Reversible Conduction Failure Research Articles

The Initial Clinical and Electrophysiological Characteristics of Different Subtypes of Guillain-Barré Syndrome Diagnosed Based on Serial Electrophysiological Examinations.

We aimed to identify different Guillain-Barré syndrome (GBS) subtypes, demyelination, axonal degeneration, and reversible conduction failure (RCF) as early as possible by analyzing the initial clinical and electrophysiological examinations. This study retrospectively collected GBS patients between October 2018 and December 2022 at Beijing Tiantan Hospital. The diagnostic criteria for the initial electrophysiological study were based on Rajabally's criteria, and the criteria for the serial electrophysiological study were based on Uncini's criteria. All subjects underwent clinical and electrophysiological evaluations at least twice within 8 weeks. A total of 47 eligible patients with GBS were included, comprising 19 acute inflammatory demyelinating polyradiculoneuropathy (AIDP), 18 axonal degenerations, and 10 RCFs. In the RCF group, 40%, 30%, and 30% patients were diagnosed as AIDP, axonal, and equivocal at the initial study, respectively. The AIDP group had significantly higher cerebrospinal fluid (CSF) protein than the RCF (123.8 [106.4, 215.1] mg/dL vs. 67.1 [36.8, 85.6] mg/dL, p=0.002) and axonal degeneration (123.8 [106.4, 215.1] mg/dL vs. 60.8 [34.8, 113.0] mg/dL, p<0.001) groups. The RCF group had significantly lower Hughes functional grades at admission (3 [2, 4] vs. 4 [4, 4], p=0.012) and discharge (1.0 [1.0, 2.0] vs. 3.0 [2.0, 3.0], p<0.001) than the axonal degeneration group and showed significantly shorter distal motor latency (DML), Fmin, Fmean, Fmax, and lower F% than the AIDP group (p<0.05). The early identification of RCF from AIDP had relatively obvious features, including slightly elevated CSF protein levels and normal or slightly prolonged DML and F-wave latencies, contrasting with the apparent elevation and prolongation seen in AIDP. Differentiating RCF from axonal degeneration remains challenging. One potential distinguishing factor is that the motor function in RCF tends to be better than in the latter.

Reversible Conduction Failure in Guillain-Barré Syndrome

Gangliosides are the primary antigenic target in acute motor axonal neuropathy. When anti-ganglioside antibodies bind to gangliosides near the motor axon node of Ranvier, complement system activation and Wallerian degeneration occur. Nevertheless, debate persists regarding the impact of anti-ganglioside antibodies on Guillain-Barré syndrome (GBS). Certain patients with these antibodies experience a swift recovery or exhibit conduction abnormalities indicative of demyelination in nerve conduction studies. The concept of reversible conduction failure was introduced by Kuwabara et al. in 1998. They proposed that this could result from compromised physiological conduction at the node of Ranvier. Auto-antibodies that bind to GM1 or GD1a gangliosides at this node can activate the complement system and disrupt sodium channel and axo-glial junctions, causing conduction failure. In 2003, Cappaso et al. described two cases of rapidly improving flaccid paralysis following Campylobacter jejuni infection. Initial nerve conduction studies indicated motor conduction block, which resolved quickly within 2 to 5 weeks. The authors termed this phenomenon acute motor conduction block neuropathy and considered it a form of arrested or partial acute motor axonal neuropathy. Since acute motor conduction block neuropathy could be misclassified as acute inflammatory demyelinating polyneuropathy based on existing electrophysiological criteria, several suggestions were made to refine the classification of GBS subtypes.

Autoimmune nodo-paranodopathies 10 years later: Clinical features, pathophysiology and treatment.

