Muscular MRI and magnetic resonance neurography in spinal muscular atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive genetic disease caused by the degeneration of the α-motor neurons in the anterior horn of the spinal cord. SMA is clinically characterized by progressive and symmetrical muscle weakness and muscle atrophy and ends up with systemic multisystem abnormalities. Quantitative MRI (qMRI) has the advantages of non-invasiveness, objective sensitivity, and high reproducibility, and has important clinical value in evaluating the severity of neuromuscular diseases and monitoring the efficacy of treatment. This article summarizes the clinical use of muscular MRI and magnetic resonance neurography in assessing the progress of SMA.

Chronic Inflammatory Demyelinating Polyneuropathy and Evaluation of the Visual Evoked Potentials: A Review of the Literature

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rare autoimmune disorder characterised by the progressive demyelination of peripheral nerves, resulting in motor and sensory deficits. While much research has focused on clinical and electrophysiological aspects of CIDP, there is an emerging interest in exploring its impact on the visual system through visual evoked potentials (VEPs). This comprehensive review synthesises existing literature on VEP findings in CIDP patients, shedding light on their potential diagnostic and prognostic value. The review thoroughly examines studies spanning the last two decades, exploring VEP abnormalities in CIDP patients. Notably, VEP studies have consistently revealed prolonged latencies and reduced amplitudes in CIDP patients compared to healthy controls. These alterations in VEP parameters suggest that the demyelinating process extends beyond the peripheral nervous system to affect the central nervous system, particularly the optic nerve and its connections. The correlation between VEP abnormalities and clinical manifestations of CIDP, such as visual impairment and sensory deficits, underscores the clinical relevance of VEP assessment in CIDP management. Furthermore, this review addresses the potential utility of VEPs in aiding CIDP diagnosis and monitoring disease progression. VEP abnormalities may serve as valuable biomarkers for disease activity, helping clinicians make timely therapeutic decisions. Moreover, this review discusses the limitations and challenges associated with VEP assessment in CIDP, including variability in recording techniques and the need for standardised protocols. In conclusion, this review highlights the evolving role of VEPs as a non-invasive tool in CIDP evaluation. The consistent VEP abnormalities observed in CIDP patients suggest the involvement of the central nervous system in this demyelinating disorder. As our understanding of CIDP and its pathophysiology continues to evolve, further research in this area may lead to improved diagnostic accuracy and monitoring strategies, ultimately enhancing the clinical management of CIDP patients.

The diagnostic value of quantitative assessment of MR neurography in chronic inflammatory demyelinating polyradiculoneuropathy: a systematic review and meta-analysis

OBJECTIVES

The purpose of this study was to evaluate the diagnostic value of quantitative magnetic resonance neurography (MRN) in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We also compared various MRN parameters and determined the best performing one.

METHODS

Through literature searches in PubMed, Embase, Cochrane, Ovid MEDLINE and ClinicalTtrials.gov until March 1, 2023, we selected studies with the diagnostic performance of MRN in CIDP patients. The pooled estimated sensitivity and specificity of quantitative MRN parameters were determined by a bivariate random-effects model. Subgroup analysis was performed to evaluate the proper quantitative parameters and nerve sites.

RESULTS

A total of 14 quantitative MRN studies with 23 results gave a pooled sensitivity of 0.73 (95% CI 0.66-0.79) and a pooled specificity of 0.89 (95% CI 0.84-0.92). The area under the curve (AUC) was 0.89 (95%CI 0.86-0.92). Subgroup analysis of quantitative parameters showed the fractional anisotropy (FA) with the highest sensitivity of 0.85 (95% CI 0.77-0.90) and cross-sectional area (CSA) with the highest specificity of 0.95 (95% CI 0.85-0.99). The pooled correlation coefficient for interobserver agreements was 0.90 (95%CI 0.82-0.95).

CONCLUSION

Quantitative MRN has considerable diagnostic value in CIDP patients with accuracy and reliability. FA and CSA can be promising parameters in the future diagnosis of CIDP patients.

