Hindbrain herniation, banana, and lemon sign after open fetal myelomeningocele repair – when do this signs disappear and is shunting predictable?

Introduction:

MRI data showed that hindbrain herniation (HH) is reversible in 80% after fetal myelomeningocele (fMMC) repair. Little is known on sonographic follow up of HH, banana, and lemon sign after fMMC repair – when they disappear and whether the time between fMMC repair and their disappearance has any predictive value for the necessity of shunting during the infants first year of life.

Patients/Methods:

The first 50 patients that underwent fMMC repair at the Zurich Center for Fetal Diagnosis and Therapy were included. We retrospectively analyzed all sonographic pictures after fMMC repair focusing on HH, banana, and lemon signs. Children ≥1 year (N = 37) of age were included in the analysis for prediction of shunting during the infants first year of life.

Results:

HH resolved in 48 fetuses (96%) before delivery. It disappeared on average at 1.6 ± 0.9 weeks after fMMC repair. Banana or lemon signs resolved at 3.1 ± 6.7 weeks or 6.1 ± 4.9 weeks after the intervention respectively. Sonographic disappearance of the HH within the first 2 weeks after fMMC repair was associated with a sign. lower incidence of shunt placement (OR 0.2; 95%, CI 0.4 – 0.9) during the infants first year of life (p = 0.03). All fetuses with persistent HH before delivery received a shunt. No significant correlation could be demonstrated between the disappearance of the banana or lemon sign and later shunting.

Conclusion:

HH reverses in 96% after fMMC repair, banana and lemon signs disappear later. Reversability of HH within two weeks after fMMC repair is associated with an 80% lower incidence of an early shunt placement.