First-time tethered cord release among adults with myelomeningocele: an analysis of people in the National Spina Bifida Patient Registry

OBJECTIVE: The authors analyzed the National Spina Bifida Patient Registry (NSBPR), a national registry that tracks the outcomes for people with various forms of spinal dysraphism, to determine the ongoing longitudinal risk for tethered cord release (TCR) among adults with myelomeningocele who had not previously undergone TCR during childhood. The authors also sought to identify the impact of lesion level, ambulation status, and prior treatments for hydrocephalus or Chiari malformations on TCR rates. METHODS: Adults in the registry who had not previously undergone TCR during childhood were studied. This group was compared with the remaining adults in the registry. The frequency of first-time TCR and time to TCR (using Kaplan-Meier analysis) were determined independently for males and females. Cox proportional hazards analysis identified correlations between sex, best lesion level and ambulation status prior to TCR, and previous treatments for hydrocephalus and Chiari decompression. RESULTS: Among 967 adults in the NSBPR (422 [43.6%] males and 545 [56.4%] females) who had not undergone TCR during childhood, the authors identified 47 people (4.9%) who underwent their first TCR during adulthood. This study cohort had significantly better mean functional motor levels and ambulation compared with the remaining adult cohort (both p < 0.001). The study group included 35 females (74.5%) and 12 males (25.5%); this sex distribution was significantly different in comparison with the remaining adult cohort (p = 0.016). The Kaplan-Meier curves for first TCR for females and males were significantly different (p = 0.01, log-rank test). TCR rates were correlated with sex (males had decreased risk; OR 0.31, 95% CI 0.16-0.62, p < 0.001), prior treatment for hydrocephalus (those who underwent prior treatment had decreased risk; OR 0.21, 95% CI 0.20-0.42, p < 0.001), and prior treatment for Chiari malformation (those who underwent prior treatment had greater risk; OR 3.84, 95% CI 1.50-9.88, p = 0.005). CONCLUSIONS: Adults with myelomeningocele who escape childhood without undergoing TCR have an ongoing, albeit decreased, risk for spinal cord tethering requiring TCR. This risk is obviously not due to spinal column growth and therefore must reflect other factors such as dynamic changes in spinal cord health over time. Among people with MMC who underwent their first TCR as adults, females seemed to be overrepresented. Similar to the authors' prior childhood study, people who underwent previous Chiari decompression seemed to be overrepresented, whereas those who underwent previous treatment for hydrocephalus seem to be underrepresented. These novel findings deserve further study.