One-Year Longitudinal Assessment of Patients With CMT1A Using Quantitative MRI

BACKGROUND AND OBJECTIVES

Intramuscular fat fraction (FF) assessed using quantitative MRI (qMRI) has emerged as one of the few responsive outcome measures in CMT1A suitable for future clinical trials. This study aimed to identify the relevance of multiple qMRI biomarkers for tracking longitudinal changes in CMT1A and to assess correlations between MRI metrics and clinical parameters.

METHODS

qMRI was performed in CMT1A patients at 2 time points, a year apart, and various metrics were extracted from 3-dimensional volumes of interest at thigh and leg levels. A semiautomated segmentation technique was used, enabling the analysis of central slices and a larger 3D muscle volume. Metrics included proton density (PD), magnetization transfer ratio (MTR), and intramuscular FF. The sciatic and tibial nerves were also assessed. Disease severity was gauged using Charcot Marie Tooth Neurologic Score (CMTNSv2), Charcot Marie Tooth Examination Score, Overall Neuropathy Limitation Scale scores, and Medical Research Council (MRC) muscle strength.

RESULTS

Twenty-four patients were included. FF significantly rose in the 3D volume at both thigh (+1.04% ± 2.19%, p = 0.041) and leg (+1.36% ± 1.87%, p = 0.045) levels. The 3D analyses unveiled a length-dependent gradient in FF, ranging from 22.61% ± 10.17% to 26.17% ± 10.79% at the leg level. There was noticeable variance in longitudinal changes between muscles: +3.17% ± 6.86% (p = 0.028) in the tibialis anterior compared with 0.37% ± 4.97% (p = 0.893) in the gastrocnemius medialis. MTR across the entire thigh volume showed a significant decline between the 2 time points -2.75 ± 6.58 (p = 0.049), whereas no significant differences were noted for the 3D muscle volume and PD. No longitudinal changes were observed in any nerve metric. Potent correlations were identified between FF and primary clinical measures: CMTNSv2 (ρ = 0.656; p = 0.001) and MRC in the lower limbs (ρ = -0.877; p < 0.001).

DISCUSSION

Our results further support that qMRI is a promising tool for following up longitudinal changes in CMT1A patients, FF being the paramount MRI metric for both thigh and leg regions. It is crucial to scrutinize the postimaging data extraction methods considering that annual changes are minimal (around +1.5%). Given the varied FF distribution, the existence of a length-dependent gradient, and the differential fatty involution across muscles, 3D volume analysis appeared more suitable than single slice analysis.

Congenital myasthenic syndromes in adults: clinical features, diagnosis and long-term prognosis

Congenital myasthenic syndromes (CMS) are clinically and genetically heterogeneous diseases caused by mutations affecting neuromuscular transmission. Even if the first symptoms mainly occur during childhood, adult neurologists must confront this challenging diagnosis and manage these patients throughout their adulthood. However, long-term follow-up data from large cohorts of CMS patients are lacking and the long-term prognosis of these patients is largely unknown. We report the clinical features, diagnostic difficulties, and long-term prognosis of a French nationwide cohort of 235 adult patients with genetically confirmed CMS followed in 23 specialized neuromuscular centres. Data were retrospectively analysed. Of the 235 patients, 123 were female (52.3%). The diagnosis was made in adulthood in 139 patients, 110 of whom presented their first symptoms before the age of 18. Mean follow-up time between first symptoms and last visit was 34 years (SD = 15.1). Pathogenic variants were found in 19 disease-related genes. CHRNE-low expressor variants were the most common (23.8%), followed by variants in DOK7 (18.7%) and RAPSN (14%). Genotypes were clustered into four groups according to the initial presentation: ocular group (CHRNE-LE, CHRND, FCCMS), distal group (SCCMS), limb-girdle group (RAPSN, COLQ, DOK7, GMPPB, GFPT1), and a variable-phenotype group (MUSK, AGRN). The phenotypical features of CMS did not change throughout life. Only four genotypes had a proportion of patients requiring intensive care unit (ICU) admission that exceeded 20%: RAPSN (54.8%), MUSK (50%), DOK7 (38.6%) and AGRN (25.0%). In RAPSN and MUSK patients most ICU admissions occurred before age 18 years and in DOK7 and AGRN patients at or after 18 years of age. Different patterns of disease course (stability, improvement and progressive worsening) may succeed one another in the same patient throughout life, particularly in AGRN, DOK7 and COLQ. At the last visit, 55% of SCCMS and 36.3% of DOK7 patients required ventilation; 36.3% of DOK7 patients, 25% of GMPPB patients and 20% of GFPT1 patients were wheelchair-bound; most of the patients who were both wheelchair-bound and ventilated were DOK7 patients. Six patients died in this cohort. The positive impact of therapy was striking, even in severely affected patients. In conclusion, even if motor and/or respiratory deterioration could occur in patients with initially moderate disease, particularly in DOK7, SCCMS and GFPT1 patients, the long-term prognosis for most CMS patients was favourable, with neither ventilation nor wheelchair needed at last visit. CHRNE patients did not worsen during adulthood and RAPSN patients, often severely affected in early childhood, subsequently improved.

