 Evaluation of the fetal brain demonstrates that the posterior fossa is small with crowding of the posterior fossa elements including the fourth ventricle. The cerebellar tonsils appear pointed in morphology and may be low lying. The atrium of the left lateral ventricle measures 10-11 mm in diameter and is larger than the right. However, the remainder of the supratentorial ventricular system is otherwise unremarkable.The corpus callosum is present. The gyral pattern is within range for reported gestational age. There is no parenchymal signal alteration or intracranial hemorrhage.Evaluation of the patient's spine demonstrates osseous dysraphism at the lower lumbar/sacral levels with extension of CSF-containing meninges and low-lying spinal cord elements through the dorsal defect.
Myelomeningocele in the lower lumbar spine/sacrum containing spinal cord elements. In addition, the posterior fossa is small with pointed and possibly low-lying cerebellar tonsils. The constellation of findings is suggestive of a Chiari II malformation.The left lateral ventricular atrium is larger than the right measuring at the upper end of normal. This could relate to normal anatomic variation, a choroid plexus cyst or other developmental cyst, or could perhaps be related to the suspected Chiari II malformation. The remainder of the supratentorial brain is within normal limits.