ADVANCES IN KNOWLEDGE

This is the first meta-analysis of quantitative MRN in the diagnosis of CIDP.We have selected reliable parameters with cut-off value and provided new insights for subsequent diagnosis of CIDP.

MRI correlates of motoneuron loss in SMA

BACKGROUND

Magnetic resonance imaging (MRI) is currently explored as supplemental tool to monitor disease progression and treatment response in various neuromuscular disorders. We here assessed the utility of a multi-parametric magnetic resonance imaging (MRI) protocol including quantitative water T₂ mapping, Dixon-based proton density fat fraction (PDFF) estimation and diffusion tensor imaging (DTI) to detect loss of spinal motor neurons and subsequent muscle damage in adult SMA patients.

METHODS

Sixteen SMA patients and 13 age-matched controls were enrolled in this prospective, longitudinal study. All participants underwent MRI imaging including measurements of Dixon-based PDFF and DTI of the sciatic nerve. SMA patients furthermore underwent measurements of muscle water T₂ (T_2w) of the biceps femoris muscle (BFM) and quadriceps femoris muscle (QFM). Ten participants returned for a second scan six months later. MRI parameter were correlated with clinical data. All patients were on nusinersen treatment.

RESULTS

There were significantly higher intramuscular fat fractions in the BFM and QFM of SMA patients compared to healthy controls at baseline and after 6 months. Furthermore, T2 values significantly correlated positively with intramuscular fat fractions. The Hammersmith functional motor scale significantly correlated with the QFM's intramuscular fat fractions. DTI scans of the sciatic nerve were not significantly different between the two groups.

CONCLUSION

This study demonstrates that, water T₂ mapping and Dixon-based PDFF estimation may distinguish between adult SMA patients and controls, due to massive intramuscular fat accumulation in SMA. More extensive long-term studies are warranted to further evaluate these two modalities as surrogate markers in SMA patients during treatment.

Chronic Inflammatory Demyelinating Polyradiculoneuropathy in Association With Concomitant Diseases: Identification and Management

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a rare, heterogeneous, but treatable autoimmune-mediated peripheral neuropathy characterized by demyelination. CIDP can occur independently or simultaneously with a variety of diseases such as diabetes, monoclonal gammopathy of undetermined significance (MGUS), connective tissue disease, and HIV. It is important to identify CIDP and specific peripheral neuropathies caused by these diseases; this review aims to summarize the CIDP literatures related to diabetes, MGUS, SLE, and HIV, and to be helpful for the management of such patients.

Feasibility of simultaneous high-resolution anatomical and quantitative magnetic resonance imaging of sciatic nerves in patients with Charcot-Marie-Tooth type 1A (CMT1A) at 7T

INTRODUCTION/AIMS

Magnetic resonance imaging (MRI) of peripheral nerves can provide image-based anatomical information and quantitative measurement. The aim of this pilot study was to investigate the feasibility of high-resolution anatomical and quantitative MRI assessment of sciatic nerve fascicles in patients with Charcot-Marie-Tooth (CMT) 1A using 7T field strength.

METHODS

Six patients with CMT1A underwent imaging on a high-gradient 7T MRI scanner using a 28-channel knee coil. Two high-resolution axial images were simultaneously acquired using a quantitative double-echo in steady-state (DESS) sequence. By comparing the two DESS echoes, T2 and apparent diffusion coefficient (ADC) maps were calculated. The cross-sectional areas and mean T2 and ADC were measured in individual fascicles of the tibial and fibular (peroneal) portions of the sciatic nerve at its bifurcation and 10 mm distally. Disease severity was measured using Charcot-Marie-Tooth Examination Score (CMTES) version 2 and compared to imaging findings.

RESULTS

We demonstrated the feasibility of 7T MRI of the proximal sciatic nerve in patients with CMT1A. Using the higher field, it was possible to measure individual bundles in the tibial and fibular divisions of the sciatic nerve. There was no apparent correlation between diffusion measures and disease severity in this small cohort.

DISCUSSION

This pilot study indicated that high-resolution MRI that allows for combined anatomical and quantitative imaging in one scan is feasible at 7T field strengths and can be used to investigate the microstructure of individual nerve fascicles.

