Table 1 Neuroimaging severity categorisation [2,49-57]

Preterm injury

• Cranial ultrasound scan (cUSS)

• Normal

• Grade III IVH

• Grade IV IVH

• Grade I/II Intraventricular haemorrhage (IVH)

• Non-cystic Periventricular leucomalacia (PVL)

• Periventricular haemorrhage infarction (PVHI)

• Ventricular index (VI) < 13 mm Term equivalent age (TEA) OR

• VI 13-15 mm TEA OR

• Cystic PVL

• VI < 97^th percentile for corrected gestational age (CGA)

• VI >97^th percentile but < 4 mm above 97^th percentile for CGA

• Subcortical leucomalacia

• VI at TEA >15 mm OR

• VI >4 mm above 97^th percentile for CGA

• Basal ganglia (BG) lesions

• Focal infarction

Term hypoxic ischaemic encephalopathy

• Magnetic resonance imaging (MRI)

• Focal subtle abnormalities of BG with normal appearance of the posterior limb of the internal capsule (PLIC)

• Multi-focal lesions in BG with equivocal or abnormal signal intensity within PLIC

• Widespread abnormalities involving all Basal ganglia-Thalamus (BGT) structures and PLIC

• cUSS where MRI unavailable

• Periventricular white matter changes difficult to differentiate from normal appearances and therefore not classified as abnormal

• Small focal lesions of without loss of grey matter (GM)/WM differentiation.

• Larger areas of abnormality with loss of GM/WM differentiation, consistent with infarction

• Changes confined to cerebral cortex and subcortical white matter (WM)

• Central grey matter hyperechogenicity +/− more extensive cortical and subcortical hyperechogenicity

Term infarction

• MRI (cUSS where MRI unavailable)

• Focal, non-territorial infarct

• Territorial infarct