Autoimmune neuropathies are classified, on the basis of pathophysiology, as demyelinating or axonal. The term nodo-paranodopathy, introduced in 2013 to better categorize the neuropathies with antiganglioside antibodies and later expanded to include neuropathies with antibodies to nodal and paranodal axoglial complexes, characterizes disorders in which the nodal region is critical in the pathogenesis. These neuropathies, although presenting electrophysiologic demyelinating features do not show pathologic evidence of segmental demyelination, or, although being classified as axonal, can show reversible nerve conduction failure and rapid recovery contrary with the communal concept of an axonal neuropathy. In this personal view is reported, with a splitting approach, an update on autoimmune nodo-paranodopathies, classified according to the domains of peripheral nerve fiber, the target antigens and the antibody class and subclass involved. The clinical features, the electrophysiologic findings, the results of the immunopathological and ultrastructural studies, the pathophysiology and treatment are also described. The nodo-paranodopathy category integrates the clinical classification of autoimmune neuropathies and expands the traditional dichotomous demyelinating and axonal classification. It helps to a better systematization pointing to the domain and target antigens of the autoimmune process, it resolves conflicting pathologic and electrophysiologic findings, reconciles the contradiction that axonal neuropathies may be rapidly reversible, avoids taxonomical confusion and possible misdiagnoses. Finally this categorization, through the identification of the specific antibody and its prevalent class and subclass, clarifies the pathophysiological mechanisms and addresses to a more targeted therapeutic approach.

Detection of anti-ganglioside antibodies in Guillain-Barré syndrome.

Gangliosides are a class of glycosphingolipid molecules that are highly enriched in cellular membranes of the nervous system. The gangliosides associated with autoimmune diseases of the nervous system are mainly GM1, GD1a, GalNAc-GD1a, GM1b, GD3, CD1b, GT1a, and GQ1b. Multiple antibodies recognizing gangliosides are associated with some acute or chronic peripheral neuropathies, especially Guillain-Barré syndrome (GBS) and its clinical variants. Antibodies binding to gangliosides can activate complement system and recruit macrophages on the axolemma at the nodes of Ranvier of motor fibers, which are found in the course of GBS, causing axonal degeneration and reversible conduction block or conduction failure. Testing of anti-gangliosides autoantibodies is helpful for diagnosis of autoimmune peripheral neuropathies or support the diagnosis of the subtypes. These anti-gangliosides antibodies are usually detected by several qualitative or quantitative methods, particularly enzyme-linked immunosorbent assay (ELISA) and immunodot assays, which have been commercialized or established in-house worldwide. Herein, we introduce the methods and clinical applications of these assays in the diagnosis of autoimmune peripheral neuropathies. Anti-gangliosides antibodies are diagnostic markers of GBS subtypes. We use GBS as an example to explain the role of anti-gangliosides antibodies in the pathogenesis and diagnostic classification of neuropathies.

Association between hyperCKemia and axonal degeneration in Guillain–Barré syndrome

BackgroundElevated serum creatine kinase (CK) levels have been reported in patients with Guillain–Barré syndrome (GBS), more frequently in patients with acute motor axonal neuropathy (AMAN) than in those with acute inflammatory demyelinating polyneuropathy (AIDP). However, some patients with AMAN show reversible conduction failure (RCF), characterized by rapid recovery without axonal degeneration. The present study tested the hypothesis that hyperCKemia is associated with axonal degeneration in GBS, regardless of the subtype.MethodsWe retrospectively enrolled 54 patients with AIDP or AMAN whose serum CK levels were measured within 4 weeks from symptom onset between January 2011 and January 2021. We divided them into hyperCKemia (serum CK ≥ 200 IU/L) and normal CK (serum CK < 200 IU/L) groups. Patients were further classified into axonal degeneration and RCF groups based on more than two nerve conduction studies. The clinical features and frequency of axonal degeneration and RCF were compared between groups.ResultsClinical characteristics were similar in the hyperCKemia and normal CK groups. Compared with that in the RCF subgroup, the frequency of hyperCKemia was significantly higher in the axonal degeneration group (p = 0.007). Patients with normal serum CK levels showed better clinical prognosis, evaluated by the Hughes score at 6 months from admission (p = 0.037).ConclusionHyperCKemia is associated with axonal degeneration in GBS, regardless of the electrophysiological subtype. HyperCKemia within 4 weeks from symptom onset might be a marker of axonal degeneration and poor prognosis in GBS. Serial nerve conduction studies and serum CK measurements will help clinicians understand the pathophysiology of GBS.

