Effect of allograft patch closure on incidence of spinal inclusion cyst formation following open fetal myelomeningocele repair

OBJECTIVE The aim of this study was to evaluate the incidence of spinal inclusion cyst (sIC) formation after open fetal myelomeningocele (fMMC) repair and the effect of dural patch closure. METHODS The authors conducted a retrospective review of patients who underwent open fMMC repair at their institution between March 2011 and June 2020. All patients met the criteria for intervention defined by the Management of Myelomeningocele Study (MOMS). The primary outcomes investigated were development of sIC and need for surgical intervention. Secondary outcomes included need for CSF diversion, extent of reversal of hindbrain herniation, and ambulatory status. RESULTS Of 56 patients who underwent open fMMC repair, 52 had adequate spinal imaging for review. Twelve of these patients (23%) developed sIC (95% CI 0.11-0.35). Six patients experienced symptoms and required surgical detethering with sIC resection. Six additional patients had evidence of sIC on surveillance MRI but remained asymptomatic. The authors found a statistically significant relationship between the use of a dural allograft patch and sIC formation (p = 0.05). In terms of sIC development, there was no statistically significant difference between patients who underwent primary closure and those who received an allograft at the level of the fascia (p = 0.34) or skin (p = 0.26). The rate of hydrocephalus requiring CSF diversion was 52%. Interestingly, 98% of patients had improvement in extent of hindbrain herniation. Dural patch closure did not have any effect on the rate of progressive hydrocephalus (p = 0.33) or degree of reversal of hindbrain herniation (p > 0.99). CONCLUSIONS This study suggested that children with prenatally repaired MMC are at higher risk for development of sIC and associated symptoms than those who undergo postnatal repair. The presentation of symptoms was also earlier in these patients than previously reported after postnatal repair. The use of a dural allograft patch appears to have a positive correlation with sIC formation. Future investigations evaluating the incidence of sIC after fetoscopic MMC repair, in which primary dural closure typically cannot be achieved and a dural patch is most often utilized, will be helpful in facilitating prenatal counseling for patients considering fetal intervention.