Marieke van Rosmalen

Chapter 7 122 Correlation with clinical data We found a moderate inverse correlation between the difference in FA between baseline and one- year follow-up ( Δ FA) and disease duration in patients with CIDP ( r = -0.50, p = 0.02; Figure 7.3 ). Correlations between the other quantitative parameters and continuous clinical variables (age, disease duration or time since last treatment) were poor and/or not significant. Sex, maintenance treatment and treatment response did not correlate with quantitative MRI parameters in patients with CIDP ( Table 7.4 ). We did not find any significant correlations between the quantitative MRI parameters and the continuous clinical variables in patients with MMN ( Table 7.4 ). Sex did not influence the differences in quantitative parameters over time. DISCUSSION This study shows that MD, AD, RD and fat fraction change over time in patients with CIDP, but not with MMN. We did not establish relevant correlations between the changes in quantitative MRI parameters and clinical data. Quantitative MRI techniques evaluated in this study, i.e. DTI, T2 mapping and fat fraction analysis, are therefore unsuited as biomarkers to predict prognosis or to monitor treatment response. DTI is a promising imaging technique for central and possibly peripheral neurological disorders. Previous longitudinal studies in patients with primary brain tumors and neurodegenerative disorders suggested a potential of quantitative MRI parameters as biomarkers 13–18 . Experimental models of sciatic nerve injury in rats (n = 62) suggested that differences in FA correlated with nerve regeneration 29 . Particularly relevant for our study is one cross-sectional DTI study in patients with CIDP (n = 14) that showed a correlation between FA in the sciatic and tibial nerves and severity of the neuropathy evaluated with the Neuropathy Impairment Score (NIS) 30 . The NIS is a composite score of weakness of the muscles innervated by the cranial nerves and proximal and distal muscles of the arms and legs, presence or absence of tendon reflexes and sensory function 31 . We did not use NIS in our patients, since it is probably less informative for disease status in MMN. However, we did not find an association with quantitative MRI of the brachial plexus and weakness (MRC sum scores) of the arms and legs or any other clinical data. We previously found differences in quantitative MRI parameters between CIDP and MMN 25 . This suggests important differences in (the dynamics of) microstructural integrity of nervous tissue between these disorders. The quantitative MRI parameters changed longitudinally in CIDP, but not in MMN. It is not likely that these changes in CIDP can be attributed to treatment. First, all quantitative MRI parameters did shift towards values found in healthy controls, except for AD. Second, we did not find a correlation between quantitative MRI data and treatment response. The differences in longitudinal data between patients with CIDP and MMN are therefore more likely to