Huntington disease (Huntington chorea), is an autosomal dominant neurodegenerative disease in which there is trinucleotide (CAG) repeat. It is caused by a loss of GABAergic neurons of the basal ganglia, especially in the caudate nucleus and putamen, resulting in atrophy of those structures.

Clinically, patients present with progressive involuntary choreoathetoid movements, dementia, and psychosis which starts in midlife.

On imaging, patients characteristically have atrophy of the caudate head, which can be quantified by two ratios:

• frontal horn width to intercaudate distance ratio (FH/CC) is decreased
• intercaudate distance to inner table width ratio (CC/IT) is increased

This particular patient had classic clinical and imaging features, and on genetic study, trinucleotide repeats were present, which confirmed the diagnosis of Huntington disease.