Serial peripheral nerve ultrasound in Guillain-Barré syndrome

Neuromuscular Ultrasound in Polyneuropathies

Neuromuscular ultrasound is a painless, radiation-free, high-resolution imaging technique for assessing the peripheral nervous system. It can accurately depict changes in the nerves and muscles of individuals with neuromuscular conditions, and it is therefore a robust diagnostic tool for the assessment of individuals with polyneuropathies. This review will outline the typical ultrasonographic changes found in a wide variety of polyneuropathies. In general, demyelinating conditions result in greater nerve enlargement than axonal conditions, and acquired conditions result in more patchy nerve enlargement compared to diffuse nerve enlargement in hereditary conditions. This review is data-driven, but more nuanced anecdotal findings are also described. The overall goal of this paper is to provide clinicians with an accessible review of the ultrasonographic approaches and findings in a wide variety of polyneuropathies.

The pathophysiological role of endoneurial inflammatory edema in early classical Guillain-Barré syndrome

The objective of this review was to analyze the pathophysiological role of endoneurial inflammatory edema in initial stages of classic Guillain-Barré syndrome (GBS), arbitrarily divided into very early GBS (≤ 4 days after symptom onset) and early GBS (≤ 10 days). Classic GBS, with variable degree of flaccid and areflexic tetraparesis, encompasses demyelinating and axonal forms. Initial autopsy studies in early GBS have demonstrated that endoneurial inflammatory edema of proximal nerve trunks, particularly spinal nerves, is the outstanding lesion. Variable permeability of the blood-nerve barrier dictates such lesion topography. In proximal nerve trunks possessing epi-perineurium, edema may increase the endoneurial fluid pressure causing ischemic changes. Critical analysis the first pathological description of the axonal form GBS shows a combination of axonal degeneration and demyelination in spinal roots, and pure Wallerian-like degeneration in peripheral nerve trunks. This case might be reclassified as demyelinating GBS with secondary axonal degeneration. Both in acute motor axonal neuropathy and acute motor-sensory axonal neuropathy, Wallerian-like degeneration of motor fibers predominates in the distal part of ventral spinal roots abutting the dura mater, another feature re-emphasizing the pathogenic relevance of this area. Electrophysiological and imaging studies also point to a predominant alteration at the spinal nerve level, which is a hotspot in any early GBS subtype. Serum biomarkers of axonal damage, including neurofilament light chain and peripherin, are increased in the great majority of patients with any early GBS subtype; endoneurial ischemia of proximal nerve trunks could contribute to such axonal damage. It is concluded that inflammatory edema of proximal nerve trunks is an essential pathogenic event in early GBS, which has a tangible impact for accurate approach to the disease.

Guillain-Barré Syndrome

OBJECTIVE

This article summarizes the clinical features, diagnostic criteria, differential diagnosis, pathogenesis, and prognosis of Guillain-Barré syndrome (GBS), with insights into the current and future diagnostic and therapeutic interventions for this neuromuscular syndrome.

LATEST DEVELOPMENTS

GBS is an acute, inflammatory, immune-mediated polyradiculoneuropathy that encompasses many clinical variants and divergent pathogenic mechanisms that lead to axonal, demyelinating, or mixed findings on electrodiagnostic studies. The type of antecedent infection, the development of pathogenic cross-reactive antibodies via molecular mimicry, and the location of the target gangliosides affect the subtype and severity of the illness. The data from the International GBS Outcome Study have highlighted regional variances, provided new and internationally validated prognosis tools that are beneficial for counseling, and introduced a platform for discussion of GBS-related open questions. New research has been undertaken, including research on novel diagnostic and therapeutic biomarkers, which may lead to new therapies.

ESSENTIAL POINTS

GBS is among the most frequent life-threatening neuromuscular emergencies in the world. At least 20% of patients with GBS have a poor prognosis and significant residual deficits despite receiving available treatments. Research is ongoing to further understand the pathogenesis of the disorder, find new biomarkers, and develop more effective and specific treatments.

Normative Reference Values of the Tibial Nerve in Healthy Individuals Using Ultrasonography: A Systematic Review and Meta-Analysis

BACKGROUND

High-resolution ultrasound of the tibial nerve has been used for screening of several neurologic disorders, but normative reference values of tibial nerve cross-sectional areas (CSA) have not been well established. Thus, the present meta-analysis was performed to generate normative estimates of tibial nerve CSA at various sites of the lower limb based on ultrasonography.