Length-dependent changes of lower limb muscle morphology in Chronic Inflammatory Demyelinating Polyneuropathy assessed with magnetic resonance imaging

The objective of the present study was to assess muscle quantity of the thigh and leg in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) compared to age and sex matched controls in exploring length-dependent changes of innervated muscles. In five people with CIDP and seven controls, magnetic resonance imaging was used to assess muscle morphology of the four parts of the quadriceps and medial hamstring muscles. Findings were compared to the triceps surae from a subset of participants. The CIDP group had less contractile tissue in the quadriceps (11.5%, P<0.05), hamstrings (15.6%, P<0.05) and triceps surae (35.9%, P<0.05) compared to controls. Additionally, CIDP had less contractile tissue (18.7%) in the triceps surae compared to the hamstrings (P<0.05). Muscle quantity in the quadriceps and hamstrings in CIDP was less than controls, but differences were greater for the distal triceps surae. These findings support a length-dependent affect of CIDP on limb musculature composition.

ACR Appropriateness Criteria® Plexopathy: 2021 Update

Plexopathy may be caused by diverse pathologies, including trauma, nerve entrapment, neoplasm, inflammation, infection, autoimmune disease, hereditary disease, and idiopathic etiologies. For patients presenting with brachial or lumbosacral plexopathy, dedicated plexus MRI is the most appropriate initial imaging modality for all clinical scenarios and can identify processes both intrinsic and extrinsic to the nerves. Other imaging tests may be appropriate for initial imaging depending on the clinical scenario. This document addresses initial imaging strategies for brachial and lumbosacral plexopathy in the following clinical situations: nontraumatic plexopathy with no known malignancy, traumatic plexopathy (not perinatal), and plexopathy occurring in the context of a known malignancy or posttreatment syndrome. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Changes of Dorsal Root Ganglion Volume in Dogs with Clinical Signs of Degenerative Myelopathy Detected by Water-Excitation Magnetic Resonance Imaging

Simple Summary

Canine degenerative myelopathy (DM) is a chronic, progressive, and fatal neurodegenerative disease. Although degenerative changes in dogs with DM are observed not only in the spinal cord white matter but also the dorsal root ganglion (DRG) neurons, these changes are undetectable on conventional magnetic resonance imaging (MRI). Therefore, we investigated the ability of water-excitation MRI to visualize the DRG in dogs, and whether volumetry of DRG has a premortem diagnostic value for DM. Using water-excitation MRI, DRG could be depicted in all dogs. To normalize the volumes of DRG, body surface area was the most suitable denominator. The normalized DRG volume in dogs with DM was significantly lower than those in control dogs and dogs with intervertebral disc herniation. The results of this study revealed that widespread atrophy of DRG was likely to occur in DM. Moreover, volume reductions of DRG were observed in dogs with DM in both the early disease stage and late disease stage. Our research suggests that the DRG volume obtained by the water-excitation technique could be used as a clinical biomarker for DM.

Abstract

Canine degenerative myelopathy (DM) is a progressive and fatal neurodegenerative disease. However, a definitive diagnosis of DM can only be achieved by postmortem histopathological examination of the spinal cord. The purpose of this study was to investigate whether the volumetry of DRG using the ability of water-excitation magnetic resonance imaging (MRI) to visualize the DRG in dogs has premortem diagnostic value for DM. Eight dogs with DM, twenty-four dogs with intervertebral disc herniation (IVDH), and eight control dogs were scanned using a 3.0-tesla MRI system, and water-excitation images were obtained to visualize and measure the volume of DRG, normalized by body surface area. The normalized mean DRG volume between each spinal cord segment and mean volume of all DRG between T8 and L2 in the DM group was significantly lower than that in the control and the IVDH groups (P = 0.011, P = 0.002, respectively). There were no correlations within the normalized mean DRG volume between DM stage 1 and stage 4 (r_s = 0.312, P = 0.128, respectively). In conclusion, DRG volumetry by the water-excitation MRI provides a non-invasive and quantitative assessment of neurodegeneration in DRG and may have diagnostic potential for DM.

