Various standardized measurements are used to follow ventricular size in infants with ultrasonography. These measurements are applied in the coronal and sagittal planes. Many studies provide reference ranges of such parameters on ultrasound in an attempt to distinguish normal from abnormal and to help clinicians improve diagnostic and therapeutic evaluation. Ratios [e.g., frontal horn ratio (FHR)] are considered to be less useful for monitoring ventricular size compared to the ventricular index. Interpretation of ventricular measurements should combine multiple lines of clinical evidence because in very premature infants considerable variation and asymmetry exist between the lateral ventricles, and variation in operator interpretation always occurs (8, 15, 47, 52, 78, 79, 88).
- Ventricular index (VI): VI is the most widely used measurement to follow ventricular growth. It is the distance between the falx and the lateral wall of the anterior horn in the coronal plane at the level of the third ventricle (foramen of Monro). Progressive ventricular enlargement as measured by the VI that exceeds 4 mm above the 97th centile for gestational age is a strong indicator for therapeutic intervention by means of CSF drainage. The VI is also superior to other measurements as a reflection of ICP in neonates with posthemorrhagic ventricular dilation.
- Other parameters: Anterior horn width (AHW), FHR, ventricular axis (VA), ventricular height (VH), and thalamo-occipital distance (TOD) are other measurements used in ultrasonography of the infant’s brain.