Correlation of fetal ventricular size and need for postnatal cerebrospinal fluid diversion surgery in open spina bifida

Perforation of cavum septi pellucidi in open spina bifida and need for hydrocephalus treatment by 1 year of age

OBJECTIVE

In-utero repair of an open neural tube defect (ONTD) reduces the risk of developing severe hydrocephalus postnatally. Perforation of the cavum septi pellucidi (CSP) may reflect increased intraventricular pressure in the fetal brain. We sought to evaluate the association of perforated CSP visualized on fetal imaging before and/or after in-utero ONTD repair with the eventual need for hydrocephalus treatment by 1 year of age.

METHODS

This was a retrospective cohort study of consecutive patients who underwent laparotomy-assisted fetoscopic ONTD repair between 2014 and 2021 at a single center. Eligibility criteria for surgery were based on those of the Management of Myelomeningocele Study (MOMS), although a maternal prepregnancy body mass index of up to 40 kg/m2 was allowed. Fetal brain imaging was performed with ultrasound and magnetic resonance imaging (MRI) at referral and 6 weeks postoperatively. Stored ultrasound and MRI scans were reviewed retrospectively to assess CSP integrity. Medical records were reviewed to determine whether hydrocephalus treatment was needed within 1 year of age. Parametric and non-parametric tests were used as appropriate to compare outcomes between cases with perforated CSP and those with intact CSP as determined on ultrasound at referral. Logistic regression analysis was performed to assess the predictive performance of various imaging markers for the need for hydrocephalus treatment.

RESULTS

A total of 110 patients were included. Perforated CSP was identified in 20.6% and 22.6% of cases on preoperative ultrasound and MRI, respectively, and in 26.6% and 24.2% on postoperative ultrasound and MRI, respectively. Ventricular size increased between referral and after surgery (median, 11.00 (range, 5.89-21.45) mm vs 16.00 (range, 7.00-43.5) mm; P < 0.01), as did the proportion of cases with severe ventriculomegaly (ventricular width ≥ 15 mm) (12.7% vs 57.8%; P < 0.01). Complete CSP evaluation was achieved on preoperative ultrasound in 107 cases, of which 22 had a perforated CSP and 85 had an intact CSP. The perforated-CSP group presented with larger ventricles (mean, 14.32 ± 3.45 mm vs 10.37 ± 2.37 mm; P < 0.01) and a higher rate of severe ventriculomegaly (40.9% vs 5.9%; P < 0.01) compared to those with an intact CSP. The same trends were observed at 6 weeks postoperatively for mean ventricular size (median, 21.0 (range, 13.0-43.5) mm vs 14.3 (range, 7.0-29.0) mm; P < 0.01) and severe ventriculomegaly (95.0% vs 46.8%; P < 0.01). Cases with a perforated CSP at referral had a lower rate of hindbrain herniation (HBH) reversal postoperatively (65.0% vs 88.6%; P = 0.01) and were more likely to require treatment for hydrocephalus (89.5% vs 22.7%; P < 0.01). The strongest predictor of the need for hydrocephalus treatment within 1 year of age was lack of HBH reversal on MRI (odds ratio (OR), 36.20 (95% CI, 5.96-219.12); P < 0.01) followed by perforated CSP on ultrasound at referral (OR, 23.40 (95% CI, 5.42-100.98); P < 0.01) and by perforated CSP at 6-week postoperative ultrasound (OR, 19.48 (95% CI, 5.68-66.68); P < 0.01).

CONCLUSIONS

The detection of a perforated CSP in fetuses with ONTD can reliably identify those cases at highest risk for needing hydrocephalus treatment by 1 year of age. Evaluation of this brain structure can improve counseling of families considering fetal surgery for ONTD, in order to set appropriate expectations about postnatal outcome. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Simple prenatal imaging predictors for postnatal cerebrospinal fluid diversion surgery in fetuses undergoing in utero surgery for spina bifida

OBJECTIVES

To determine simple prenatal imaging parameters that can easily be acquired to predict the need for postnatal CSF diversion (PCD) surgery in fetuses undergoing open fetal surgery for open spina bifida (OSB).

