Pre-natal diagnosis of occult spinal dysraphism by ultrasonography and post-natal evaluation by MR scanning.

Eight children born with occult spinal dysraphism were diagnosed in utero by ultrasonography. Post-natally, they were evaluated by MR scans. The ultrasound scans in all 8 fetuses revealed a spina bifida: the spinal cord was long in 5 and in 3 a meningocele was thought to be present, however, in 1, a post-natal MR scan revealed a lipomeningocele instead of a simple meningocele. In 3 fetuses an echogenic area was seen on the ultrasound scan which raised the possibility that an intradural lipoma was present, and was confirmed by post-natal MR scans. In 3 fetuses vertebral body anomalies and an additional ossification centre in a midline bony spur together with widening of the spinal canal were seen in the lower lumbar region. The lesions in all 8 fetuses were skin-covered. None had ventriculomegaly or an Arnold-Chiari malformation. The prognosis for fetuses with spina bifida aperta is well documented in contrast to that for those with spina bifida occulta. The ability to identify a spinal dysraphic lesion pre-natally allows a more accurate assessment to be made of the likely outcome for an individual fetus.