Role of New High Resolution Ultrasonographic Modalities for Diagnosis of Fetal Nervous System Anomalies

The neural system malformation is one of the more common congenital anomalies encountered in pregnancy. They represent about 0.3-1 percent of all live births. During a prenatal anomaly scan, detection of CNS malformations is important, especially since these anomalies have a poor prognosis and are also associated with genetic syndromes or chromosomal anomalies. Such malformations have clinical importance because they are associated with high rates of morbidity and mortality, influencing the neurocognitive and motor development of the survivors, who may have lifelong sequelae. Thus, it's extremely important to assess the fetal CNS during the prenatal period in order to identify any changes in its development and give appropriate advice to parents regarding pregnancy follow-up. Also, it is vital to explore options for fetal therapy and the timing/type of delivery, as well as postnatal treatment and prognosis.

The fetal CNS screening examination during the mid-trimester scan in low-risk pregnancies should include evaluation of the fetal head and spine, using transabdominal sonography. Evaluation of two axial planes allows visualization of the relevant cerebral structures to assess the anatomic integrity of the fetal brain.These planes are commonly referred to as the transventricular and transcerebellar planes. A third plane, the so-called transthalamic plane, is frequently added, mostly for the purpose of biometry. Structures that should be noted in the routine examination include the lateral ventricles, the cerebellum, the cisterna magna, and the cavum septi pellucidi (CSP). Head shape and brain texture should also be noted on these views.