Morphological evaluation of fetus CNS and its related anomalies

The fetus central nervous system was evaluated morphologically by ultrasonography (US), magnetic resonance imaging (MRI), and CT scan to analyze the prenatal diagnostic value for CNS anomalies. A total of 31 patients with 42 lesions had been diagnosed during the preceding 7 years. The patients included 24 with hydrocephalus, three with anencephaly, three with myeloschisis, three with holoprosencephaly, three with an encephalocele, two with a Dandy-Walker cyst, one with hydroencephalodysplasia, one with an intracranial neoplasm, one with sacrococcygeal teratoma, and one with sacral agenesis. Compared with US and MRI, CT proved to be more accurate in the detection of spine and cranium-bone morphology. This finding seems to be valuable in the diagnosis of spina bifida, cranium bifidum and some cases of hypertensive hydrocephalus, especially in the axial view. MRI was definitely superior in the anatomico-pathological diagnosis of cerebral dysgenesis, ventriculomegaly, intracranial tumors, and other brain parenchymal changes in view of multi-dimensional analysis. The most considerable disadvantage of MRI in the diagnosis of a fetus CNS anomaly is the poor information about spine and cranium morphology. A super-conducting MRI system is still insufficient to demonstrate the spinal cord of a fetus. US was routinely used, and the multidimensional slices were useful for screening the CNS abnormalies. Some of the fetus brain lesions, such as intracranial hematomas, had a specific echogenecity on US. However, US sometimes failed to demarcate the cerebral parenchymal or subdural morphological changes because its artifacts had hyperchoic shadows. While US, MRI, and CT were valuable diagnostic tools in the morphological evaluation of fetus CNS and its related anomalies, each modality has different diagnostic advantages and disadvantages. Improvement can be expected when these diagnostic imaging modalities are complementary, depending upon the nature of the anatomy. (J.P.N.)