Lumbar fenestration to avoid shunting after posterior fossa tumor resection and failed ventriculostomy clamp trial.

OBJECTIVE: Posterior fossa tumors in children frequently present with hydrocephalus. Cerebrospinal fluid (CSF) diversion with an external ventriculostomy drain (EVD) is often used preoperatively or inserted at the time of surgery and continued into the postoperative setting. Despite tumor resections to restore fourth ventricular CSF passage, some patients fail EVD clamping and still require shunting for persistent hydrocephalus despite postoperative imaging showing patent CSF pathways. Increasing CSF gradient and transient CSF absorption during the postoperative period with a percutaneous, modified lumbar puncture technique-referred to herein as "lumbar fenestration"-may help avoid a permanent shunt in some of these patients. The aim of this study was to evaluate the safety and potential benefit of lumbar fenestration for avoiding a shunt in patients who fail a ventriculostomy clamp trial following resection of posterior fossa tumor.

METHODS: Procedurally, a 14-gauge Touhy needle percutaneously enters the L4-5 lumbar subarachnoid space. Once CSF is encountered, it is angled cranially and caudally to widen the needle durotomy. A retrospective review of pediatric patients was conducted at a single children's hospital from January 1, 2006, to January 1, 2022, for lumbar fenestration. All patients who underwent lumbar fenestration had clinical factors suggesting the need for ongoing CSF diversion during a clamp trial of their ventriculostomy. Inclusion criteria were 1) resection of a newly diagnosed posterior fossa tumor; 2) hydrocephalus on presentation; 3) ventriculostomy drain insertion at the time of or prior to surgery; and 4) lumbar fenestration following surgery.

RESULTS: In total, 44 patients met the inclusion criteria. The follow-up ranged from 1.8 to 191.1 months; the median follow-up was 84.2 months, the mean was 84.6 months, with a standard deviation of 60.2 months. There were 5 patients with < 1 year of follow-up. The most common pathology was medulloblastoma (n = 21), followed by pilocytic astrocytoma (n = 11), atypical teratoid/rhabdoid tumor (n = 5), ependymoma (n = 4), pineoblastoma (n = 2), and malignant glioneuronal tumor (n = 1). The age at time of surgery ranged from 3 months to 15 years. Of the 44 patients included, 33 avoided a shunt. Stable or increased ventricular size after lumbar fenestration was statistically correlated with subsequent shunt placement (p = 0.0019). There were no complications linked to lumbar fenestration.

CONCLUSIONS: In this retrospective cohort, there were minimal complications linked to lumbar fenestration and 75% of patients who had lumbar fenestration after failing a clamp trial avoided a shunt.