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.

Nodopathies in the Early Diagnosis of Axonal Forms of Guillain-Barré Syndrome.

Introduction:Guillain-Barré syndrome (GBS) has been classified into demyelinating and axonal subtypes or forms, such as acute motor axonal neuropathy (AMAN) and regional pharyngeal-cervical-brachial variant (PCBv).ObjectiveTo study the relationship between motor nerve conduction blocks (CBs) and prognosis in AMAN and PCBv.Patients and MethodsWe retrospectively analyzed six cases of AMAN and PCBv with serial nerve conduction studies (NCS) and electromyography (EMG).ResultsThe serial NCS (1st−2nd and 3rd week) showed, as the most constant data, a decreased amplitude of the compound muscle action potential (CMAP) in 100% of cases. CBs were present in 66.6% of cases. EMG (3rd week) showed signs of severe denervation in 33.3%. All patients were treated from the 1st−2nd week of evolution with intravenous immunoglobulins (IVIGs). Patients with CBs (1st−2nd and 3rd week), showed reversible CBs or reversible conduction failure (RCF) and complete recovery at 1 month. Patients without CBs, with persistent reduced distal CMAP amplitude (dCMAP), showed severe acute denervation due to axonal degeneration (3rd week and 1st−3rd month) and a slow recovery of several months.ConclusionsNot all axonal forms of GBS have a poor prognosis. This study of AMAN and PCBv shows that patients with CBs can have reversible CBs or RCF, and good prognosis. Patients without CBs, with persistent reduction of dCMAP amplitude decrement, have severe acute denervation, and a worse prognosis. AMAN and PCBv have a continuous spectrum ranging from CBs due to dysfunction/disruption of Nodes of Ranvier, called nodopathies, with reversible CBs or RCF and good prognosis, to axonal degeneration with worse prognosis.

P-PN029. Clinical and electrophysiological profile of patients with Guillain-Barré Syndrome with conduction blocks

Introduction . Clinical data is limited in patients with Guillain Barre syndrome (GBS) who show conduction block (CB) on nerve conduction study (NCS). We aim to describe the clinical and electrophysiological profiles of GBS with CB. Methods . Between 2017 and 2020, 111 patients fulfilling the National Institute of Neurological Disorders and Stroke (NINDS) criteria for GBS and Brighton level of certainty one or two were seen in a single neurology unit. NCS of three motor (median, ulnar and common peroneal (CP)) and three sensory (median, ulnar and sural) nerves were performed. Definite and probable CBs were defined as proximal/distal latency of 20% of lower limit of normal (LLN). Results . Mean interval from symptom-onset to NCS was 9.4±6.5 days. Twenty patients had CB (one nerve: 15, two nerves: 4, three nerves: 1). This included probable CB in median (n=3), ulnar (n=2) and CP (n=4) nerves, and definite CB in median (n=5), ulnar (n=6) and CP (n=6) nerves. Electrophysiological subtypes included demyelinating (n=11), axonal (n=4) and equivocal (n=5). Demographic and clinical features included M:F of 3:1, mean age of 38.5±19.9 years, facial weakness (n=8), ophthalmoparesis (n=1), respiratory muscle weakness (n=2) and antecedent infection (n=12). At the time of peak neurological deficits, the mean Medical Research Council (MRC) sum score was 35.4±14.9 and Hughes disability score (HDS) was 3.5±0.8. The mean duration of hospital stay was 14.7±15.9 days. At the time of discharge, the mean MRC sum score was 39.8±15.2 and mean HDS was 3.1±0.7. Conclusion . We report CBs across non-entrapment sites in both demyelinating and axonal sub-types of GBS. Interruption of saltatory conduction due to distortion of paranodal myelin leads to reversible conduction failure and rapid recovery as noted in the present study.

