Novel endoscopic posterior fossa cyst fenestration via an occipital meningocele defect in neonatal Dandy-Walker malformation: illustrative case

BACKGROUND: Dandy-Walker malformation (DWM) is characterized by cerebellar vermis hypoplasia, absence of the lateral apertures (of Luschka) and the median aperture (of Magendie), cystic dilation of the fourth ventricle, and posterior fossa enlargement. Occipital meningoceles (OMCs) involve an occipital skull defect with herniation of the meninges and CSF. Fewer than 40 cases of concurrent OMC and DWM (DWM-OMC) have been reported in the literature, with none managed with transmeningocele endoscopic fenestration. OBSERVATIONS: A preterm female neonate, delivered via cesarean section, presented with an OMC. MRI revealed DWM with a concurrent OMC and hydrocephalus. Given that the OMC was not covered by skin and the presence of hydrocephalus, endoscopic cyst fenestration of the DWM-associated dilated fourth ventricle through the OMC defect into the posterior spinal cord CSF space was performed. Shunt placement was avoided given concern for infection from exposed dura. LESSONS: Following surgery, the infant demonstrated normal neurological and developmental function. Follow-up MRI demonstrated an interval decrease in the size of the posterior fossa cyst and hydrocephalus, without complications. Endoscopic fenestration is a feasible option that facilitates CSF diversion despite distorted posterior fossa anatomy. Longer follow-up is required to determine durability and if this can be applied to other similar patients. https://thejns.org/doi/10.3171/CASE26259.