Ventriculomegaly and hydrocephalus

Definition

• Fetal ventriculomegaly is a prenatally detected enlargement of the lateral ventricles with a diameter of 10 mm or more in the axial transventricular plane.
• Hydrocephalus denotes a symptomatic accumulation of CSF in the cerebral ventricles due to obstructed CSF flow or impaired absorption.

Classification

• By ventricular diameter, mild (10 to 12 mm), moderate (13 to 15 mm) and severe forms (16 mm or more) are distinguished.
• It is considered isolated when no further structural or genetic abnormalities are identified on ultrasound.

Occurrence & epidemiology

Epidemiology

• It occurs in about 2 per 1,000 live births and is one of the most common fetal anomalies detected in the second trimester.

Aetiopathogenesis

Aetiology

• Causes are parenchymal loss, obstruction and overproduction of CSF; the most common structural causes are aqueductal stenosis, Chiari II malformation, dysgenesis of the corpus callosum and posterior fossa anomalies.
• Chromosomal abnormalities are found in 2 to 12%, most commonly trisomy 21; intrauterine infections such as toxoplasmosis, rubella, CMV and herpes simplex in about 5%.

Clinical features

• Neurodevelopment depends mainly on severity and associated anomalies; severe forms usually have obstructive causes and are associated with hydrocephalus.

Diagnosis

• The normal ventricular diameter is 4.5 to 7.6 mm between 15 and 40 weeks; the atrium remains stable during the second and third trimesters.
• Fetal MRI detects additional abnormalities in about 50% of cases; genetic testing uses karyotyping and chromosomal microarray.

Keep learning in the app

Further reading (selection)

1. StatPearls: Hydrocephalus (NCBI Bookshelf)

Cross-references