Evidence for axonal membrane hyperpolarization in multifocal motor neuropathy with conduction block

Axonal excitability as an early biomarker of nerve involvement in hereditary transthyretin amyloidosis

OBJECTIVES

The treatment of hereditary transthyretin amyloidosis polyneuropathy (ATTRv-PN) has been revolutionised by genetic therapies, with dramatic improvements in patient outcomes. Whilst the optimal timing of treatment initiation remains unknown, early treatment is desirable. Consequently, the aim of the study was to develop biomarkers of early nerve dysfunction in ATTRv-PN.

METHODS

Ulnar motor and sensory axonal excitability studies were prospectively undertaken on 22 patients with pathogenic hereditary transthyretin amyloid (ATTRv) gene variants, 12 with large fibre neuropathy (LF+) and 10 without (LF-), with results compared to age- and sex-matched healthy controls.

RESULTS

In motor axons we identified a continuum of change from healthy controls, to LF- and LF+ ATTRv with progressive reduction in hyperpolarising threshold electrotonus (TEh40(10-20 ms): p = 0.04, TEh40(20-40 ms): p = 0.01 and TEh40(90-10 ms): p = 0.01), suggestive of membrane depolarisation. In sensory axons lower levels of subexcitability were observed on single (SubEx) and double pulse (SubEx2) recovery cycle testing in LF+ (SubEx: p = 0.015, SubEx2: p = 0.015, RC(2-1): p = 0.04) suggesting reduced nodal slow potassium conductance, which promotes sensory hyperexcitability, paraesthesia and pain. There were no differences in sensory or motor excitability parameters when comparing different ATTRv variants.

CONCLUSIONS

These progressive changes seen across the disease spectrum in ATTRv-PN suggest that axonal excitability has utility to identify early and progressive nerve dysfunction in ATTRv, regardless of genotype.

SIGNIFICANCE

Axonal excitability is a promising early biomarker of nerve dysfunction in ATTRv-PN.

Altered flexor carpi radialis motor axon excitability properties after cerebrovascular stroke

Background

Spinal motoneurons may become hyperexcitable after a stroke. Knowledge about motoneuron hyperexcitability remains clinically important as it may contribute to a number of phenomena including spasticity, flexion synergies, and abnormal limb postures. Hyperexcitability seems to occur more often in muscles that flex the wrist and fingers (forearm flexors) compared to other upper limb muscles. The cause of hyperexcitability remains uncertain but may involve plastic changes in motoneurons and their axons.

Aim

To characterize intrinsic membrane properties of flexor carpi radialis (FCR) motor axons after stroke using nerve excitability testing.

Methods

Nerve excitability testing using threshold tracking techniques was applied to characterize FCR motor axon properties in persons who suffered a first-time unilateral cortical/subcortical stroke 23 to 308  days earlier. The median nerve was stimulated at the elbow bilaterally in 16 male stroke subjects (51.4 ± 2.9 y) with compound muscle action potentials recorded from the FCR. Nineteen age-matched males (52.7 ± 2.4 y) were also tested to serve as controls.

Results

Axon parameters after stroke were consistent with bilateral hyperpolarization of the resting potential. Nonparetic and paretic side axons were modeled by a 2.6-fold increase in pump currents (IPumpNI) together with an increase (38%-33%) in internodal leak conductance (GLkI) and a decrease (23%-29%) in internodal H conductance (Ih) relative to control axons. A decrease (14%) in Na⁺ channel inactivation rate (Aah) was also needed to fit the paretic axon recovery cycle. "Fanning out" of threshold electrotonus and the resting I/V slope (stroke limbs combined) correlated with blood potassium [K⁺] (R = -0.61 to 0.62, p< 0.01) and disability (R = -0.58 to 0.55, p < 0.05), but not with spasticity, grip strength, or maximal FCR activity.

Conclusion

In contrast to our expectations, FCR axons were not hyperexcitable after stroke. Rather, FCR axons were found to be hyperpolarized bilaterally post stroke, and this was associated with disability and [K⁺]. Reduced FCR axon excitability may represent a kind of bilateral trans-synaptic homeostatic mechanism that acts to minimize motoneuron hyperexcitability.

Immune-Mediated Neuropathies: Pathophysiology and Management

Dysfunction of the immune system can result in damage of the peripheral nervous system. The immunological mechanisms, which include macrophage infiltration, inflammation and proliferation of Schwann cells, result in variable degrees of demyelination and axonal degeneration. Aetiology is diverse and, in some cases, may be precipitated by infection. Various animal models have contributed and helped to elucidate the pathophysiological mechanisms in acute and chronic inflammatory polyradiculoneuropathies (Guillain-Barre Syndrome and chronic inflammatory demyelinating polyradiculoneuropathy, respectively). The presence of specific anti-glycoconjugate antibodies indicates an underlying process of molecular mimicry and sometimes assists in the classification of these disorders, which often merely supports the clinical diagnosis. Now, the electrophysiological presence of conduction blocks is another important factor in characterizing another subgroup of treatable motor neuropathies (multifocal motor neuropathy with conduction block), which is distinct from Lewis-Sumner syndrome (multifocal acquired demyelinating sensory and motor neuropathy) in its response to treatment modalities as well as electrophysiological features. Furthermore, paraneoplastic neuropathies are also immune-mediated and are the result of an immune reaction to tumour cells that express onconeural antigens and mimic molecules expressed on the surface of neurons. The detection of specific paraneoplastic antibodies often assists the clinician in the investigation of an underlying, sometimes specific, malignancy. This review aims to discuss the immunological and pathophysiological mechanisms that are thought to be crucial in the aetiology of dysimmune neuropathies as well as their individual electrophysiological characteristics, their laboratory features and existing treatment options. Here, we aim to present a balance of discussion from these diverse angles that may be helpful in categorizing disease and establishing prognosis.

Neuroplasticity of peripheral axonal properties after ischemic stroke

OBJECTIVE

This study investigated how peripheral axonal excitability changes in ischemic stroke patients with hemiparesis or hemiplegia, reflecting the plasticity of motor axons due to corticospinal tract alterations along the poststroke stage.

