Background:Shunt-dependent hydrocephalus (SDH) is a well-known sequela following aneurysmal hemorrhage, adversely affecting the outcome after securing ruptured aneurysm. Fenestration of lamina terminalis (FLT) creates an anterior ventriculostomy, facilitates cerebrospinal fluid circulation and clot clearance in the basal cistern. However, controversy exists over whether microsurgical FLT during aneurysm repair can decrease the incidence of SDH.Aims:The study is designed to determine the efficacy of lamina terminalis fenestration on the reduction of SDH after aneurysm clipping.Methods/Design:A total of 288 patients who meet the inclusion criteria will be randomized into single aneurysm clipping or aneurysm clipping plus FLT in the Department of Neurosurgery, West China Hospital. Follow-up was performed 1, 3, 6, and 12 months after aneurysm clipping. The primary outcome is the incidence of SDH and the secondary outcomes include cerebral vasospasm, functional outcome evaluated by the modified Rankin Scale and Extended Glasgow Outcome Scale, and mortality.Discussion:The FISH trial is a large randomized, parallel controlled clinical trial to define the therapeutic value of FLT, the results of which will help to guide the surgical procedure and resolve the long-puzzled debate in the neurosurgical community.Conclusions:This protocol will determine the efficacy of FLT in the setting of aneurysmal subarachnoid hemorrhage.Trial registration identifier:http://www.chictr.org.cn/edit.aspx?pid=15691&htm=4Chinese Clinical Trial Registry:ChiCTR-INR-16009249.