Utility of Serial Nerve Conduction Studies in the Electrodiagnosis of Guillain-Barre Syndrome.

Guillain-Barre syndrome can be electrophysiologically classified into demyelinating and axonal subtypes and nerve conduction studies remain the mainstay in electrodiagnosis. Accurate electrodiagnosis has both therapeutic and prognostic significance and different criteria sets have been proposed for classification. To electrophysiologically classify GBS patients into AIDP and axonal subtypes according to various published criteria (Cornblath, 1990: Hadden, 1998, Rajabally, 2015), investigate if serial NCS changes the classification, and to identify additional parameters which may support the electrodiagnosis. In a retrospective study, we included all patients aged 15 to 80 years, admitted with a diagnosis of GBS between August 2015 and July 2017, who had at least two serial NCS. The various published criteria were applied to the two serial NCS and subtype classification along with diagnostic shifts on serial NCS were ascertained. At the first test, the established criteria gave a yield of 45.2% to 71% for AIDP, while 29% to 54.8% of patients were classified as axonal GBS. In the second study, there was a change in electrodiagnosis, ranging from 9.6% to 16.1%. The resolution of reversible conduction failure and misclassification of subtypes were the major reason for diagnostic shifts. Sural sparing pattern, facial nerve dysfunction, abnormal blink reflex, and phrenic nerve dysfunction were more common in AIDP. Serial nerve conduction studies allow an accurate electrodiagnosis of GBS subtypes, which has both therapeutic and prognostic implications. Also, the use of additional parameters such as blink reflex facial and phrenic nerve conduction may supplement routine NCS.

Nerve conduction studies in Guillain-Barré syndrome: Influence of timing and value of repeated measurements

ObjectiveNerve conduction studies (NCS) are essential to differentiate between demyelinating and axonal subtypes in Guillain-Barré syndrome (GBS). However, it is debated to which extent the delay of NCS after symptom onset and repeated measurements during the disease course influence the diagnostic accuracy. MethodsWe evaluated NCS in 93 patients with a classical GBS applying two widely used criteria (Hadden's and Rajabally's). The initial measurements after symptom onset were compared to follow-up studies where available (n = 43). We analyzed the influence of NCS timing after symptom onset and clinical severity on fulfilling the electrophysiological criteria for axonal or demyelinating subtypes and evaluated the impact of repeated measurements. We further evaluated the presence of reversible conduction failure. ResultsA higher GBS disability scale at nadir correlated with a successful subclassification whereas the delay of the first NCS after symptom onset did not influence the diagnostic yield (75% for Hadden's and 68% for Rajabally's criteria for the first assessment). A second measurement allowed the additional successful classification in 19% and 14% of patients, respectively. On the other hand, a repeated measurement in patients with an initial successful classification resulted in a different subtype in 5% and 7%, respectively. Reversible conduction failure was found in 7% of patients. ConclusionClinical severity but not timing of NCS influenced the fulfilment of electrophysiological criteria for either the axonal or demyelinating subtype. Repeated electrophysiological measurements led to a further specification or a change in subtype classification in a relevant proportion of patients.

Clinical features of Guillain\u2013Barr\xe9 syndrome patients with elevated serum creatine kinase levels

BackgroundIt 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.MethodsWe 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.ResultsOf 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).ConclusionsThe 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.

