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.