Cortical ischaemic patterns in term partial-prolonged hypoxic-ischaemic injury—the inter-arterial watershed demonstrated through atrophy, ulegyria and signal change on delayed MRI scans in children with cerebral palsy

Abstract

The inter-arterial watershed zone in neonates is a geographic area without discernible anatomic boundaries and difficult to demarcate and usually not featured in atlases. Schematics currently used to depict the areas are not based on any prior anatomic mapping, compared to adults. Magnetic resonance imaging (MRI) of neonates in the acute to subacute phase with suspected hypoxic-ischaemic injury (HII) can demonstrate signal abnormality and restricted diffusion in the cortical and subcortical parenchyma of the watershed regions. In the chronic stage 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 sizable 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 term pattern of partial-prolonged HII 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 whole 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. The images presented in this pictorial review provide 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.Lack of clear anatomic structural demarcation of the inter-arterial watershed makes appreciation difficult in normal brains. Recognition of this zone and its potential involvement is essential for diagnosing partialprolonged hypoxic-ischaemic injury in term neonates.Watershed injury at any stage should be distinguished from arterial territory involvement. In the chronic phase, watershed injury must be distinguished from generalised atrophy of the brain. This pictorial review provides a template for identifying the cortical watershed distribution in milder regional or wider more severe injury in a continuum.

Connexin Hemichannel Mimetic Peptide Attenuates Cortical Interneuron Loss and Perineuronal Net Disruption Following Cerebral Ischemia in Near-Term Fetal Sheep

“…Damage to the parasagittal cortex in term infants after HI is highly associated with poor neurodevelopmental outcomes including cognitive and learning deficits and epilepsy [28][29][30][31]. In the present study, cerebral ischemia in near-term fetal sheep was associated with a pattern of parasagittal cortical damage after 7 days of recovery, which included a marked reduction in the survival of cortical GAD + , parvalbumin + , calretinin + , and calbindin + interneuron populations.…”

A pictorial review of the pathophysiology and classification of the magnetic resonance imaging patterns of perinatal term hypoxic ischemic brain injury – What the radiologist needs to know…

“…These parasagittal injuries are described at the overlapping and contiguous watershed zones between named vascular territories including the anterior watershed (between the anterior and middle cerebral artery territories), the perisylvian watershed and the posterior watershed (between the posterior and middle cerebral artery territories). 24 We have however found that injury to the parasagittal cortex (of predominantly the frontal and parietal lobes) may also be because of severe acute profound HIBI. In API parasagittal injuries, there is involvement of the perirolandic cortex as well as the paracentral lobule and the subsequent Wallerian degeneration, which leads to subsidence of the parasagittal mantle.…”

“… 14 This results in sparing of these high metabolic areas at the expense of the watershed areas of the cerebral hemispheres between the major arterial territories, especially at the borders between perfused zones, shown in Figure 13 . For term neonates, the external or cortical watershed area is more peripherally positioned at the grey–white matter interface between the major branches of the anterior and posterior circulation 24 (see Figure 14 ). The internal watershed or boundary zones are at the parasagittal subcortical white matter secondary to the cerebral arterial tree arrangement with the junction of the ventriculofugal vessels coursing outward from the ventricles and ventriculopetal vessels coursing inward from the cortex (see Figure 15 ).…”

“…FIGURE24: Axial T2-weighted image at the level of the basal nuclei performed on a 7-year-old male child. There is bifrontal encephalomalacia involving the middle and inferior frontal gyri (orange arrows) with ulegyria.…”

Pathogenesis and Prevention of Fetal and Neonatal Brain Injury

“…In severe cases the whole cortex may be involved, while with milder injury, the principal areas damaged are the interfaces between the perfusion zones of the anterior, middle and posterior cerebral arteries. An excellent schematic derived from a medicolegal database of MR images of term neonates with partial-prolonged HI injury illustrates the geography of the inter-arterial watershed zone [89].…”