Magnetic Resonance Neurography in a Patient with Distal Neuralgic Amyotrophy

The pathophysiology of neuralgic amyotrophy (NA) remains to be elucidated. However, high-resolution magnetic resonance imaging and ultrasound sonography have provided new insights into the mechanism underlying the development of NA and its diagnosis. We report a case of idiopathic distal NA with hyperintensity and thickening in the inferior trunk extending to the posterior and medial fasciculus of the left brachial plexus, which was detected by magnetic resonance neurography (MRN) with diffusion-weighted whole-body imaging with background body signal suppression (DWIBS). The abnormal signal intensity diminished after the improvement of symptoms following corticosteroid treatment. MRN with DWI can help diagnose distal NA and evaluate the post-therapeutic response.

Variable echo time imaging for detecting the short T2* components of the sciatic nerve: a validation study

OBJECTIVE

The aim of this study was to develop and validate an MRI protocol based on a variable echo time (vTE) sensitive to the short T2* components of the sciatic nerve.

MATERIALS AND METHODS

15 healthy subjects (M/F: 9/6; age: 21-62) were scanned at 3T targeting the sciatic nerve at the thigh bilaterally, using a dual echo variable echo time (vTE) sequence (based on a spoiled gradient echo acquisition) with echo times of 0.98/5.37 ms. Apparent T2* (aT2*) values of the sciatic nerves were calculated with a mono-exponential fit and used for data comparison.

RESULTS

There were no significant differences in aT2* related to side, sex, age, and BMI, even though small differences for side were reported. Good-to-excellent repeatability and reproducibility were found for geometry of ROIs (Dice indices: intra-rater 0.68-0.7; inter-rater 0.70-0.72) and the related aT2* measures (intra-inter reader ICC 0.95-0.97; 0.66-0.85) from two different operators. Side-related signal-to-noise-ratio non-significant differences were reported, while contrast-to-noise-ratio measures were excellent both for side and echo.

DISCUSSION

Our study introduces a novel MR sequence sensitive to the short T2* components of the sciatic nerve and may be used for the study of peripheral nerve disorders.

Magnetic resonance neurography in diagnosing childhood chronic inflammatory demyelinating polyradiculoneuropathy

BACKGROUND

Peripheral nerve imaging is increasingly recognized as a powerful tool to evaluate nerve hypertrophy in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and Charcot-Marie-Tooth diseases (CMT), whereas data in pediatric patients are limited.

CASE DESCRIPTION

We describe the case of a 15-year-old Japanese girl with asymmetric demyelinating polyneuropathy, who, at the age of 10 years, was initially diagnosed with a demyelinating form of CMT. Fluorescence in situ hybridization for peripheral myelin 22 was negative, and already-known pathogenic variants were not detected by whole-genome sequencing, and nerve conduction studies revealed multifocal conduction blocks. Over the next 5 years, the patient showed gradual improvement in muscle weakness and sensory disturbance without immunological treatment and was referred to our hospital.

RESULTS

At the age of 15 years, magnetic resonance (MR) neurography showed asymmetric multifocal fusiform enlargement of nerve roots, brachial and lumbosacral plexuses, and intermediated nerve trunks, as well as cranial nerves. Based on the MR neurography findings and multifocal nerve conduction blocks, she was diagnosed as having multifocal CIDP (multifocal demyelinating sensory and motor neuropathy [MADSAM]) according to the European Federation of Neurological Societies/Peripheral Nerve Society diagnostic criteria.

DISCUSSION

Clinical diagnosis of childhood CIDP is challenging because its neurological manifestations and nerve conduction study findings occasionally resemble those of inherited demyelinating neuropathies. MR neurography is helpful for the assessment of patterns of nerve hypertrophy; MADSAM-CIDP is characterized by multiple fusiform nerve enlargement, whereas CMT shows symmetric and diffuse nerve hypertrophy.

CONCLUSION

The MR neurography patterns would help in diagnosing pediatric demyelinating neuropathies.

