and 5.64 (CI = 1.876 to 16.96, p = 0.002), respectively. In the anti-Caspr1+ group, we included 3 patients presenting with antibodies against both CNTN1 and Caspr1 proteins in the acute phase, in which the anti-CNTN1 antibodies disappeared in the chronic phase.Discussion HLA-DRB1*11 alleles are associated with the detection of anti-CNTN1 antibodies in AN patients, and HLA-DRB1*03:01 alleles associate with anti-Caspr1 antibodies. In addition, our study suggests that antiparanodal antibodies targeting both Caspr1 and CNTN1 are present in a small number of patients with AN. These data reinforce the idea that these patients represent specific subsets with clinical features and risk factors that differ from seronegative CIDP patients and from other AN patients. However, further studies should address the functional relevance of these associations and their pathophysiologic implications.

The Gut microbiota is crucial for regulating immune responses in autoimmune neuropathies like Guillain–Barré syndrome (GBS). Yet, its influence on disease course and recovery remains unclear. This study examined gut microbiota dysbiosis in 57 GBS patients and 57 age- and gender-matched healthy controls, following 32 patients for six months to identify microbial signatures associated with disease onset and clinical progression. Gut microbiota profile was obtained through 16S rRNA sequencing (V4-region) and processed using Qiime2-Dada2. Alpha/beta diversity matrices and linear discriminant analysis were applied. Acute-GBS showed significantly altered microbial composition compared to controls, with elevated Enterococcus, Streptococcus, Bacteroides, Ruminococcues-gnavus-group, Lachnoclostridium, taxa, along with reduced Prevotella, Alloprevotella, Megasphaera, Dialister, and Agathobacter. Severe GBS correlated with lower Prevotella, Agathobacter, Subdoligranulum, Dialister, and elevated Enterococcus abundance. At six-months, Streptococcus, Agathobacter, and Eubacterium hallii trended toward normalization, while Enterococcus, Clostridium sensu stricto-1, Romboutsia, Dialistes, Alloprevotella, and Prevotella remained persistently altered. Patients with good 6-months outcomes exhibited reduced Bacteroides, Weissella, UCG-002 and increased Lactobacillus, Ruminococcus gauvreauii, Blautia, Collinsella, and Megasphaera. These findings identify distinct gut microbial signatures associated with GBS onset and clinical course, highlighting their potential as exploratory microbiome-associated biomarkers linked with prognosis that require further validation.

Guillain–Barré syndrome (GBS) is an acute immune-mediated polyneuropathy with a high disease impact, even after good clinical recovery. The Inflammatory Rasch-built Overall Disability Scale (I-RODS) is a Patient-Reported Outcome Measure (PROM) developed for patients with immune-mediated neuropathies that measures limitations in daily activities and social participation. It consists of 24 items, scored from 0–48. The present study aimed to validate the measurement properties of the I-RODS in patients with GBS included in the prospective International GBS Outcome Study (IGOS). The current study focussed on structural validity, cross-cultural validity, internal consistency, and construct validity of I-RODS using Rasch-based methods. The study was conducted in 1226 patients diagnosed with GBS with a median I-RODS score of 28 (IQR 10–41) 4 weeks after inclusion into IGOS. Rasch analyses revealed adequate internal consistency (PSI = 0.95; α = 0.98) and sufficient construct validity, indicated by strong correlations (R = − 0.91 to − 0.77). Targeting was acceptable, although there was a skew towards the floor (10.1

BACKGROUND:Diagnosing chronic inflammatory demyelinating polyneuropathy (CIDP) relies on clinical and electrodiagnostic features. In 2021, the European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) revised the CIDP guideline, superseding the 2010 European Federation of Neurological Societies (EFNS)/PNS guideline. This study compares the diagnostic accuracy of both guidelines and evaluates the impact of specific criterion changes and nerve conduction study (NCS) extensiveness. METHODS:Patients with CIDP were included if they fulfilled the 2010 EFNS/PNS electrodiagnostic criteria for at least possible CIDP or had a presumptive clinical CIDP diagnosis with objective treatment response. Matched controls were patients with suspected chronic immune-mediated neuropathy who received a diagnosis other than CIDP. Diagnostic accuracy was evaluated using two thresholds: one including possible CIDP and one restricted to (probable/definite) CIDP. The impact of electrodiagnostic criteria changes and NCS extensiveness on diagnostic performance was assessed. RESULTS:We included 339 patients and 339 matched controls. Sensitivity of the 2010 EFNS/PNS guideline was 92% when including possible CIDP and 91% for probable/definite CIDP, with specificities of 67% and 78%, respectively. For the 2021 EAN/PNS guideline, sensitivity was 94% when including possible CIDP and 83% for CIDP, with specificities of 66% and 86%, respectively. Differences were due to sensory criteria and changes in conduction block criteria. Unilateral NCS would miss 77 possible CIDP diagnoses. CONCLUSION:Sensitivity and specificity were comparable when including possible CIDP, but the 2021 EAN/PNS guideline showed lower sensitivity and higher specificity for CIDP alone. Modifying criteria, including removal of sensory abnormalities, and more extensive NCS enhanced accuracy.

