患者女,32岁。因发作性头晕2年就诊。体检:神志清楚,语言流利,智力正常,头颅无畸形,双瞳等大等圆,光反射灵敏,左视时有不恒定眼震。肌力肌张力正常。Romberg征阴性,病理反射未引出。MRI示四脑室向后扩大,呈三角形扩张,并与枕大池连通,整个后颅窝大片脑脊液信号,左侧小脑半球缩 Female patient, 32 years old. Due to episodes of dizziness 2 years treatment. Physical examination: Consciousness, fluent language, normal intelligence, skull without deformity, double pupil and other large round, sensitive to light reflex, left when there is not constant nystagmus. Muscle tone normal. Romberg sign negative, pathological reflex did not lead. MRI showed ventricular enlargement of the rear four, triangular expansion, and connected with the pillow pool, the entire posterior fossa cerebrospinal fluid signal, the left cerebellar hemispheres shrink