Association between chronic inflammatory demyelinating polyneuropathy and gastrointestinal malignancies

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an uncommon and under-recognized immune-mediated disorder of the peripheral nervous system. It is associated with both infectious and non-infectious etiologies and presents in several variant forms. In rare instances, CIDP has been reported in association with gastrointestinal (esophageal, hepatic, colorectal, and pancreatic) malignancies. The diagnosis of malignancy is typically preceded by weeks to months by that of CIDP, though the inverse may also be seen. As with other etiologies of CIDP, cases associated with gastrointestinal malignancies are often treated with corticosteroids, intravenous immunoglobulins, and/or plasma exchange, with improvement or resolution of neurological symptoms in the majority of cases. In this review, we provide a practical overview of CIDP, with an emphasis on recognizing the clinical association between CIDP and gastrointestinal malignancies.

The Noninvasive Diagnostic Value of MRN for CIDP: A Research from Qualitative to Quantitative

STUDY DESIGN

We examined the chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) patients and non-CIDP patients who have similar symptoms and difficult to differential diagnosis with CIDP by magnetic resonance neurography to find the difference among them.

OBJECTIVE

To investigate the differential diagnostic value of magnetic resonance neurography (MRN) for CIDP and other peripheral neuropathies.

SUMMARY OF BACKGROUND DATA

Thirty-two consecutive patients with CIDP and 22 non-CIDP patients with symptoms similar to CIDP and difficult to be discriminate were recruited and imaged as a control group between May 2017 and May 2019.

METHODS

In this prospective study, the brachial plexus and lumbosacral plexus of 32 CIDP patients and 22 non-CIDP patients were examined by MRN. The clinical features and the nerve roots cross-sectional area (CSA) of the brachial plexus and lumbosacral plexus were measured.

RESULTS

The CSA of nerve roots of CIDP, Charcot-Marie-Tooth disease type-1 and polyneuropathy, organomegaly, endocrinopathy, M protein, and skin changes syndrome patients were all shown extensive by MRN. The sensitivity of MRN in diagnosing CIDP was 81.25% (26/32), the specificity was 68.18% (15/22), the positive predictive value was 78.79% (26/33), the negative predictive value was 71.43% (15/21), the accuracy was 75.93% (40/54), the misdiagnosis rate was 24.07% (13/54), and the kappa value was 0.498. Receiver operating characteristic analysis showed higher diagnostic accuracy for CIDP with the CSA of the lumbosacral plexus (area under the curve [AUC] = 0.762) and that of the brachial plexus (AUC = 0.762), and the combined of both examinations did not improve the diagnostic efficacy compared with either (AUC = 0.769).

CONCLUSIONS

The nerve roots of CIDP, Charcot-Marie-Tooth disease type-1, and polyneuropathy, organomegaly, endocrinopathy, M protein, and skin changes syndrome were difficult to distinguish by MRN. Atypical CIDP patients had less nerve root injury compared with typical CIDP patients. MRN of either the brachial plexus or the lumbosacral plexus had a high diagnostic accuracy for CIDP, and it is not necessary to perform both parts of the examination.

LEVEL OF EVIDENCE

2.

The comparison of MRN, electrophysiology and progression among typical CIDP and atypical CIDP subtypes

We aimed to compare the electrophysiology and magnetic resonance neurography (MRN) results of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) subtypes and to explore the progression from atypical CIDP to typical CIDP. We collected the medical records of 45 CIDP patients to analyse the rate of progression from atypical CIDP to typical CIDP subtypes. The cerebrospinal fluid (CSF) protein (p = 0.024) and overall disability sum score (ODSS) (p = 0.000) differed among patients with typical CIDP, distal acquired demyelinating symmetric neuropathy (DADS) and Lewis-Sumner syndrome (LSS). The compound motor action potential (CMAP) of typical CIDP was lower than that of the other subtypes (p = 0.016, p = 0.022 and p = 0.012). The cross-sectional area (CSA) of nerve roots in typical CIDP was significantly thicker than that of nerve roots in DADS and LSS. There were fewer DADS and LSS patients who progressed to typical CIDP than those who progressed to pure motor and pure sensory CIDP (p = 0.000), and the progression from pure motor to typical CIDP required a significantly longer time than the progression from pure sensory to typical CIDP (p = 0.007). Typical CIDP was more severe than the other subtypes not only in terms of clinical and electrophysiology factors but also in terms of MRN factors.

