Case Report: Endoscopic-assisted cistern ostomy with Ommaya reservoir insertion for trapped temporal horn: surgical technique and case illustration.

Background: Neuro-endoscopy offers solutions to several challenges encountered during intraventricular tumor surgery. In this case, technical nuances included performing a ventriculo-subarachnoid cisternostomy for cerebrospinal fluid (CSF) diversion, and the postoperative application of a tightly stitched dressing gauze secured with silk sutures for a few weeks to minimize the development of CSF collections (pseudomeningocele) beneath the skin. Such collections can exhibit high protein content due to slow absorption, complicating patient management. Case presentation: We report the case of a 25-year-old male who presented with bilateral visual loss leading to blindness, secondary to an intraventricular tumor with longstanding hydrocephalus. He initially underwent a biopsy at another healthcare facility and was diagnosed with papilloma. The patient was subsequently referred to our center for a re-attempt at gross total resection via a standard temporal craniotomy, followed by histopathological evaluation. The final pathology revealed a myxoid variant with angiomatous features, confirmed by an internationally recognized reference laboratory. Following tumor resection, a trapped temporal horn developed due to the intraventricular location of the lesion. This was managed using an endoscopic approach aimed at diverting the cyst to the basal cistern through fenestration under intraoperative image-guidance (S7 Navigation, AxiEM system). A 2.7 mm rigid endoscope (Karl Storz) was employed to establish communication between the trapped ventricle and the subarachnoid space via fenestration toward the basal cisterns. An Ommaya reservoir was subsequently placed to prevent reaccumulation. These steps are described in detail in the surgical technique section. Discussion: Endoscopic ventriculo-cisternostomy is a safe and effective procedure for the treatment of symptomatic temporal horn entrapment in carefully selected cases. However, it carries risks of morbidity and complications in inexperienced hands and requires further validation before being established as a standard approach for this condition.