METHODS

Google Scholar, Scopus and PubMed were searched for potential studies. Studies were required to report tibial nerve CSA in healthy individuals to be included. A random-effect meta-analysis was performed to calculate tibial nerve CSA values. Subgroup and statistical analyses were performed to study covariates.

RESULTS

Forty-eight eligible articles consisting of 2695 limbs were included. The average tibial nerve CSA was found to be 10.9 mm2 at the ankle (95% CI: 9.9-11.8) and should not exceed 11.8 mm2 in healthy adults. At the popliteal fossa, the overall CSA was 21.7 mm2 (95% CI: 17.5-25.8) in healthy adults. At both sites, the average tibial nerve CSA was significantly larger in adults than in children, and the differences by geographical region were not statistically significant. At the ankle, tibial nerve CSA increased with age and body mass index, while at the popliteal fossa it increased with age and weight.

CONCLUSIONS

our findings indicate that the tibial nerve varied not only along its course but also among sub-variables. Establishing normal references values of tibial nerve CSA is helpful to differentiate healthy from diseased tibial nerves such as in diabetic peripheral neuropathy or tarsal tunnel syndrome.

Emerging biomarkers to predict clinical outcomes in Guillain-Barré syndrome

INTRODUCTION

Guillain-Barré syndrome (GBS) is an immune-mediated poly(radiculo)neuropathy with a variable clinical outcome. Identifying patients who are at risk of suffering from long-term disabilities is a great challenge. Biomarkers are useful to confirm diagnosis, monitor disease progression, and predict outcome.

AREAS COVERED

The authors provide an overview of the diagnostic and prognostic biomarkers for GBS, which are useful for establishing early treatment strategies and follow-up care plans.

EXPERT OPINION

Detecting patients at risk of developing a severe outcome may improve management of disease progression and limit potential complications. Several clinical factors are associated with poor prognosis: higher age, presence of diarrhea within 4 weeks of symptom onset, rapid and severe weakness progression, dysautonomia, decreased vital capacity and facial, bulbar, and neck weakness. Biological, neurophysiological and imaging measures of unfavorable outcome include multiple anti-ganglioside antibodies elevation, increased serum and CSF neurofilaments light (NfL) and heavy chain, decreased NfL CSF/serum ratio, hypoalbuminemia, nerve conduction study with early signs of demyelination or axonal loss and enlargement of nerve cross-sectional area on ultrasound. Depicting prognostic biomarkers aims at predicting short-term mortality and need for cardio-pulmonary support, long-term patient functional outcome, guiding treatment decisions and monitoring therapeutic responses in future clinical trials.

Nerve Ultrasound Score in Chronic Inflammatory Demyelinating Polyneuropathy

Background and Objectives: Studies have suggested that, by applying certain nerve ultrasound scores, demyelinating and axonal polyneuropathies can be differentiated. In the current study, we investigated the utility of ultrasound pattern sub-score A (UPSA) and intra- and internerve cross-sectional area (CSA) variability in the diagnostic evaluation of demyelinating neuropathies. Materials and Methods: Nerve ultrasound was performed in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and acute inflammatory demyelinating polyneuropathy (AIDP) and compared to patients with axonal neuropathies. The UPSA, i.e., the sum of ultrasound scores at eight predefined measurement points in the median (forearm, elbow and mid-arm), ulnar (forearm and mid-arm), tibial (popliteal fossa and ankle) and fibular (lateral popliteal fossa) nerves, was applied. Intra- and internerve CSA variability were defined as maximal CSA/minimal CSA for each nerve and each subject, respectively. Results: A total of 34 CIDP, 15 AIDP and 16 axonal neuropathies (including eight axonal Guillain-Barré syndrome (GBS), four hereditary transthyretin amyloidosis, three diabetic polyneuropathy and one vasculitic neuropathy) were included. A total of 30 age- and sex-matched healthy controls were recruited for comparison. Significantly enlarged nerve CSA was observed in CIDP and AIDP with significantly higher UPSA in CIDP compared to the other groups (9.9 ± 2.9 vs. 5.9 ± 2.0 vs. 4.6 ± 1.9 in AIDP vs. axonal neuropathies, p < 0.001). A total of 89.3% of the patients with CIDP had an UPSA score ≥7 compared to the patients with AIDP (33.3%) and axonal neuropathies (25.0%) (p < 0.001). Using this cut-off, the performance of UPSA in differentiating CIDP from other neuropathies including AIDP was excellent (area under the curve of 0.943) with high sensitivity (89.3%), specificity (85.2%) and positive predictive value (73.5%). There were no significant differences in intra- and internerve CSA variability between the three groups. Conclusion: The UPSA ultrasound score was useful in distinguishing CIDP from other neuropathies compared to nerve CSA alone.