METHODS

Each subject received a clinical evaluation, nerve conduction study, and nerve excitability test. Nerve excitability tests were performed on motor median nerves in paretic and non-paretic limbs in the acute stage of stroke. Control nerve excitability test data were obtained from age-matched control subjects. Some patients underwent excitability examinations several times in subacute or chronic stages.

RESULTS

A total of thirty patients with acute ischemic stroke were enrolled. Eight patients were excluded due to severe entrapment neuropathy in the median nerve. The threshold current for 50% compound muscle action potential (CMAP) was higher in paretic limbs than in control subjects. Furthermore, in the cohort with severe patients (muscle power ≤ 3/5 in affected hands), increased threshold current for 50% CMAP and reduced subexcitability were noted in affected limbs than in unaffected limbs. In addition, in the subsequent study of those severe patients, threshold electrotonus increased in the hyperpolarization direction: TEh (100-109 ms), and the minimum I/V slope decreased. The above findings suggest the less excitable and less accommodation in lower motor axons in the paretic limb caused by ischemic stroke.

CONCLUSION

Upper motor neuron injury after stroke can alter nerve excitability in lower motor neurons, and the changes are more obvious in severely paretic limbs. The accommodative changes of axons progress from the subacute to the chronic stage after stroke. Further investigation is necessary to explore the downstream effects of an upper motor neuron insult in the peripheral nerve system.

Motor unit integrity in multifocal motor neuropathy: A systematic evaluation with CMAP scans

Introduction/Aims

Progressive axonal loss in multifocal motor neuropathy (MMN) is often assessed with nerve conduction studies (NCS), by recording maximum compound muscle action potentials (CMAPs). However, reinnervation maintains the CMAP amplitude until a significant portion of the motor unit (MU) pool is lost. Therefore, we performed more informative CMAP scans to study MU characteristics in a large cohort of patients with MMN.

Methods

We derived the maximum CMAP amplitude (CMAP_max), an MU number estimate (MUNE), and the largest MU amplitude stimulus current required to elicit 5%, 50%, and 95% of CMAP_max (S5, S50, S95) and relative ranges ([S95 − S5] × 100 / S50) from the scans. These metrics were compared with clinical, laboratory, and NCS results.

Results

Forty MMN patients and 24 healthy controls were included in the study. CMAP_max and MUNE were reduced in MMN patients (both P < .001). Largest MU amplitude as a percentage of CMAP_max was increased in MMN patients (P < .001). Disease duration and treatment duration were not associated with MUNE. Relative range was larger in patients with anti‐GM1 antibodies than in those without anti‐GM1 antibodies (P = .016) and controls (P < .001). The largest MU amplitudes were larger in patients without anti‐GM1 antibodies than in patients with anti‐GM1 antibodies (P = .037) and controls (P = .044).

Discussion

We found that MU loss is common in MMN and accompanied by enlarged MUs. Presence of anti‐GM1 antibodies was associated with increased relative range of MU thresholds and reduction in largest MU amplitude. Our findings indicate that CMAP scans complement routine NCS, and may have potential for practical monitoring of treatment efficacy and disease progression.

Unexpected postmortem diagnoses in cases of clinically diagnosed amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a motor neuron disease that is clinically and pathologically characterized by impairment of the upper and lower motor neurons. The clinical diagnosis of ALS is not always straightforward because of the lack of specific biomarkers and clinical heterogeneity. This review presents the clinical and pathological findings of four autopsied cases that had been diagnosed with ALS before death. These cases had demonstrated definite and progressive motor neuron signs and symptoms, whereas postmortem assessment revealed miscellaneous disorders, including fungal infection, paraneoplastic syndrome, and amyloidosis. Importantly, nonmotor neuron signs and symptoms, including seizures, extra-pyramidal signs, ocular movement disorders, sensory disturbance, and dysautonomia, had also been documented during the disease course of the cases in the present study. The ALS-unlike symptoms were indicative of the "true" diagnosis in each case when those symptoms were isolated from motor neuron signs/symptoms.

Fasciculation differences between ALS and non-ALS patients: an ultrasound study

Background

Fasciculation is an important sign for the diagnosis of amyotrophic lateral sclerosis (ALS). Our study aimed to analyze the difference in fasciculation detected with muscle ultrasonography (MUS) between ALS patients and non-ALS patients with symptoms resembling ALS.

Methods

Eighty-eight ALS patients and fifty-four non-ALS (eight multifocal motor neuropathy, 32 chronic inflammatory demyelinating polyneuropathy/Charcot-Marie-Tooth, and 14 cervical spondylopathy or lumbar spondylopathy) patients were recruited. MUS was performed on 19 muscle groups in cervical, lumbosacral, bulbar, and thoracic regions for each patient. The intensity of fasciculation was divided into five grades based on firing frequency and number in the involved muscle groups.

Results

The overall detection rates were 72.8% in ALS and 18% in non-ALS patients. The fasciculation grades (median [IQR]) were 2 (0–3) in ALS and 0 (0–0) in non-ALS patients (P < 0.001). Fasciculations were observed in four regions for ALS patients and primarily distributed in proximal limbs. Fasciculations in non-ALS patients were primarily low-grade and mostly distributed in distal limbs.

Discussion

The fasciculation grade was higher in ALS than non-ALS patients. The distribution pattern of fasciculation was different between ALS and non-ALS patients.

Conclusions

The fasciculation grade and distribution pattern detected with MUS could help distinguish ALS from non-ALS patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02473-5.

Review Article "Spotlight on Ultrasonography in the Diagnosis of Peripheral Nerve Disease: The Evidence to Date"

Neuromuscular ultrasound is rapidly becoming incorporated into clinical practice as a standard tool in the assessment of peripheral nerve diseases. Ultrasound complements clinical phenotyping and electrodiagnostic evaluation, providing critical structural anatomical information to enhance diagnosis and identify structural pathology. This review article examines the evidence supporting neuromuscular ultrasound in the diagnosis of compressive mononeuropathies, traumatic nerve injury, generalised peripheral neuropathy and motor neuron disease. Extending the sonographic evaluation of nerves beyond simple morphological measurements has the potential to improve diagnostics in peripheral neuropathy, as well as advancing the understanding of pathological mechanisms, which in turn will promote precise therapies and improve therapeutic outcomes.

