Which of the following statements about Dandy-Walker syndrome are true and which are false? 1 Most common posterior fossa malformation 2 Consists of a cystic expansion of 4th ventricle in the posterior fossa & midline cerebellar hypoplasia 3 Triad of Hypoplasia of vermis + Cephalad rotation of the vermian remnant & cystic dilatation of 4th ventricle extending posteriorly + Small posterior fossa 4 Most common manifestation is Macrocephaly 5 Managed by shunting the cystic cavity

**Core Concept**
Dandy-Walker syndrome is a rare congenital disorder characterized by the malformation of the cerebellum and its surrounding structures, leading to hydrocephalus and other neurological symptoms.

**Why the Correct Answer is Right**
Dandy-Walker syndrome is indeed the most common posterior fossa malformation. It is caused by the failure of the cerebellar vermis to develop properly, resulting in a cystic expansion of the 4th ventricle in the posterior fossa and midline cerebellar hypoplasia. The classic triad of symptoms includes hypoplasia of the vermis, cephalad rotation of the vermian remnant, and cystic dilatation of the 4th ventricle extending posteriorly, accompanied by a small posterior fossa. Macrocephaly is a common manifestation of Dandy-Walker syndrome due to the increased intracranial pressure and hydrocephalus. Shunting the cystic cavity is a common management strategy to relieve the hydrocephalus and reduce intracranial pressure.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect, as Dandy-Walker syndrome is not the only posterior fossa malformation.
**Option B:** Incorrect, as while the cystic expansion of the 4th ventricle is a characteristic feature, the other options in statement 2 are also true.

**Clinical Pearl / High-Yield Fact**
Dandy-Walker syndrome is often associated with other congenital anomalies, such as cardiac and genitourinary defects, and may be part of a larger syndrome.

**Correct Answer:** 2. Statement 2 is true.

✓ Correct Answer: B. 1-T, 2-T, 3-F, 4-T, 5-T