Nerve Ultrasonography for the Diagnosis and Evaluation of Neuralgic Amyotrophy: A Case Report

Neuralgic amyotrophy (NA) is a peripheral nervous system disorder involving multifocal distribution. Although nerve ultrasonography has shown potential for detecting NA lesions, no established detection method exists for distal forearm NA. A 59-year-old man presented with weakness of the muscles innervated by the left posterior interosseous nerve (PIN), median nerve (MN), anterior interosseous nerve (AIN), and ulnar nerve (UN), following severe left shoulder pain. This case suggests that nerve ultrasonography can help accurately diagnose distal forearm NA.

Axonal pathology in early stages of Guillain-Barré syndrome

INTRODUCTION

Guillain-Barré syndrome (GBS) is an acute-onset, immune-mediated disease of the peripheral nervous system. It may be classified into 2 main subtypes: demyelinating (AIDP) and axonal (AMAN). This study aims to analyse the mechanisms of axonal damage in the early stages of GBS (within 10 days of onset).

DEVELOPMENT

We analysed histological, electrophysiological, and imaging findings from patients with AIDP and AMAN, and compared them to those of an animal model of myelin P2 protein-induced experimental allergic neuritis. Inflammatory oedema of the spinal nerve roots and spinal nerves is the initial lesion in GBS. The spinal nerves of patients with fatal AIDP may show ischaemic lesions in the endoneurium, which suggests that endoneurial inflammation may increase endoneurial fluid pressure, reducing transperineurial blood flow, potentially leading to conduction failure and eventually to axonal degeneration. In patients with AMAN associated with anti-ganglioside antibodies, nerve conduction block secondary to nodal sodium channel dysfunction may affect the proximal, intermediate, and distal nerve trunks. In addition to the mechanisms involved in AIDP, active axonal degeneration in AMAN may be associated with nodal axolemma disruption caused by anti-ganglioside antibodies.

CONCLUSION

Inflammatory oedema of the proximal nerve trunks can be observed in early stages of GBS, and it may cause nerve conduction failure and active axonal degeneration.

Axonal pathology in early stages of Guillain-Barré syndrome

INTRODUCTION

Guillain-Barré syndrome (GBS) is an acute-onset, immune-mediated disease of the peripheral nervous system. It may be classified into 2 main subtypes: demyelinating (AIDP) and axonal (AMAN). This study aims to analyse the mechanisms of axonal damage in the early stages of GBS (within 10days of onset).

DEVELOPMENT

We analysed histological, electrophysiological, and imaging findings from patients with AIDP and AMAN, and compared them to those of an animal model of myelin P2 protein-induced experimental allergic neuritis. Inflammatory oedema of the spinal nerve roots and spinal nerves is the initial lesion in GBS. The spinal nerves of patients with fatal AIDP may show ischaemic lesions in the endoneurium, which suggests that endoneurial inflammation may increase endoneurial fluid pressure, reducing transperineurial blood flow, potentially leading to conduction failure and eventually to axonal degeneration. In patients with AMAN associated with anti-ganglioside antibodies, nerve conduction block secondary to nodal sodium channel dysfunction may affect the proximal, intermediate, and distal nerve trunks. In addition to the mechanisms involved in AIDP, active axonal degeneration in AMAN may be associated with nodal axolemma disruption caused by anti-ganglioside antibodies.

CONCLUSION

Inflammatory oedema of the proximal nerve trunks can be observed in early stages of GBS, and it may cause nerve conduction failure and active axonal degeneration.