Eribulin Mesylate-related Multifocal Demyelinating Neuropathy with Myokymia in a Breast Cancer Patient

We herein report a 48-year-old woman receiving eribulin mesylate for breast cancer who presented with gait disorder, distal limb paresthesia, and weakness progressing monthly. A nerve conduction study indicated demyelination with multifocal conduction block. Considering the immune-mediated pathology of her condition, she was administered intravenous immunoglobulin. Her neurological symptoms improved promptly after intravenous immunoglobulin therapy and eribulin withdrawal. Furthermore, the limb myokymia seen at the time of admission disappeared. Her symptoms continued to improve without additional treatment. We conclude that eribulin was a rare cause of demyelinating neuropathy with multifocal conduction block derived from immune-mediated pathology.

Nerve Pathology Distinguishes Focal Motor Chronic Inflammatory Demyelinating Polyradiculoneuropathy From Multifocal Motor Neuropathy

OBJECTIVES

The objective of the study is to distinguish the mechanisms of disease for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and multifocal motor neuropathy (MMN), which we believe to be fundamentally different. However, distinguishing the mechanisms is more difficult when the presentation of CIDP is motor-predominant, focal, or asymmetric.

METHODS

We describe 3 focal, motor-predominant, representative cases that could be interpreted on clinical and/or electrophysiological grounds as either MMN or focal CIDP, and present pathological findings.

RESULTS

We highlight pathological differences in these cases, and provide an argument that CIDP and MMN are distinct entities with different pathophysiological mechanisms-chronic demyelination for CIDP, and an immune-mediated attack on paranodal motor axons for MMN.

CONCLUSIONS

Based on clinical evaluation, electrophysiology, and nerve biopsy pathology, we can divide the conditions into inflammatory demyelinating neuropathy (focal CIDP) versus chronic axonal neuropathy (MMN). The divergent pathological findings provide further evidence that CIDP and MMN are fundamentally different disorders.

Difference in distribution of fasciculations between multifocal motor neuropathy and amyotrophic lateral sclerosis

OBJECTIVE

To examine differences in fasciculation distribution between patients with multifocal motor neuropathy (MMN) and amyotrophic lateral sclerosis (ALS) based on muscle ultrasound.

METHODS

Forty-one muscles (tongue muscle and 40 muscles of the trunk and limbs on both sides) in 5 MMN patients and 21 muscles (tongue muscle and 20 muscles on the onset side) in 21 ALS patients were subjected to muscle ultrasound individually for 60 seconds to detect the presence of fasciculations.

RESULTS

Fasciculation detection rates on the onset side were significantly higher in ALS (42.4 ± 18.3%, mean ± SD) than in MMN (21.9 ± 8.8%) patients (p < 0.05). In MMN patients, no fasciculation was detected in the tongue or truncal muscles. There was no difference in the fasciculation detection rate between the onset and non-onset sides or between upper and lower limbs in MMN patients.

CONCLUSIONS

In MMN patients, fasciculations were detected extensively in the limbs. However, the detection rate in patients with MMN was lower than in those with ALS.

SIGNIFICANCE

Demonstration of the absence of fasciculations in the tongue and truncal muscles in MMN patients by extensive muscle ultrasound examination may help distinguish MMN from ALS.

Excitability of motor and sensory axons in multifocal motor neuropathy

OBJECTIVE

To assess excitability differences between motor and sensory axons of affected nerves in patients with multifocal motor neuropathy (MMN).

METHODS

We performed motor and sensory excitability tests in affected median nerves of 20 MMN patients and in 20 age-matched normal subjects. CMAPs were recorded from the thenar and SNAPs from the 3rd digit. Clinical tests included assessment of muscle strength, two-point discrimination and joint position.

RESULTS

All MMN patients had weakness of the thenar muscle and normal sensory tests. Motor excitability testing in MMN showed an increased threshold for a 50% CMAP, increased rheobase, decreased stimulus-response slope, fanning-out of threshold electrotonus, decreased resting I/V slope, shortened refractory period, and more pronounced superexcitability. Sensory excitability testing in MMN revealed decreased accommodation half-time and S2-accommodation and less pronounced subexcitability. Mathematical modeling indicated increased Barrett-Barrett conductance for motor fibers and increase in internodal fast potassium conductance for sensory fibers.

CONCLUSIONS

Excitability findings in MMN suggest myelin sheath or paranodal seal involvement in motor fibers and, possibly, paranodal detachment in sensory fibers.

SIGNIFICANCE

Excitability properties of affected nerves in MMN differ between motor and sensory nerve fibers.

Multifocal motor neuropathy: controversies and priorities

Despite 30 years of research there are still significant unknowns and controversies associated with multifocal motor neuropathy (MMN) including disease pathophysiology, diagnostic criteria and treatment. Foremost relates to the underlying pathophysiology, specifically whether MMN represents an axonal or demyelinating neuropathy and whether the underlying pathophysiology is focused at the node of Ranvier. In turn, this discussion promotes consideration of therapeutic approaches, an issue that becomes more directed in this evolving era of precision medicine. It is generally accepted that MMN represents a chronic progressive immune-mediated motor neuropathy clinically characterised by progressive asymmetric weakness and electrophysiologically by partial motor conduction block. Anti-GM1 IgM antibodies are identified in at least 40% of patients. There have been recent developments in the use of neuromuscular ultrasound and MRI to aid in diagnosing MMN and in further elucidation of its pathophysiological mechanisms. The present Review will critically analyse the knowledge accumulated about MMN over the past 30 years, culminating in a state-of-the-art approach to therapy.

Measurement of axonal excitability: Consensus guidelines

Measurement of axonal excitability provides an in vivo indication of the properties of the nerve membrane and of the ion channels expressed on these axons. Axonal excitability techniques have been utilised to investigate the pathophysiological mechanisms underlying neurological diseases. This document presents guidelines derived for such studies, based on a consensus of international experts, and highlights the potential difficulties when interpreting abnormalities in diseased axons. The present manuscript provides a state-of-the-art review of the findings of axonal excitability studies and their interpretation, in addition to suggesting guidelines for the optimal performance of excitability studies.

