Nerve ultrasound studies in POEMS syndrome

The difference in nerve ultrasound and motor nerve conduction studies between autoimmune nodopathy and chronic inflammatory demyelinating polyneuropathy

INTRODUCTION/AIMS

Nerve enlargement has been described in autoimmune nodopathy and chronic inflammatory demyelinating polyneuropathy (CIDP). However, comparisons of the distribution of enlargement between autoimmune nodopathy and CIDP have not been well characterized. To fill this gap, we explored differences in the ultrasonographic and electrophysiological features between autoimmune nodopathy and CIDP.

METHODS

Between March 2015 and June 2023, patients fulfilling diagnostic criteria for CIDP were enrolled; among them, those with positive antibodies against nodal-paranodal cell-adhesion molecules were distinguished as autoimmune nodopathy. Nerve ultrasound and nerve conduction studies (NCS) were performed.

RESULTS

Overall, 114 CIDP patients and 13 patients with autoimmune nodopathy were recruited. Cross-sectional areas (CSA) at all sites were larger in patients with CIDP and autoimmune nodopathy than in healthy controls. CSAs at the roots and trunks of the brachial plexus were significantly larger in patients with anti-neurofascin-155 (NF155), anti-contactin-1 (CNTN1), and anti-contactin-associated protein 1 (CASPR1) antibodies than in CIDP patients. The patients with anti-NF186 antibody did not have enlargement in the brachial plexus. NCS showed more frequent probable conduction block at Erb's point in autoimmune nodopathy than in CIDP (61.9% vs. 36.6% for median nerve, 52.4% vs. 39.5% for ulnar nerve). Markedly prolonged distal motor latencies were also present in autoimmune nodopathy.

DISCUSSION

Patients with autoimmune nodopathies had distinct distributions of peripheral nerve enlargement revealed by ultrasound, as well as distinct NCS patterns, which were different from CIDP. This suggests the potential utility of nerve ultrasound and NCS to supplement clinical characteristics for distinguishing nodopathies from CIDP.

The Role of Neuromuscular Ultrasound in the Diagnosis of Peripheral Neuropathy

The classification of peripheral neuropathies has traditionally been based on etiology, electrodiagnostic findings, or histopathologic features. With the advent of modern imaging, they now can also be characterized based on their varied distribution of imaging findings. We describe the major morphologic patterns of these changes, which include homogeneous enlargement; homogeneous thinning; focal, multifocal, and segmental enlargement; and focal thinning and beading (multifocal thinning). Representative disorders in each of these categories are discussed, along with examples of the more complex imaging manifestations of neuralgic amyotrophy, nerve transection, and hereditary amyloidosis. An appreciation of the diverse morphologic manifestations of neuropathy can help neuromuscular clinicians conduct appropriate imaging studies with ultrasound and, when needed, order suitable investigations with magnetic resonance neurography.

Characteristics of after-discharges following compound muscle action potential or F-wave in primary peripheral nerve hyperexcitability syndrome

INTRODUCTION/AIMS

F-wave testing frequently reveals after-discharges of varied morphologies in patients with primary peripheral nerve hyperexcitability syndrome (PNHS), although reports are scant. This study aimed to explore the morphological characteristics of the after-discharges during F-wave tests in PNHS, and to assess the association between after-discharges and the disease classification.

METHODS

We conducted a retrospective analysis of patients diagnosed with PNHS between 2014 and 2022. The morphological characteristic and duration of after-discharges during F-wave tests were analyzed. After-discharges in the Morvan syndrome group were compared with those in non-Morvan group, and between groups with positive or negative voltage-gated potassium channel (VGKC) complex antibodies.

RESULTS

Twenty-nine patients were included in the study, of which 25 exhibited after-discharges. All after-discharges in Morvan patients occurred following compound muscle action potential (CMAP). In non-Morvan patients, after-discharges occurred following F-wave (32%) and CMAP (47%). The durations of after-discharges following CMAP were significantly prolonged in Morvan (54.2 ± 18.8 ms) compared to non-Morvan patients (34.5 ± 15.0 ms). The majority of antibody-positive patients (18/20) exhibited after-discharges following CMAP, whereas 67% of antibody-negative patients (6/9) showed after-discharges following F-wave.

DISCUSSION

The varying presentations of after-discharges, including their location (after CMAP or F-wave) and the duration of after-discharge can assist in clinically classifying PNHS.

Paraproteinemic Neuropathies

OBJECTIVE

Coexistence of polyneuropathy and gammopathy is a common but potentially challenging situation in clinical practice. This article reviews the clinical, electrophysiologic, and hematologic phenotypes of the paraproteinemic neuropathies and the diagnostic and treatment strategies for each.

LATEST DEVELOPMENTS

Advances in our understanding of the underlying pathophysiology of various paraproteinemic neuropathies and their corresponding phenotypes have identified potential new therapeutic targets. Therapeutic strategies to diminish anti-myelin-associated glycoprotein (MAG) IgM antibodies have shown partial and inconsistent efficacy; however, antigen-specific immune therapy is being investigated as a novel treatment to remove the presumably pathogenic anti-MAG antibody. Advances in genetic and cell signaling studies have resulted in the approval of Bruton tyrosine kinase inhibitors for Waldenström macroglobulinemia. Monoclonal antibodies are being investigated for the treatment of light chain amyloidosis.

