Chiari II malformation is associated with deformity of which brain structure?

• A. Cerebellum
• B. Medulla
• C. Cervical spinal cord
• D. Frontal lobe

Answer: (A)

Chiari II malformation features downward displacement of the hindbrain through the foramen magnum, and this deformation is most prominently seen in the cerebellum. The cerebellar tissue, especially the vermis and tonsils, herniates below the foramen magnum along with distortion of the brainstem, often in the setting of meningomyelocele. This cerebellar involvement is the hallmark that makes the cerebellum the best answer. The medulla can be involved as part of the same herniation, but the frontal lobe is not typically deformed in this condition, and the cervical spinal cord, while affected by the associated spinal defect, is not the brain structure referred to in this pattern of hindbrain deformation.