Elucidating Unique Axonal Dysfunction Between Nitrous Oxide Abuse and Vitamin B12 Deficiency

Introduction: Abuse of nitrous oxide (N₂O) has an unusually high lifetime prevalence in developed countries and represents a serious concern worldwide. Myeloneuropathy following the inhalant abuse is commonly attributed to the disturbance of vitamin B12 metabolism, with severe motor deficits are often noted. The present study aims to elucidate its underlying pathophysiology.

Methods: Eighteen patients with N₂O abuse or vitamin B12 deficiency were recruited. Comprehensive central and peripheral neuro-diagnostic tests were performed, including whole spine MRI, and thermal quantitative sensory testing (QST). Specifically, paired motor and sensory nerve excitability tests were performed in order to obtain a complete picture of the sensorimotor axonal damage.

Results: The mean duration of N₂O exposure for the N₂O abuse patients was 17.13 ± 7.23 months. MRI revealed T2 hyperintensity in 87.5% of the N₂O abuse patients and 50% of the vitamin B12 deficiency patients. In N₂O abuse patients, the motor nerve excitability test showed decreased in peak response (7.08 ± 0.87 mV, P = 0.05), increased latency (7.09 ± 0.28 ms, P < 0.01), increased superexcitability (−32.95 ± 1.74%, P < 0.05), and decreased accommodation to depolarizing current [TEd (40–60 ms) 56.53 ± 0.70%, P < 0.05]; the sensory test showed only decreased peak response (30.54 ± 5.98 μV, P < 0.05). Meanwhile, motor test in vitamin B12 deficiency patients showed only decreased accommodation to depolarizing current [TEd (40–60 ms) 55.72 ± 1.60%, P < 0.01]; the sensory test showed decreased peak response (25.86 ± 3.44 μV, P < 0.05) increased superexcitability (−28.58 ± 3.71%, P < 0.001), increased subexcitability (8.31 ± 1.64%, P < 0.05), and decreased accommodation to depolarizing current [TEd (peak) 67.31 ± 3.35%, P < 0.001].

Conclusion: Compared to vitamin B12 deficiency, N₂O abuse patients showed prominent motor superexcitability changes and less prominent sensory superexcitability changes, hinting a unique pathological process different from that of vitamin B12 deficiency. N₂O abuse might cause axonal dysfunction not only by blocking methionine metabolism but also by toxicity affecting the paranodal region.

Warming nerves for excitability testing

INTRODUCTION

The aim of this study was to find the best method of warming the median nerve before excitability testing to a standard temperature.

METHODS

In 5 healthy subjects, the forearm and hand were warmed for 1 h to 37°C by infrared lamp, water blanket, or water bath. Recordings were performed before and during warming every 10 min. Excitability indices were fitted by exponential relations, thereby calculating the time needed to reach 95% of their asymptotic end value.

RESULTS

Distal motor latency, refractory period, and superexcitability at 10 ms changed exponentially with time. Warming by water bath took the shortest time (24 min); this was followed by warming by infrared lamp (34 min) and water blanket (35 min).

CONCLUSIONS

Warming by water bath is the quickest way. The other methods took only moderately more time. Future studies need to specify both warming method and warming time before excitability testing. Muscle Nerve, 2019.

Conduction block in immune-mediated neuropathy: paranodopathy versus axonopathy

BACKGROUND AND PURPOSE

Conduction block is a pathognomonic feature of immune-mediated neuropathies. The aim of this study was to advance understanding of pathophysiology and conduction block in chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN).

METHODS

A multimodal approach was used, incorporating clinical phenotyping, neurophysiology, immunohistochemistry and structural assessments.

RESULTS

Of 49 CIDP and 14 MMN patients, 25% and 79% had median nerve forearm block, respectively. Clinical scores were similar in CIDP patients with and without block. CIDP patients with median nerve block demonstrated markedly elevated thresholds and greater threshold changes in threshold electrotonus, whilst those without did not differ from healthy controls in electrotonus parameters. In contrast, MMN patients exhibited marked increases in superexcitability. Nerve size was similar in both CIDP groups at the site of axonal excitability. However, CIDP patients with block demonstrated more frequent paranodal serum binding to teased rat nerve fibres. In keeping with these findings, mathematical modelling of nerve excitability recordings in CIDP patients with block support the role of paranodal dysfunction and enhanced leakage of current between the node and internode. In contrast, changes in MMN probably resulted from a reduction in ion channel density along axons.

CONCLUSIONS

The underlying pathologies in CIDP and MMN are distinct. Conduction block in CIDP is associated with paranodal dysfunction which may be antibody-mediated in a subset of patients. In contrast, MMN is characterized by channel dysfunction downstream from the site of block.

Increased IP-10 production by blood-nerve barrier in multifocal acquired demyelinating sensory and motor neuropathy and multifocal motor neuropathy

OBJECTIVE

Dysfunction of the blood-nerve barrier (BNB) plays important roles in chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). The aim of the present study was to identify the candidate cytokines/chemokines that cause the breakdown of the BNB using sera from patients with CIDP and MMN.

METHODS

We determined the levels of 27 cytokines and chemokines in human peripheral nerve microvascular endothelial cells (PnMECs) after exposure to sera obtained from patients with CIDP variants (typical CIDP and multifocal acquired demyelinating sensory and motor neuropathy [MADSAM]), MMN and amyotrophic lateral sclerosis (ALS), and healthy controls (HC), using a multiplexed fluorescent bead-based immunoassay system.

RESULTS

The induced protein (IP)10 level in the cells in both the MADSAM and MMN groups was markedly increased in comparison with the typical CIDP, ALS and HC groups. The other cytokines, including granulocyte colony-stimulating factor,vascular endothelial growth factor (VEGF) and interleukin-7, were also significantly upregulated in the MADSAM group. The increase of IP-10 produced by PnMECs was correlated with the presence of conduction block in both the MADSAM and MMN groups.

