Chiari II malformation representing an abnormality of the spine and posterior fossa characterized by a small posterior fossa with the descent of its structures (hindbrain herniation). Multiple associated abnormalities are frequently seen.

About 95% of a newborn with myelomeningocele have an associated Chiari II.

It can be associated with multiple spinal, cerebral, and cranial vault abnormalities.

Brain and spine MRI are essential modalities for the assessment of Chiari II malformation.