Electrophysiological Testing in Chronic Inflammatory Demyelinating Polyneuropathy Patients Treated with Subcutaneous Immunoglobulin: The Polyneuropathy And Treatment with Hizentra (PATH) Study

Objective: To assess electrophysiology parameters that can reflect patients' clinical status and show changes in nerve function with treatment, in a study of subcutaneous immunoglobulin in chronic inflammatory demyelinating polyneuropathy.

Methods: Nerve conduction studies (latency, conduction velocity, conduction block and compound muscle action potential [CMAP] on upper limb median, ulnar, and lower limb peroneal motor nerves) were conducted in the placebo-controlled PATH (Polyneuropathy And Treatment with Hizentra) study of two doses of maintenance subcutaneous immunoglobulin (SCIG) IgPro20 in CIDP.

Results: Averaged proximal latency substantially increased with placebo (+1.1 ms) indicating electrophysiologic deterioration but remained stable with IgPro20 (0.2 g/kg bodyweight [bw]: +0.1 ms; 0.4 g/kg bw: -0.1 ms). Distal latencies were also more prolonged with placebo versus IgPro20. Averaged motor nerve conduction velocity substantially decreased with placebo (-1.6 m/s) versus increasing in both IgPro20 groups (+0.2 m/s and +1.0 m/s, respectively). Conduction block and CMAP amplitudes did not change substantially.

Conclusion: These findings support the effectiveness of maintenance IgPro20, as nerve function changed in the direction of increasing nerve dysfunction with placebo but remained stable with ongoing IgPro20 therapy.

Significance: Electrophysiology testing can support assessment of clinical status in CIDP to determine treatment efficacy.