Cavum veli interpositi

In the brain, the cavum veli interpositi (CVI) is a condition in which the cistern of the velum interpositum becomes dilated. The phenomenon usually occurs in newborns.

Axial MR/CT show a triangular-shaped cerebrospinal fluid (CSF) space between the lateral ventricles. On sagittal images, CVI can appear as a slit-like, linear-to-round/ovoid CSF collection below the fornices, and above the 3rd ventricle.

There are usually no associated abnormalities, although larger lesions may cause an obstructive hydrocephalus. No treatment is usually necessary.