Nerve ultrasound can distinguish chronic inflammatory demyelinating polyneuropathy from demyelinating diabetic sensorimotor polyneuropathy.

Diabetic patients with poor glycaemic control can demonstrate demyelinating distal sensorimotor polyneuropathy (D-DSP) on electrophysiology. Distinguishing D-DSP from chronic inflammatory demyelinating polyneuropathy (CIDP) can be challenging. In this study, we investigated the role of nerve ultrasound in differentiating the two neuropathies. Nerve ultrasound findings of D-DSP patients (fulfilling the electrophysiological but not clinical criteria for CIDP) were compared with non-diabetic CIDP patients (fulfilling both criteria). We studied 108 and 95 nerves from 9 D-DSP and 10 CIDP patients respectively. CIDP patients had significantly larger cross-sectional areas of the median nerve at the mid-arm (17.0 ± 12.5 vs 8.7 ± 2.6; p = 0.005), ulnar nerve at the wrist (7.3 ± 3.1 vs 4.1 ± 1.0; p = 0.001), mid forearm (8.8 ± 5.3 vs 5.5 ± 1.5; p = 0.002) and mid-arm (14.5 ± 14.1 vs 7.5 ± 1.9; p = 0.013), and radial nerve at mid forearm (4.1 ± 2.4 vs 1.2 ± 0.4; p < 0.001). In comparison to D-DSP, CIDP patients had markedly larger nerves at the proximal and non-entrapment sites of the upper limbs, suggesting that nerve ultrasound is useful in differentiating the two neuropathies.