Prenatal prediction of need for ventriculoperitoneal shunt in open spina bifida

Abstract

Objective: To investigate whether the need for ventriculoperitoneal shunting in neonates with open spina bifida can be predicted prenatally.

Methods: This was a retrospective cohort study of all fetuses with open spina bifida identified at a single referral center between 1998 and 2012. Ultrasound records were reviewed and outcomes were ascertained from maternal, neonatal and pediatric records. The performance of screening was determined by receiver-operating characteristics (ROC) curve analysis.

Results: We identified 124 cases of isolated open spina bifida, of which 48 were liveborn. Detailed postnatal follow-up was available for 39 cases, with an average follow-up time of 3.6 years. A shunt was inserted in 22 (56.4%) cases. The width of the posterior horn of the lateral ventricle (Vp) and the ratio between its width and that of the cerebral hemisphere (Vp/H) at diagnosis were significantly greater in cases that required a shunt compared with those that did not subsequently require a shunt (Vp: median 12.4 mm vs 7.7 mm, P < 0.001, and Vp/H: median 0.54 vs 0.33, P < 0.001, respectively). Similarly, at the last scan before delivery, Vp and Vp/H were significantly higher in those requiring a shunt (Vp: median 23.1 mm vs 8.2 mm, P < 0.001; and Vp/H: 0.54 vs 0.21, P < 0.001, respectively). Using Vp and Vp/H at the initial assessment, the rates of detection of fetuses requiring a shunt postnatally were 68.2% and 86.4% for a false-positive rate of 13%, with positive likelihood ratios of 6 and 7, respectively. All fetuses with a Vp of ≥ 12 mm or a Vp/H of ≥ 0.6 at the time of diagnosis required postnatal shunt insertion (positive predictive value = 100%).

Conclusions: In cases with open spina bifida the need for a postnatal shunt can be predicted prenatally. This novel observation should be useful in the prediction of outcome and therefore for accurate prenatal counseling and triaging cases for fetal surgery.

Keywords: hydrocephalus; lateral ventricle; posterior horn; prenatal diagnosis; screening; ultrasound; ventriculomegaly.