Ordinal scales are categories ordered by their clinical preference, such as the modified Rankin Scale and Glasgow Outcome Scale Extended. They are widely used as key outcome measures in neurologic trials. Compared with binary outcomes, ordinal scales allow a more detailed assessment of the effect of the treatment and provide more statistical power. Typically, the proportional odds (PO) model (or "shift analysis") is used to quantify the treatment effect in a common odds ratio (cOR) and to test the null hypothesis that the treatment has no effect. Clinical researchers and trialists may worry that the PO assumption will not hold and therefore decide to dichotomize the ordinal scale into a binary outcome. Here, we explain that for the purpose of testing the presence of a treatment effect, it is irrelevant whether the PO assumption holds. In fact, pretesting this assumption to decide which test to use for the treatment effect is invalid and can inflate the type I error probability. Although the PO assumption is not relevant for testing, it is definitely relevant for the purpose of describing and summarizing the treatment effect. We suggest a simple graphical check of the PO assumption as more informative than formal testing. If we are satisfied that there is no substantial violation of the PO assumption, it is reasonable to summarize the treatment effect into a single number such as the cOR. Otherwise, no single-number summary measure provides a faithful representation. We illustrate these practical considerations with 3 neurologic trials: the Endovascular Therapy in Acute Anterior Circulation Large Vessel Occlusive Patients with a Large Infarct Core (ANGEL-ASPECT) trial and the Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands ([MR CLEAN], which investigated endovascular therapy in stroke) and the RESCUEicp trial (which investigated decompressive craniectomy in traumatic brain injury). We conclude with recommendations for the statistical workflow. Undue concerns about the PO assumption should not deter researchers from using ordinal scales in neurologic trials. We provide an R package CORPlot to facilitate the graphical check of the PO assumption.

BACKGROUND AND AIMS:Intravenous immunoglobulin (IVIg) is the primary treatment for Guillain-Barré syndrome (GBS), yet its immunological mechanisms underlying variable clinical outcomes remain unclear. This study investigated the immunomodulatory effect of IVIg on regulatory T cells (Tregs), cytokines, and their association with treatment response and clinical outcomes. METHODS:In this prospective case-controlled study, 57 GBS patients and 57 age- and sex-matched healthy controls (HCs) were investigated. CD4+CD25+FoxP3+ Treg percentages, cytokine production (IL-10, TNF-α, IFN-γ, and IL-12), and serum C3 levels were measured using flow cytometry, Luminex assay, and turbidimetric methods, respectively. Treatment response was defined as ≥ 1-point GBS-disability score improvement during evaluation. RESULTS:GBS patients exhibited lower CD4+CD25+FoxP3+ Tregs frequencies compared to HCs (p = 0.006), which were inversely associated with serum C3 levels (p = 0.003) during the acute phase. At 4 weeks post-onset, patients with normal C3 levels (90-180 mg/dL) exhibited higher Treg frequencies (p = 0.005) compared to acute GBS, whereas patients with persistently elevated C3 levels showed reduced Treg percentage (p = 0.009). Among I VIg-treated patients, Tregs significantly increased at 2 and 4 weeks post-treatment, alongside significantly higher IL-10 and lower TNF-α, IFN-γ, and IL-12 levels at 4 weeks. However, patients with supportive care showed no such changes in Tregs and cytokine levels. Furthermore, Tregs elevated significantly in patients responsive to IVIg at 2 and 4 weeks (p < 0.05), but not in non-responsive or supportive care patients. INTERPRETATION:IVIg treatment modulates immune dysregulation in GBS by expanding CD4+CD25+FoxP3+ Tregs and altering cytokines and serum C3 levels, which are associated with clinical improvement. These findings indicate Tregs as potential biomarkers for monitoring initial clinical response to IVIg in GBS.