CONCLUSION

The autocrine secretion of IP-10 induced by patient sera in PnMECs was markedly upregulated in both the MADSAM and MMN groups. The overproduction of IP-10 by PnMECs leads to the focal breakdown of the BNB and may help to mediate the transfer of pathogenic T cells across the BNB, thereby resulting in the appearance of conduction block in electrophysiological studies of patients with MADSAM and MMN.

Comparison of cross-sectional areas and distal-proximal nerve ratios in amyotrophic lateral sclerosis

INTRODUCTION

This study explored potential diagnostic markers of nerve ultrasound in differentiating amyotrophic lateral sclerosis (ALS) from mimic disorders.

METHODS

Ultrasound of the median, ulnar, and tibial nerves was conducted in 53 patients with ALS, 32 patients with ALS-mimic disorders, and 30 controls. Nerve cross-sectional area (CSA) and distal-proximal ratios were calculated.

RESULTS

The median nerve CSA in the upper arm was decreased (7.9 ± 1.3 mm² vs. 9.0 ± 1.4 mm² , P < 0.05), and the median nerve wrist-upper arm ratio was increased in ALS patients compared with controls (1.3 ± 0.4 vs. 1.1 ± 0.2; P < 0.01). In differentiating ALS from mimic presentations, assessment of median nerve CSA in the upper arm and comparison of a median and ulnar nerve CSA distal-proximal ratio provide diagnostic potential.

DISCUSSION

Assessment of nerve CSA combined with calculation of nerve CSA distal-proximal ratio provides a useful marker to aid in the diagnosis of ALS. Muscle Nerve 58:777-783, 2018.

Immune-mediated neuropathies

Since the discovery of an acute monophasic paralysis, later coined Guillain-Barré syndrome, almost 100 years ago, and the discovery of chronic, steroid-responsive polyneuropathy 50 years ago, the spectrum of immune-mediated polyneuropathies has broadened, with various subtypes continuing to be identified, including chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and multifocal motor neuropathy (MMN). In general, these disorders are speculated to be caused by autoimmunity to proteins located at the node of Ranvier or components of myelin of peripheral nerves, although disease-associated autoantibodies have not been identified for all disorders. Owing to the numerous subtypes of the immune-mediated neuropathies, making the right diagnosis in daily clinical practice is complicated. Moreover, treating these disorders, particularly their chronic variants, such as CIDP and MMN, poses a challenge. In general, management of these disorders includes immunotherapies, such as corticosteroids, intravenous immunoglobulin or plasma exchange. Improvements in clinical criteria and the emergence of more disease-specific immunotherapies should broaden the therapeutic options for these disabling diseases.

Chronic Demyelinating Polyneuropathies

PURPOSE OF REVIEW

This article reviews the chronic demyelinating neuropathies, with a focus on the diagnosis and treatment of immune-mediated neuropathies and the features that can help differentiate immune-mediated neuropathies from other chronic demyelinating peripheral nerve conditions.

RECENT FINDINGS

Advances in clinical phenotyping and outcomes assessment have enabled neurologists to improve disease recognition, treatment, and disease monitoring. Our understanding of the immunopathogenesis of demyelinating neuropathies is evolving. Identification of new antibodies and recognition that node of Ranvier dysfunction may be an early pathogenic feature may herald further diagnostic and treatment advancements.

SUMMARY

The chronic demyelinating polyneuropathies are heterogeneous. The clinical and diagnostic features are sometimes overlapping, and the specific disorders are variable in pathogenesis, treatment, and prognosis. This heterogeneity underscores the importance of achieving diagnostic accuracy and implementing disease-specific treatment approaches.

Acute Effects of Riluzole and Retigabine on Axonal Excitability in Patients With Amyotrophic Lateral Sclerosis: A Randomized, Double-Blind, Placebo-Controlled, Crossover Trial

Increased excitability of motor neurons in patients with amyotrophic lateral sclerosis (ALS) may be a relevant factor leading to motor neuron damage. This randomized, double-blind, three-way crossover, placebo-controlled study evaluated peripheral motor nerve excitability testing as a biomarker of hyperexcitability and assessed the effects of riluzole and retigabine in 18 patients with ALS. We performed excitability testing at baseline, and twice after participants had received a single dose of either 100 mg riluzole, 300 mg retigabine, or placebo. Between- and within-day repeatability was at least acceptable for 14 out of 18 recorded excitability variables. No effects of riluzole on excitability testing were observed, but retigabine significantly decreased strength-duration time-constant (9.2%) and refractoriness at 2 ms (10.2) compared to placebo. Excitability testing was shown to be a reliable biomarker in patients with ALS, and the acute reversal of previously abnormal variables by retigabine justifies long-term studies evaluating the impact on disease progression and survival.

Contraction response to muscle percussion: A reappraisal of the mechanism of this bedside test

OBJECTIVE

To study whether the contraction evoked by muscle percussion stems from the excitation of the muscle or of the nerve and to discuss the changes of this response in neuromuscular disorders.

METHODS

In 30 neurologically healthy patients undergoing surgery (for ear, nose, or throat problems unrelated to the study) under general anesthesia with propofol and sufentanil we measured with an electrogoniometer the maximal dorsiflexion of the ankle evoked by reflex hammer percussion of the tibialis anterior muscle before and under neuromuscular junction blockade with rocuronium bromide. In 3 additional healthy volunteers we searched for F-waves to disclose whether percussion excites axons within the muscle.

RESULTS

Responses from 28 neurologically healthy patients (15 women) were analyzed after exclusion of 2 due to technical problems. Mean age (SD) was 28 (9) years. Maximal dorsiflexion of the ankle was not significantly modified by neuromuscular junction blockade (mean difference 0.01 mV [95%CI, -0.07 to 0.08], p=0.879). Muscle percussion evoked F-waves in the 3 healthy volunteers tested.

CONCLUSIONS

Maximal contraction response to muscle percussion has a muscular rather than a neural origin. However, percussion also excites axons within the muscle.

SIGNIFICANCE

These findings may provide clues to understand the changes observed in neuromuscular disorders.