[Pathophysiological and diagnostic aspects of Guillain-Barré syndrome]

Guillain-Barré syndrome (GBS) is the most common cause of acute neuropathy. It usually onset with a rapidly progressive ascending bilateral weakness with sensory disturbances, and patients may require intensive treatment and close monitoring as about 30% have a respiratory muscle weakness and about 10% have autonomic dysfunction. The diagnosis of GBS is based on clinical history and examination. Complementary examinations are performed to rule out a differential diagnosis and to secondarily confirm the diagnosis. GBS is usually preceded by an infectious event in ≈ 2/3 of cases. Infection leads to an immune response directed against carbohydrate antigens located on the infectious agent and the formation of anti-ganglioside antibodies. By molecular mimicry, these antibodies can target structurally similar carbohydrates found on host's nerves. Their binding results in nerve conduction failure or/and demyelination which can lead to axonal loss. Some anti-ganglioside antibodies are associated with particular variants of GBS: the Miller-Fisher syndrome, facial diplegia and paresthesias, the pharyngo-cervico-brachial variant, the paraparetic variant, and the Bickerstaff brainstem encephalitis. Their semiological differences might be explained by a distinct expression of gangliosides among nerves. The aim of this review is to present pathophysiological aspects and the diagnostic approach of GBS and its variants.

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.

Nerve ultrasound evaluation of Guillain-Barré syndrome subtypes in northern China

INTRODUCTION/AIMS

Ultrasound (US) studies have demonstrated patchy enlargement of spinal and peripheral nerves in Guillain-Barré syndrome (GBS). However, whether ultrasound yields useful information for early classification of GBS has not been established. We aimed to evaluate nerve ultrasound in patients with GBS in northern China and compare the sonographic characteristics between demyelinating and axonal subtypes.

METHODS

Between November 2018 and October 2019, 38 hospitalized GBS patients within 3 wk of disease onset and 40 healthy controls were enrolled. Ultrasonographic cross-sectional areas (CSA) of the peripheral nerves, vagus nerve, and cervical nerve roots were prospectively recorded in GBS subtypes and controls.

RESULTS

Ultrasonographic CSA exhibited significant enlargement in most patients' nerves compared with healthy controls, most prominent in cervical nerves. The CSA tended to be larger in acute inflammatory demyelinating polyneuropathy (AIDP) than in acute motor axonal neuropathy (AMAN)/acute motor and sensory axonal neuropathy (AMSAN), especially in cervical nerves (C5: 5.9 ± 1.6 mm² vs. 7.0 ± 1.7 mm² , p = .042; C6: 10.5 ± 1.8 mm² vs. 12.0 ± 2.1 mm² , p = .033). The chi-squared test revealed significant differences in nerve enlargement in C5 (p < .001), C6 (p < .001), the proximal median nerve (p < .001), and the vagus nerve (p = .003) between GBS and controls. The vagus nerve was larger in patients with autonomic dysfunction than in patients without it (2.3 ± 1.0 mm² vs. 1.4 ± 0.5 mm² , p = .003).

DISCUSSION

The demyelinating subtype presented with more significant cervical nerve enlargement in GBS. Vagus nerve enlargement may be a useful marker for autonomic dysfunction.

A model incorporating ultrasound to predict the probability of fast disease progression in amyotrophic lateral sclerosis

OBJECTIVE

We aimed to develop a model to predict amyotrophic lateral sclerosis (ALS) disease progression based on clinical and neuromuscular ultrasound (NMUS) parameters.

METHODS

ALS patients were prospectively recruited. Muscle fasciculation (≥2 over 30-seconds, examined in biceps brachii-brachialis (BB), brachioradialis, tibialis anterior and vastus medialis) and nerve cross-sectional area (CSA) (median, ulnar, tibial, fibular nerve) were evaluated through NMUS. Ultrasound parameters were correlated with clinical data, including revised ALS Functional Rating Scale (ALSFRS-R) progression at one year. A predictive model was constructed to differentiate fast progressors (ALSFRS-R decline ≥ 1/month) from non-fast progressors.

RESULTS

40 ALS patients were recruited. Three parameters emerged as strong predictors of fast progressors: (i) ALSFRS-R slope at time of NMUS (p = 0.041), (ii) BB fasciculation count (p = 0.027) and (iii) proximal to distal median nerve CSA ratio < 1.22 (p = 0.026). A predictive model (scores 0-5) was built with excellent discrimination (area under curve: 0.915). Using a score of ≥ 3, the model demonstrated good sensitivity (81.3%) and specificity (91.0%) in differentiating fast from non-fast progressors.

CONCLUSION

The current model is simple and can predict the probability of fast disease progression.

SIGNIFICANCE

This model has potential as a surrogate biomarker of ALS disease progression.

Anti-GM1 IgM antibody positive axonal variant of Guillain-Barre-syndrome in a pediatric patient with dengue fever

INTRODUCTION

While children of all ages may be affected by Guillain-Barre-Syndrome (GBS), there are no reports of Dengue Fever (DF) as the preceding or concurrent infection in this age group. In addition, the presence of anti-GM1 IgM antibody, commonly seen in Multifocal Motor Neuropathy, is rarely encountered in both axonal and demyelinating variants of GBS. Moreover, only few neuromuscular ultrasound findings of the axonal variant in children were reported in the literature.

CASE

Here we present a nine-year-old female who developed the classic signs, symptoms and neurophysiologic findings of axonal type of GBS during DF. She had elevated anti-GM1 IgM antibody atypical of this variant and diffusely enlarged nerves via neuromuscular ultrasound.

CONCLUSION

In a pediatric patient with DF and acute flaccid paralysis, GBS should always be one of the considerations. Although rare, anti-ganglioside GM1 IgM antibody can still be found in axonal variant of GBS.

Guillain-Barré syndrome

Guillain-Barré syndrome is the most common cause of acute flaccid paralysis worldwide. Most patients present with an antecedent illness, most commonly upper respiratory tract infection, before the onset of progressive motor weakness. Several microorganisms have been associated with Guillain-Barré syndrome, most notably Campylobacter jejuni, Zika virus, and in 2020, the severe acute respiratory syndrome coronavirus 2. In C jejuni-related Guillain-Barré syndrome, there is good evidence to support an autoantibody-mediated immune process that is triggered by molecular mimicry between structural components of peripheral nerves and the microorganism. Making a diagnosis of so-called classical Guillain-Barré syndrome is straightforward; however, the existing diagnostic criteria have limitations and can result in some variants of the syndrome being missed. Most patients with Guillain-Barré syndrome do well with immunotherapy, but a substantial proportion are left with disability, and death can occur. Results from the International Guillain-Barré Syndrome Outcome Study suggest that geographical variations exist in Guillain-Barré syndrome, including insufficient access to immunotherapy in low-income countries. There is a need to provide improved access to treatment for all patients with Guillain-Barré syndrome, and to develop effective disease-modifying therapies that can limit the extent of nerve injury. Clinical trials are currently underway to investigate some of the potential therapeutic candidates, including complement inhibitors, which, together with emerging data from large international collaborative studies on the syndrome, will contribute substantially to understanding the many facets of this disease.

Nerve Ultrasound as Helpful Tool in Polyneuropathies

Background: Polyneuropathies (PNP) are a broad field of diseases affecting millions of people. While the symptoms presented are mostly similar, underlying causes are abundant. Thus, early identification of treatable causes is often difficult. Besides clinical data and basic laboratory findings, nerve conduction studies are crucial for etiological classification, yet limited. Besides Magnetic Resonance Imaging (MRI), high-resolution nerve ultrasound (HRUS) has become a noninvasive, fast, economic and available tool to help distinguish different types of nerve alterations in neuropathies. Methods: We aim to describe typical ultrasound findings in PNP and patterns of morphological changes in hereditary, immune-mediated, diabetic, metabolic and neurodegenerative PNP. Literature research was performed in PubMed using the terms ‘nerve ultrasound’, neuromuscular ultrasound, high-resolution nerve ultrasound, peripheral nerves, nerve enlargement, demyelinating, hereditary, polyneuropathies, hypertrophy’. Results: Plenty of studies over the past 20 years investigated the value of nerve ultrasound in different neuropathies. Next to nerve enlargement, patterns of nerve enlargement, echointensity, vascularization and elastography have been evaluated for diagnostic terms. Furthermore, different scores have been developed to distinguish different etiologies of PNP. Conclusions: Where morphological alterations of the nerves reflect underlying pathologies, early nerve ultrasound might enable a timely start of available treatment and also facilitate follow up of therapy success.