P87-T Rapid recovery of motor and sensory conduction block in multifocal motor neuropathy

Background Multifocal motor neuropathy (MMN) almost purely involves motor nerve. About 20% MMN patients develop minor sensory symptoms in the course of disease. Material and method We reported a 62-year-old male who developed a slowly progressive asymmetrical limb weakness for five years. Motor nerve conduction studies showed definite CB in left median and ulnar nerves, and probable CB in right tibial nerve. Although the patient complained of no sensory symptom, sensory never conduction studies showed absent sensory nerve action potential (SNAP) for bilateral medial plantar and fibular nerves, left sural nerve and reduced amplitude for left median, ulnar and radial nerves. Conduction velocities were otherwise normal. One month after receiving intravenous immunoglobulin (IVIg), his weakness alleviated apparently. A substantial increase in motor amplitude recorded with stimulation at the PF indicated a partial reversal of CB. The SNAP amplitude of left median, ulnar and radial nerves increased more than 50% and the return of bilateral fibular nerve potentials provided evidence of reversible conduction failure in sensory nerves. We reviewed related literature for this performance. Result Three previously published studies reported such a decrease of SNAP amplitude in MMN patients. Such features suggest a more prominent axonal damage more than demyelination. The hyperpolarization of axolemma, resulting from axonal Na+/K+ pump inhibition at the lesion site and overactivity at the adjacent site may constitutes the prominent mechanism of CB. Conclusion Amplitude reduction of SNAP combined with motor CB, which recovered rapidly after IVIg, may suggest axonal damage rather than demyelination.

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

We report a prospective study analysing clinical characteristics, subtyping and prognosis in Guillain-Barré syndrome (GBS). The study was based on consecutive GBS patients admitted between 2009 and 2017. Disability was serially assessed using the GBS disability scale. Fifty-six GBS patients were identified with an average age of 55years (range, 5-86years) and a male/female ratio of 2.1. The interval to nadir was <7days in 59% of cases, and 7 to 28days 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 4days 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. 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.

Guillain-Barre syndrome in North Indian children: Clinical and serial electrophysiological features.

Guillain-Barre syndrome (GBS) is a common acquired polyneuropathy in children. To describe the clinical and serial electrophysiological features along with short-term outcomes of children with GBS in north India. This was a prospective study conducted at a tertiary care pediatric hospital in north India. Consecutive children, aged 2 to 18 years, with GBS, presenting within 4-weeks of onset of weakness, diagnosed on clinical and/or electrophysiological grounds, were enrolled. The enrolled children underwent a detailed clinical-assessment followed by nerve conduction studies. Repeat nerve conduction studies were performed after 2-weeks of the first study to determine changes in the electrophysiological subtype. The patients were followed up for 3 months. Thirty-six children were studied. The mean age at presentation was 5.1 years [standard deviation (SD): 2.1]. The mean medical research council (MRC)-sum-score at admission was 24.1 (SD: 10.4). Thirty-three children (91%) had loss of ambulation, 24 (66%) had cranial nerve involvement, and 6 (16.6%) required ventilation. At presentation, 20 had acute motor axonal neuropathy (AMAN), 13 had acute inflammatory demyelinating polyneuropathy (AIDP), 2 had in-excitable nerves, and 1 had normal findings. Four children, initially diagnosed as AIDP, had AMAN with reversible conduction failure on the repeat study. The final classification was AMAN in 25 (69.4%; 95% confidence interval (CI), 51.9-83.7%) and AIDP in 9 children (25%; 95% CI, 12.1-42.2%). Only one patient was nonambulatory at a 3-month follow-up (n = 32). The Erasmus GBS outcome score was 2 in 2 (5.6%), 3 in 5 (13.9%), 4 in 26 (72.2%), and 5 in 3 (8.3%) patients. The serial electrophysiological studies were helpful in establishing the final correct diagnosis.

Guillain-Barré Syndrome.

Guillain-Barré syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy, and pathophysiologically classified into acute inflammatory demyelinating polyneuropathy (AIDP), acute motor axonal neuropathy (AMAN), and acute motor and sensory axonal neuropathy (AMSAN). The main pathophysiological mechanism is complement-mediated nerve injury caused by antibody-antigen interaction in the peripheral nerves. Antiglycolipid antibodies are most pathogenic factors in the development of GBS, but not found in 40% of patients with GBS. One of the principal target regions in GBS is the node of Ranvier where functional molecules including glycolipids are assembled. Nodal dysfunction induced by the immune response in nodal axolemma, termed "nodopathy," can electrophysiologically show reversible conduction failure, axonal degeneration, or segmental demyelination. To detect new target molecules in antiglycolipid antibody-negative GBS and to elucidate the pathophysiology in the subacute and the subsequent phases of the disorder are the next problems.