Hyperpolarization-activated cyclic-nucleotide-gated channels potentially modulate axonal excitability at different thresholds

Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels mediate differences in sensory and motor axonal excitability at different thresholds in animal models. Importantly, HCN channels are responsible for voltage-gated inward rectifying (I_h) currents activated during hyperpolarization. The I_h currents exert a crucial role in determining the resting membrane potential and have been implicated in a variety of neurological disorders, including neuropathic pain. In humans, differences in biophysical properties of motor and sensory axons at different thresholds remain to be elucidated and could provide crucial pathophysiological insights in peripheral neurological diseases. Consequently, the aim of this study was to characterize sensory and motor axonal function at different threshold. Median nerve motor and sensory axonal excitability studies were undertaken in 15 healthy subjects (45 studies in total). Tracking targets were set to 20, 40, and 60% of maximum for sensory and motor axons. Hyperpolarizing threshold electrotonus (TEh) at 90-100 ms was significantly increased in lower threshold sensory axons times (F = 11.195, P < 0.001). In motor axons, the hyperpolarizing current/threshold (I/V) gradient was significantly increased in lower threshold axons (F = 3.191, P < 0.05). The minimum I/V gradient was increased in lower threshold motor and sensory axons. In conclusion, variation in the kinetics of HCN isoforms could account for the findings in motor and sensory axons. Importantly, assessing the function of HCN channels in sensory and motor axons of different thresholds may provide insights into the pathophysiological processes underlying peripheral neurological diseases in humans, particularly focusing on the role of HCN channels with the potential of identifying novel treatment targets.NEW & NOTEWORTHY Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels, which underlie inward rectifying currents (I_h), appear to mediate differences in sensory and motor axonal properties. Inward rectifying currents are increased in lower threshold motor and sensory axons, although different HCN channel isoforms appear to underlie these changes. While faster activating HCN channels seem to underlie I_h changes in sensory axons, slower activating HCN isoforms appear to be mediating the differences in I_h conductances in motor axons of different thresholds. The differences in HCN gating properties could explain the predilection for dysfunction of sensory and motor axons in specific neurological diseases.

Fasciculation in amyotrophic lateral sclerosis: origin and pathophysiological relevance

This review considers the origin and significance of fasciculations in neurological practice, with an emphasis on fasciculations in amyotrophic lateral sclerosis (ALS), and in benign fasciculation syndromes. Fasciculation represents a brief spontaneous contraction that affects a small number of muscle fibres, causing a flicker of movement under the skin. While an understanding of the role of fasciculation in ALS remains incomplete, fasciculations derive from ectopic activity generated in the motor system. A proximal origin seems likely to contribute to the generation of fasciculation in the early stages of ALS, while distal sites of origin become more prominent later in the disease, associated with distal motor axonal sprouting as part of the reinnervation response that develops secondary to loss of motor neurons. Fasciculations are distinct from the recurrent trains of axonal firing described in neuromyotonia. Fasciculation without weakness, muscle atrophy or increased tendon reflexes suggests a benign fasciculation syndrome, even when of sudden onset. Regardless of origin, fasciculations often present as the initial abnormality in ALS, an early harbinger of dysfunction and aberrant firing of motor neurons.

Peripheral Neuropathy and Nerve Compression Syndromes in Burns

Peripheral neuropathy and nerve compression syndromes lead to substantial morbidity following burn injury. Patients present with pain, paresthesias, or weakness along a specific nerve distribution or experience generalized peripheral neuropathy. The symptoms manifest at various times from within one week of hospitalization to many months after wound closure. Peripheral neuropathy may be caused by vascular occlusion of vasa nervorum, inflammation, neurotoxin production leading to apoptosis, and direct destruction of nerves from the burn injury. This article discusses the natural history, diagnosis, current treatments, and future directions for potential interventions for peripheral neuropathy and nerve compression syndromes related to burn injury.

Axonal Excitability in Amyotrophic Lateral Sclerosis : Axonal Excitability in ALS

Axonal excitability testing provides in vivo assessment of axonal ion channel function and membrane potential. Excitability techniques have provided insights into the pathophysiological mechanisms underlying the development of neurodegeneration and clinical features of amyotrophic lateral sclerosis (ALS) and related neuromuscular disorders. Specifically, abnormalities of Na+ and K+ conductances contribute to development of membrane hyperexcitability in ALS, thereby leading to symptom generation of muscle cramps and fasciculations, in addition to promoting a neurodegenerative cascade via Ca2+-mediated processes. Modulation of axonal ion channel function in ALS has resulted in significant symptomatic improvement that has been accompanied by stabilization of axonal excitability parameters. Separately, axonal ion channel dysfunction evolves with disease progression and correlates with survival, thereby serving as a potential therapeutic biomarker in ALS. The present review provides an overview of axonal excitability techniques and the physiological mechanisms underlying membrane excitability, with a focus on the role of axonal ion channel dysfunction in motor neuron disease and related neuromuscular diseases.

Peripheral Nerve Ultrasonography in Chronic Inflammatory Demyelinating Polyradiculoneuropathy and Multifocal Motor Neuropathy: Correlations with Clinical and Neurophysiological Data

Objective. This cross-sectional study analyzes the pattern of ultrasound peripheral nerve alterations in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and multifocal motor neuropathy (MMN) at different stages of functional disability. Material and Methods. 22 CIDP and 10 MMN patients and a group of 70 healthy controls were evaluated with an ultrasound scan of the median, ulnar, peroneal, tibial, and sural nerves. Results were correlated with clinical disability scales and nerve conduction studies. Results. Patients with intermediate functional impairment showed relatively larger cross-sectional areas than subjects with either a milder (p < 0.05) or more severe impairment (p < 0.05), both in CIDP and in MMN. In addition, MMN was associated with greater side-to-side intranerve variability (p < 0.05), while higher cross-sectional areas were observed in CIDP (p < 0.05) and in nerve segments with predominantly demyelinating features (p < 0.05). Higher CSA values were observed in nerves with demyelinating features versus axonal damage (p < 0.05 for CIDP; p < 0.05 for MMN). Discussion and Conclusions. Greater extent of quantitative and qualitative US alterations was observed in patients at intermediate versus higher functional disability and in nerves with demyelinating versus axonal damage. CIDP and MMN showed differential US aspects, with greater side-to-side intranerve variability in MMN and higher cross-sectional areas in CIDP.