Factors affecting the topography of nitrous oxide-induced neurological complications

BACKGROUND

The factors underlying the topography of nitrous oxide (N2O)-induced neurological complications are unknown.

METHODS

We included all consecutive patients admitted to the university hospital of Marseille for N2O-induced neurological complications in a prospective observational study. Patients underwent neurological examination, spinal cord magnetic resonance imaging, and nerve conduction studies within the first 4 weeks after admission.

RESULTS

In total, 61 patients were included: 45% with myeloneuropathy, 34% with isolated myelopathy, and 21% with isolated neuropathy. On multivariable analysis, the odds of myelopathy were associated with the amount of weekly N2O consumption (~600 g cylinder per week, odds ratio [OR] = 1.11, 95% confidence interval [CI] = 1.001-1.24). The extent of the myelopathy (number of vertebral segments) was correlated with the number of ~600-g cylinders consumed weekly (ρ = 0.40, p < 0.005). The odds of neuropathy were associated with the duration of consumption (per month; OR = 1.29, 95% CI = 1.05-1.58). Mean lower-limb motor nerve amplitude was correlated with the duration of consumption (in months; ρ = -0.34, p < 0.05).

CONCLUSIONS

The odds of myelopathy increased with the amount of N2O consumption, and the odds of neuropathy increased with the duration of N2O exposure, which suggests distinct pathophysiological mechanisms underlying these two neurological complications.

Clinical, biological, electrophysiological and therapeutic profile of patients with anti-MAG neuropathy according to MYD88L265P and CXCR4 mutations and underlying haemopathy

INTRODUCTION

Anti-MAG neuropathies are associated with an IgM monoclonal gammopathy of undetermined significance (MGUS) or with a malignant haemopathy. Our objective was to determine whether the presence of a haemopathy or somatic mutations of MYD88 and CXCR4 genes influences disease presentation and response to rituximab (RTX).

METHODS

We included 79 patients (mean age 74 years, disease duration 9.68 years) who had a bone marrow aspiration with morphologic and immunophenotypic analysis. MYD88L265P and CXCR4 mutations were analysed in peripheral B cells. Information collected included: inflammatory neuropathy cause and treatment sensory sum score (ISS), MRC testing, overall neuropathy limitation scale (ONLS), Rash-built Overall Disability Score (RODS), ataxia score, anti-MAG titres, peak IgM dosage, neurofilament light chain levels, motor and sensory amplitudes, motor unit index (MUNIX) and motor unit size index (MUSIX) sum scores. Efficacy of RTX was evaluated at 12 months in 26 patients.

RESULTS

Malignant haematological disorders were discovered in 17 patients (22%): 13 Waldenstrom macroglobulinemia, 3 marginal zone lymphoma and one mantle cell lymphoma. MYD88L265P mutation was detected in 29/60 (48%) patients and CXCR4 in 1 single patient. Disease severity, biological and electrophysiological data and response to RTX were comparable in patients with MGUS/lymphoma and patients with/without MYD88L265P mutation. ISS was lower and MUSIX higher in patients improved by RTX.

