Marieke van Rosmalen

Prognostic value of quantitative MRI in chronic inflammatory neuropathies 113 7 INTRODUCTION Chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN) are both rare chronic inflammatory neuropathies that respond to treatment with immunomodulation. Treatment may improve motor (MMN and CIDP) and sensory deficits (CIDP only). 1,2 However, treatment response varies between patients and some patients may worsen over time despite treatment. 3 Biomarkers that predict course of disease and correlate with treatment response are currently lacking which complicates management of these neuropathies. Early electrophysiological studies showed that axonal damage correlates with weakness and a functional impairment, but not with response to treatment or unfavorable disease course. 4–6 Nerve ultrasound studies in patients with CIDP initially suggested that changes of nerve size and echotexture could correlate with clinical disease activity, 7 but this has not been corroborated in other studies. 8 Quantitative magnetic resonance imaging (MRI) techniques, including diffusion tensor imaging (DTI), T2 mapping and fat fraction analysis, can provide quantitative information on microstructural integrity of (nervous) tissue. 9–12 Longitudinal DTI studies of the brain have shown differences in diffusion parameters over time in patients with primary brain tumors, Alzheimer’s disease and Parkinson’s disease. 13–19 Cross-sectional DTI, T2 mapping and fat fraction analysis studies of the brachial plexus and peripheral nerves in patients with CIDP and MMN showed differences between patients and controls, but follow-up studies have not been published. 20–25 Therefore, we performed a longitudinal study in newly diagnosed patients with CIDP and MMN who did not use treatment at baseline. METHODS Study design We performed a longitudinal study in a cohort of patients with CIDP and MMN. All patients started immunomodulatory treatment after enrollment (i.e. were treatment naive at baseline). We obtained quantitative MRI parameters of the brachial plexus at baseline and after approximately one-year. We compared quantitative MRI parameters between timepoints and studied correlations with clinical data. Patients and clinical data All patients participated in a previous DTI study and had a diagnosis of CIDP or MMN according to consensus criteria (definite, probable, possible). 26,27 They were treatment naive at the time of the first research MRI 25 . We excluded patients who did not start treatment between the first (t 0 ) and the second MRI (t 1 ) and patients who met one of the routine contraindications to MRI ( Figure 7.1 ).