Ventriculomegaly

Overview

Ventriculomegaly is a structural anomaly whereby the lateral ventricle is 10 to 15 millimetres in diameter. It is usually diagnosed at the routine fetal anomaly ultrasound at 20 weeks, and is seen in 1–2 per 1,000 pregnancies.

Clinical features

Ventriculomegaly is subdivided according to its severity, which is determined by the diameter of the lateral ventricle (see table 1). The level of severity, together with any associated anomalies that are present, generally determines the likely impact and prognosis of ventriculomegaly.

Table 1: The subdivisions of ventriculomegaly

Classification	Lateral ventricle measurement	Presentation and prognosis
Mild	10mm–12mm	90% of patients will develop normally. 10% will have neurodevelopmental delay of varying significance.
Moderate	13mm–15mm	90% of patients will develop normally. 10% will have neurodevelopmental delay of varying significance.
Severe (also called hydrocephaly)	Over 15mm	Antenatal signs include atypically rapid head growth. Postnatal signs include seizures, irritability, unusual or extreme sleepiness and poor feeding. 50% will have neurodevelopmental delay and/or severe mental disability.

Potential genetic causes

The probability of a chromosomal or genetic cause for ventriculomegaly is inversely related to the severity of the case.

Genetic syndromes are found to be the underlying cause in 50% of cases.
10% of cases will have aneuploidy (most commonly trisomy 13, 18 or 21.
In isolated ventriculomegaly, the probability of trisomy 21 is four times as high.

Inheritance and genomic counselling

Isolated ventriculomegaly is not an inherited condition; rather, it is a structural anomaly usually detected during an ultrasound. However, ventriculomegaly in the presence of other structural anomalies can be related to a chromosomal or genetic condition. The risk of recurrence will depend on the underlying cause.

Management

At diagnosis:

prenatal genomic testing should be offered, usually by amniocentesis; and
a maternal blood sample should be taken to exclude infections, such as cytomegalovirus and toxoplasmosis.

After diagnosis:

a serial ultrasound should be performed to monitor ventricles, reassess for other anomalies and review fetal wellbeing;
an MRI, which will allow for a more detailed review of the fetal brain anatomy, should be undertaken;
a shunt should be placed if the baby is showing signs of developing hydrocephalus;
a neonatologist should assess the baby at birth; and
a referral for genomic counselling should be offered to family members if an underlying genetic cause is identified.

Resources

For clinicians

Fetal Medicine Foundation: Ventriculomegaly

For patients

Great Ormond Street Hospital for Children NHS Foundation Trust: Ventriculomegaly
International Society of Ultrasound in Obstetrics and Gynaecology: Ventriculomegaly