ESSENTIAL POINTS

Early recognition and treatment of underlying plasma cell disorders improves clinical outcomes in patients with paraproteinemic neuropathy. Despite significant progress, our knowledge regarding underlying mechanisms for paraproteinemic neuropathy is still limited. Clinicians' awareness of clinical phenotypes, electrophysiologic hallmarks, and hematologic findings of the different paraproteinemic neuropathies is crucial to promptly identify and treat patients and to avert misdiagnosis. Multidisciplinary collaboration among specialists, including neurologists and hematologists, is paramount for the optimal treatment of these patients with overlapping conditions.

Ultrasound-based radiomic analysis of the peripheral nerves for differentiation between CIDP and POEMS syndrome

BACKGROUND

Demyelinating peripheral neuropathy is characteristic of both polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes (POEMS) syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP). We hypothesized that the different pathogeneses underlying these entities would affect the sonographic imaging features.

PURPOSE

To investigate whether ultrasound (US)-based radiomic analysis could extract features to describe the differences between CIDP and POEMS syndrome.

MATERIAL AND METHODS

In this retrospective study, we evaluated nerve US images from 26 with typical CIDP and 34 patients with POEMS syndrome. Cross-sectional area (CSA) and echogenicity of the median and ulnar nerves were evaluated in each US image of the wrist, forearm, elbow, and mid-arm. Radiomic analysis was performed on these US images. All radiomic features were examined using receiver operating characteristic analysis. Optimal features were selected using a three-step feature selection method and were inputted into XGBoost to build predictive machine-learning models.

RESULTS

The CSAs were more enlarged in patients with CIDP than in those with POEMS syndrome without significant differences, except for that of the ulnar nerve at the wrist. Nerve echogenicity was significantly more heterogeneous in patients with CIDP than in those with POEMS syndrome. The radiomic analysis yielded four features with the highest area under the curve (AUC) value of 0.83. The machine-learning model showed an AUC of 0.90.

CONCLUSION

US-based radiomic analysis has high AUC values in differentiating POEM syndrome from CIDP. Machine-learning algorithms further improved the discriminative ability.

Nerve Ultrasound Performances in Differentiating POEMS Syndrome from CIDP

Chronic inflammatory demyelinating polyneuropathy (CIDP) and polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes (POEMS) syndrome are both acquired demyelinating polyneuropathies. We aim to explore the different features of ultrasonographic changes between CIDP and POEMS syndrome. Nerve ultrasonographic studies were performed in 120 patients with CIDP and 34 patients with POEMS syndrome. Cross-sectional areas (CSAs) were measured on the bilateral median nerve, ulnar nerve, and brachial plexus. Nerve conduction studies were performed on median and ulnar nerves to detect motor conduction blocks (CBs). CSAs at all sites were larger in patients with CIDP and POEMS syndrome than in healthy controls. Maximal CSA (median (min to max)) was 14 (6-194) mm2 for median nerve, 9 (4-92) mm2 for ulnar nerve, and 14 (7-199) mm2 for brachial plexus in CIDP and 11 (8-16) mm2 for median nerve, 8.5 (6-13) mm2 for ulnar nerve, and 14 (10-20) mm2 for brachial plexus in POEMS syndrome. The ratio of maximum/minimum CSA of the median nerve was significantly larger in CIDP (2.8 ± 2.8) than in POEMS syndrome (1.7 ± 0.3). CBs or probable CBs were detected in 60 out of 120 CIDP patients but in none of the POEMS syndromes. For distinguishing CIDP and POEMS syndrome, a two-step protocol using CB and maximum/minimum CSA of the median nerve yields a sensitivity of 93% and a specificity of 79%. In conclusion, compared with CIDP, nerve CSA enlargement was more homogeneous along the same nerve in individual POEMS patients, as well as among different POEMS patients. The addition of nerve ultrasound to nerve conduction studies significantly improves the differential diagnosis between the two diseases.

Contemporary challenges in the diagnosis and management of chronic inflammatory demyelinating polyneuropathy

INTRODUCTION

Despite extensive research, multiple inter-related diagnostic and management challenges remain for chronic inflammatory demyelinating polyneuropathy (CIDP).

AREAS COVERED

A literature review was performed on diagnosis and treatment in CIDP. The clinical features and disease course were evaluated. Investigative techniques, including electrophysiology, cerebrospinal fluid examination, neuropathology, imaging and neuroimmunology, were considered in relation to technical aspects, sensitivity, specificity, availability and cost. Available evidenced-based treatments and those with possible efficacy despite lack of evidence, were considered, as well as current methods for evaluation of treatment effects.

EXPERT OPINION

CIDP remains a clinical diagnosis, supported first and foremost by electrophysiology. Other investigative techniques have limited impact. Most patients with CIDP respond to available first-line treatments and immunosuppression may be efficacious in those who do not. Consideration of the natural history and of the high reported remission rate, of under-recognised associated disabling features, of treatment administration modalities and assessment methods, require enhanced attention.