Secondary Tethering and Urodynamic Findings after Prenatal Closure for Myelomeningocele
Duncan R. Morhardt, MD,PhD, Shahram Khoshbin, MD, Benjamin Warf, MD, Mohammad Alkhawaldeh, PhD, Caleb Nelson, MD, MPH, Carlos Estrada, Jr., MD, MBA, Stuart B. Bauer, MD.
Boston Childrens Hospital, Boston, MA, USA.
Background: Prenatal closure of spina bifida (SB) has been closely examined in the prospective MOMS trial. While results were encouraging for motor and neurosurgical outcomes, lower urinary tract (LUT) function has not shown significant improvement. Lack of standardization of urodynamic (UDS) assessment for SB patients across participating institutions meant that few parameters could be reliably reported on from all centers. A review of prenatally closed patients with postnatal management at a single institution with well-reported and standardized UDS practices may provide insight into any postnatal functional improvements after prenatal repair. This study examined early UDS findings with respect to secondary untethering surgery in patients who had undergone prenatal closure of myelomeningocele.
Methods: Using our SB patient registry we identified patients who underwent prenatal closure and presented to our SB clinic between 1999 - 2017. A retrospective review was performed to determine secondary spinal cord tethering and associated UDS findings. Inclusion criteria included a history of prenatal myelomeningocele closure, UDS at our center, and at least one follow-up visit. UDS was performed supine, employing urethral and rectal balloon catheters. A concentric needle electrode measured external urethral sphincter function (EMG). Sacral spinal reflexes were determined by a neurologist.
Results: Eighteen children met the inclusion criteria. Median age of initial UDS was 1.65 years (0.2-5.3 years). Patients were followed for a median of 6 years (1-18 years). Sixty-two percent (10/18) were male. The bladders were deemed normal in six (33%) patients, whereas 12 (67%) exhibited detrusor overactivity, eight of whom (67%) also had poor compliance. Sphincter EMG demonstrated normal motor unit potentials in 15 (84%), abnormal units in two (11%) and absent motor unit activity in one (5%). Sacral spinal reflexes were present in 15, 14 of whom had normal baseline EMG activity. Detrusor sphincter dyssynergy was observed in 13 (72%) with four having synergic voiding and one with no activity due to complete sphincter denervation. At initial UDS, eight (44%) were voiding while ten required clean intermittent catheterization (CIC) to empty. Over time, all but one child required CIC and medication to manage their bladder dysfunction. Nine children required secondary spinal surgery (6/10 initially requiring CIC versus 3/8 who were initially voiding, p =0.34). A ventriculoperitoneal shunt was required in one. The high incidence (50%) of progressive tethering requiring secondary spinal surgery, regardless of early UDS findings or type of treatment undertaken, was surprising.
Conclusions: A high proportion of infants who undergo prenatal repair of spina bifida will demonstrate significant urodynamic abnormalities during infancy and many of these will also require secondary spinal surgery to correct cord tethering. This suggests that, despite the apparent neurological benefits of prenatal closure, LUT function often worsens in early childhood. Long term vigilance in these children is mandatory irrespective of early UDS findings.
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