Supplementary Material for: Cross-Sectional Area Analysis of the Head of the Caudate Nucleus in Huntington’s Disease

<b><i>Background:</i></b> Caudate nucleus atrophy is a well-known neuroimaging feature of Huntington’s disease (HD). Some researchers have reported a decrease in the volume of the striatum on magnetic resonance images (MRIs) even in the presymptomatic stage of the disease. Despite the many neuroimaging studies on HD, the optimal method for measuring the caudate nucleus area on MRIs and the most effective cutoff values for diagnosing HD remain unclear. <b><i>Objectives and Methods:</i></b> To define suitable imaging sequences and cutoff values for HD, we measured the area of the head of the caudate nucleus (HCN) in 11 patients with HD, 22 age- and sex-matched individuals without neurodegenerative disorders in the central nervous system, 22 sex-matched patients with Alzheimer’s disease, 22 sex-matched patients with Parkinson’s disease, and 7 patients with dentatorubral-pallidoluysian atrophy. <b><i>Results:</i></b> On T2-weighted images (T2WIs), we found significantly reduced HCN area at the rostral level in individuals with HD relative to those of the individuals in the other groups. A significant inverse correlation (ρ = –0.61, <i>p</i> = 0.046) was observed between the HD duration and HCN area at the rostral slice level on T2WIs. The cutoff value for distinguishing patients with HD from healthy individuals and those with other neurodegenerative diseases was 85 mm² at the rostral level on T2WIs (100% sensitivity and specificity). <b><i>Conclusions:</i></b> This cutoff value can be applied clinically to evaluate brain atrophy in HD. Our method is advantageous because it is simple and can be implemented easily in daily clinical practice.