本文报道47例流行性乙型脑炎患儿的血清钠离子测定。脑性低钠的发生率为72.3％,其中以～3岁组发生率最高,为86.6％。重型乙脑脑性低钠的发生率为87.8％,显著高于普通型乙脑(35％)。文中初步讨论了脑性低钠的病因及发生机制。作者认为,应重视乙脑患者的血清钠测定,以便早期发现并及时纠正脑性低钠。 This paper reports 47 cases of Japanese encephalitis in children with serum sodium. The incidence of cerebral hyponatremia was 72.3%, of which the highest incidence was 86.6% in ~ 3 years old group. The incidence of severe B-brain hyponatremia was 87.8%, significantly higher than that of normal B (35%). The paper initially discussed the etiology and pathogenesis of hyponatremia. The authors believe that, should pay attention to serum sodium in patients with Japanese encephalitis in order to early detection and prompt correction of cerebral hyponatremia.