Huntington's disease is a progressive neurodegenerative disorder. There is an autosomal dominant mode of inheritance with complete penetrance. Patients usually exhibit clinical manifestations of the disease in the fourth through sixth decades of life. Clinically, the disease is characterized by a movement disorder and progressive dementia. The disease is depicted radiographically by atrophy of the caudate and putamen followed later by cortical atrophy. There is loss of cholinergic and GABA-nergic neurons in the neostriatum. The cortical atrophy is initially noted in the frontal lobes with progressive involvement more posteriorly as the disease advances. The functional and cognitive impairments are related to the degree of cortical atrophy.
While imaging studies are insensitive for detecting the early stages of the disease, metabolic studies with PET have described hypometabolic regions in the caudate preceding any radiographically detectable changes. In general, MR more readily demonstrates the findings of atrophy - especially in the head of the caudate nucleus.