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.

Myotonia, i.e., delayed muscle relaxation in certain hereditary muscle disorders, can be assessed quantitatively using different techniques ranging from force measurements to electrodiagnostics. Ultrasound shear wave elastography (SWE) has been proposed as a novel tool in biomechanics and neuromuscular medicine for the non-invasive estimation of muscle elasticity and, indirectly, muscle force. The aim of this study is to provide ‘proof-of-principle’ that SWE allows a quantitative measurement of the duration of delayed muscle relaxation in myotonia in a simple clinical setting. In six myotonic muscle disorder patients and six healthy volunteers, shear wave velocities (SWV) parallel to the fiber orientation in the flexor digitorum superficialis muscle in the forearm were recorded with a temporal resolution of one per second during fist-clenching and subsequent relaxation; the relaxation time to 10% of normalized shear wave velocity (RT_0.1) was calculated. Forty-six SWE imaging sequences were acquired, yielding a mean RT_0.1 of 7.38 s in myotonic muscle disorder patients, significantly higher than in healthy volunteers (1.36 s), which is comparable to data obtained by mechanical dynamometry. SWV measurements during the baseline relaxation and voluntary contraction phases did not differ significantly between groups. We conclude that SWE is a promising, non-invasive, widely available tool for the quantitative assessment of myotonia to aid in diagnosis and therapeutic monitoring.

Background: High-resolution nerve ultrasound (HRUS) has been proven to be a valuable tool in the diagnosis of immune-mediated neuropathies, such as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M-protein, skin changes) is an important differential diagnosis of CIDP. Until now, there have been no studies that could identify specific HRUS abnormalities in POEMS syndrome patients. Thus, the aim of this study was to assess possible changes and compare findings with CIDP patients. Methods: We retrospectively analyzed HRUS findings in three POEMS syndrome and ten CIDP patients by evaluating cross-sectional nerve area (CSA), echogenicity and additionally calculating ultrasound pattern scores (UPSA, UPSB, UPSC and UPSS) and homogeneity scores (HS). Results: CIDP patients showed greater CSA enlargement and higher UPSS (median 14 vs. 11), UPSA (median 11.5 vs. 8) and HS (median 5 vs. 3) compared with POEMS syndrome patients. However, every POEMS syndrome patient illustrated enlarged nerves exceeding reference values, which were not restricted to entrapment sites. In CIDP and POEMS syndrome, heterogeneous enlargement patterns could be identified, such as inhomogeneous, homogeneous and regional nerve enlargement. HRUS in CIDP patients visualized both increased and decreased echointensity, while POEMS syndrome patients pictured hypoechoic nerves with hyperechoic intraneural connective tissue. Discussion: This is the first study to demonstrate HRUS abnormalities in POEMS syndrome outside of common entrapment sites. Although nerve enlargement was more prominent in CIDP, POEMS syndrome patients revealed distinct echogenicity patterns, which might aid in its differentiation from CIDP. Future studies should consider HRUS and its possible role in determining diagnosis, prognosis and treatment response in POEMS syndrome.

Background: Diagnosis of immune-mediated neuropathies and their differentiation from amyotrophic lateral sclerosis (ALS) can be challenging, especially at early disease stages. Accurate diagnosis is, however, important due to the different prognosis and available treatment options. We present one patient with a left-sided dorsal flexor paresis and initial suspicion of ALS and another with multifocal sensory deficits. In both, peripheral nerve imaging was the key for diagnosis. Methods: We performed high-resolution nerve ultrasound (HRUS) and 7T or 3T magnetic resonance neurography (MRN). Results: In both patients, HRUS revealed mild to severe, segmental or inhomogeneous, nerve enlargement at multiple sites, as well as an area increase of isolated fascicles. MRN depicted T2 hyperintense nerves with additional contrast-enhancement. Discussion: Peripheral nerve imaging was compatible with the respective diagnosis of an immune-mediated neuropathy, i.e., multifocal motor neuropathy (MMN) in patient 1 and multifocal acquired demyelinating sensory and motor neuropathy (MADSAM) in patient 2. Peripheral nerve imaging, especially HRUS, should play an important role in the diagnostic work-up for immune-mediated neuropathies and their differentiation from ALS.

Myasthenia gravis is a neuromuscular disease typically associated with acetylcholine receptor (AChR) autoantibodies. However, in AChR-negative cases, autoantibodies against muscle-specific receptor tyrosine kinase (MuSK) may be present. Given the rarity of MuSK autoantibodies, there is limited information on their development and significance as biomarkers of disease activity. In a retrospective 10-year study, we tested 749 serum samples from 641 patients for MuSK autoantibodies. For MuSK-positive Myasthenia gravis cases, we extended the observation period to almost 17 years and analyzed the correlation between MuSK titers and clinical severity (Besinger score). We also examined the association between elevated but formally negative MuSK titers and other autoimmune diseases. Of the 749 samples, 21 (3 %, n = 7 patients) were MuSK-positive. In these patients, MuSK titers did not correlate with disease severity or treatment changes. 78 samples (10 %, n = 73 patients) showed elevated but formally negative MuSK titers, with no link to other autoimmune diseases. Our results contradict previous studies suggesting that MuSK autoantibodies could serve as biomarkers of Myasthenia gravis severity, and they shed light on the clinical relevance of elevated but formally negative MuSK titers.

Introduction/Aims: Nerve enlargement has been reported in patients with Friedreich ataxia (FRDA). The underlying cause remains unclear, and both inflammatory processes and dysmyelination have been suggested as potential mechanisms. This study was aimed at assessing nerve morphology with high‐resolution ultrasound, to identify and describe patterns of nerve pathology. Methods: Patients with genetically confirmed FRDA were included, clinically examined, and assessed with high‐resolution ultrasound. Cross‐sectional area measurements were compared with previously published normal values. Results: Among 20 included patients, ultrasound abnormalities were found in 17 (85%). Nerve enlargement of the median and/or ulnar nerve in the proximal nerve segments was observed in 45% of patients and was statistically significant compared to published normal values. Lower extremity nerve enlargement was observed in 20% of patients. Eight patients did not show any nerve enlargement. Diminished cross‐sectional area, indicative of nerve atrophy, was present, particularly in the distal segments of the ulnar nerve (in 25% of patients, p < 0.05) and the tibial nerve (popliteal fossa in 30% of patients, medial malleolus in 30% of patients, both p < 0.05). Nerve enlargement showed no significant correlations with disease severity or age of disease onset. Discussion: Peripheral nerve morphology in FRDA is variable and includes not only nerve enlargement but also nerve atrophy, thus reflecting complex segmental pathology beyond axonal degeneration.