MEASURENT OF THE VENTRICULAR ATRIUM

• Measured in an axial plane close to the plane used to measure the BPD.
• Size = 0.65 ± 0.15cm.

< 1-1.2cm = normal
1.2-1.5cm = mild hydrocephalus
>1.5cm = marked hydrocephalus

• Low inter- and intra-observer variability.
• Measurement does vary according to gestational age (1).

Gestational age (wks)	Lateral Ventricular Atrium Diameter (mm)
	Mean ±SD	Range
14-20 21-25 26-30 31-38 All	7.6 ± 0.7 7.7 ± 0.5 7.5 ± 0.7 7.6 ± 0.5 7.6 ± 0.6	6.0-9.0 7.9-9.0 6.5-9.0 7.0-8.5 6.0-9.0

* Medial ventricular wall separation.
< 3mm = normal

3-5mm = equivocal (requires follow up as it may be normal or associated with colpocephaly, migrational disorders or early ventriculomegaly).

> 5mm = abnormal

REFERENCE

1. Cardosa JD, Goldstein BB, Filly RA. Exclusion of fetal ventriculomegaly with a single measurement: The width of the lateral ventricular atrium. Radiology 1988;169:711-714.