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

Introduction/Aims:

MRI data showed that hindbrain herniation is reversible in about 80% of cases after fetal myelomeningocele (fMMC) repair. Little is known on the sonographic follow up of the hindbrain herniation, the 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 and methods:

The first 50 patients that underwent fMMC repair at the Zurich Center for Fetal Diagnosis and Therapy were included in this study. We retrospectively analyzed all sonographic pictures performed once weekly after fMMC repair focusing on hindbrain herniation as well as the banana, and lemon signs. Additionally, 37 of the 50 children were ≥1 year of age and could be included in the analysis for prediction of shunting during the infants first year of life. An independent Mann-Whitney-U-test or a Chi-square test was applied where appropriate. Data is presented as mean ± SD. Statistical significance was given with p < 0.05.

Results:

Hindbrain herniation resolved in 48 fetuses (96%), i.e. before delivery. It disappeared on average at 1.6 ± 0.9 weeks after fMMC repair. Banana and lemon signs resolved at 3.1 ± 6.7 weeks and 6.1 ± 4.9 weeks after the intervention, respectively. Sonographic disappearance of the hindbrain herniation within the first 2 weeks after fMMC repair was associated with a significant lower incidence of shunt placement (OR 0.19; 95% CI 0.4 – 0.9) during the infants first year of life (p = 0.03). All fetuses with persistent hindbrain herniation before delivery received a shunt. No significant correlation could be demonstrated between the disappearance of the banana sign within the first 3 weeks (OR 1.2; 95% CI 0.2 – 3.2; p = 0.7), nor the lemon sign within the first 6 weeks (OR 1.2; 95% CI 0.2 0.3 – 4.7; p = 0.7) after fMMC repair and the necessity of a shunt placement during the infants first year of life.

Conclusion:

We demonstrate here that hindbrain herniation reverses in 96% of all fetuses undergoing fMMC repair, banana and lemon signs disappear later. Reversability of hindbrain herniation within two weeks after fMMC repair is associated with an 80% lower incidence of shunt placement during the infants first year of life.