Quantitative analysis of the compound muscle action potential in early acute inflammatory demyelinating polyneuropathy

Clinical and Electrophysiological Characteristics of Very Early Guillain-Barré Syndrome

PURPOSE

This study compared the clinical and electrodiagnostic (EDX) features and long-term outcomes of patients with very early Guillain-Barré syndrome (VEGBS, duration of illness ≤4 days) and those with early/late (>4 days)-presenting GBS.

METHODS

One hundred patients with GBS were clinically evaluated and categorized into VEGBS and early/late GBS groups. Electrodiagnostic studies were performed on the bilateral median, ulnar, and fibular motor nerves and the bilateral median, ulnar, and sural sensory nerves. Admission and peak disability were assessed using the 0 to 6 Guillain-Barré Syndrome Disability Scale (GBSDS). The primary outcome was disability at 6 months, which was categorized as complete (GBSDS ≤1) or poor (GBSDS ≥2). The secondary outcomes were frequencies of abnormal electrodiagnostic findings, in-hospital progression, and mechanical ventilation (MV).

RESULTS

Patients with VEGBS had higher peak disability (median 5 vs. 4; P = 0.02), frequent in-hospital disease progression (42.9% vs. 19.0%, P < 0.01), needed MV (50% vs. 22.4%; P < 0.01), and less frequent albuminocytologic dissociation (52.4% vs. 74.1%; P = 0.02) than those with early/late GBS. Thirteen patients were lost to follow-up at 6 months (nine patients with VEGBS and four patients with early/late GBS). The proportion of patients with complete recovery at 6 months was comparable (60.6% vs. 77.8%; P = ns ). Reduced d-CMAP was the most common abnormality, noted in 64.7% and 71.6% of patients with VEGBS and early/late GBS, respectively ( P = ns). Prolonged distal motor latency (≥130%) was more common in early/late GBS than in VEGBS (36.2% vs. 25.4%; P = 0.02), whereas absent F-waves were more frequent in VEGBS (37.7% vs. 28.7%; P = 0.03).

CONCLUSIONS

Patients with VEGBS were more disabled at admission than those with early/late GBS. However, 6 month's outcomes were similar between the groups. F-wave abnormalities were frequent in VEGBS, and distal motor latency prolongation was common in early/late GBS.

Study of total duration of distal compound muscle action potential in demyelinating and axonal Guillain-Barre' syndrome

OBJECTIVES

Electrophysiology plays a crucial role in Guillain-Barré syndrome (GBS) diagnosis and subtype classification. The aim of our study was to assess the potential role of distal compound muscle action potential (dCMAP) for early differentiation between acute inflammatory demyelinating polyneuropathy (AIDP) and axonal GBS.

METHODS

We retrospectively reviewed the medical records of 24 subjects with AIDP and 18 subjects with axonal GBS. We built up receiver operating characteristic curves for total dCMAP duration and negative phase of dCMAP duration, in order to derive cut-off values able to differentiate between AIDP and axonal GBS.

RESULTS

The total duration of dCMAP was significantly prolonged in AIDP compared to axonal GBS. AUCs, odds ratio and positive predictive values were higher for total duration than for negative peak duration. Nerve conduction parameters in the lower limbs were more sensitive than those in the upper limbs in distinguishing AIDP from axonal GBS.

DISCUSSION

Total duration of dCMAP dispersion may capture an adjunctive component of distal demyelination, not measured by the more traditional parameters and may thus represent a useful tool for early differentiation between AIDP and axonal GBS.

Re-evaluating the accuracy of optimized electrodiagnostic criteria in very early Guillain-Barré syndrome: a sequential study

Using recent optimized electrodiagnostic criteria sets, we aimed at verifying the accuracy of initial nerve conduction studies (NCS) in classic very early Guillain-Barré syndrome (VEGBS), ≤ 4 days after onset, compared with the results of serial NCS. This is a retrospective study based on unreported and consecutive VEGBS patients admitted to two university hospitals between 2015 and 2019. Each patient had serial NCS in at least four nerves. Initial NCS studies were done within 4 days after onset, and serial ones from days 20 to 94. Electrophysiological recordings were blinded evaluated by four of the authors, GBS subtype being established accordingly. Seven adult classic VEGBS patients were identified with a median age of 58 years. At first NCS, GBS subtyping was only possible in 1 case that exhibited an axonal pattern, the remaining patterns being equivocal in 3, and mixed (combining axonal and demyelinating criteria) in the remaining 3. Upon serial NSC there was a rather intricate evolution of electrophysiological GBS patterns, 3 of them being classified as axonal or demyelinating, and the remaining 4 as equivocal or mixed. NCS in VEGBS systematically allows detection of changes suggestive of peripheral neuropathy, though even after serial studies accurate GBS subtyping was only possible in 43% of cases. We provide new pathophysiological insights for better understanding of the observed electrophysiological changes.