Conference lecture: Electrophysiological diagnosis of inflammatory demyelinating neuropathies

Electrophysiology plays a crucial role in the characterization and diagnosis of peripheral neuropathies. It provides insight in the type and mechanism of peripheral neuropathy by giving information on the spatial pattern, the fibre type involved, pathology (axonal, demyelinating), and the severity and time course. Inflammatory demyelinating neuropathies constitute a significant proportion of the acquired peripheral neuropathies. They include Guillain-Barre syndrome (GBS), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), multifocal motor neuropathy (MMN), multifocal demyelinating neuropathy with persistent conduction block (Lewis-Sumner syndrome), and paraproteinemic neuropathies. A proper diagnosis as early as possible is very important because timely immune treatment can largely reduce morbidity and disability. The diagnosis is based on a constellation of clinical and laboratory features, including electrophysiological studies, spinal fluid examination, and in selected cases serological studies and peripheral nerve biopsy. Electrophysiological studies are key in the early detection and characterization of inflammatory demyelinating neuropathies and in differentiating these from primary axonal neuropathies. In CIDP, electrophysiological criteria for demyelination are designed to exclude abnormalities that can be explained by axonal degeneration (Eur J Neurol 2010). Therefore, lesser degrees of demyelination cannot be defined with certainty. Optimised electrophysiological criteria are capable, however, to support the diagnosis with different levels of probability (possible, probable, definite) in the very large majority of cases. In GBS, much effort has gone into developing criteria which can distinguish axonal and demyelinating subtypes. The discovery of reversible conduction failure (RCF) has led to the concept of nodopathy/paranodopathy, where conduction slowing and conduction block are due to the immune attack mainly at the nodal axolemma level. There is no actual demyelinisation as defined pathologically and if the immune attack continues, conduction failure may not reverse and axonal degeneration will ensue. Recent electrophysiological studies support this pathophysiological mechanism and show that the dichotomous distinction between axonal and demyelinating in GBS is not tenable (Muscle nerve, 2018).

Guillain-BarrÉ syndrome subtype diagnosis: A prospective multicentric European study.

There is uncertainty as to whether the Guillain-Barré syndrome (GBS) subtypes, acute inflammatory demyelinating polyradiculoneuropathy (AIDP) and acute motor axonal neuropathy (AMAN), can be diagnosed electrophysiologically. We prospectively included 58 GBS patients. Electrodiagnostic testing (EDX) was performed at means of 5 and 33 days after disease onset. Two traditional and one recent criteria sets were used to classify studies as demyelinating or axonal. Results were correlated with anti-ganglioside antibodies and reversible conduction failure (RCF). No classification shifts were observed, but more patients were classified as axonal with recent criteria. RCF and anti-ganglioside antibodies were present in both subtypes, more frequently in the axonal subtype. Serial EDX has no effect on GBS subtype proportions. The absence of exclusive correlation with RCF and anti-ganglioside antibodies may challenge the concept of demyelinating and axonal GBS subtypes based upon electrophysiological criteria. Frequent RCF indicates that nodal/paranodal alterations may represent the main pathophysiology. Muscle Nerve, 2018.