METHODS

All fetuses with OSB that underwent open fetal surgery between June 2017 and June 2021 with available follow-up outcomes were included. Imaging parameters including clivus-supraocciput angle (CSA) on magnetic resonance imaging, transcerebellar diameter (TCD) and lateral ventricle size (Vp) on ultrasound (US), were collected pre- and postoperatively. The requirement for PCD surgery was determined at 1 year of age. The predictive strength of each parameter was determined by Receiver Operating Characteristic curve analysis.

RESULTS

Among 36 babies eligible for the analyses, 41.7% required PCD by one year of age. Pre-operative Vp (AUC 0.71; 95% confidence interval [CI] 0.54-0.88; p = 0.03), TCD (AUC 0.72; 95% CI 0.55-0.89; p = 0.02) and CSA (AUC 0.72; 95% CI 0.51-0.93; p = 0.04) were fair predictors for PCD surgery. After fetal surgery, TCD (AUC 0.93; 95% CI 0.83-1.00; p < 0.0001) and CSA (AUC 0.94; 95% CI 0.83-1.00; p = 0.0005) were outstanding predictors of PCD, whereas post-operative Vp was a fair predictor (AUC 0.71, 95% CI 0.54-0.88, p = 0.03).

CONCLUSION

Post-operative CSA and TCD were outstanding predictors for the need for PCD surgery.

Midline suprapineal pseudocyst in brain of fetuses with open spina bifida

OBJECTIVES

Recently, it was noted that fetuses with open spina bifida (OSB) may have a midline cystic structure evident on ultrasound. Our aims were to determine the prevalence of this cystic structure, shed light on its pathophysiology and investigate the association between its presence and other characteristic brain findings in fetuses with OSB.

METHODS

This was a single-center retrospective study of all fetuses with OSB and available cineloop images in the axial plane referred to the Ontario Fetal Centre, Toronto, Canada, between June 2017 and May 2022. Ultrasound and magnetic resonance imaging (MRI) data obtained between 18 + 0 and 25 + 6 weeks were reviewed in search of a midline cystic structure. Pregnancy and lesion characteristics were collected. Transcerebellar diameter (TCD), clivus-supraocciput angle (CSA) and additional brain abnormalities (abnormal cavum septi pellucidi (CSP), abnormal corpus callosum (CC) and periventricular nodular heterotopia (PNH)) were assessed. In cases of in-utero repair, imaging findings were reviewed postoperatively. In cases of termination, neuropathological findings were reviewed, if available.

RESULTS

Of 76 fetuses with OSB, 56 (73.7%) had a suprapineal cystic structure on ultrasound. The percentage of agreement between ultrasound and MRI detection was 91.5% (Cohen's kappa coefficient, 0.78 (95% CI, 0.57-0.98)). Brain autopsy in terminated cases revealed a dilatation of the posterior third ventricle, with redundant tela choroidea and arachnoid forming the membranous roof of the third ventricle, anterior and superior to the pineal gland. A cyst wall could not be identified, indicating that the structure was a pseudocyst. The presence of the pseudocyst was associated with a smaller CSA (pseudocyst absent, 62.11 ± 9.60° vs pseudocyst present, 52.71 ± 8.22°; P = 0.04). When the pseudocyst was present, its area was correlated inversely with TCD (r, -0.28 (95% CI, -0.51 to -0.02); P = 0.04). Fetal surgery did not have any impact on the growth rate of the pseudocyst (fetal surgery, 5.07 ± 3.29 mm2 /week vs expectant management, 4.35 ± 3.17 mm2 /week; P = 0.58). The presence of the pseudocyst was not associated with abnormal CSP, CC or presence of PNH. None of the cases with available postnatal follow-up required surgical procedure related to the pseudocyst.

CONCLUSIONS

Approximately 75% of all OSB cases have a suprapineal pseudocyst. Its presence is associated with the degree of hindbrain herniation but not with abnormalities of the CSP and CC or presence of PNH. Thus, it should not be regarded as additional brain pathology and should not preclude fetuses from undergoing fetal surgery for OSB. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.