Low interrater reliability of brachial plexus MRI in chronic inflammatory neuropathies

Introduction

Magnetic resonance imaging of the brachial plexus shows nerve thickening in approximately half of the patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). The reliability of qualitative evaluation of brachial plexus MRI has not been studied previously.

Methods

We performed an interrater study in a retrospective cohort of 19 patients with CIDP, 17 patients with MMN, and 14 controls. The objective was to assess interrater variability between radiologists by using a predefined scoring system that allowed the distinction of no, possible, or definite nerve thickening.

Results

Raters agreed in 26 of 50 (52%) brachial plexus images; κ‐coefficient was 0.30 (SE 0.08, 95% confidence interval 0.14–0.46, P < .0005).

Discussion

Our results provide evidence that interrater reliability of qualitative evaluation of brachial plexus MRI is low. Objective criteria for abnormality are required to optimize the diagnostic value of MRI for inflammatory neuropathies.

See editorial on pages 679–680 in this issue.

Peripheral nerve magnetic resonance imaging

Magnetic resonance imaging (MRI) has been used extensively in revealing pathological changes in the central nervous system. However, to date, MRI is very much underutilized in evaluating the peripheral nervous system (PNS). This underutilization is generally due to two perceived weaknesses in MRI: first, the need for very high resolution to image the small structures within the peripheral nerves to visualize morphological changes; second, the lack of normative data in MRI of the PNS and this makes reliable interpretation of the data difficult. This article reviews current state-of-the-art capabilities in in vivo MRI of human peripheral nerves. It aims to identify areas where progress has been made and those that still require further improvement. In particular, with many new therapies on the horizon, this review addresses how MRI can be used to provide non-invasive and objective biomarkers in the evaluation of peripheral neuropathies. Although a number of techniques are available in diagnosing and tracking pathologies in the PNS, those techniques typically target the distal peripheral nerves, and distal nerves may be completely degenerated during the patient’s first clinic visit. These techniques may also not be able to access the proximal nerves deeply embedded in the tissue. Peripheral nerve MRI would be an alternative to circumvent these problems. In order to address the pressing clinical needs, this review closes with a clinical protocol at 3T that will allow high-resolution, high-contrast, quantitative MRI of the proximal peripheral nerves.

Chronic inflammatory demyelinating polyneuropathy: update on diagnosis, immunopathogenesis and treatment

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an immune-mediated neuropathy typically characterised by symmetrical involvement, and proximal as well as distal muscle weakness (typical CIDP). However, there are several 'atypical' subtypes, such as multifocal acquired demyelinating sensory and motor neuropathy (Lewis-Sumner syndrome) and 'distal acquired demyelinating symmetric neuropathy', possibly having different immunopathogenesis and treatment responses. In the absence of diagnostic and pathogenetic biomarkers, diagnosis and treatment may be difficult, but recent progress has been made in the application of neuroimaging tools demonstrating nerve hypertrophy and in identifying subgroups of patients who harbour antibodies against nodal proteins such as neurofascin and contactin-1. Despite its relative rarity, CIDP represents a significant economic burden, mostly due to costly treatment with immunoglobulin. Recent studies have demonstrated the efficacy of subcutaneous as well as intravenous immunoglobulin as maintenance therapy, and newer immunomodulating drugs can be used in refractory cases. This review provides an overview focusing on advances over the past several years.

Nerve ultrasound and magnetic resonance imaging in the diagnosis of neuropathy

PURPOSE OF REVIEW

This review summarizes the most relevant developments in the fields of nerve ultrasound and MRI in the diagnosis of treatable inflammatory neuropathies over the last 18 months.

RECENT FINDINGS

MRI and nerve ultrasound can accurately identify potentially treatable neuropathies and thereby help to improve diagnosis. Advanced MRI techniques also show potential to dissect pathophysiology. The apparent mismatch between nerve function and morphology is not surprising and reflects different dimensions of the disease process in neuropathies.

