Fetal mild ventriculomegaly: still a challenging problem.

Ventriculomegaly (VM) is defined as an enlargement of the lateral ventricles of the developing fetal brain. Measurement of the size of the fetal cerebral lateral ventricles is recommended as part of the fetal scan routinely performed during the second trimester to screen for fetal anomalies. The measurement is done at the level of the atria of the lateral ventricles filled by the echogenic choroid plexuses, visible in an axial plane of the fetal brain showing also the frontal horns of the lateral ventricles and the cavum septi pellucidi. The calipers are positioned on the internal margin of the medial and lateral walls of the atria, at the level of the glomus of the choroid plexus, on an axis perpendicular to the long axis of the lateral ventricle [14]. An atrial width of < 10 mm is considered normal. VM is diagnosed when the width of one or both lateral ventricles, measured according to the criteria described so far, is ≥ 10 mm. Measurements between 10 and 15 mm constitute mild VM, also defined as borderline (Figure 1); values above 15 mm constitute severe VM. Some authors [27] use the term “milder VM” and “moderate VM” to indicate measurements of 10–12 and 12.1–15 mm, respectively. Other authors [4] restrict the term “mild VM” to measurements between 10 and 12 mm. The most commonly used terminology, however, is “mild VM” referring to atrial measurements between 10 and 15 mm and this terminology will be used in the following discussion. Mild VM can be bilateral or unilateral [15]. Usually in the screening ultrasound examinations, only the lateral ventricle distal to the transducer is measured as the proximal one is obscured by reverberation artifacts. Efforts should be made in order to visualize both ventricles and recognize unilateral and bilateral mild VM (Figure 2). Mild VM may be associated with a variety of anomalies (brain malformations, genetic syndromes, chromosomopathies, and infections) or can be isolated. The prevalence of isolated mild VM is extremely variable and has been reported ranging from 0.15% to 0.7% [1, 25]. The finding of mild VM represents a cause of anxiety for the parents and a difficult task for the clinician. In order to offer appropriate counseling, an accurate diagnostic work-up is needed. The diagnostic work-up should include the following steps: – ruling out for associated anomalies – ruling out for congenital infections – ruling out for feto-neonatal alloimmune throm bocytopenia – ruling out for chromosomal abnormalities – monitoring the development of mild VM in the progressing pregnancy.