**Core Concept:** Miller-Dieker syndrome is a primary microdeletion syndrome characterized by a specific brain malformation known as lissencephaly. Lissencephaly is a condition where the brain lacks the normal convolutions (gyri and sulci) that are present in a normal brain. This leads to a smooth appearance on neuroimaging.

**Why the Correct Answer is Right:** In the context of Miller-Dieker syndrome, the absence of convolutions on neuroimaging is due to a specific genetic defect on chromosome 17p13.1. The microdeletion leads to the disruption of the protein PAFAH1B1, which is essential for proper neuronal migration during brain development. The lack of proper migration results in the absence of convolutions.

**Why Each Wrong Option is Incorrect:**

A. Lissencephaly with cobblestone lissencephaly (Option C) is a different condition characterized by the presence of numerous, small bumps on the brain surface instead of a smooth appearance.
B. Lissencephaly with pachygyria (Option D) is another type of lissencephaly where the brain has increased thickness due to abnormal layering of brain tissue.

**Clinical Pearl:** Understanding the etiology of Miller-Dieker syndrome and the different types of lissencephaly is crucial for diagnosing and differentiating these conditions from other similar neurological disorders. A thorough neuroimaging and genetic evaluation should be performed for an accurate diagnosis.