Presentation (CTI)

OBJECTIVES: Multifocal motor neuropathy (MMN) is a rare immune-mediated motor neuropathy characterized by asymmetric weakness in the limbs without sensory abnormalities which often leads to disability. With a prevalence of 1 in 100,000 in the US and symptom overlap with other neuropathies and motor neuron disease, MMN diagnosis is challenging. When the diagnosis is delayed, treatment is as well, which may lead to accumulation of irreversible neurologic impairment and disability. This study aimed to explore how MMN patients are diagnosed and identified in a real-world dataset.
METHODS: A retrospective cohort study was conducted using a US claims dataset (Komodo Health Jan 2017 - March 2024). Adult MMN patients were identified based on specified inclusion criteria and continuous enrollment one year pre-index date. Patients required ≥ 2 MMN ICD-10 diagnoses and ≥ 1 relevant test before the 2nd MMN diagnosis to be included for further analysis.
RESULTS: We identified 540 patients who met our inclusion criteria. First, misdiagnosis was common. In the last one-year of data, 210 patients had frequent diagnoses of another condition (e.g., CIDP and ALS) without presence of MMN. Second, many patients had years of medical history preceding diagnosis and treatment of MMN, which included a plethora of other neuropathy-related diagnoses. Third, there were many cases where a patient’s diagnosis couldn’t be discerned due to MMN being interspersed in near-equal frequency with CIDP or unspecified codes.
CONCLUSIONS: Misdiagnosis and diagnostic delays tend to be relatively common, with symptoms attributed to CIDP, ALS or unspecified neuropathies. Many patients face years of misdiagnosis before treatment, which could result in delayed access to needed treatment. Improved diagnostic strategies are urgently needed to reduce delays and optimize care for MMN patients.