Multifocal motor neuropathy: А literature review and case report

Abstract

Multifocal motor neuropathy (MMN) is a rare immune-­mediated disease of the peripheral nervous system manifesting as progressive asymmetric muscle weakness and motor conduction blocks. This article presents a clinical case of a patient with verified MMN in whom the use of rituximab was not accompanied by clinical improvement and was associated with further progression of paresis. Subsequent administration of intravenous immunoglobulin (IVIG) led to pronounced positive dynamics with an increase in muscle strength and a decrease in the severity of motor deficit. Introduction. MMN is a rare dysimmune neuropathy clinically characterized by asymmetric muscle weakness, atrophy, and fasciculations with absent or minimal sensory impairments. The most significant diagnostic signs include the detection of IgM antibodies to ganglioside GM1 and the registration of motor conduction blocks during electroneuromyographic examination. IVIG is considered the mainstay of pathogenetic therapy for MMN, while the efficacy of other immunomodulatory drugs, including rituximab, remains insufficiently defined. Materials and methods. We analyzed a clinical case of a female patient born in 1961 who was admitted with complaints of increasing weakness in the left hand, clumsiness during movements, and fasciculations in the muscles of the left upper limb. The diagnostic evaluation included a neurological examination, electroneuromyography, ultrasound examination of peripheral nerves and the brachial plexus, as well as magnetic resonance imaging. To clarify the nosological entity of the process, an analysis of the cerebrospinal fluid and a laboratory assessment of anti-­GM1 antibodies were performed. Results. The examination revealed motor conduction blocks outside typical compression sites, as well as an elevated titer of anti-­GM1 antibodies, which confirmed the diagnosis of MMN. The administration of rituximab, necessitated in part by organizational and economic limitations of therapy, did not lead to clinical stabilization. After transferring the patient to IVIG therapy, clear positive dynamics were noted in the form of reduced severity of paresis and increased muscle strength. Conclusion. The presented clinical observation emphasizes the importance of timely diagnosis of MMN and early initiation of pathogenetic therapy. In this case, the use of rituximab did not provide clinical stabilization, whereas IVIG demonstrated high therapeutic efficacy. Improving the availability of immunoglobulin therapy and physicians’ awareness of MMN is essential to prevent the progression of motor deficit and patient disability.