[en] Cavum septi pellucidi (CSP) and Cavum vergae (CaV) are primitive midline structures of the premature brain. Retrospectively we looked up the CSP and the CaV at birth, 1st week, 1st, 2nd, 3rd and 4th month of the done transcranial sonographies. Then we compared preterms with terms and standardized these data to one population. The results were that the CaV begins to close in the 30th week of gestational age (ga), increases in the 31st and 36th week and shows the highest rate of reduction between the 33rd to 35th week of ga. The CSP starts closing in the 35th week of ga. We observed an increase of relative rates in the 36th and 39th week of ga and the period of the greatest reduction between the 2nd and 4th month. In the perinatal period there are unknown mechanisms in the leaves of the Septum pellucidum. By a documentation system we found out in all MRI (n=3743) of the last five years which were done in children between 0 and 15 years. There was a relative rate of Cusps 1,31 %, according to the age 0 to 1 there was a rate of 2,67 %. The rate of CaV was 0,85 % and 2,23 %. The highest period of reduction is after the 5th year for the CSP and after the first year for CaV. In the CCT we observed a relative rate of 0,62 % (CSP) and of 0,25 % (CaV). The association between Cava and neurological disorder showed that 20 % are combined with seizures (MRI) and 20 % with hydrocephalus (CT). More boys than girls show CSP and CaV. In the last examination we compared the rates of CSP/CaV in all MRI (n=3743) with the CSP/CaV associated with the neurological disorder hydrocephalus. In the population hydrocephalus there is a division in obstructive and communicating (ratio 80:20). From birth to the 15th year the relative rates (CSP) with hydrocephalus keeps constant (0,73 %), as the rates in the normal population decreases continuously; these of CaV show an increase between the 2nd and 5th year and are above the normal CaV rate. (author)