Coronal STIR cervical MRI of a patient with CIDP showing the way in which diameters and nerve-to-muscle CNRs of the cervical nerve roots were measured: TR/TE/TI, 6600/72/180 ms. Diameter was measured as the vertical length of the root at the outlet of the intervertebral foramen. SIs in the C5–C8 roots and SCM, as well as SD of the background noise, were measured using an operator-defined ROI. Nerve-to-muscle CNR=SInerve−SISCM/SDbackground noise. Notably, this patient showed obvious thickening of the cervical nerve roots. CIDP, chronic inflammatory demyelinating polyradiculoneuropathy; CNR, contrast-to-noise ratio; ROI, region of interest; SCM, sternocleidomastoid muscle; SI, mean signal intensity; STIR, short tau inversion recovery; TE, echo time; TI, inversion time; TR, repetition time.