SUMMARY

MRI and nerve ultrasound have become useful tools in the diagnosis of inflammatory neuropathies. VIDEO ABSTRACT.

MR microneurography and quantitative T2 and DP measurements of the distal tibial nerve in CIDP

OBJECTIVE

In this study we investigated the potential of magnetic resonance (MR) micro-neurography to detect morphological and relaxometric changes in distal tibial nerves in patients affected with chronic inflammatory demyelinating polyneuropathy (CIDP), and their associations with clinical and electrophysiological features.

MATERIALS AND METHODS

10 subjects affected with CIDP and 10 healthy subjects were examined. Multiple MR parameters, including the number of fascicles (N), fascicles diameter (FD), total fascicles area (FA), epineurium area (EA), total nerve area (NA), fascicles to nerve ratio (FNR) and quantitative T2 and proton density (PD) were investigated on high resolution MR images of the distal tibial nerve. Those parameters were correlated with clinical scores, age of onset, disease duration and electrophysiologic data.

RESULTS

Median NA and FA were significantly increased in the CIDP population (median values for NA in cm² in CIDP: 0.185; controls: 0.135; p: 0.028; for FA in CIDP 0.136; controls 0.094; p: 0.021). There was no correlation between the parameters investigated and clinical or electrophysiologic features.

CONCLUSION

MR microneurography can detect increased total nerve and fascicle area in distal tibial nerves in CIDP and may be useful for diagnosing CIDP.

Lumbar plexus in patients with chronic inflammatory demyelinating polyradiculoneuropathy: evaluation with simultaneous T2 mapping and neurography method with SHINKEI

OBJECTIVE:

To evaluate the usefulness of simultaneous T₂ mapping and neurography with nerve-sheath signal increased with inked rest-tissue rapid acquisition of relaxation enhancement imaging (SHINKEI) in the lumbar plexus to distinguish patients with chronic inflammatory demyelinating polyneuropathy (CIDP) from healthy controls.

METHODS:

Our institutional review boards approved this retrospective study, and written informed consent was waived. 10 patients with CIDP from 2015 to 2017 were studied along with 5 healthy controls on a 3 T scanner. The T₂ relaxation time and the size of the dorsal root ganglia and nerves of the lumbar plexus at L3-S1 were measured. Statistical analyses were performed with the Mann-Whitney U test and a receiver operating characteristics analysis.

RESULTS:

The T₂ relaxation times of the dorsal root ganglia and the nerves of the lumbar plexus were longer in the CIDP patients (133.34  ±  41.36 and 130.40 ± 47.78 ms) compared to the healthy controls (114.69 ± 24.90 and 83.72 ± 17.51 ms, p = 0.0265 and p < 0.0001, respectively). The sizes of the nerves were larger in the CIDP patients (6.19  ±  2.28 mm) compared to the controls (4.54  ±  0.86 mm, p < 0.0001). However, there was no significant difference between the sizes of the ganglia in the CIDP patients and the controls. The receiver operating characteristics analysis revealed that the T₂ relaxation time of the nerves was best at distinguishing the CIDP patients from the controls (Az  =  0.848).

CONCLUSION:

Patients with CIDP could be distinguished from healthy controls using simultaneous T₂ mapping and neurography with SHINKEI in the lumbar plexus.

ADVANCES IN KNOWLEDGE:

Patients with CIDP could be distinguished from healthy controls using simultaneous T₂ mapping and neurography with SHINKEI in the lumbar plexus.

