A Novel Composite Index Could Help Predict Which Patients Need Cerebrospinal Fluid Diversion Surgery After Prenatal Myelomeningocele Repair
The landmark Management of Myelomeningocele Study (MOMS) demonstrated the unequivocal efficacy of prenatal surgery in achieving primary outcome measures for children with this condition. When compared to postnatal closure, open prenatal surgery cut the risk of hydrocephalus in half, increased a child’s chances of being able to ambulate independently, and reversed hindbrain herniation in nine out of 10 patients.
Regardless of when their spinal defect is closed, many children with myelomeningocele (MMC) develop enlarged ventricles of the brain. This can cause symptoms of hydrocephalus, including developmental regression, rapidly increasing head circumference, and vomiting and progressive neurological deficits, which indicate an urgent need for cerebrospinal fluid (CSF) diversion surgery. However, during the MOMS study, researchers observed that repairing the defect prenatally imparted a protective effect against enlarged ventricles. About 70% of children in the study who had a prenatal repair developed larger-than-normal ventricles, but many didn’t develop associated clinical signs or symptoms of hydrocephalus. In many children who met the criteria for shunt surgery to treat hydrocephalus due to enlarged ventricular size, their care team elected not to shunt since the children were completely asymptomatic.
Deciding which patients need CSF diversionary surgery has been a hot topic ever since, says pediatric neurosurgeon Charles Stevenson, MD, FAANS. “The decision to operate often depends on where a child receives care, since different providers utilize different criteria for diagnosing progressive hydrocephalus,” he says. “We need to serve patients and families better by developing a more objective, scientific way of determining which children need surgery.”
For the last several years, Stevenson and his colleagues at Cincinnati Children’s have been doing just that. Their most recent study, published in August 2022 in the American Journal of Neuroradiology, highlights the development of a predictive composite index based on conventional indicators and diffuse tensor imaging (DTI). DTI measures are obtained via magnetic resonance imaging (MRI) and can characterize microstructural alterations in the brain’s white matter fibers.
The retrospective study included 33 patients of Stevenson’s who had a prenatal myelomeningocele repair at Cincinnati Children’s, 14 of whom ultimately required CSF diversion surgery. All underwent DTI as part of their routine care and follow-up in the neurosurgery clinic (neuroradiologists at Cincinnati Children’s perform DTI acquisition as part of every brain MRI at Cincinnati Children’s).
“Our DTI metrics included several neuroimaging biomarkers that have been applied frequently in previous hydrocephalus-related analysis,” explains Stevenson. “We integrated these biomarkers into a model that included additional clinical and demographic measures, such as ventricle size and head circumference. In this small patient population, our model was better at predicting who went on to develop hydrocephalus than any other clinical method alone.”
The “CSF diversion surgery index” is still in the early stage of development, and Stevenson hopes the team can create a sensitive and robust tool to help guide clinical decision-making for children who have undergone prenatal MMC repair.
Since 2011, the Cincinnati Children’s Fetal Care Center has performed more than 120 fetal MMC repairs, 66 of them utilizing a novel endoscopic technique. The center is in the top three prenatal MMC surgical centers in the United States. In September 2022, the Spina Bifida Coalition named the Fetal Care Center a “Top 50 Influencer” for its contributions to the organization’s growth and well-being of people living with spina bifida in Greater Cincinnati and beyond.
(Published October 2022)
