481 Endoscopic third ventriculostomy versus ventriculoperitoneal shunting for treatment of hydrocephalus in patients with myelomeningocele

Objectives/Goals: Optimal hydrocephalus treatment with permanent cerebrospinal fluid (CSF) diversion in myelomeningocele (MMC) patients is not well understood, especially how treatment response varies with time of MMC repair. We evaluate two treatment methods in this population–endoscopic third ventriculostomy (ETV) and ventriculoperitoneal shunting (VPS). Methods/Study Population: We retrospectively identified patients from St. Louis Children’s Hospital who were diagnosed with MMC prenatally and underwent either prenatal or postnatal repair and subsequently underwent permanent treatment for hydrocephalus (VPS or ETV +/- choroid plexus cauterization) between 2018 and 2024. The primary outcome was failure (defined as need for revision) of procedure and time to failure. All revisions were shunt insertions/revisions. Differences in preoperative and 6-month postoperative head circumference (HC) and WHO standard HC z-score were examined. Differences in preoperative and 6-month follow-up fronto-occipital horn ratios (FOHR), a validated age-independent measure of CSF within the brain, on CT and MRI were additionally examined. Results/Anticipated Results: Eighty-three MMC patients were identified. 46 (55%) underwent CSF diversion: 37 (80.4%, 9 pre- and 28 postnatal) VPS and 9 (19.6%, 5 pre- and 4 postnatal) ETV +/- choroid plexus cauterization. Six (16%) VPS patients required revision vs. 3 (33%) ETV patients (∆17%; 95% CI -9 – 50). Mean time to failure was longer after VPS vs. ETV (516, SD 470 vs. 34, SD 7 days) [∆482; 95% CI 163 – 800]. The decrease between pre- and postoperative FOHR was greater after VPS vs. ETV (6 mo: -0.14, SD 0.10 vs. -0.03, SD 0.07) [∆0.11; 95% CI 0.04 – 0.18]. Differences in pre- and postoperative HC were similar (VPS 5.67, SD 2.91 vs. ETV 4.04, SD 1.66 cm) [∆1.63; 95% CI -0.71 – 3.98]. Greater, but not significant, z-score decreases were seen after VPS vs. ETV (-1.04, SD 2.22 vs. -0.13, SD 1.11) [∆-0.91; 95% CI -2.68 – 0.86]. Similar trends were observed in pre- and postnatal MMC repair groups. Discussion/Significance of Impact: Failure rates in MMC-associated hydrocephalus patients were greater in the ETV group, but no definitive conclusion can be made due to imprecision. Those treated with ETV have less time to failure and smaller FOHR decreases than those treated with VPS, indicating less CSF drainage. Due to the need for more subjects, future research should be multicenter.