Recent advances in magnetic resonance neuroimaging of lumbar nerve to clinical applications: A review of clinical studies utilizing Diffusion Tensor Imaging and Diffusion-weighted magnetic resonance neurography

Much progress has been made in neuroimaging with Magnetic Resonance neurography and Diffusion Tensor Imaging (DTI) owing to higher magnetic fields and improvements in pulse sequence technology. Reports on lumbar nerve DTI have also increased considerably. Many studies have shown that the use of DTI in lumbar nerve lesions, such as lumbar foraminal stenosis and lumbar disc herniation, makes it possible to capture images of interruptions of tractography at stenotic sties, enabling the diagnosis of stenosis. DTI can also reveal significant decreases in fractional anisotropy (FA) with significant increases in apparent diffusion coefficient (ADC) values in compression lesions. FA values have higher accuracy than ADC values. Furthermore, strong correlations exist between FA values and indications of neurological severity, including the Japanese Orthopedic Association (JOA) score, the Oswestry Disability Index (ODI), and the Roland-Morris Disability Questionnaire (RDQ) in patients with lumbar disc herniation-induced radiculopathy. Most lumbar DTI has become 3T; 3T MRI has made it possible to take high-resolution DTI measurements in a short period of time. However, increased motion artifacts in the magnetic susceptibility effect lead to signal irregularities and image distortion. In the future, high-resolution DTI with reduced field-of-view may become useful in clinical applications, since visualization of nerve lesions and quantification of DTI parameters could allow more accurate diagnoses of lumbar nerve dysfunctions. Future translational studies will be necessary to successfully bring MR neuroimaging of lumbar nerve into clinical use.

Autoantibodies in chronic inflammatory neuropathies: diagnostic and therapeutic implications

The chronic inflammatory neuropathies (CINs) are rare, very disabling autoimmune disorders that generally respond well to immune therapies such as intravenous immunoglobulin (IVIg). The most common forms of CIN are chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), multifocal motor neuropathy, and polyneuropathy associated with monoclonal gammopathy of unknown significance. The field of CIN has undergone a major advance with the identification of IgG4 autoantibodies directed against paranodal proteins in patients with CIDP. Although these autoantibodies are only found in a small subset of patients with CIDP, they can be used to guide therapeutic decision-making, as these patients have a poor response to IVIg. These observations provide proof of concept that identifying the target antigens in tissue-specific antibody-mediated autoimmune diseases is important, not only to understand their underlying pathogenic mechanisms, but also to correctly diagnose and treat affected patients. This state-of-the-art Review focuses on the role of autoantibodies against nodes of Ranvier in CIDP, a clinically relevant emerging field of research. The role of autoantibodies in other immune-mediated neuropathies, including other forms of CIN, primary autoimmune neuropathies, neoplasms, and systemic diseases that resemble CIN, are also discussed.

Large coverage MR neurography in CIDP: diagnostic accuracy and electrophysiological correlation

The objective of this study was to evaluate large coverage magnetic resonance neurography (MRN) in chronic inflammatory demyelinating polyneuropathy (CIDP). In this prospective study, 18 patients with CIDP and 18 healthy controls were examined by a standardized MRN protocol at 3 T. Lumbosacral plexus was imaged by a T2-weighted 3D sequence and peripheral nerves of the upper and lower extremity by axial T2-weighted turbo spin-echo sequences. Lesions were characterized by nerve cross-sectional area (CSA) and T2-weighted signal (nT2). Additionally, T2 relaxometry of the sciatic nerve was performed using a multi-spin-echo sequence. All patients received a complementary electrophysiological exam. Patients with CIDP exhibited increased nerve CSA and nT2 compared to controls (p < 0.05) in a proximally predominating pattern. Receiver operating characteristic analysis revealed the best diagnostic accuracy for CSA of the lumbosacral plexus (AUC = 0.88) and nT2 of the sciatic nerve (AUC = 0.88). CSA correlated with multiple electrophysiological parameters of demyelinating neuropathy (F wave latency, nerve conduction velocity) of sciatic and median nerve, while nT2 only correlated with F wave latency of sciatic and not median nerve. T2 relaxometry indicated that MR signal increase in CIDP was due to an increase in proton-spin-density (p < 0.05), and not due to the increase in T2 relaxation time. Both nT2 and CSA might aid in the diagnosis of CIDP, but CSA correlates more robustly with established electrophysiological parameters for CIDP. Since the best diagnostic accuracy was shown for proximal nerve locations, MRN may be a useful complementary tool in selected CIDP cases.