Marieke van Rosmalen

General introduction and thesis outline 17 1 plexus is in the current diagnostic guidelines the last supportive criterium and may show thickening of the cervical nerve roots ( Figure 1.4A ) or T2 hyperintensity ( Figure 1.4B ) in patients with CIDP or MMN. 14,15 Enhancement of the nerve roots could be seen in patients with CIDP after injection with gadolinium but is less common and the diagnostic value is low. 16 Abnormalities on brachial plexus MRI are more frequently present in patients with CIDP (74% of patients) than in patients with MMN (50% of patients). 16 Asymmetrical thickening of the nerve roots seems to be more common in patients with MMN compared to patients with CIDP. 17 Figure 1.4 Pathology of the brachial plexus in chronic inflammatory neuropathies In the left panel (A) an example of thickening of the cervical nerve roots is shown (for example compared to figure 1.2C) using T2-weighted imaging with fat suppression. In the right panel (B) an example of T2 hyperintensity (yellow arrow) is shown using T2-weighted imaging. A major drawback of current clinical practice is that brachial plexus MRI is qualitatively assessed by (neuro)radiologists. Obviously enlarged cervical nerve roots are easily seen but less evident thickening may result in an uncertain and subjective assessment as clear cut-off values for nerve size are lacking. Furthermore, variability and reliability of these qualitative assessments are unknown which hampers the diagnostic value of brachial plexus MRI even more. Asystematic assessment with quantitative cut-off values for cervical nerve root size, and a comparison of interrater reliabilities between qualitative and quantitative assessments, is needed if we want to improve the diagnostic value of brachial plexus MRI for the diagnosis of CIDP and MMN.