Multifocal Motor Neuropathy Presenting as Pseudodystonia

Multifocal motor neuropathy (MMN) is an immune-mediated neuropathy. Wasting and weakness typically dominate the clinical presentation. We describe four cases presenting with prominent cramping resembling a primary movement disorder. All cases had features of focal motor conduction block on neurophysiological studies. The involuntary movements resolved in all four patients following treatment with intravenous immunoglobulin. The presented cases highlight an unusual presentation of MMN and emphasize that peripheral nerve pathology can present with movement disorders mimicking central nervous system disease. Furthermore, the movement disorder appears particularly sensitive to standard therapy.

The Temporal Profiles of Changes in Nerve Excitability Indices in Familial Amyloid Polyneuropathy

Familial amyloid polyneuropathy (FAP) caused by a mutation in transthyretin (TTR) gene is an autosomal dominant inherited disorder. The aim of this study is to explore the pathophysiological mechanism of FAP. We prospectively recruited 12 pauci-symptomatic carriers, 18 patients who harbor a TTR mutation, p.A97S, and two-age matched control groups. Data of nerve excitability test (NET) from ulnar motor and sensory axons were collected.NET study of ulnar motor axons of patients shows increased threshold and rheobase, reduced threshold elevation during hyperpolarizing threshold electrotonus (TE), and increased refractoriness. In sensory nerve studies, there are increased threshold reduction in depolarizing TE, lower slope of recovery and delayed time to overshoot after hyperpolarizing TE, increased refractoriness and superexcitability in recovery cycle. NET profiles obtained from the ulnar nerve of carriers show the increase of threshold and rheobase, whereas no significant threshold changes in hyperpolarizing TE and superexcitability. The regression models demonstrate that the increase of refractoriness and prolonged relative refractory period are correlated to the disease progression from carriers to patients. The marked increase of refractoriness at short-width stimulus suggests a defect in sodium current which may represent an early, pre-symptomatic pathophysiological change in TTR-FAP. Focal disruption of basal lamina and myelin may further increase the internodal capacity, manifested by the lower slope of recovery and delayed time to overshoot after hyperpolarization TE as well as the increase of superexcitability. NET could therefore make a pragmatic tool for monitoring disease progress from the very early stage of TTR-FAP.

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.

Different electrophysiological profiles and treatment response in 'typical' and 'atypical' chronic inflammatory demyelinating polyneuropathy

BACKGROUND

Chronic inflammatory demyelinating polyneuropathy (CIDP) is currently classified into 'typical' CIDP and 'atypical' subtypes such as multifocal acquired demyelinating sensory and motor neuropathy (MADSAM).

OBJECTIVES

To assess the frequency of CIDP subtypes, and to elucidate clinical and electrophysiological features, and treatment response in each subtype.

METHODS

We reviewed data from 100 consecutive patients fulfilling criteria for CIDP proposed by the European Federation of Neurological Societies and the Peripheral Nerve Society. The Kaplan-Meier curve was used to estimate long-term outcome.

RESULTS

Patients were classified as having typical CIDP (60%), MADSAM (34%), demyelinating acquired distal symmetric neuropathy (8%) or pure sensory CIDP (1%). Compared with patients with MADSAM, patients with typical CIDP showed more rapid progression and severe disability, and demyelination predominant in the distal nerve segments. MADSAM was characterised by multifocal demyelination in the nerve trunks. Abnormal median-normal sural sensory responses were more frequently found for typical CIDP (53% vs 13%). Patients with typical CIDP invariably responded to corticosteroids, immunoglobulin or plasmapheresis, whereas patients with MADSAM were more refractory to these treatments. The Kaplan-Meier analyses showed that 64% of patients with typical CIDP and 41% of patients with MADSAM had a clinical remission 5 years later (p=0.02).

CONCLUSIONS

Among the CIDP spectrum, typical CIDP and MADSAM are the major subtypes, and their pathophysiology appears to be distinct. In typical CIDP, the distal nerve terminals and possibly the nerve roots, where the blood-nerve barrier is anatomically deficient, are preferentially affected, raising the possibility of antibody-mediated demyelination, whereas cellular immunity with breakdown of the barrier may be important in MADSAM neuropathy.

Office immunotherapy in chronic inflammatory demyelinating polyneuropathy and multifocal motor neuropathy

Intravenous immunoglobulin [IVIg], plasma exchange [PE], and corticosteroids are efficacious treatment in chronic inflammatory demyelinating polyneuropathy [CIDP]. IVIg is effective in multifocal motor neuropathy [MMN]. NIS, NIS-weakness, sum scores of raw amplitudes of motor fiber (CMAPs) amplitudes, and Dyck/Rankin score provided reliable measures to detect and scale abnormality and reflect change; they are therefore ideal for office management of response-based immunotherapy (R-IRx) of CIDP. Using efficacious R-IRx, a large early and late therapeutic response (≥ one-fourth were in remission or had recovered) was demonstrated in CIDP. In MMN only an early improvement with late non-significant worsening was observed. The difference in immunotherapy response supports a fundamental difference between CIDP (immune attack on Schwann cells and myelin) and MMN (attack on nodes of Ranvier and axons).

Precise correlation between structural and electrophysiological disturbances in MADSAM neuropathy

Multifocal acquired demyelinating sensory and motor neuropathy is characterised by multifocal clinical deficits. Imaging studies have identified multifocal enlargements of nerve trunks, but a precise correlation between structural abnormalities and electrophysiological dysfunction has not been elucidated. Two patients diagnosed with multifocal acquired demyelinating sensory and motor neuropathy were evaluated with nerve conduction studies, including short segment nerve conduction studies to precisely localise motor conduction block, and ultrasound studies of corresponding nerve trunks. Motor conduction block was identified in each patient (upper limb nerves in two patients), superimposed on additional demyelinating neurophysiological features. Upper limb ultrasound studies demonstrated focal nerve enlargement that precisely correlated with neurophysiological conduction block. The results of this study suggest that factors contributing to focal structural abnormalities in multifocal acquired demyelinating sensory and motor neuropathy are also those that produce conduction block.

Sensory axonal dysfunction in cervical radiculopathy

OBJECTIVE

The aim of this study was to evaluate changes in sensory axonal excitability in the distal nerve in patients with cervical radiculopathy.