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

Background

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

Methods

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

Results

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

Conclusions

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

Very early Guillain-Barré syndrome: A clinical-electrophysiological and ultrasonographic study

Objectives

Using recent optimized electrodiagnostic criteria sets, we primarily aimed at verifying the accuracy of the initial electrophysiological test in very early Guillain-Barré syndrome (VEGBS), ≤4 days of onset, compared with the results of serial electrophysiology. Our secondary objective was to correlate early electrophysiological results with sonographic nerve changes.

Methods

This is a retrospective study based on consecutive VEGBS patients admitted to the hospital. Each patient had serial nerve conduction studies (NCS) in at least 4 nerves. Initial NCS were done within 4 days after onset, and serial ones from the second week onwards. Electrophysiological recordings of each case were re-evaluated, GBS subtype being established accordingly. Nerve ultrasonography was almost always performed within 2 weeks after onset.

Results

Fifteen adult VEGBS patients were identified with a mean age of 57.8 years. At first NCS, VEGBS sub-typing was only possible in 3 (20%) cases that showed an axonal pattern, the remaining patterns being mixed (combining axonal and demyelinating features) in 6 (40%), equivocal in 5 (33.3%), and normal in 1 (6.7%). Upon serial NCS, 7 (46.7%) cases were categorized as acute demyelinating polyneuropathy, 7 (46.7%) as axonal GBS, and 1 (6.6%) as unclassified syndrome. Antiganglioside reactivity was detected in 5 out of the 7 axonal cases. Nerve US showed that lesions mainly involved the ventral rami of scanned cervical nerves.

Conclusions

Serial electrophysiological evaluation is necessary for accurate VEGBS subtype classification. Ultrasonography helps delineate the topography of nerve changes.

Significance

We provide new VEGBS pathophysiological insights into nerve conduction alterations within the first 4 days of the clinical course.

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.

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

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

Pathophysiology and diagnosis of Guillain-Barré syndrome - challenges and needs

Guillain-Barré syndrome (GBS) is an autoimmune polyneuropathy which presents with acute onset and rapid progression of flaccid, hyporeflexi quadriparesis. Both sensory and autonomic nerve involvement is seen. GBS has various subtypes that vary in their pathophysiology. The pathogenesis involves an immune response triggered by a preceding event which may be an infection, immunisation or surgical procedure. Clinical diagnosis has been largely the primary diagnosing criterion for GBS along with electrodiagnosis, which has several pitfalls and is supported by ancillary testing of cerebrospinal fluid (CSF) analysis and Nerve Conduction Studies. Measurement of anti-ganglioside antibodies is also an effective tool in its diagnosis. Further understanding of pathophysiology and better diagnostic methods are required for better management of GBS.

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

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

Acute inflammatory demyelinating polyneuropathy: Contribution of a dispersed distal compound muscle action potential to electrodiagnosis

Prolonged duration of the distal compound muscle action potential (DCMAP) ("DCMAP dispersion") is useful in the electrodiagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP) with good specificity in distinguishing CIDP from amyotrophic lateral sclerosis (ALS) and diabetic polyneuropathy, but its role in the electrodiagnosis of acute inflammatory demyelinating polyneuropathy (AIDP) is unclear. This study addresses this issue by determining the optimal cutoff for DCMAP duration using receiver operating characteristic (ROC) analysis in 207 motor nerves from 53 clinically defined AIDP patients compared to 148 motor nerves from 55 ALS patients. We also determined whether the presence of DCMAP dispersion improves the sensitivity of four of the most sensitive published sets of electrodiagnostic criteria for AIDP. Using the ROC-derived optimal DCMAP duration cutoff of 8.5 ms, DCMAP dispersion was found in at least one motor nerve in 66% of subjects with AIDP compared to 9% of subjects with ALS. DCMAP dispersion improved the sensitivity of the four tested criteria sets to 76%-87% from 43%-77%. Moreover, of 13 AIDP patients who met none of the four published criteria sets, 5 (38%) had at least one dispersed DCMAP. These findings indicate that the presence of DCMAP dispersion adds electrodiagnostic sensitivity to the currently published criteria sets, while maintaining reasonably high specificity against a prototypical disorder of the primary motor neuron with axon loss.