CONCLUSIONS

MYD88L265P mutation and underlying haemopathies are not predictive of a more severe disease. However, in cases of resistant and progressive neuropathy, they provide an opportunity to prescribe newly available drugs such as Bruton tyrosine kinase inhibitors.

Face to Face: deciphering facial involvement in inclusion body myositis

OBJECTIVE

The objective of this study is to evaluate the frequency and characteristics of facial involvement in inclusion body myositis (IBM) patients and to compare it to the one previously described in facioscapulohumeral dystrophy (FSHD) patients.

METHODS

Thirty-two IBM patients were included and compared to 29 controls and 39 FSHD patients. All participants were recorded in a video as they performed a series of seven facial tasks. Five raters independently assessed facial weakness using both a qualitative evaluation and a semi-quantitative facial weakness score (FWS).

RESULTS

IBM patients had higher FWS than controls (7.89 ± 7.56 vs 1.06 ± 0.88, p < 0.001). Twenty IBM patients (63%) had a facial weakness with a FWS above the maximum value for controls. All facial tasks were significantly more impaired in IBM patients compared to controls (p < 0.001), task 2 evaluating orbiculari oculi muscle weakness being the most affected. IBM patients with facial weakness reported more swallowing troubles than IBM patients without facial weakness (p = 0.03). FSHD patients displayed higher FWS than IBM patients (12.16 ± 8.37 vs 7.89 ± 7.56, p = 0.01) with more pronounced facial asymmetry (p = 0.01). FWS inter-rater ICC was 0.775.

CONCLUSION

This study enabled us to estimate the frequency of facial impairment in IBM in more than half of patients, to detail its characteristics and to compare them with those of FSHD patients. The standardized, semi-quantitative FWS is an interesting diagnostic help in IBM as it appeared more sensitive than qualitative evaluation to detect mild facial weakness.

The Impact of Fatty Infiltration on MRI Segmentation of Lower Limb Muscles in Neuromuscular Diseases: A Comparative Study of Deep Learning Approaches

BACKGROUND

Deep learning methods have been shown to be useful for segmentation of lower limb muscle MRIs of healthy subjects but, have not been sufficiently evaluated on neuromuscular disease (NDM) patients.

PURPOSE

Evaluate the influence of fat infiltration on convolutional neural network (CNN) segmentation of MRIs from NMD patients.

STUDY TYPE

Retrospective study.

SUBJECTS

Data were collected from a hospital database of 67 patients with NMDs and 14 controls (age: 53 ± 17 years, sex: 48 M, 33 F). Ten individual muscles were segmented from the thigh and six from the calf (20 slices, 200 cm section).

FIELD STRENGTH/SEQUENCE

A 1.5 T. Sequences: 2D T1 -weighted fast spin echo. Fat fraction (FF): three-point Dixon 3D GRE, magnetization transfer ratio (MTR): 3D MT-prepared GRE, T2: 2D multispin-echo sequence.

ASSESSMENT

U-Net 2D, U-Net 3D, TransUNet, and HRNet were trained to segment thigh and leg muscles (101/11 and 95/11 training/validation images, 10-fold cross-validation). Automatic and manual segmentations were compared based on geometric criteria (Dice coefficient [DSC], outlier rate, absence rate) and reliability of measured MRI quantities (FF, MTR, T2, volume).

STATISTICAL TESTS

Bland-Altman plots were chosen to describe agreement between manual vs. automatic estimated FF, MTR, T2 and volume. Comparisons were made between muscle populations with an FF greater than 20% (G20+) and lower than 20% (G20-).

RESULTS

The CNNs achieved equivalent results, yet only HRNet recognized every muscle in the database, with a DSC of 0.91 ± 0.08, and measurement biases reaching -0.32% ± 0.92% for FF, 0.19 ± 0.77 for MTR, -0.55 ± 1.95 msec for T2, and - 0.38 ± 3.67 cm3 for volume. The performances of HRNet, between G20- and G20+ decreased significantly.

