Question

Identify the condition shown in the CT scan image below.

• A. Dandy Walker malformation
• B. Cerebellar vermis hypoplasia
• C. Mega cisterna magna
• D. None

Hint:

Absent vermis plus cystic fourth ventricle in an enlarged posterior fossa.

Answer 1

The Correct Option is A

Step 1: The CT shows the classic triad of Dandy-Walker malformation: agenesis or hypoplasia of the cerebellar vermis, cystic dilatation of the fourth ventricle filling an enlarged posterior fossa, and upward displacement of the tentorium and torcula.
Step 2: Because the cystic fourth ventricle communicates widely with the posterior fossa and the vermis is largely absent, the two cerebellar hemispheres are pushed apart and splayed, which is the defining appearance here.
Step 3: This combination, with an enlarged posterior fossa, distinguishes Dandy-Walker from the distractors. Isolated cerebellar vermis hypoplasia lacks the large posterior fossa cyst, and mega cisterna magna has an enlarged cisterna magna with an intact vermis and normal fourth ventricle.
Step 4: Dandy-Walker malformation is commonly associated with hydrocephalus and may present with macrocephaly and developmental delay, so option a is correct.