Clinical impact of fetal sac size on closed neural tube defects

To evaluate the association between lesion volume and postnatal outcomes in patients with closed spina bifida (SB).

Single-center retrospective review of all patients diagnosed with a closed SB evaluated between 2013 and 2023. Prenatal lesion volume < 3 mL was categorized as "no sac," and volume ≥ 3 mL was categorized as "sac."

Of eligible patients, 22 had a sac, and 33 did not. Myelocystocele patients more commonly had an associated saccular lesion than lipomyelomeningoceles (80% vs. 28%, p = 0.02). Lipomyelomeningocele patients demonstrated less prenatal lesion growth compared to myelocystocele patients (6.26 vs. 58.0 mL) over a median of 12.7 and 10.5 weeks, respectively. Patients with a sac had a higher proportion of talipes (40.9% vs. 9.1%; p = 0.007) compared to those without. At 5 years old, a higher proportion of patients with no sac was able to ambulate independently and required less CIC than patients with a sac (80% vs. 42%; 0% vs. 41.7%). VUDS showed a greater frequency of detrusor overactivity (60.0% vs. 45.0%) and abnormal bladder compliance (60.0% vs. 5.0%) in those with a sac compared to those without. Repeat tethered cord release was also more common (30.0% vs. 3.4%) among patients with a sac-associated defect.

Patients with a sac had an increased risk of prenatal talipes, decreased ability to ambulate independently, increased use of CIC, and increased need for repeat tethered cord release compared to patients without a sac. Given numerous associated morbidities reported in this study, longitudinal multidisciplinary follow-up is critical in the care of these patients.