Chiari II malformation: computed tomographic evaluation.
In this study cranial computed tomographic (CT) features of 28 cases with Chiari II malformation are presented. 26 of these cases had hydrocephalus (92.9%) and the fourth ventricle was either absent or small in 25 (89.3%) of the cases. Caudal displacement of the fourth ventricle was noted in 15 (53.6%) of the cases, and craniolacunia was present in 18 (64.3%) of the cases with seven of them being more than one-year-old (up to 18-years-old). We found CT to be a safe, non-invasive and effective method of elucidating the types of abnormalities associated with this disorder. Preoperative computed tomographic evaluation of patients with Chiari II malformation helps to differentiate it from other types of hydrocephalus, thus yielding a change in the operative approach.