DATA CONCLUSION

HRNet was the most appropriate network, as it did not omit any muscle. The accuracy obtained shows that CNNs could provide fully automated methods for studying NMDs. However, the accuracy of the methods may be degraded on the most infiltrated muscles (>20%).

EVIDENCE LEVEL

4.

TECHNICAL EFFICACY

Stage 1.

How to distinguish Guillain-Barré syndrome from nitrous oxide-induced neuropathy: A 2-year, multicentric, retrospective study

BACKGROUND

Recreational use of nitrous oxide (N2 O) has dramatically increased in recent years, resulting in numerous cases of acute sensorimotor tetraparesis secondary to nitrous oxide-induced neuropathy (N2 On). Challenging clinical features can mimic Guillain-Barré syndrome (GBS), the main differential diagnosis upon admission. The most sensitive biomarkers for distinguishing between these two conditions remain to be determined.

METHODS

Fifty-eight N2 On patients from three referral centers were retrospectively included over a 2-year period and compared to GBS patients hospitalized during the same timeframe (47 patients). Collected demographic, clinical, biological, and electrophysiological data were compared between the two groups.

RESULTS

The typical N2 On clinical pattern included distal sensorimotor deficit in lower limbs with absent reflexes, proprioceptive ataxia, and no cranial involvement (56.7% of our cohort). Misleading GBS-like presentations were found in 14 N2 On patients (24.1%), and 13 patients (22.4%) did not report N2 O use during initial interview. Only half the N2 On patients presented with reduced vitamin B12 serum levels upon admission. A slightly increased cut-off (<200 pmol/L) demonstrated 85.1% sensitivity and 84.5% specificity in distinguishing N2 On from GBS. Only 6.9% of N2 On patients met the criteria for primary demyelination (p < 0.01), with only one presenting conduction blocks. A diagnostic algorithm combining these two biomarkers successfully classified all GBS-like N2 On patients.

CONCLUSIONS

Vitamin B12 serum level < 200 pmol/L cut-off and conduction blocks in initial electrophysiological study are the two most sensitive biomarkers for rapidly distinguishing N2 On from GBS patients. These two parameters are particularly useful in clinically atypical N2 On with GBS-like presentation.

Kidney involvement in hereditary transthyretin amyloidosis: a cohort study of 103 patients

Background

Hereditary transthyretin amyloidosis (ATTRv) is a disabling and life-threatening disease that primarily affects the nervous system and heart. Its kidney involvement has not been systematically studied, particularly in non-V30M mutations, and is not well known to nephrologists.

Methods

We conducted a retrospective study describing the kidney phenotype of all prevalent patients with ATTR mutations, with neurological or cardiac involvement or presymptomatic carriers, followed up in two university hospitals from the South of France between June 2011 and June 2021.

Results

A total of 103 patients were included, among whom 79 were symptomatic and 24 were presymptomatic carriers. Patients carried 21 different ATTR mutations and 54% carried the V30M mutation. After a mean follow-up of 7.9 ± 25.7 years, 30.4% of the symptomatic patients had developed chronic kidney disease (CKD) and 20.3% had a urinary protein:creatinine ratio ≥0.5 g/g. None of the presymptomatic carriers had CKD or proteinuria. In a multivariate analysis, late onset of symptoms (after 60 years), the V122I mutation and proteinuria were significantly associated with CKD. The median CKD-free survival in symptomatic patients was estimated at 81.0 years (interquartile range 77.1–84.9). It did not differ between V30M and non-V30M patients, but was lower in patients with the V122I mutation. The average age of the onset of CKD was 69.3 ± 13.0 years. In one 38-year-old V30M female who presented a kidney-predominant phenotype, treatment with patisiran resulted in remission of the nephrotic syndrome.

Conclusion

CKD affects almost one-third of patients with symptomatic ATTRv. The role of ATTRv per se in the development of CKD in this population remains to be determined, but some patients may benefit from specific therapies.

