From the case:
Frontal horn, intercaudate and inner table ratios (diagram)
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Diagram demonstrating how to measure:
- frontal horn width
- intercaudate distance
- inner table width
FH/CC ratio: normal mean 2.2 to 2.6 (this ratio decreases with aging as a result of enlargement of the frontal horns of the lateral ventricles).
CC/IT ratio : normal mean 0.09 to 0.12
Adapted from: Ho VB, HS Chuang, MJ Rovira and B Koo. “Juvenile Huntington disease: CT and MR features.” AJNR Am J Neuroradiol 16, no. 7 (August 1, 1995): 1405-1412.
Case Discussion
Both of these ratios are useful in younger patients with suspected Huntington disease and become abnormal before the caudates appear abnormal to visual inspection alone.