New criteria for early electrodiagnosis of acute inflammatory demyelinating polyneuropathy

A variety of electrodiagnostic methods are used to confirm the diagnosis of acute inflammatory demyelinating polyneuropathy (AIDP), but difficulties are frequent during the first few weeks of weakness. We compared the nerve conduction studies (NCS) of patients with AIDP to those with critical illness polyneuropathy (CIP), a subacute axonal polyneuropathy. New electrodiagnostic criteria with graded certainty (normal, nondiagnostic, suggestive, highly suggestive, and definite) were designed and applied in a blinded manner to both groups. Among the AIDP patients, 64% met the highly suggestive and definite criteria (specificity 95-100%, P < 0.01), whereas 80% of the CIP group fell in the nondiagnostic criteria (P < 0.001). The relative preservation of the sural sensory response in spite of at least two abnormal sensory NCS in the upper limb suggested acute demyelination (sensitivity 48%, specificity 96%, P < 0.001) and was even more conclusive when associated with absent or prolonged F waves. Motor and sensory response amplitudes were lower in the CIP group, with comparable mean motor and sensory distal latencies and motor conduction velocities. Motor conduction blocks were present in 10% of nerves in AIDP and were not encountered in CIP. The frequency of absent or delayed F waves and absent H reflex was similar in both groups. The correlation coefficient of the cerebrospinal fluid protein concentration with the designed criteria was higher in the AIDP group (r = 0.9). We conclude that a new criterion with graded certainty is of higher specificity in the majority of patients with early AIDP.

Neurophysiologic findings in early acute inflammatory demyelinating polyradiculoneuropathy

BACKGROUND

Patients with early acute inflammatory demyelinating polyradiculoneuropathy (AIDP) may not meet the current neurophysiologic criteria.

OBJECTIVE

To document neurophysiologic findings in early AIDP.

METHODS

Clinical and neurophysiologic data from 38 AIDP patients, assessed within 10 days of symptom onset were reviewed.

RESULTS

In addition to absent H reflexes and abnormal F-wave responses in the acute stage of AIDP, abnormalities of blink reflexes, upper limb sensory responses abnormalities with spared sural responses, presence of distal CMAP dispersion, and A-waves were frequently observed. Established demyelinating neurophysiologic parameters were infrequently seen.

CONCLUSIONS

Abnormalities of H reflexes and F responses were most frequently noted in early AIDP. Additionally, distal temporal dispersion, prolonged or absent blink reflexes, and A-waves were often present in the acute stage of AIDP when classic diagnostic criteria of AIDP were not satisfied.

SIGNIFICANCE

Neurophysiologic studies in early AIDP frequently reveal abnormalities that are not specific of primary demyelinating neuropathy.

Electrophysiology to predict mechanical ventilation in Guillain-Barré syndrome

To determine whether electrophysiological features predict endotracheal mechanical ventilation (ETMV) in Guillain-Barré syndrome (GBS). Non-ventilated GBS patients admitted to an ICU underwent standard electrophysiological testing. Endotracheal mechanical ventilation was decided by physicians who were unaware of electrophysiological results. Sixty consecutive patients underwent electrophysiological testing within 17 days of GBS onset; based on Hadden's criteria, 37 (62%) had primary demyelinating, 18 (30%) equivocal and five (8%) axonal disease. Time at electrophysiological testing and proportions of patients treated by plasma exchange and intravenous immunoglobulins were similar in the three groups, whereas primary demyelinating patients had worse results for disability grade and arm grade. The ETMV was required within 20 days of electrophysiological testing in 20 patients, 17 (46%) in the primary demyelinating group, three (17%) in equivocal group and none in the axonal group (P = 0.02). This prospective study suggests that electrophysiological demyelination may predict a need for ETMV in GBS.

Isolated absence of F waves and proximal axonal dysfunction in Guillain-Barré syndrome with antiganglioside antibodies

OBJECTIVES

To investigate the pathophysiology of selective absence of F waves and its relation with antiganglioside antibodies in Guillain-Barré syndrome (GBS). Some patients with GBS show the absence of F waves as an isolated conduction abnormality, which has been interpreted as demyelination in the proximal nerve segments.

