Brachial plexus sonography could complement MRI in the diagnostic work-up of patients with suspected CIDP and MMN. Our results indicate that combined imaging studies may add value to the current diagnostic consensus criteria for chronic inflammatory neuropathies.

ObjectivesTo study disease mechanisms in multifocal motor neuropathy (MMN) with magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) of the median and ulnar nerves.MethodsWe enrolled ten MMN patients, ten patients with amyotrophic lateral sclerosis (ALS) and ten healthy controls (HCs). Patients underwent MRI (in a prone position) and nerve conduction studies. DTI and fat-suppressed T2-weighted scans of the forearms were performed on a 3.0T MRI scanner. Fibre tractography of the median and ulnar nerves was performed to extract diffusion parameters: fractional anisotropy (FA), mean (MD), axial (AD) and radial (RD) diffusivity. Cross-sectional areas (CSA) were measured on T2-weighted scans.ResultsForty-five out of 60 arms were included in the analysis. AD was significantly lower in MMN patients (2.20 ± 0.12 × 10-3 mm2/s) compared to ALS patients (2.31 ± 0.17 × 10-3 mm2/s; p < 0.05) and HCs (2.31± 0.17 × 10-3 mm2/s; p < 0.05). Segmental analysis showed significant restriction of AD, RD and MD (p < 0.005) in the proximal third of the nerves. CSA was significantly larger in MMN patients compared to ALS patients and HCs (p < 0.01).ConclusionsThickening of nerves is compatible with changes in the myelin sheath structure, whereas lowered AD values suggest axonal dysfunction. These findings suggest that myelin and axons are diffusely involved in MMN pathogenesis.Key Points• Diffusion magnetic resonance imaging provides quantitative information about multifocal motor neuropathy (MMN). • Diffusion tensor imaging allows non-invasive evaluation of the forearm nerves in MMN. • Nerve thickening and lowered diffusion parameters suggests myelin and axonal changes. • This study can help to provide insight into pathological mechanisms of MMN. Electronic supplementary materialThe online version of this article (doi:10.1007/s00330-016-4575-0) contains supplementary material, which is available to authorized users.

ObjectiveThe main objective of this study was to evaluate the correlation between the distribution of brachial plexus magnetic resonance imaging (MRI) abnormalities and clinical weakness, and to evaluate the value of brachial plexus MRI in predicting disease course and response to treatment in multifocal motor neuropathy (MMN), Lewis‐Sumner syndrome (LSS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).MethodsSixty‐seven patients with an inflammatory neuropathy diagnosed at our tertiary referral center for neuromuscular diseases had undergone bilateral T2‐weighted short tau inversion recovery (STIR) MRI of the brachial plexus. We obtained clinical follow‐up data and scored all MRIs for abnormalities and the symmetry of their distribution.ResultsBrachial plexus MRI abnormalities were detected in 45% of the patients. An abnormal MRI did not predict disease course in terms of patterns of weakness, sensory disturbances or response to treatment. Within the spectrum of radiological abnormalities, asymmetrical clinical syndromes, MMN and LSS were significantly associated with asymmetrical radiological abnormalities, whereas symmetrical abnormalities predominated in CIDP (p < .001, phi 0.791).ConclusionT2 STIR brachial plexus MRI abnormalities correspond with the distribution of neurological deficits in inflammatory neuropathies, but do not correlate with specific clinical characteristics, response to treatment or disease course.

Objective:To assess the clinical course of multifocal motor neuropathy (MMN) in a large cohort of patients and to identify predictive factors of a progressive disease course.Methods:Between May 2015 and February 2016, we collected clinical data from 100 patients with MMN of whom 60 had participated in a nationwide cross-sectional cohort study in 2007. We documented clinical characteristics using standardized questionnaires and performed a standardized neurological examination. We used multiple linear regression analysis to identify factors that correlated with worse outcome.Results:We found that age of diagnosis (45.2 vs. 48.6 years, p<0.02) significantly increased between 2007 and 2015-2016, whereas diagnostic delay decreased with 15 months. Seven out of ten outcome measures deteriorated over time (all p<0.01). Patients who had a lower MRC sum score and absence of one or more reflexes at the baseline visit showed a greater functional loss at follow up (p=0.007 and p=0.016).Conclusions:Our study shows that MMN is a progressive disease. Although 87% of patients received maintenance treatment, muscle strength, reflexes, vibration sense, and the Self-Evaluation Scale significantly deteriorated over time. Lower MRC sum score and absence of reflexes predicted a more progressive disease course.Classification of evidence:This study provides Class II evidence that lower MRC sum score and the absence of reflexes predict a more progressive disease course in patients with MMN.