ABSTRACT
The size of the cisterna magna is still detatable. Robertson13) stated that the cisterna magna varies greatly in capacity and described the large cisterna magna as a separate entity. He also found that in most cases the cisterna magna extended approximately 2.5cm above the foramen magnum and was usually 5mm deep with a variable width. Liliequist8) proposed a mean heigh of 28mm for the normal cisterna magna with a wide variation of 15 to 60mm, and a depth of 6mm at the foramen magnum with a variation of 2 to 10mm:however, he did not quote measurements for the width. Gonsette, et al.5) reported 28 cases of enlarged cisterna magna diagnosed by ventriculography and coined the phrase "mega grande citerne" or mega cisterna magna. All of these cases, however, had symptoms of posterior fossa disease. Our study of the syndrome of the mega cisterna magna without specific syndrome is presented nystagmus, transient syncope in the first & third cases were operated under suboccipital craniectomy and was confimed the large cisterna magna. This paper presents the clinical diagnosis with vertebral angiogrraphy, pneumoencephalography and computed tomography.