Reversible conduction failure on the deep tendon reflex response recording in early Guillain-Barré syndrome

ObjectiveTo describe the case of a patient with Guillain-Barré syndrome (GBS) showing early reversible conduction failure (RCF) detected by means of serial deep tendon reflex response (T-reflex) study. MethodsA 36-year-old woman had a 5-day history of foot and hand paresthesias ascending to thighs and arms, throbbing interscapular and neck pain, mild to moderate tetraparesis, and areflexia. Nerve conduction studies (NCS) were performed on days 7 and 33 after onset. ResultsNCS showed an equivocal electrophysiologic pattern, just an isolated distal RCF being detected on the right radial nerve at initial examination. Motor latency on deltoid muscle after Erb’s point stimulation was preserved. Sensory conduction velocities were normal or slightly slowed. Somatosensory evoked potentials from median and tibial nerves were normal. Initially, F-wave study demonstrated reversible abnormalities, consisting of multiple A waves and low F-wave persistence, minimal F-wave latencies being preserved. Biceps brachii T-reflex was normal, whereas Achilles T-reflex was absent bilaterally, appearing on the second study with normal T-wave morphology and latency, thus conforming to the requirements for RCF diagnosis. Soleus H-reflex was also initially absent. ConclusionsSerial T-reflex study is a useful technique for detecting early RCF of proximal nerve trunks in early GBS. SignificanceT-reflex is useful tool for GBS in association with NCS.

S87 Issues in the electrodiagnosis of Guillain-Barré syndrome subtypes

Electrophysiology plays a determinant role in Guillain–Barre syndrome (GBS) diagnosis, classification of the subtypes and in establishing prognosis. Acute inflammatory demyelinating polyradiculoneuropathy (AIDP) has been electrophysiologically characterized by conduction slowing, conduction block, and temporal dispersion. Acute motor axonal neuropathy (AMAN) was initially thought to be characterized by simple axonal degeneration and the electrophysiological correlate limited to reduced amplitude of compound muscle action potentials. However AMAN and acute motor and sensory axonal neuropathy (AMSAN) patients show transient conduction block/slowing due to nodal dysfunction mimicking demyelination but without the development of abnormal temporal dispersion. This has been referred to as reversible conduction failure (RCF) and it is thought to be due to the attack of antiganglioside antibodies at the Ranvier node inducing a transitory dysfunction not progressing to axonal degeneration both in motor and sensory fibers. RCF it can be recognized only by serial studies and it is not included in the current electrodiagnostic criteria of GBS. The lack of distinction between RCF and demyelinating conduction block led to erroneous classification in up to 38% of patients. There is a need for an innovative approach to reach an earlier and more accurate electrodiagnosis based on a single study. In this talk the pitfalls in GBS electrodiagnosis will be highlighted and the inadequacy of current criteria discussed. A new criteria set for AIDP, AMAN and AMSAN, defining also the cut-offs for RCF in motor and sensory fibers, will be illustrated and the electrodiagnostic accuracy of a statistical method of supervised classification (sparse linear discriminant analysis) reported.

O123 Optimizing the electrodiagnostic accuracy in Guillain–Barré syndrome subtypes: Sparse linear discriminant analysis versus criteria sets

Objective To optimize the electrodiagnostic accuracy for Guillain-Barre (GBS) subtypes at the first test and define the criteria for reversible conduction failure (RCF). 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 (SLDA), a supervised statistical method of classification, two existing electrodiagnostic criteria sets (Hadden et al., 1988; Rajabally et al., 2015) and one we propose that additionally evaluates duration of motor responses, sural sparing pattern and RCF in motor and sensory nerves at the second study. Results At first study the misclassification error rates, compared to reference diagnoses, were: 15.3% for sparse SLDA, 30 % for our criteria, 45% for Rajabally’s and 48% for Hadden’s criteria. SLDA identified seven most powerful electrophysiological variables differentiating demyelinating and axonal subtypes and assigned to each patient the diagnostic probabilityof belonging to either subtype. At second test 46.6% of axonal GBS patients showed RCF in two motor and 8.8% in two sensory nerves. Discussion and conclusions Basing on a single test, SLDA showed the highest diagnostic accuracy. Anyway RCF is present in a considerable percentage of axonal GBS patients and can be assessed only with serial tests. Significance Algorithms for SLDA are already available in several statistical packages and even the electromyographic machines could be easily equipped with the appropriated algorithms providing the physician with a decision support system for the diagnosis of neuropathies.