MO045: Kidney involvement in hereditary transthyretin amyloidosis: a cohort study of 103 patients

BACKGROUND AND AIMS

Hereditary transthyretin amyloidosis (ATTR) is a disabling and life-threatening disease that primarily affects the nervous system and heart. Its kidney involvement has been poorly studied and is not well known to nephrologists.

METHOD

We conducted a retrospective study describing kidney phenotype of all prevalent patients with ATTR mutations, with symptomatic amyloidosis or asymptomatic carriers, followed-up in two university hospitals from the South of France, between June 2011 and June 2021.

RESULTS

103 patients were included, among whom 79 were symptomatic and 24 asymptomatic carriers, and 54% carried a V30M mutation. After a mean follow-up of 7.9 ± 25.7 years, 30.4% of the symptomatic patients had developed chronic kidney disease (CKD) and 20.7% had a urinary protein/creatinine ratio ≥0.5 g/g. None of the asymptomatic carriers had CKD or proteinuria. Median CKD-free survival in the global cohort was 81.0 years, and the average age of CKD onset was 69.3 ± 13.0 years. In a multivariate analysis, late onset of ATTR symptoms (after 60 years), the V122I mutation and proteinuria were significantly associated with CKD. In a 38-year-old V30M female, who presented a kidney-predominant phenotype, treatment with Patisiran resulted in remission of the nephrotic syndrome.

CONCLUSION

CKD affects almost one-third of patients with symptomatic ATTR amyloidosis. The role of ATTR amyloidosis per se in the development of CKD in this population remains to be determined, but some patients may benefit from specific therapies.

Shoulder palsy following SARS‐CoV2 infection: 2 cases of typical Parsonage‐Turner syndrome

Background and purpose

Coronavirus disease 2019 (COVID‐19) is now known to cause neurological complications in both the central and the peripheral nervous system. Two new cases of typical neuralgic amyotrophy or Parsonage–Turner (PT) syndrome following coronavirus 2 infection (SARS‐CoV‐2) are reported here with explicit electrophysiological and imaging pathological features, underlining the possible association between COVID‐19 and PT syndrome.

Case reports

Case 1 was a 45‐year‐old schoolteacher presenting with acute pain in the right shoulder a few days after SARS‐CoV‐2 infection, with shoulder abduction and elbow flexion weakness. Needle electromyography showed a decrease in motor unit recruitment in the biceps brachii, and plexus magnetic resonance imaging (MRI) revealed a hyperintense signal involving the right C6 root and the superior truncus of the brachial plexus. Case 2 was a 21‐year‐old man hospitalized for dyspnea secondary to SARS‐CoV‐2 infection. Ten days after symptom onset, he presented right shoulder pain with difficulty in raising his right arm, revealing an isolated deficit of the serratus major muscle with a right scapula winging. Electrophysiological evaluation exhibited an isolated involvement of the long thoracic nerve with a neurogenic recruitment pattern in the serratus major muscle. Plexus MRI displayed a thickening and hyperintense signal involving the right long thoracic nerve.

Discussion

Parsonage–Turner syndrome triggered by SARS‐CoV‐2 seems to present clinical, electrophysiological and MRI characteristics similar to classic para‐infectious PT syndrome, including the time frame between viral infection and neurological symptom onset.

Conclusion

SARS‐CoV‐2 might be a new infectious trigger of PT syndrome.

Motor unit number index as an individual biomarker: Reference limits of intra-individual variability over time in healthy subjects

OBJECTIVE

Motor unit number index (MUNIX) is proposed to monitor neuromuscular disorders. Our objective is to determine the intra-individual variability over time of the MUNIX.

METHODS

In 11 different hospital centres, MUNIX was assessed twice, at least 3 months apart (range 90-360 days), in tibialis anterior (TA), abductor pollicis brevis (APB), abductor digiti minimi (ADM) and deltoid muscles in 118 healthy subjects. MUNIX sum score 2, 3 and 4 were respectively the sum of the MUNIX of the TA and ADM, of the TA, APB and ADM and of the TA, APB, ADM and deltoid muscles.