OBJECTIVES:Intravenous immunoglobulin (IVIg) is an effective treatment for Guillain-Barré syndrome (GBS), but recovery varies between patients. This study aims to evaluate the pharmacokinetics (PK) and pharmacodynamics (PD) of a single and a second IVIg dose (SID) in patients with GBS. METHODS:Data were analyzed from the SID-GBS trial, a double-blind, randomized, placebo-controlled study. Patients with poor prognosis (modified Erasmus GBS Outcome Score, mEGOS ≥6) after a standard course of IVIg (0.4 g/kg for 5 days) were randomized to receive either SID or placebo. Serum IgG levels were measured at standard serial time points and clinical outcomes were assessed using the GBS disability score and Medical Research Council sum score. PK modeling was performed to predict IVIg exposure and its association with clinical outcomes. RESULTS:Serum IgG concentration after a single and double course of IVIg was variable, but accurately described by the current PK model. Lower ΔIgG and IVIg exposure were associated with poorer clinical outcomes. SID increased the IgG concentration, but did not result in an improvement in clinical outcome. Serious adverse events, including thromboembolic events, occurred more frequently in the SID group and were associated with lower IVIg exposure. INTERPRETATION:SID increases serum IgG levels in GBS patients as predicted by the current PK model, but does not improve clinical outcomes and increases the risk of serious adverse events. Model-informed precision dosing may guide individualization of treatment.

PURPOSE OF REVIEW:Guillain-Barré syndrome (GBS) is a severe but treatable form of immune-mediated neuropathy. The purpose of this review is to provide an update on current immune treatments for GBS, highlight challenges in clinical practice and research, and discuss new developments in therapies that focus on reducing inflammation and preventing further nerve damage. RECENT FINDINGS:In 2023, a GRADE-based guideline was published on the diagnosis and treatment of GBS on behalf of EAN/PNS. Several clinical trials have been conducted in GBS recently, including studies with an observational comparative study design. SUMMARY:Since 30 years, intravenous immunoglobulins and plasma exchange are the only proven effective immune treatments for GBS. Despite these treatments, a substantial proportion of patients recover incompletely and have residual disability or complaints with a high impact on quality of life. New treatment trials focus on reducing immunoglobulin G antibodies to nerves and inhibition of complement activation. Observational comparative studies based on extensive and well defined cohorts are an alternative method to evaluate the effect of treatments in GBS. Several novel study designs are discussed that aim to facilitate the conduct of future trials with more sustainable use of data.

Guillain–Barré syndrome (GBS) and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) are rare immune-mediated disorders of the peripheral nervous system. They cause significant physical and mental symptoms and functional impairments that impact patients’ daily lives. Current treatment does not effectively prevent the occurrence of these residual symptoms and functional limitations. Patient-Reported Outcomes (PROs) and Patient-Reported Outcome Measures (PROMs) are essential tools that capture patients’ perspectives on their own health, which can be used to assess disease impact and evaluate treatment efficacy. The commonly used Inflammatory Rasch-Built Overall Disability Scale (I-RODS) primarily focuses on activity limitations, social participation, but has been noted to have certain clinimetric shortcomings. This highlights the need for a tailored PROM set that comprehensively assesses relevant aspects of health-related quality of life (HRQL) in patients with GBS or CIDP. This prospective mixed-method study consists of a multiphase approach for developing a PROM set in a Dutch adult population with GBS and CIDP. The first phase involves a systematic review and an (online) survey with open-ended questions to identify relevant patient-reported outcomes (PROs), which will be analyzed qualitatively. Subsequently, stakeholder panel meetings will be held with patients and healthcare providers to discuss the identified PROs, including generic and disease specific symptoms and existing suitable PROMs, using the generic Patient Reported Outcomes Measurement Information System (PROMIS) as a basis. Following this, cognitive interviews will be performed to pilot-test a new disease-specific symptom checklist. A Delphi study will then be conducted to achieve consensus on the final PROM set. Finally, a validation study of the selected PROMIS measures and the newly developed disease-specific symptom checklist will be performed. The final phase of the study involves a consensus meeting with the stakeholders to discuss dissemination and implementation strategies for the proposed PROM set. This PROM set is being developed to measure HRQL outcomes relevant for patients with GBS and CIDP. The aim is to develop a tool for clinical practice and research to evaluate the clinical course and effect of treatments from the perspective of patients. Not applicable.

