Contribution of plexus MRI in the diagnosis of atypical chronic inflammatory demyelinating polyneuropathies.

Nerve enlargement has early been recognized in CIDP and plexus MRI hypertrophy has been reported in typical CIDP cases. Our aim is to determine plexus MRI value in the diagnosis of CIDP with an initial atypical presentation, which, up to now, has not been demonstrated. Retrospective study of 33 consecutive patients suspected of CIDP. Plexus MRI was performed on the most affected territory (brachial or lumbar). Were assessed: plexus trophicity, T2-STIR signal intensity and gadolinium enhancement. Final CIDP diagnosis was made after comprehensive workup. A histo-radiological correlation was performed. Final CIDP diagnosis was made in 25 (76%) including 21 with initial atypical clinical presentation. Eleven CIDP patients (52%) with initial atypical clinical presentation had abnormal plexus MRI including 9 suggestive of CIDP (43%) and none of the patients with an alternative diagnosis. Hypertrophy of the proximal plexus and/or extraforaminal roots was found in 8 cases and Gadolinium enhancement in 2 cases. Abnormalities were more frequent on brachial (86%) than lumbosacral MRIs (29%) and asymmetrical (72%) and most often associated with histological signs of demyelination. The nerve biopsy was suggestive of CIDP in 9/13 patients with normal MRI. Plexus MRI seems useful in the diagnostic strategy of patients with suspicion of CIDP with atypical presentation. Nerve biopsy remains important when other investigations are inconclusive.