The purpose of the present study is to determine accurate incidence rates of stroke and acute myocardial infarction among the residents in Okinawa, where the census population was 1,222,398 in 1990 and mortality due to cerebrovascular and heart diseases is lowest in Japan. A co-operative study group including almost all hospitals and clinics in Okinawa was established for the survey. Between April 1, 1988 and March 31, 1991, 4,756 cases of stroke and 1,059cases of acute myocardial infarction were identified. The average age-adjusted annual incidence per 100,000 population was 137 for stroke and 31 for acute myocardial infarction. In the population aged 40 years and older, the respective values were 315 and 72, indicating the stroke incidence to be 4.4 times higher than that of acute myocardial infarction. The incidence ratio for men to women was 1.7: 1 for stroke and 2.9: 1 for acute myocardial infarction. Among stroke cases, 51.3% were diagnosed as cerebral infarction, 35.7% as cerebral hemorrhage, 7.7% as subarachnoid hemorrhage and 5.3% as others. Computed tomography of the head was performed in 98.4% of all stroke cases. The case ascertainment, evaluated by comparing the registered cases and death certificates in a certain city, was almost complete. The incidence of acute myocardial infarction is still much lower than that of stroke in Japan. (Hypertens Res 1992;15: 111-119)

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Acase of respiratory myoclonus in a 45 year-old male was studied by electromyography. He complained of anorexia, involuntary swinging movement of the thorax and trunk, and epigastric pulsation. Electromyographic studies showedsynchronous rhythmic grouped discharges at the rate of 2 to 3 Hz from the bilateral 8th to 10th intercostal muscles, the right iliocostalis lumborum muscle, and the left hemidiaphragm* only during the expiratory phase. They disappeared on inspiration and forced expiration. Anesthetic block of the left phrenic nerve abolished both the voluntary and myoclonic movementsof the left hemidiaphragm. Abnormal excitation of the central nervous system and possible irritation of the afferent pathways were postulated.

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