Fc-gamma receptors (FcγRs) are important for the effector functions of immunoglobulin G (IgG) and are therefore expected to play a role in the pathophysiology of Guillain-Barré syndrome (GBS). The FCGR2/3 locus, which encodes low-to-medium-affinity FcγRs, contains extensive genetic variation. We hypothesized that genetic variation in the FCGR2/3 locus influences GBS susceptibility, muscle weakness, outcomes, and the pharmacokinetics of intravenous immunoglobulin (IVIg). Copy number variation and single nucleotide polymorphisms in the FCGR2/3 locus were studied using multiplex ligation-dependent probe amplification (MLPA). The study cohort consisted of 467 GBS patients and 919 healthy controls of European descent. Severe weakness was defined as an MRC sum score < 40 at nadir. The increase in serum IgG one or two weeks after start of IVIg treatment was determined. No significant associations were found between genetic variation in the FCGR2/3 locus and susceptibility to GBS. However, in patients with an antecedent Campylobacter jejuni infection, a higher frequency of three or more FCGR3A copies was observed compared to healthy controls (p = 0.023). FCGR3A copy numbers were also associated with more severe disease (OR = 2.02; 95

Guillain-Barré syndrome is an acute polyradiculoneuropathy in which preceding infections often elicit the production of antibodies that target peripheral nerve antigens, principally gangliosides. Anti-ganglioside antibodies are thought to play a key role in the clinical diversity of the disease and can be helpful in clinical practice. Extensive research into clinical associations of individual anti-ganglioside antibody specificities has been performed. Recent research has highlighted glycolipid complexes, glycolipid combinations that may alter antibody binding, as targets. In this study, we investigated antibody reactivity patterns to glycolipids and glycolipid complexes using combinatorial array, in relation to clinical features in Guillain-Barré syndrome. In total, 1413 patients from the observational International Guillain-Barré syndrome Outcome Study (0-91 years, 60.3% male) and 1061 controls (healthy, family, infectious, vaccination, other neurological disease) were included. Acute-phase sera from patients were screened for IgM, IgG, and IgA reactivity against 15 glycolipids and one phospholipid and their heteromeric complexes, similarly to archived control sera. Antibody specificities and reactivity patterns were analysed in relation to clinical features. Of all patients, 1309 (92.6%) were positive for at least one anti-glycolipid (complex) antibody. Anti-GM1 and anti-GQ1b (complex) antibodies best distinguished motor Guillain-Barré syndrome and Miller Fisher syndrome from controls, with antibodies to glycolipid complexes outperforming antibodies to single glycolipids. Three models consisting of anti-glycolipid (complex) antibodies distinguished patients with Guillain-Barré syndrome, the motor variant, and Miller Fisher syndrome from controls with high sensitivity and specificity, performing better than antibodies to single glycolipids used in clinical practice. Seven patient clusters with particular antibody reactivity patterns were identified. These clusters were distinguished by geographical region, clinical variants, preceding Campylobacter jejuni infection, electrophysiological subtypes, the Medical Research Council sum score at study entry, and the ability to walk 10 m unaided at 26 weeks. Two patient clusters with distinct anti-GM1 (complex) reactivity (broad versus restricted) differed in frequency of the axonal subtype. In cumulative incidence analyses, 15 anti-glycolipid (complex) antibodies were associated with the time required to regain the ability to walk 10 m unaided. After adjustment for known prognostic factors, IgG anti-GQ1b:GM4, GQ1b:PS and GQ1b:Sulfatide remained associated with faster recovery. Addition of anti-glycolipid antibodies to clinical prognostic models slightly improved their discriminative capacity, though insufficiently to improve the models. Measurement of anti-glycolipid antibodies by combinatorial array increases the diagnostic yield compared to assaying single glycolipids, identifies clinically relevant antibody reactivity patterns to glycolipids and glycolipid complexes, and may be useful in outcome prediction in Guillain-Barré syndrome.

