- cerebellar tonsillar herniation under the basion-opisthion line of about 1.6-cm with crowding of the cerebrum and cervicomedullary junction at the foramen magnum and disappearance of the cisterna magna, consistent with Chiari I malformation
- abnormal flattening of the skull base is seen, due to hypoplasia of the clivus
- atlantooccipital assimilation
- congenital C5 and C6 vertebral body fusion
- syrinx from C4 to C7 with no evidence of a solid component (evaluation with contrast would be helpful)
- no obvious features in the part of the brain imaged to suggest a Chiari II malformation.