A Pilot Study on Serial Nerve Ultrasound in Miller Fisher Syndrome

Objective: Miller Fisher syndrome (MFS) is predominantly a clinical diagnosis, with classic triad of ophthalmoplegia, ataxia, and generalized reduced reflexes. Previous studies in chronic and acute immune-mediated neuropathies indicated that ultrasound, may help to detect changes that could correspond with disease activity. We studied the feasibility of serial nerve ultrasound in MFS, using a healthy controls. Methods: All MFS patients (n = 5) and healthy controls (n = 18), underwent a standardized sonographic protocol that evaluated nerve sizes of facial, large arm and leg nerves, and spinal nerve roots. All MFS patients underwent routine ancillary investigations, including electrodiagnostic testing and for presence of anti-GQ1b antibodies. In addition, four MFS patients had 2nd, and 3rd clinical and sonographic evaluation at 14 and 90 days from onset. Results: The width of the facial nerve was significantly larger in the MFS group than in the control group (MFS: 1.19 ± 0.31 mm vs. normal: 0.67 ± 0.13 mm, P = 0.01). The size of the cervical roots and the nerves in the limbs were similar between the two groups. Two patients' facial nerve size subsided with time, but the decrease in other nerves' sizes were not obvious. Conclusion: Our study showed that serial nerve ultrasound studies are feasible in MFS, and can capture changes in facial nerve size that could complement routine diagnostic tests. Further studies are warranted to determine and compare its test characteristics in MFS.

Current and future applications of ultrasound imaging in peripheral nerve disorders

Neuromuscular ultrasound (NMUS) is a rapidly evolving technique used in neuromuscular medicine to provide complimentary information to standard electrodiagnostic studies. NMUS provides a dynamic, real time assessment of anatomy which can alter both diagnostic and management pathways in peripheral nerve disorders. This review describes the current and future techniques used in NMUS and details the applications and developments in the diagnosis and monitoring of compressive, hereditary, immune-mediated and axonal peripheral nerve disorders, and motor neuron diseases. Technological advances have allowed the increased utilisation of ultrasound for management of peripheral nerve disorders; however, several practical considerations need to be taken into account to facilitate the widespread uptake of this technique.

Diagnosis and management of Guillain-Barré syndrome in ten steps

Guillain-Barré syndrome (GBS) is a rare, but potentially fatal, immune-mediated disease of the peripheral nerves and nerve roots that is usually triggered by infections. The incidence of GBS can therefore increase during outbreaks of infectious diseases, as was seen during the Zika virus epidemics in 2013 in French Polynesia and 2015 in Latin America. Diagnosis and management of GBS can be complicated as its clinical presentation and disease course are heterogeneous, and no international clinical guidelines are currently available. To support clinicians, especially in the context of an outbreak, we have developed a globally applicable guideline for the diagnosis and management of GBS. The guideline is based on current literature and expert consensus, and has a ten-step structure to facilitate its use in clinical practice. We first provide an introduction to the diagnostic criteria, clinical variants and differential diagnoses of GBS. The ten steps then cover early recognition and diagnosis of GBS, admission to the intensive care unit, treatment indication and selection, monitoring and treatment of disease progression, prediction of clinical course and outcome, and management of complications and sequelae.

Neuromuscular Ultrasound: Clinical Applications and Diagnostic Values

Advances in high-resolution ultrasound have provided clinicians with unique opportunities to study diseases of the peripheral nervous system. Ultrasound complements the clinical and electrophysiology exam by showing the degree of abnormalities in myopathies, as well as spontaneous muscle activities in motor neuron diseases and other disorders. In experienced hands, ultrasound is more sensitive than MRI in detecting peripheral nerve pathologies. It can also guide needle placement for electromyography exam, therapeutic injections, and muscle biopsy. Ultrasound enhances the ability to detect carpal tunnel syndrome and other focal nerve entrapment, as well as pathological nerve enlargements in genetic and acquired neuropathies. Furthermore, ultrasound can potentially be used as a biomarker for muscular dystrophy and spinal muscular atrophy. The combination of electromyography and ultrasound can increase the diagnostic certainty of amyotrophic lateral sclerosis, aid in the localization of brachial plexus or peripheral nerve trauma and allow for surveillance of nerve tumor progression in neurofibromatosis. Potential limitations of ultrasound include an inability to image deeper structures, with lower sensitivities in detecting neuromuscular diseases in young children and those with mitochondrial myopathies, due to subtle changes or early phase of the disease. As well, its utility in detecting critical illness neuromyopathy remains unclear. This review will focus on the clinical applications of neuromuscular ultrasound. The diagnostic values of ultrasound for screening of myopathies, neuropathies, and motor neuron diseases will be presented.

