Which condition involves downward displacement of the medulla and cerebellum through the foramen magnum with bulbar symptoms?

• A. Dandy-Walker syndrome
• B. Chiari malformation
• C. Spina bifida
• D. Syringomyelia

Answer: (B)

Chiari malformation is a hindbrain herniation where parts of the cerebellum, and sometimes the lower brainstem (medulla), descend through the foramen magnum. When the medulla and cerebellum protrude downward, this compresses brainstem structures and produces bulbar symptoms such as difficulty swallowing, hoarseness, coughing or choking with feeding, stridor, and sometimes apnea. This displacement through the foramen magnum is the hallmark that distinguishes Chiari malformation from other conditions.

Dandy-Walker syndrome, by contrast, involves a malformation of the posterior fossa with an enlarged fourth ventricle and hypoplasia or absence of the cerebellar vermis, but it does not feature downward herniation of the medulla and cerebellum through the foramen magnum. Spina bifida is a spinal column defect and does not describe brainstem descent, though Chiari II can be associated with myelomeningocele. Syringomyelia is a syrinx formation within the spinal cord and again does not entail brainstem herniation through the foramen magnum.