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KEY POINTS
Ventriculomegaly is not a diagnosis. It is a sign; when diagnosed, a search for all underlying causes should be immediately undertaken.
Ventriculomegaly is frequently associated with a significant number of intra- and extracranial chromosomal as well as nonchromosomal anomalies as well as microarray abnormalities.
For measuring the lateral ventricle, it is recommended to use an axial view of the brain and to place the calipers at the level of the parieto-occipital fissure that is usually well demonstrated from 20 weeks’ gestation.
Congenital ventriculomegaly has an increased recurrence rate and after the birth of an affected infant a targeted neuroscan is recommended in a subsequent pregnancy.
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The ventricular system is composed of communicating cavities or ventricles, which are responsible for the production, transport, and removal of cerebrospinal fluid. The main function of the cerebrospinal fluid is to protect the brain and spinal cord from trauma, provide nutrients, and remove waste products from the cerebral metabolism. In total, there are four ventricles: right and left lateral ventricles, third ventricle, and fourth ventricle. However, a small cystic process at the end of the neural canal if frequently named (called) the fifth ventricle (see Chapter 3, Figure 3–49).
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The lateral ventricles are located within their respective hemispheres and are connected to the third ventricle via the foramen of Monro (see Chapter 3, Figure 3–61). The third ventricle is situated in between the right and the left thalamus and communicates to the distal part of the ventricular system, the fourth ventricle, via the cerebral aqueduct (see Chapter 3, Figures 3–59, 3–62, 3–88, and 3–89). Cerebral spinal fluid is formed mostly at the level of the choroid plexus and flows from the lateral ventricles through the foramina of Monro into the third ventricle, and then via the aqueduct of Sylvius into the fourth ventricle. At this level, it passes through the foramen of Magendie (in the roof of the fourth ventricle), or through the foramina of Luschka (at the sides of the fourth ventricle) into the subarachnoid space around the cerebral hemispheres. From there, cerebral spinal fluid is reabsorbed by the arachnoid granulations that are mainly distributed along the superior sagittal sinus (see Chapter 3, Figure 3–91).
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Ventriculomegaly, a term commonly employed to indicate the enlargement of the lateral cerebral ventricles, is found in ~1% of fetuses at midgestation and is the most common abnormal fetal cerebral diagnosis. Enlargement of the cerebral lateral ventricles is not an anomaly per se. The clinical significance of this finding is that it signals to the possibility of associated anomalies of the brain or other organs. The final prognosis depends more on such anomalies than on the degree of ventricular dilation. Mild forms in most cases are normal variants that are found with normal cerebral structures and are usually stable throughout gestation. ...