Neuroendoscopic fenestration for intracranial unilocular cysts and isolated lateral ventricles: four pediatric cases

The purpose of treatment for unilocular intracranial cysts (UICs) is to release elevated intracranial pressure. Neuroendoscopic fenestration (NF) is one of the most effective and minimally invasive options for treating UICs, especially in young children; however, the optimal location and number of fenestrations, the necessity of using endoscopic third ventriculostomy (ETV) in combination with fenestration, and the course of treatment are not well known. We retrospectively reviewed the hospital records between 2012 and 2019. The patients were studied in terms of sex, age at surgery, preoperative symptoms, cyst localization and size, course of treatment, ventricular diameter, developmental assessment, anatomical location, and the number of fenestrations. There were four eligible patients in the relevant period: two boys and two girls. The median age at the time of surgery was 16 months. With regard to the location of the cysts, there were two cases of cavum velum interpositum (CVI), one case of quadrigeminal cistern, and one case of an isolated lateral ventricle. The most common preoperative finding was an enlarged head circumference. All the patients were treated with NF, including one case of reoperation after open head surgery. Postoperatively, we used the frontal and occipital horn ratio (FOHR) to evaluate the ventricular size. The average reduction in the FOHR was 0.003. In the most recent developmental assessment or examination during the follow-up period, two patients showed normal development, and two patients showed developmental delay. Based on our past experience and reports, we believe that it is recommended to perform two fenestrations for a single cyst. This is because it creates a flow of cerebrospinal fluid (CSF) within the cyst into normal CSF reflux. For lesions with obstruction of the aqueduct, such as cysts in the quadrigeminal cistern, ETV should be considered if it can be performed safely, in preparation for the worsening of hydrocephalus due to obstruction by enlargement of the cyst.