Purpose or Case Report: The inter-arterial watershed zone in neonates is a geographic area without discernible anatomic boundaries, is difficult to demarcate and usually not featured in atlases. Schematics currently used to depict the areas are not based on any prior anatomic mapping, as compared to adults. Magnetic resonance imaging (MRI) of neonates in the acute to subacute phase with suspected hypoxic ischaemic injury can demonstrate signal abnormality and restricted diffusion in the cortical and subcortical parenchyma of the watershed regions, although this can often be subtle.

In contrast, in the chronic stage of evolution of partial prolonged hypoxic-ischaemic injury, atrophy and ulegyria can make the watershed zone more conspicuous as a region. Our aim is to use images extracted from a large medicolegal database (approximately 2000 cases), of delayed MRI scans in children with cerebral palsy, to demonstrate the watershed region.

To achieve this, we have selected cases diagnosed on imaging as having sustained a pattern of term, partial-prolonged hypoxic-ischaemic injury affecting the hemispheric cortex, based on the presence of bilateral, symmetric atrophy with ulegyria. From these we have identified those patients demonstrating injury along the entire watershed continuum as well as those demonstrating selective anterior or posterior watershed predominant injury for demonstration.

Recognition of this zone is essential for diagnosing partial-prolonged hypoxic-ischaemic injury sustained in term neonates, which also has implications for potential compensation in litigation. The set of images presented in this pictorial review provides a template for identifying the cortical watershed distribution when there is milder regional (anterior, parasagittal, peri-Sylvian and posterior) watershed injury and for more severe injury where multiple regions are injured in combination or as a continuum.
Methods & Materials:
Results:
Conclusions: