Endoscopic third ventriculostomy for patients with Blake’s pouch cyst with adult-onset hydrocephalus: Importance of improved cerebrospinal fluid flow in the prepontine cistern – A case report

Background: Blake’s pouch cyst (BPC) is a posterior fossa cystic malformation that commonly occurs in children with rare adult onset. Herein, we report a case of adult onsets BPC. Case Description: A 61-year-old man presented with gait and cognitive disturbance. Preoperative magnetic resonance imaging (MRI) revealed scarring in the prepontine cistern, and cine phase-contrast MRI revealed no pulsation. Endoscopic third ventriculostomy (ETV) was performed with opening the scarring in the prepontine cistern. Postoperative cine phase-contrast MRI revealed that cerebrospinal fluid (CSF) flow in the prepontine cistern improved, resolving the patient’s symptoms. Conclusion: We report a case of adult-onset BPC. The mechanism by which is becomes symptomatic is still unclear. We opened the scar in prepontine cistern in addition to ETV with good results. In this report, we discussed the importance of the improvement in CSF dynamics in the prepontine cistern.