Clinical presentation of hydrocephalus following pre- and postnatal myelomeningocele repair: a Hydrocephalus Clinical Research Network study

OBJECTIVE Despite improvements in rates of hydrocephalus with prenatal repair of myelomeningocele (MMC), a significant number of children still require CSF diversion. While previous studies have focused on uncovering predictors of future hydrocephalus, differences in timing and presentation of MMC-associated hydrocephalus following pre- and postnatal surgery are not well-characterized. This study aimed to determine how age, head size, and ventricle size differ at hydrocephalus presentation in patients treated with pre- and postnatal surgery for MMC. METHODS The Hydrocephalus Clinical Research Network Core Data Project was queried to identify patients with MMC who underwent pre- or postnatal repair and required permanent CSF diversion—by shunting or endoscopic third ventriculostomy, with or without choroid plexus cauterization—between April 2008 and June 2024. The primary variable of interest was chronological age at the primary CSF diversion procedure. Secondary variables of interest included absolute head circumference (HC), HC percentile/z-score, and frontal-occipital horn ratio (FOHR). RESULTS One thousand forty-four patients from 14 centers were included: 125 (12%) underwent prenatal MMC repair and 919 (88%) underwent postnatal MMC closure. The median patient age at primary CSF diversion procedure was 4.1 months in the prenatal MMC repair cohort versus 0.6 months in the postnatal closure cohort (p < 0.001). Absolute HC (45.0 vs 38.0 cm, p < 0.001), HC percentile (> 99.9 vs 97.0, p < 0.001), HC z-score (3.4 vs 1.9, p < 0.001), and FOHR (0.60 vs 0.56, p < 0.001) were greater in the pre- versus postnatal surgery cohort. Linear mixed models adjusting for treatment center and time period in which CSF diversion was performed revealed that patients with MMC treated prenatally underwent CSF diversion 3.02 (95% CI 0.39–5.64) months later (p = 0.024) and had greater HC z-scores (+1.27, 95% CI 0.81–1.73; p < 0.001), but similar FOHRs (−1.08, 95% CI −5.07 to 2.90; p = 0.593) compared to those treated postnatally. CONCLUSIONS Patients developing hydrocephalus following prenatal MMC repair undergo CSF diversion later and have larger heads than those developing hydrocephalus following postnatal MMC closure; however, FOHRs are similar between groups. The disparity between HC and FOHR may suggest the presence of increased overall brain parenchymal and/or extra-axial volume in children receiving prenatal MMC repair, although further study is required. These findings may inform prenatal counseling and follow-up timing for patients with MMC.