Ultrasound of inherited vs. acquired demyelinating polyneuropathies

We compared features of nerve enlargement in inherited and acquired demyelinating neuropathies using ultrasound. We measured median and ulnar nerve cross-sectional areas in proximal and distal regions in 128 children and adults with inherited [Charcot-Marie-Tooth-1 (CMT-1) (n = 35)] and acquired [chronic inflammatory demyelinating polyneuropathy (CIDP) (n = 55), Guillaine-Barre syndrome (GBS) (n = 21) and multifocal motor neuropathy (MMN) (n = 17)] demyelinating neuropathies. We classified nerve enlargement by degree and number of regions affected. We defined patterns of nerve enlargement as: none, no enlargement; mild, nerves enlarged but never more than twice normal; regional, nerves normal in at least one region and enlarged more than twice normal in at least one region; diffuse, nerves enlarged at all four regions with at least one region more than twice normal size. Nerve enlargement was commonly diffuse (89 %) and generally more than twice normal size in CMT-1, but not (p < 0.001) in acquired disorders which mostly had either no, mild or regional nerve enlargement [CIDP (64 %), GBS (95 %), and MMN (100 %)]. In CIDP, subjects treated within 3 months of disease onset had less nerve enlargement than those treated later. Ultrasound identified patterns of diffuse nerve enlargement can be used to screen patients suspected of having CMT-1. Normal, mildly, or regionally enlarged nerves in demyelinating polyneuropathy suggests an acquired etiology. Early treatment in CIDP may impede nerve enlargement.