Computed tomography of primary intrathecal Wilms tumor with diastematomyelia.

A 2-year-old girl evaluated for diastematomyelia proved to have nearly complete block from an associated primary intraarachnoid Wilms tumor (nephroblastoma) situated immediately caudal to the bone spur and dorsal to the reunited hemicords and conus medullaris. No second focus of Wilms tumor could be detected. The computed tomographic appearance of the tumor and a possible embryological explanation for its relationship to the spinal cord are presented.