RESULTS

The repeatability of the MUNIX was better for sum scores than for single muscle recordings. The variability of the MUNIX was independent of sex, age, interval between measurements and was lower for experienced than non-experienced operators. The 95th percentile of the coefficient of variability of the MUNIX sum score 2, 3 and 4 were respectively 22%, 18% and 15% for experienced operators.

CONCLUSIONS

The MUNIX technique must be performed by experienced operators on several muscles to reduce its variability and improve its reliability.

SIGNIFICANCE

A variation of the MUNIX sum score ≥20% can be interpreted as a significant change of muscle innervation.

Quantitative assessment of sciatic nerve changes in Charcot-Marie-Tooth type 1A patients using magnetic resonance neurography

BACKGROUND AND PURPOSE

Nerve tissue alterations have rarely been quantified in Charcot-Marie-Tooth type 1A (CMT1A) patients. The aim of the present study was to quantitatively assess the magnetic resonance imaging (MRI) anomalies of the sciatic and tibial nerves in CMT1A disease using quantitative neurography MRI. It was also intended to seek for correlations with clinical variables.

METHODS

Quantitative neurography MRI was used in order to assess differences in nerve volume, proton density and magnetization transfer ratio in the lower limbs of CMT1A patients and healthy controls. Disease severity was evaluated using the Charcot-Marie-Tooth Neuropathy Score version 2, Charcot-Marie-Tooth examination scores and Overall Neuropathy Limitations Scale scores. Electrophysiological measurements were performed in order to assess the compound motor action potential and the Motor Unit Number Index. Clinical impairment was evaluated using muscle strength measurements and Charcot-Marie-Tooth examination scores.

RESULTS

A total of 32 CMT1A patients were enrolled and compared to 13 healthy subjects. The 3D nerve volume, magnetization transfer ratio and proton density were significantly different in CMT1A patients for the whole sciatic and tibial nerve volume. The sciatic nerve volume was significantly correlated with the whole set of clinical scores whereas no correlation was found between the tibial nerve volume and the clinical scores.

CONCLUSION

Nerve injury could be quantified in vivo using quantitative neurography MRI and the corresponding biomarkers were correlated with clinical disability in CMT1A patients. The sensitivity of the selected metrics will have to be assessed through repeated measurements over time during longitudinal studies to evaluate structural nerve changes under treatment.

Quantitative sudomotor test helps differentiate transthyretin familial amyloid polyneuropathy from chronic inflammatory demyelinating polyneuropathy

OBJECTIVE

Transthyretin familial amyloid polyneuropathy (TTR-FAP) is an aggressive hereditary neuropathy characterized by sensory and autonomic dysfunction. There are numerous reports of TTR-FAP misdiagnosed and treated as chronic inflammatory demyelinating polyneuropathy (CIDP), leading to delayed diagnosis, risk of iatrogenic adverse events and increased socio-economic costs. Quantitative sudomotor function measured by electrochemical skin conductance (ESC) appears to be a sensitive test in TTR-FAP. We aimed to evaluate the performance of ESC in differentiating TTR-FAP from CIDP.

METHODS

Thirty-eight patients with genetically confirmed hereditary TTR amyloidosis and 26 with definite CIDP according to the EFNS/PNS guidelines and negative TTR-FAP genetic testing were involved in this study. We compared the ESC for feet and hands measured by Sudoscan for each patient.

RESULTS

ESC (µS) was significantly lower in TTR-FAP for both hands (72 vs 45, p < 0.0001) and feet (77 vs 35, p < 0.0001). Feet ESC < 64 µS had a 89% sensitivity and a 96% specificity to differentiate between CIDP and TTR-FAP.

CONCLUSION

Sudoscan is a fast, non-invasive and easy to perform test, able to distinguish CIDP and TTR-FAP patients with good sensitivity and specificity.

SIGNIFICANCE

Sudoscan can be helpful in distinguishing between CIDP and TTR-FAP.

