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Object: Myelomeningocele (MMC) is characterized by a defect in caudal neurulation and appears at birth with a constellation of neuroanatomical abnormalities, including Chiari malformation Type II. The authors investigated the effects of antenatal versus postnatal repair of MMC through a quantitative analysis of morphometric changes in the posterior fossa (PF)., Methods: The authors retrospectively reviewed the records of 29 patients who underwent in utero MMC repair, 24 patients who underwent postnatal repair, and 114 fetal and pediatric controls. Tonsillar displacement, cerebellum length, pons length, clivus-supraocciput (CSO) angle, and PF area were compared in antenatal and postnatal MMC repair groups as well as in controls without neural tube defects by using t-tests and correlation coefficients., Results: Initially, the in utero CSO angle was significantly more acute in all patients with MMC--prenatally and postnatally repaired--as compared with controls (57.8° vs 75.4°, p < 0.001); however, the angle rapidly changed and became similar to that in controls between 30 and 31 weeks' gestation to approximately 80°, with antenatal repair having little effect. Postnatally, the CSO angle decreased in controls (R = -0.58) and in the antenatal repair group (R = -0.17). The cerebellum and pons length demonstrated no significant differences in any group. Overall, tonsil descent was corrected in the antenatal repair group as compared with postnatal repair (p < 0.001), and the PF area increased in all 3 groups in utero. Growth was less rapid in patients with MMC compared with controls, but this was corrected by antenatal repair (p = 0.015)., Conclusions: Myelomeningocele was associated with tonsillar herniation and a smaller PF than in control fetuses. Antenatal surgical repair corrected both abnormalities. The CSO angle began significantly more acutely in patients with MMC, but normalized with development regardless of when surgery was performed. Determining the clinical effects of antenatal repair requires further follow-up.

Object: The goal in this study was to evaluate the incidence and clinical implications of the development of cutaneously derived intradural inclusion cysts (ICs) following fetal myelomeningocele (fMMC) closure., Methods: Retrospective databases and responses to a parental questionnaire were reviewed to determine the incidence, clinical presentation, and outcomes of fMMCs in children in whom ICs developed at follow-up., Results: Prior to the National Institutes of Health (NIH)-sponsored Management of Myelomeningocele Study (MOMS), 54 patients underwent fMMC closure at the authors' institution. Sixteen (30%) presented with symptomatic tethered cord syndrome (TCS) at a median age of 27 months (range 4-93 months). Ten (63%) of the 16 (19% of the total) developed TCS in association with an intradural IC. In 9 (90%) of 10 patients, the IC was seen on preoperative MR imaging, and in 1 it was found during surgery. Four additional children (7% of the total) with evidence of an IC on surveillance MR imaging are currently asymptomatic at 94, 84, 60, and 60 months of age, respectively. All but 1 (an L-3 level lesion) IC developed in infants with L-4 and L-5 defects. After cyst removal, 6 children are asymptomatic at a median follow-up of 36 months (range 12-63 months). Following IC removal, 4 children lost normal bladder function and now require clean intermittent catheterization, and 1 lost normal leg function and now requires a walking aid for ambulation. Histologically, 8 lesions were dermoid, 1 was an epidermoid, and 1 was a mixed dermoid-epidermoid IC. Three patients developed another IC and required its removal at 24, 39, and 51 months, respectively. One required another tethered cord release within 57 months after IC removal., Conclusions: Cutaneously derived intradural ICs can develop following fMMC surgery. Deterioration of bladder function, risk of recurrence, and loss of lower-extremity function appear to be the most important long-term complications of IC in children with fMMCs. The ongoing NIH-sponsored MOMS may help determine whether children with fMMC are at increased risk of IC development compared with children treated with postnatal MMC closure. Parents seeking fMMC closure should be informed about the possibility of IC formation and the potential clinical consequences.