The bicaudate index is the ratio of width of two lateral ventricles at the level of the head of the caudate nucleus to distance between outer tables of skull at the same level. It can be a useful marker of ventricular volume and in the diagnosis of hydrocephalus.

B/B1

In the series, upper limit of the BCI (99th percentile) was 0.13 for the first three decades. In the fourth and fifth decade it increases to 0.15 and 0.19, respectively. Conclusions: After the age of 50, BCI progressively increases and rises to levels that are nearly double those found in the age group of 30 or younger. This is important in CT assessments of potential developments of hydrocephalus in older patients ¹⁾.