Technical note: durable resolution of hydrocephalus after ultrasound-guided percutaneous fenestration of giant suprasellar arachnoid cyst in a neonate.

Arachnoid cysts are relatively common, but rarely require intervention. While most arachnoid cysts in typical middle or posterior cranial fossa locations are seldom symptomatic, suprasellar cysts may become symptomatic due to the potential for ventricular outflow obstruction and hydrocephalus. Typical standard of care for the treatment of these lesions is endoscopic fenestration with third ventriculostomy, or the placement of ventriculoperitoneal or cystoperitoneal shunts. The surgical and anaesthetic risks of traditional interventions may be higher in the early neonatal period, including leak of cerebrospinal fluid, infection, and premature failure of ventriculostomy or shunts. This note describes a novel bedside ultrasound-guided technique to percutaneously fenestrate large suprasellar arachnoid cysts under local anaesthesia. The technique involves insertion of a 25-g spinal needle until contact with the membrane of the arachnoid cyst medially, followed by a lateral sweeping to widely incise/fenestrate the lesion into the ventricular space under continuous ultrasound visualisation. This note describes an example case which demonstrates durable radiological and clinical improvement after 2 years of follow-up. This may represent a management option to temporise, or perhaps definitively manage suprasellar arachnoid cysts in the neonatal period.