Differences between myelomeningocele and myeloschisis lesions in patients undergoing open in-utero spina bifida repair

Spina bifida lesions are broadly classified as myelomeningocele (MMC: with sac) and myeloschisis (MSC: without sac) lesions, with MSC being the most severe type. Although prenatal repair methods are similar, baseline differences, surgical management, and postnatal outcomes remains largely unknown. The objective was to compare prenatal findings, closure methods, and 12-month outcomes. A prospective cohort of 111 open in-utero repair consecutive patients at a single institution were assessed (2011-2022). Lesion type was defined by ultrasound for the presence of a sac elevated from the lesion. Surgical eligibility was similar to the MOMS study, but expanded BMI inclusion criteria to ≤40 from 2018. Intraoperative management was pediatric neurosurgeon dependent. We compared preoperative differences in ventricular sizes, tonsillar herniation levels, extremity function, skin patch requirement, and neonatal outcomes including cerebrospinal fluid (CSF) leakage, wound dehiscence, and CSF diversion procedures until 12 months of age. Significance was considered at a p=0.05. Ultrasound and MRI identified 60 cases that were MMC and 51 as MSC. Maternal demographics, the gestational age (GA) at prenatal evaluation and the upper level of lesion were similar between groups (Table 1). Preoperative ventricular measurements were greater in the MMC cases. There were no differences in the upper level of lesions. MSC has severe baseline tonsillar herniation compared to MMC. There was higher talipes and loss of baseline motor function in the MMC group. The need for a skin closure patch was 21.7% in MMC vs 43.1% in MSC (p=0.002; Table 2). The length of NICU stay was 17 days longer in the MSC vs. the MMC group. There were no differences in ventricular diversion rates within a year from birth. Prenatally diagnosed MMC is associated with greater ventriculomegaly and talipes, and with less tonsillar herniation and fetal movement than those with MSC defects. Longer NICU stays in the MSC group is secondary to the higher need for skin closure with a patch and delayed healing.View Large Image Figure ViewerDownload Hi-res image Download (PPT)