A new look at myelomeningoceles: functional level, vertebral level, shunting, and the implications for fetal intervention.
OBJECTIVE: Previous reports have suggested that 80% to 85% of patients who have a myelomeningocele (MMC) and undergo surgical repair after birth develop hydrocephalus and require the placement of a ventricular shunt. However, the rate of shunting as a function of spinal level is not well established. We sought to determine the distribution of postnatally repaired MMC lesions as characterized by both functional and radiologic assessment, as well as the incidence of shunting when patients were categorized according to these 2 methods. METHODS: A retrospective chart review of 297 patients who were born with open MMCs and followed in the spina bifida clinic at the Children's Hospital of Philadelphia was performed. The presence or absence of a shunt was determined for each patient. Functional spinal level was determined by the best-recorded neurologic examination and vertebral level by spine radiographs. RESULTS: The overall rate of ventricular shunting was 81%. The level of the lesion significantly affected the incidence of shunting, with more cephalad lesions correlating with higher rates. This was true both for functional and radiologic categorizations. A significantly higher shunt rate was found among patients with sacral lesions when categorized by radiologic rather than functional criteria. In 86% of patients, the functional level was found to be equal to or higher (worse) than the radiologic level. CONCLUSIONS: This study describes the natural history of ventricular shunting in MMC patients with relation to both radiologic and functional criteria. Fetal MMC closure is being performed in some centers in an attempt to decrease the incidence of shunting and to improve leg function in selected patients. The present data may serve as a comparison group and aid in the design and analysis of a prospective trial to assess the efficacy of this new procedure.