Indications for neuromuscular ultrasound: Expert opinion and review of the literature

Over the last two decades, dozens of applications have emerged for ultrasonography in neuromuscular disorders. We wanted to measure its impact on practice in laboratories where the technique is in frequent use. After identifying experts in neuromuscular ultrasound and electrodiagnosis, we assessed their use of ultrasonography for different indications and their expectations for its future evolution. We then identified the earliest papers to provide convincing evidence of the utility of ultrasound for particular indications and analyzed the relationship of their date of publication with expert usage. We found that experts use ultrasonography often for inflammatory, hereditary, traumatic, compressive and neoplastic neuropathies, and somewhat less often for neuronopathies and myopathies. Usage significantly correlated with the timing of key publications in the field. We review these findings and the extensive evidence supporting the value of neuromuscular ultrasound. Advancement of the field of clinical neurophysiology depends on widespread translation of these findings.

Nerve ultrasound in polyneuropathies

Ultrasound can be used to visualize pathology in the peripheral nerves of patients with polyneuropathy. Nerve enlargement is the most frequent pathology, but other abnormalities, including abnormal nerve echogenicity and vascularity, are also encountered. This monograph presents an overview of the role of nerve ultrasound in the evaluation and management of both inherited and acquired polyneuropathies. A description of the sonographic techniques and common abnormalities is provided, followed by a presentation of typical findings in different neuropathies. Scoring systems for characterizing the presence and pattern of nerve abnormalities as they relate to different polyneuropathies are presented. Muscle Nerve 57: 716-728, 2018.

Spinal nerve involvement in early Guillain-Barré syndrome: The Haymaker and Kernohan's legacy

Pathological studies of early Guillain-Barré syndrome (GBS), defined as of 10days of disease onset, are scanty making it difficult to interpret the physiopathology of clinical and electrophysiological features. In 1949, Webb Haymaker and James Kernohan reported 50 clinico-pathological studies of fatal GBS cases, 32 of them having died between days 2 and 10 after onset. They established that the brunt of initial lesions, consisting of endoneurial oedema interpreted as degenerative, relied on spinal nerves. That this oedema was inflammatory was soon thereafter recognized. Two decades later, however, the pathogenic role of endoneurial oedema was disputed. In experimental allergic neuritis, considered an animal model of GBS, the initial lesion appearing on day 4 post-inoculation is marked inflammatory oedema in the sciatic nerve and lumbosacral nerve roots. Additional detailed clinico-pathological studies corroborated that the appearance of epi-perineurium at the subarachnoid angle, where anterior and posterior roots join to form the spinal nerve, is a pathological hotspot in early GBS, there developing inflammatory oedema, incipient demyelination and endoneurial ischemic zones with axonal degeneration. Furthermore, nerve ultrasonography has demonstrated predominant spinal nerve changes in early GBS, either demyelinating or axonal. Other outstanding Haymaker and Kernohan's contributions were to clarify the complex nosology of the syndrome bringing under the same rubric Landry's paralysis, acute febrile polyneuritis and GBS, and critically analyzing GBS exclusion criteria by then prevailing. It is concluded that the authors' legacy remains as relevant as ever.

Proximal nerve lesions in early Guillain-Barré syndrome: implications for pathogenesis and disease classification

Guillain-Barré syndrome (GBS) is an acute-onset, immune-mediated disorder of the peripheral nervous system. In early GBS, arbitrarily established up to 10 days of disease onset, patients could exhibit selective manifestations due to involvement of the proximal nerves, including nerve roots, spinal nerves and plexuses. Such manifestations are proximal weakness, inaugural nerve trunk pain, and atypical electrophysiological patterns, which may lead to delayed diagnosis. The aim of this paper was to analyze the nosology of early GBS reviewing electrophysiological, autopsy and imaging studies, both in acute inflammatory demyelinating polyneuropathy (AIDP) and acute motor/motor-sensory axonal neuropathy (AMAN/AMSAN). Early electrophysiology showed either well-defined demyelinating or axonal patterns, or a non-diagnostic pattern with abnormal late responses; there may be attenuated M responses upon lumbar root stimulation as the only finding. Pathological changes predominated in proximal nerves, in some studies, most prominent at the sides where the spinal roots unite to form the spinal nerves; on very early GBS endoneurial inflammatory edema was the outstanding feature. In the far majority of cases, spinal magnetic resonance imaging showed contrast enhancement of cauda equina, selectively involving anterior roots in AMAN. Both in AIDP and AMAN/AMSAN, ultrasonography has demonstrated frequent enlargement of ventral rami of C5-C7 nerves with blurred boundaries, whereas sonograms of upper and lower extremity peripheral nerves exhibited variable and less frequent abnormalities. We provide new insights into the pathogenesis and classification of early GBS.