Objective: To clarify the clinical and long-term characteristics of multifocal motor neuropathy (MMN).
Methods: We retrospectively evaluated data from 8 consecutive MMN patients in Yamaguchi University Hospital from 2005 to 2020. Clinical information including dominant hand, occupations, hobbies, nerve conduction data, protein level in cerebrospinal fluid (CSF), responsiveness to intravenous immunoglobulin (IVIg) therapy as initial therapy as well as maintenance therapy were collected.
Results: Unilateral upper limb was initially affected in all patients and a dominant upper extremity was affected in six of them. Seven patients had occupations or hobbies which were associated with overuse of their dominant upper extremity. CSF protein level was normal or slightly elevated. Nerve conduction studies showed conduction blocks in 4 cases. Effectiveness of IVIg treatment as initial therapy was observed in all patients. Maintenance therapy was not needed in 2 patients because of mild symptoms with stable clinical course. Long-term maintenance therapy with immunoglobulin was effective in 5 patients during the follow-up period.
Conclusion: Dominant upper extremity was frequently affected and most patients had job or habit associated with its overuse, suggesting that physical overload induces inflammation or demyelination in MMN. IVIg was commonly effective as both introduction and long-term maintenance therapies. Complete remission was achieved after several IVIg treatments in some patients.
Keywords: IVIg; clinical profiles; long-term treatment; multifocal motor neuropathy.