Marieke van Rosmalen

Our study comprises a relatively large number of patients with MMN and CIDP, although we acknowledge that the group sizes in studies on rare neuropathies are almost always a limitation. Our control group was homogeneous and did not include a spectrum of mimics as in previous studies. This was a deliberate choice since ultrasound studies showed that it is unlikely that nerve root sizes are enlarged in patients with axonal neuropathies. 10 We also acknowledge that both nerve imaging and NCS may fail to discriminate CIDP from certain rare mimics, such as hereditary demyelinating polyneuropathies, paraproteinemic polyneuropathies and amyloidosis. However, clinical phenotypes and laboratory findings in these rare mimics will often guide a clinician to the right diagnosis without the use of nerve imaging techniques. We show that quantitative assessment of MRI of the brachial plexus and cervical nerve roots is a reliable and useful tool for the diagnostic workup of patients who may have a chronic inflammatory neuropathy. A quantitative approach is feasible and does not have the limitation of high interrater variability of the currently used qualitative assessments.