Neuroradiological study of the human brain in the fetal period

This presentation intends to clarify the development of the fetal brain as seen by CT. The materials were a total of 50 cases consisting of embryos, fetuses, and newborns. Cranio-cerebral CT scans were performed in all cases within 12 hours after delivery. Fetuses were divided into 3 stages. The first stage ranged from the 8th gestational week to the 12th gestational week, and the second stage, from the 13th to the 23rd week. Beyond 24 gestational weeks, fetuses were classified as the third stage. In the cases of the first stage, for instance, at the 12th gestational week, it is difficult to recognize the intracranial structure on CT. The authors consider that this stage is the limit for the recognition of the intracranial structure of fetuses with the CT scanners in general use. In the second stage, the intracranial structures on CT become clearer in comparison with those in the first stage. The anterior horn and the anterior part of the trigon of the lateral ventricles are in a high-density area of CT corresponding to the germinal matrix which can be stained with hematoxylin. However, in fetuses beyond 24 weeks, that is, at the third stage, the high-density area around the ventricles disappears on CT. The germinal matrix on CT in the second stage shows a symmetrical high-density area, which then disappears. Moreover, the ventricular system varies in morphology to a great extent with growth, especially at the anterior horn of the lateral ventricle. Initially it is like a large cavern, and then its shape becomes like the reindeer's horn and gradually shows the inverted mustache-shape. However, the trigon of the lateral ventricle shows the form of Colpocephaly until a late stage. The ventricular system at birth assumes a morphology similar to that for adults. The morphological changes in the ventricular system with growth may be ascribed to a remarkable development of the cerebral parenchyma, especially the frontal lobe. (author)