澁谷 和幹

Abstract Introduction/Aims Multifocal motor neuropathy (MMN) is a rare disease for which epidemiological and clinical data are limited. We conducted a nationwide survey to determine disease prevalence, incidence, clinical profile, and current treatment status in Japan. Methods A nationwide survey was conducted in 2021 using an established epidemiological method. Questionnaires were sent to all neurology and pediatric neurology departments in Japan. An initial questionnaire was administered to determine the number of patients with and incidence of MMN. A second questionnaire was administered to collect detailed clinical information. The European Federation of Neurological Societies/Peripheral Nerve Society 2010 guidelines were used as diagnostic criteria. Results The estimated number of patients with MMN was 507. The estimated prevalence was 0.40 per 100,000 individuals. Detailed clinical profiles were available for 120 patients. The male‐to‐female ratio was 2.3:1 and the median onset age was 42 years. The median disease duration at diagnosis was 25 months. Most patients presented with upper limb‐dominant muscle weakness. Motor nerve conduction blocks were found in 62% of patients and positive anti‐GM1 IgM antibody results in 54%. A total of 117 (98%) patients received immunoglobulin therapy, and 91% of them showed improvement. At the time of the last visit (median, 82 months from treatment initiation), 89 (74%) patients were receiving maintenance immunoglobulin therapy. A slight progression of neurological deficits was observed during follow‐up. Discussion Most patients with MMN in Japan received induction and maintenance immunoglobulin therapies, which appear to suppress long‐term disease progression.

Decreased cough strength in myasthenia gravis (MG) leads to aspiration and increases the risk of MG crisis. The aim of this study was to clarify the reliability and validity of cough peak flow (CPF) measurements in MG. A total of 26 patients with MG who underwent CPF measurements using the peak flow meter by themselves were included. MG symptoms were evaluated by pulmonary function tests and clinical MG assessment scales before and after immune-treatments. The relationship between CPF and pulmonary function tests and MG comprehensive were assessed. The cut-off value of CPF for aspiration risk was determined and the area under the curve (AUC) was calculated. The intraclass correlation coefficient was more than 0.95 for pre-and post-treatment. Positive correlations were found between CPF and almost all spirometric values as well as between the differences of pre-and post-treatment in CPF and quantitative myasthenia gravis score. The CPF for identifying the aspiration risk was used to calculate the CPF cut-off value of 205 L/min with a sensitivity of 0.77, specificity of 0.90, and AUC of 0.85. The CPF, a convenient measure by patients themselves, has a high reliability in patients with MG, and is a useful biomarker reflecting MG symptoms.