METHODS

The patients were classified by the findings of cervical MRI into two subgroups: 22 patients with C6/7 root compression and 25 patients with cervical cord and root compression above/at C6/7. Patients were investigated using conventional nerve conduction studies (NCS) and nerve excitability testing. Sensory nerve excitability testing was undertaken with stimulation at the wrist and recording from digit II (dermatome C6/7). The results were compared with healthy controls. Both preoperative and postoperative tests were performed if the patient underwent surgery.

RESULTS

Sensory axonal excitability was significantly different in both cohorts compared with healthy controls, including prolonged strength-duration time constant, reduced S2 accommodation, increased threshold electrotonus hyperpolarisation (TEh (90-100 ms)), and increased superexcitability. The changes in these excitability indices are compatible with axonal membrane hyperpolarisation. In five patients who underwent surgery, the postoperative sensory excitability was tested after 1 week, and showed significant changes in TE (TEh (90-100 ms) and TEh slope, p<0.05) between presurgery and postsurgery.

CONCLUSIONS

The present study demonstrated distal nerve axonal hyperpolarisation in patients with cervical radiculopathy. These findings suggest that the hyperpolarised pattern might be due to Na(+)-K(+) ATPase overactivation induced by proximal ischaemia, or could reflect the remyelinating process. Distal sensory axons were hyperpolarised even though there were no changes in NCS, suggesting that nerve excitability testing may be more sensitive to clinical symptoms than NCS in patients with cervical radiculopathy.

The pathogenesis of multifocal motor neuropathy and an update on current management options

Multifocal motor neuropathy (MMN) is a rare and disabling disease. Several experimental studies and clinical data are strongly suggestive of an immune-mediated pathogenesis, although underlying mechanisms in MMN seem to be very specific, mainly because of the presence of IgM anti-GM1 serum antibodies and the dramatic response to intravenous immunoglobulins (IVIg). The origin of antiganglioside antibodies and the way in which they act at the molecular level remain unclear. Several studies have demonstrated the key role of complement activation in the underlying mechanisms of MMN, as well as in animal models of acute motor axonal neuropathy (AMAN). Deposition of the membrane attack complex may disrupt the architecture of the nodes of Ranvier and paranodal areas, causing local disruption of nodal sodium-channel clusters. In patients with MMN, muscle weakness is the consequence of conduction blocks (CB), which leads to secondary axonal degeneration, consequently the aim of the treatment is to reverse CB at early stages of the disease. High-dose immunoglobulin is to date the only therapy which has proven efficacy in MMN patients in providing transient improvement of muscle strength, but long-term follow-up studies show a progressive motor decline. Therefore, other therapies are needed to improve the conduction nerve properties in long-term design. The reduction of complement activation and more generally the gain in paranodal stabilization could be directions for future therapeutic strategies.

Peripheral nerve axonal excitability studies: expanding the neurophysiologist's armamentarium

Nerve excitability studies have emerged as a recent novel non-invasive technique that offers complementary information to that provided by more conventional nerve conduction studies, the latter which provide only limited indices of peripheral nerve function. Such novel tools allow for the assessment of peripheral axonal biophysical properties that include ion channels, energy-dependent pumps and membrane potential in health and disease. With improvements in technique and development of protocols, a typical study can be completed in a short period of time and rapid measurement of multiple excitability indices can be achieved that provide insight into different aspects of peripheral nerve function. The advent of automated protocols for the assessment of nerve excitability has promoted their use in previous studies investigating disease pathophysiology such as in metabolic, toxic and demyelinating neuropathies, amyotrophic lateral sclerosis, stroke, spinal cord injury and inherited channelopathies. In more recent years, the use of nerve excitability studies have additionally provided insights into the pathophysiological mechanisms underlying cerebellar disorders that include stroke and familial cerebellar ataxias such as episodic ataxia types 1 and 2. Moreover, this technique may have diagnostic and therapeutic implications that may encompass a broader range of neurodegenerative cerebellar ataxias in years to come. In the foreseeable future, this technique may eventually be incorporated into clinical practice expanding the currently available armamentarium to the neurophysiologist.

Increased supernormality in patients with multiplet discharges: Evidence for a common pathophysiological mechanism behind multiplets and fasciculations

OBJECTIVE

To determine whether there is a relation between electrically evoked multiplet discharges (MDs) and motor axonal excitability properties. We hypothesized that electrically evoked MDs share their underlying pathophysiological mechanism with fasciculations.

METHODS

High-density surface EMG and motor nerve excitability recordings of the thenar muscles were performed in 22 patients with motor neuron disease (MND) in their differential diagnosis and who were referred for EMG examination.

RESULTS

Supernormality (hyperexcitable phase following the refractory period) was significantly increased in patients with MDs (n=10) compared to patients without MDs (n=12) (25.5% vs 17.0%; p=0.02). Depolarizing threshold electrotonus differed significantly between both groups as well (TEdpeak, 76.6% vs 66.6%, p<0.01; TEd90-100ms, 51.7% vs 44.3%, p<0.01) CONCLUSIONS: Our findings imply that the same pathophysiological excitability changes are involved in generating MDs and fasciculations. Yet, MDs may be quantified more easily, and may be more specific for abnormal distal excitability than fasciculations, because fasciculations may originate along the motor axon as well as in the neuron cell body.

SIGNIFICANCE

MDs are potentially useful as objective measure of increased distal axonal excitability at individual motor unit level and might complement clinical studies in MND.

Antibodies to neurofascin exacerbate adoptive transfer experimental autoimmune neuritis

Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy are autoimmune disorders of the peripheral nervous system in which autoantibodies are implicated in the disease pathogenesis. Recent work has focused on the nodal regions of the myelinated axon as potential autoantibody targets. Here we screened patient sera for autoantibodies to neurofascin and assessed the pathophysiological relevance of anti-neurofascin antibodies in vivo. Levels of anti-neurofascin antibodies were higher in sera from patients with Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy when compared with those of controls. Anti-neurofascin antibodies exacerbated and prolonged adoptive transfer experimental autoimmune neuritis and caused conduction defects when injected intraneurally.