METHODS

In 62 consecutive patients with GBS, sequential nerve conduction and F wave studies were reviewed, and antibodies against ganglioside GM1, GM1b, GD1a, GalNAc-GD1a, GD1b, and GQ1b were measured by an enzyme linked immunosorbent assay.

RESULTS

In the first electrophysiological studies, isolated absence of F waves was found in 12 (19%) patients. Sequential studies in 10 of these patients showed two electrophysiological sequel patterns; rapid restoration of F waves (six patients), and persistent absence of F waves with distal motor nerve degeneration (acute motor axonal neuropathy, four patients). None of the 10 patients showed evidence of demyelination in the proximal, intermediate, or distal nerve segments throughout the course. Of the 62 patients, IgG antibodies against GM1, GM1b, GalNAc-GD1a, or GD1b were significantly associated with the electrodiagnosis of acute motor axonal neuropathy, and patients with these antibodies more often had isolated absence of F waves than patients without them (11 of 36 (31%) v one of 26 (4%); p<0.01). Eleven of the 12 patients with isolated absence of F waves had positive serology for one or more antiganglioside antibodies.

CONCLUSIONS

In GBS with antiganglioside antibodies, isolated absence of F waves is a frequent conduction abnormality especially in the early phase of the disease, and may be caused by axonal dysfunction, such as physiological conduction block or axonal degeneration at the nerve roots.

Sensory and mixed nerve action potential temporal dispersion in median neuropathy at the wrist

This retrospective pilot study was undertaken to help determine the usefulness of measuring sensory nerve action potential and mixed nerve action potential temporal dispersion in median neuropathy at the wrist (MNW; i.e., carpal tunnel syndrome). The records were reviewed for 34 patients who were referred to an electrodiagnostic medicine laboratory with normal antidromic median sensory nerve action potential (recording from the index finger), median transcarpal mixed nerve action potential, and ulnar transcarpal mixed nerve action potential peak distal latencies (NO group) and 29 patients with prolongation (>2.2 ms) of the left median transcarpal mixed nerve action potential peak distal latency or relative prolongation of this response (>0.4 ms) compared with the ipsilateral normal ulnar transcarpal mixed nerve action potential peak distal latency (MNW group). By using the time difference between onset and negative peak as a measure of waveform temporal dispersion, mean +/- standard deviation of the median transcarpal mixed nerve action potential time difference for the MNW group (0.57 +/- 0.15 ms) was found to be greater than the NO group (0.44 +/- 0.09 ms; P < 0.01). No statistically significant differences were found for the median sensory nerve action potential time difference between the two groups or between the subgroup of MNW patients with concurrent prolongation of the median sensory nerve action potential peak distal latency and the NO group. These findings suggest that increased median transcarpal mixed nerve action potential temporal dispersion may occur in association with median transcarpal mixed nerve action potential peak distal latency prolongation in MNW. The small magnitude of this increase, however, makes the clinical usefulness of this observation unclear.

IgG anti-GM1 antibody is associated with reversible conduction failure and axonal degeneration in Guillain-Barré syndrome

To investigate the pathophysiological role of anti-GM1 antibody in Guillain-Barré syndrome (GBS), we reviewed sequential nerve conduction studies of 345 nerves in 34 GBS patients. Statistically significant correlation between IgG anti-GM1 antibodies and electrodiagnoses was found. Sixteen IgG anti-GM1-positive patients were classified as having acute motor or acute motor sensory axonal neuropathy (AMAN or AMSAN) (12 patients), as having acute inflammatory demyelinating polyneuropathy (AIDP) (3 patients), or as undetermined (1 patient) by electrodiagnostic criteria. Besides axonal features, there was rapid resolution of conduction slowing and block. In 3 patients initially diagnosed as having AIDP, conduction slowing was resolved within days, and 1 of them and 3 AMAN patients showed markedly rapid increases in amplitudes of distal compound muscle action potentials that were not accompanied by prolonged duration and polyphasia. The time courses of conduction abnormalities were distinct from those in IgG anti-GM1-negative AIDP patients. Rapid resolution of conduction slowing and block, and the absence of remyelinating slow components, suggest that conduction failure may be caused by impaired physiological conduction at the nodes of Ranvier. Reversible conduction failure as well as axonal degeneration constitutes the pathophysiological mechanisms in IgG anti-GM1-positive GBS. In both cases, immune-mediated attack probably occurs on the axolemma of motor fibers.