Structural Connectivity Alterations in Amyotrophic Lateral Sclerosis: A Graph Theory Based Imaging Study

Background

Amyotrophic lateral sclerosis (ALS) is a relentlessly progressive neurodegenerative disorder. Diffusion magnetic resonance imagining (MRI) studies have consistently showed widespread alterations in both motor and non-motor brain regions. However, connectomics and graph theory based approaches have shown inconsistent results. Hub-centered lesion patterns and their impact on local and large-scale brain networks remain to be established. The objective of this work is to characterize topological properties of structural brain connectivity in ALS using an array of local, global and hub-based network metrics.

Materials and Methods

Magnetic resonance imagining data were acquired from 25 patients with ALS and 26 age-matched healthy controls. Structural network graphs were constructed from diffusion tensor MRI. Network-based statistics (NBS) and graph theory metrics were used to compare structural networks without a priori regions of interest.

Results

Patients with ALS exhibited global network alterations with decreased global efficiency (Eglob) (p = 0.03) and a trend of reduced whole brain mean degree (p = 0.05) compared to controls. Six nodes showed significantly decreased mean degree in ALS: left postcentral gyrus, left interparietal and transverse parietal sulcus, left calcarine sulcus, left occipital temporal medial and lingual sulcus, right precentral gyrus and right frontal inferior sulcus (p < 0.01). Hub distribution was comparable between the two groups. There was no selective hub vulnerability or topological reorganization centered on these regions as the hub disruption index (κ) was not significant for the relevant metrics (degree, local efficiency and betweenness centrality). Using NBS, we identified an impaired motor subnetwork of 11 nodes and 10 edges centered on the precentral and the paracentral nodes (p < 0.01). Significant clinical correlations were identified between degree in the frontal area and the disease progression rate of ALS patients (p < 0.01).

Conclusion

Our study provides evidence that alterations of structural connectivity in ALS are primarily driven by node degree and white matter tract degeneration within an extended network around the precentral and the paracentral areas without hub-centered reorganization.

Quantitative Brain Sodium MRI Depicts Corticospinal Impairment in Amyotrophic Lateral Sclerosis

Background Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that mainly affects the upper and lower motor neurons. Recent sodium (²³Na) MRI studies have shown that abnormal sodium concentration is related to neuronal suffering in neurodegenerative conditions. Purpose To use ²³Na MRI to investigate abnormal sodium concentrations and map their distribution in the brains of study participants with ALS as compared with healthy control subjects. Materials and Methods Twenty-seven participants with ALS (mean age, 54 years ± 10 [standard deviation], eight women) and 30 healthy control subjects (mean age, 50 years ± 10; 16 women) were prospectively recruited between September 2015 and October 2017 and were examined by using conventional proton MRI and sodium MRI at 3 T. Voxel-based statistical mapping was used to compare quantitative whole-brain total sodium concentration (TSC) maps in participants with ALS with those in control subjects and to localize regions of abnormal elevated TSC. Potential overlap of abnormal elevated TSC with regions of atrophy as detected with ¹H MRI also was investigated. Results Voxel-based statistical mapping analyses revealed higher sodium concentration in motor regions (bilateral precentral gyri, corticospinal tracts, and the corpus callosum) of participants with ALS (two-sample t test, P < .005; age and sex as covariates). In these regions, mean TSC was higher in participants with ALS (mean, 45.6 mmol/L wet tissue ± 3.2) than in control subjects (mean, 41.8 mmol/L wet tissue ± 2.7; P < .001; Cohen d = 1.28). Brain regions showing higher TSC represented a volume of 15.4 cm³ that did not overlap with gray matter atrophy occupying a volume of 16.9 cm³. Elevated TSC correlated moderately with corticospinal conduction failure assessed with transcranial magnetic stimulation in the right upper limb (Spearman ρ = -0.57; 95% confidence interval: -0.78, -0.16; P = .005; n = 23). Conclusion Quantitative ²³Na MRI is sensitive to alterations of brain sodium homeostasis within disease-relevant regions in patients with amyotrophic lateral sclerosis (ALS). This supports further investigation of abnormal sodium concentration as a potential marker of neurodegenerative processes in patients with ALS that could be used as a secondary endpoint in clinical trials. © RSNA, 2019 Online supplemental material is available for this article.