Intravenous immunoglobulin frequency in multifocal motor neuropathy: a retrospective study of nerve conduction...

In resource-limited rural settings, patients with multifocal motor neuropathy (MMN) often present late due to limited access to neurophysiology services, by which time significant axonal damage may have occurred, rendering them less responsive to immunotherapy-yet this clinically subgroup is consistently underrepresented in randomized controlled trials. In this study, we aimed to examined the impact of intravenous immunoglobulin (IVIg) frequency on electrophysiological changes in such undertreated MMN patients.

A retrospective analysis was conducted across three rural medical centers. Patients receiving > 2 IVIg cycles annually were classified as group A, others as group B. Nerve conduction was assessed at baseline, after the first treatment course, and at the final follow-up.

Thirty-nine MMN patients initially identified, 11 patients with confirmed conduction block (CB) were included. 27 nerves exhibited definite CB, with 7 (25.9%) in the median nerve, 8 (29.6%) in the ulnar nerve, and 6 (18.5%) in both the tibial and peroneal nerves. The treatment intervals was 4.9 ± 1.8 (range, 2.6 to 8.0) months, The follow-up period was 17.2 ± 3.3 months (range, 12.0 to 21.0). 7 (63.6%) were in group A, while 4 patients (36.4%) were in group B. There was a clear improvement in mRS scores at the last follow-up compared to baseline (z = -2.795, p = 0.007). We compared the variations in distal compound muscle action potential (CMAP) amplitude at baseline and the last follow-up, after adjusting for baseline CMAP amplitude, it showed significantly greater improvements in distal CMAP amplitude in group A versus group B (F = 40.217, P < 0.001; B = 2.881, 95% CI 1.941 ~ 3.821, P < 0.001), with the model accounting for 71.5% of the variance (adjusted R²= 0.715). The number of CBs decreased from 17 to 14 in group A, with no change in group B (p > 0.05).

High frequency IVIg treatment may be associated with improved CMAP amplitude and mRS in undertreated MMN patients, suggesting potential benefits that require further validation.