Cavum septi pellucid. From http://neuro. Psychiatryonline. Org/article. Aspx? Articleid=100939 - enlarged cavum septi pellucidi (csp) is a neurodevelopmental anomaly associated with schizophrenia...A small csp is common in a large proportion of healthy control subjects and is therefore considered to be a "normal variant." determination of how large a csp must be in order to reflect pathology is unclear. Normal is 1-4 mm.