Prenatal ultrasound evaluation of fetal diastematomyelia: two cases of type I split cord malformation.

Isolated diastematomyelia is a rare form of spinal dysraphism characterized by a sagittal cleft in the spinal cord, conus medullaris and/or filum terminale with splaying of the posterior vertebral elements. This condition is the result of the presence of an osseous or fibrocartilaginous septum producing a complete or incomplete sagittal division of the spinal cord into two hemicords. It may be isolated or associated with other segmental anomalies of the vertebral bodies. Prenatal diagnosis of this anomaly is possible in the early midtrimester by sonography, thus allowing for early surgical intervention and a favorable prognosis. Two cases of fetal diastematomyelia diagnosed by prenatal sonography are presented, each demonstrating the typical sonographic features diagnostic of this condition. The first case, detected at 28 weeks' gestation, presented with disorganization of the bony processes of the vertebral column with a midline echogenic focus. The second fetus, diagnosed at 17 weeks' gestation, had a similar appearance with widening of the posterior elements and the presence of a midline echogenic bony spur. Postnatally, both infants underwent magnetic resonance imaging for a definitive diagnosis. Surgical repair of the defect was performed in the neonatal period in both cases.