The posterior fontanelle: a neglected acoustic window.

The additional information, obtained when using the posterior fontanelle routinely as the second acoustic window, is illustrated in four infants. Three of them are full-term infants with hypoxic ischaemic encephalopathy. In newborn infants, who are still too unstable to be transported to the magnetic resonance unit, extensive damage in the occipital subcortical white matter and/or cortex can be visualised by performing cranial ultrasound through the posterior fontanelle.