Can neurophysiology and nerve ultrasound differentiate acute-onset CIDP from GBS with treatment-related fluctuations?

Distinguishing acute-onset chronic inflammatory demyelinating polyneuropathy (A-CIDP) from Guillain- Barré syndrome (GBS) with treatment-related fluctuations (TRF) in the early phase of disease can be challenging. Although characteristic clinical features have been previously reported, there is limited data on neurophysiological features. We aim to identify the electrophysiological and ultrasonographic features that might help differentiate between these two conditions. Patients with GBS-TRF and A-CIDP were identified from an existing cohort of GBS patients presenting to University of Malaya Medical Centre, Kuala Lumpur, Malaysia from 2011 to 2020. The clinical, electrophysiological and nerve ultrasound data were recorded and analysed. Five GBS-TRF (mean age 42 ± 23 years) and five A-CIDP (mean age 66 ± 13 years) patients were included. The mean time to first neurological deterioration was longer in A-CIDP compared to GBS-TRF (11 ± 5 vs 5 ± 1 weeks, p=0.028). Based on two sets of nerve conduction studies (NCS), both GBS-TRF and A-CIDP patients fulfilled the electrodiagnostic criteria for demyelinating neuropathy. A-CIDP patients had more prolonged ulnar minimal F-wave latencies (40.8 ± 5.8 vs 28.6 ± 2.2 ms, p=0.020) and slower sural conduction velocities (26.3 ± 8.6 vs 41.4 ± 3.4 m/s, p=0.015) on NCS. Nerve ultrasound showed significantly larger cross- sectional area of ulnar nerve at the wrist (7 ± 2 vs 5 ± 1 mm2, p=0.037) and forearm (8 ± 1 vs 5 ± 1 mm2, p=0.025) in A-CIDP patients. The Ultrasound Pattern Sum Score-A was significantly higher in A-CIDP compared to GBS-TRF (10 ± 3 vs 5 ± 1, p=0.015). We found nerve electrophysiological and ultrasonographic features can be useful in differentiating between GBS-TRF and A-CIDP.