The Electrophysiology of Disease Remission in Chronic Inflammatory Demyelinating Polyneuropathy

Background: Whether serial electrophysiology may be useful in chronic inflammatory demyelinating polyneuropathy (CIDP), in remission off treatment, is unknown. Methods: We retrospectively studied electrophysiological findings during active disease and post-remission, in subjects with CIDP, at 2 UK neuropathy centres. Results: We included 24 consecutive subjects. Eighteen (75%) had typical CIDP, 3 (12.5%) motor CIDP and 3 (12.5%) distal CIDP. Mean age was 61.3 years (SD: 15.8). Mean interval between electrophysiological study during active disease and post-remission was 63.25 months (SD: 52.0). Mean distal motor latency improved for median (p < 0.001), ulnar (p < 0.001), fibular (p = 0.01) and tibial (p = 0.002) nerves. Mean motor conduction velocity improved for median (p < 0.001), ulnar (p < 0.001) and fibular (p = 0.012) nerves. Mean minimum F-wave latency improved for median (p = 0.003), ulnar (p = 0.002), and tibial (p = 0.027) nerves. The proportion of nerves showing conduction block was greater during active disease than post-remission (26/66 vs. 10/67; p = 0.002). Criteria for demyelination were initially fulfilled by all subjects, but not post-remission (24/24 vs. 14/24; p = 0.006). Electrophysiological quasi-normalisation correlated with shorter pre-treatment disease duration (p = 0.002). Amplitude of functional improvement correlated with fibular nerve motor amplitude at first study (p = 0.024). Conclusions: Electrophysiological quasi-normalisation may occur in a third of subjects with typical CIDP in clinical remission off treatment and may be more likely with prompt diagnosis/treatment. Amelioration may be observed in all tested nerves. Initial fibular nerve motor amplitude may predict clinical improvement amplitude. The value of electrophysiology for prognostication/disease monitoring/management may merit further study in CIDP. Further research is warranted for subjects with variant and possible CIDP.