The tethered spinal cord in patients with anorectal malformations

The aims of this study were to find the prevalence of tethered cord in patients with anorectal malformations; to determine if the presence of tethered cord relates to the severity of the anorectal defect, and to certain symptoms, signs, radiologic findings, and associated anomalies; and finally to determine whether tethered cord impacted on a patient's functional prognosis and whether surgical untethering improved the patient. The authors studied 934 patients with anorectal malformations, 111 of whom had magnetic resonance imaging (MRI) of the spine. We compared patients with and without tethered cord by using parametric and nonparametric statistical tests. Tethered cord occurred in 24% of the patients. The prevalence varied according to the type of anorectal defect from 43% in the complex group to 11% in patients with rectovestibular fistula. Patients with tethered cord had a lateral sacral ratio lower than that of patients without tethered cord (0.410 versus 0.702). Tethered cord was present in 90% of patients with myelodysplasia, 60% of patients with a presacral mass, 57% of patients with sacral hemivertebrae, and 56% of patients with a single kidney. The greater number of associated anomalies a patient had, the greater the risk of having tethered cord (P < .05 for all differences). The authors noted differences between patients with and without tethered cord in the presence of voluntary bowel movements (46% versus 70%), fecal soiling (91% versus 63%), constipation (21% versus 43%), and urinary incontinence (86% versus 42%). The data indicate that patients with tethered cord have a worse functional prognosis than patients without tethered cord. However, the incontinence in our patients was also predictable based on the type of anorectal defect and the character of the sacrum irrespective of the presence of tethered cord. Eighteen patients underwent surgical untethering of the cord, and none had any significant change in bowel or urinary function postoperatively. No patient with tethered cord experienced incontinence that could be attributed to the cord defect alone. This study suggests that tethered cord occurs more frequently in patients with severe anorectal defects, sacral hypodevelopment, myelodysplasia, presacral mass, sacral hemivertebrae, or a single kidney, or in those with an anorectal defect with poor functional prognosis. At present no solid evidence supports the concept that tethered cord by itself affects the functional prognosis of patients with anorectal malformations. Also, there is no good evidence demonstrating that surgical untethering improves the prognosis.