Abstract
Background: Multifocal motor neuropathy (MMN) is a rare, slowly progressive nerve disorder characterized by asymmetric limb weakness without sensory abnormalities. MMN is often misdiagnosed due to similarities in clinical symptoms with conditions including amyotrophic lateral sclerosis (ALS), making diagnosis and treatment challenging. Objectives: This study assessed patient characteristics, treatment patterns, and the economic burden of MMN in the United States. Methods: Using the Optum Research Database, this retrospective analysis included patients with ≥1 diagnostic or nondiagnostic medical claim with an MMN diagnosis code between 2016 and 2020 (date of first diagnosis-related claim =index date), and continuous enrollment for 12 months preindex and postindex. Patients with MMN within this group were identified using more specific criteria; ≥2 MMN nondiagnostic claims separated by ≥30 days, with no subsequent ALS diagnosis during follow-up. All patients who did not meet these criteria were included in the MMN-mimic cohort. Outcomes included treatment patterns, differential diagnoses, healthcare utilization, and costs. Results: Of 904 patients identified, 37% had MMN and 63% had an MMN-mimic condition. Patients with MMN were significantly younger than patients in the MMN-mimic cohort (mean, 64.9 vs 66.8 years; P = .047). At preindex, significantly more patients with MMN received MMN-related medications than patients in the MMN-mimic cohort (20.5% vs 9.0%, respectively; P < .001). Intravenous immunoglobulin (IVIG) was the most common MMN-related medication. At postindex, more patients with MMN used IVIG (28.0%) compared with preindex (16.4%). In the 12 months preindex and postindex, >70% of patients had ≥1 differential diagnosis. The MMN cohort had higher all-cause total costs than the MMN-mimic cohort (mean preindex, 58 974vs 48 132, respectively [P = .100]; mean postindex, 74 187vs 50 652 [P = .002]); they also had significantly higher MMN-related healthcare costs (mean preindex, 23 625vs 12 890 [P = .011]; mean postindex, 39 521vs 11 938 [P < .001]). Discussion: This study showed that most patients with initial MMN diagnoses had an alternative disorder after subsequent evaluation/follow-up, and patients with MMN incurred higher costs. Many patients with MMN did not receive IVIG, suggesting that undertreatment or misattribution of diagnosis codes are common. Conclusions: Further education is needed regarding accurate diagnosis of MMN to ensure patient access to guideline-recommended treatment.