In Huntington disease, atrophy of which brain structure leads to enlargement of the frontal horns of the lateral ventricles?

• A. Putamen
• B. Thalamus
• C. Amygdala
• D. Caudate nucleus

Answer: (D)

Degeneration of the caudate nucleus drives this finding. In Huntington disease, the caudate (a key part of the striatum) undergoes early neuron loss, causing atrophy of its tissue. The caudate forms part of the wall of the frontal horns of the lateral ventricles, so when it wasting occurs, the ventricle enlarges to fill the space—a process known as ex vacuo ventriculomegaly. This pattern is a classic imaging sign of Huntington disease. The other structures listed are not specifically responsible for the enlargement of the frontal horns in this condition.