Background Several prognostic models predict clinical outcomes in Guillain-Barr & eacute; syndrome (GBS). Recently, neurofilament light chain (NfL) has emerged as a prognostic biomarker. We investigated the added prognostic value of NfL in serum (sNfL) and cerebrospinal fluid (cNfL) to models based on clinical factors predicting respiratory failure and inability to walk in GBS.Methods We included patients from a randomised placebo-controlled trial (second intravenous immunoglobulin dose in GBS). Serum was acquired at entry and week 1, 2, 4 and 12 and cerebrospinal fluid at entry. NfL levels were determined on a single molecule array. The additional prognostic value of NfL to the (modified) Erasmus GBS Outcome Score ((m)EGOS) and (modified) Erasmus GBS Respiratory Insufficiency Score was evaluated using logistic regression analyses.Results In total, 293 patients were included (74 (25%) mechanically ventilated, 38/275 (13%) unable to walk at 26 weeks). Higher sNfL at entry, week 1 and week 2 and cNfL at entry were associated with inability to walk at 4 and 26 weeks. Neither sNfL nor cNfL levels at entry were associated with respiratory failure. The EGOS and mEGOS improved after adding NfL (triangle C-statistic range: 0.01-0.11), especially the models predicting outcome at 26 weeks. A new model predicting inability to walk at 26 weeks consisting of sNfL at entry, GBS disability score at entry and Medical Research Council sum score at week 2 performed best (C-statistic: 0.88 (95% CI 0.83 to 0.94)).Conclusions Addition of NfL may improve clinical prognostic models for the prediction of inability to walk, but not of respiratory failure.Trial registration number NTR2224/NL2107.

BackgroundINCbase is an international, multicenter prospective observational study using a customizable web-based modular registry to study the clinical, biological and electrophysiological variation and boundaries of chronic inflammatory demyelinating polyneuropathy (CIDP). The primary objective of INCbase is to develop and validate a clinical prediction model for treatment response.MethodsAll patients meeting clinical criteria for CIDP can be included in INCbase. Collected data include demographics, clinical history, diagnostics and various domains of clinical outcomes. Data is collected at a minimum of every 6 months for two years, and more frequently at the discretion of the investigational site to allow for assessment of unexpected changes in treatment response or clinical status. Participants can be enrolled in various sub-studies designed to capture data relevant to specific groups of interest. Data is entered directly into the web-based data entry system by local investigators and/or participants. Collection and local storage of biomaterial is optional. To develop a clinical prediction model for treatment response, newly diagnosed patients with active disease warranting start of first-line treatment will be included. The study population will be split into a development and validation cohort. Univariate and multivariate logistic regression analysis will be used to identify and combine predictors at start of treatment for treatment response at six months. Model performance will be assessed through discrimination and calibration in an external validation cohort. The externally validated prediction model will be made available to researchers and clinicians on the INCbase website.DiscussionWith this study, we aim to create a clinically relevant and implementable prediction model for treatment response to first line treatments in CIDP. INCbase enrollment started in April 2021, with 29 centers across 8 countries and 303 patients participating to date. This collaborative effort between academia, patient advocacy organizations and pharmaceutical industry will deepen our understanding of how to diagnose and treat CIDP.

BACKGROUND AND PURPOSE:Various electrodiagnostic criteria have been developed in Guillain-Barré syndrome (GBS). Their performance in a broad representation of GBS patients has not been evaluated. Motor conduction data from the International GBS Outcome Study (IGOS) cohort were used to compare two widely used criterion sets and relate these to diagnostic amyotrophic lateral sclerosis criteria. METHODS:From the first 1500 patients in IGOS, nerve conduction studies from 1137 (75.8%) were available for the current study. These patients were classified according to nerve conduction studies criteria proposed by Hadden and Rajabally. RESULTS:Of the 1137 studies, 68.3% (N = 777) were classified identically according to criteria by Hadden and Rajabally: 111 (9.8%) axonal, 366 (32.2%) demyelinating, 195 (17.2%) equivocal, 35 (3.1%) inexcitable and 70 (6.2%) normal. Thus, 360 studies (31.7%) were classified differently. The areas of differences were as follows: 155 studies (13.6%) classified as demyelinating by Hadden and axonal by Rajabally; 122 studies (10.7%) classified as demyelinating by Hadden and equivocal by Rajabally; and 75 studies (6.6%) classified as equivocal by Hadden and axonal by Rajabally. Due to more strictly defined cutoffs fewer patients fulfilled demyelinating criteria by Rajabally than by Hadden, making more patients eligible for axonal or equivocal classification by Rajabally. In 234 (68.6%) axonal studies by Rajabally the revised El Escorial (amyotrophic lateral sclerosis) criteria were fulfilled; in axonal cases by Hadden this was 1.8%. CONCLUSIONS AND DISCUSSION:This study shows that electrodiagnosis in GBS is dependent on the criterion set utilized, both of which are based on expert opinion. Reappraisal of electrodiagnostic subtyping in GBS is warranted.