Furthermore, in this study, it was found that subdural and interhemispheric hygromas formed earlier than that of PTH, which was in accordance with multiple previous reports.17,20 In PTH group, six patients (27.3%) had concurrent formation of subdural hygroma and interhemispheric hygroma; while 83.3% of the patients formed subdural hygroma firstly, then interhemispheric hygroma, and finally developed into hydrocephalus. Here, PTH is linked to cystic hygroma.