The cavum septi pellucidi and cavum vergae are midline developmental cavities in the brain. They usually communicate and obliterate from posterior to anterior, the posterior cavum vergae obliterating first and then usually the anterior cavum septi pellucidi. A cavum vergae without a cavum septi pellucidi would thus be unexpected; however, such a case was seen at the time of autopsy, which suggests that the embryologic events in this region may not always occur in the usual sequence.