Paediatric ImagingAnoxia
absent or reduced (hypoxia) oxygenation of tissues, including the brain, causing injury.
Pure anoxic/hypoxic injury to the brain is rare and occurs where there is ventilatory failure resulting in continuous normal blood flow to the brain but with decreased or absent oxygenation of that blood, for example, carbon monoxide poisoning. Carbon monoxide poisoning causes
focal abnormalities in the deep grey nuclei, specifically the globi pallidi. On
CT this is evident acutely as low attenuation areas which may be later followed by
calcification (
Fig.1). On
MRI the abnormities consist of
focal high signal in the globi pallidi on T2-weighted sequences. If
haemorrhage is present this may be seen as isodense, low or high signal depending on the age of the
haemorrhage. Clinically this may result in athetosis.
More commonly cerebral injury results from a combination of anoxia/hypoxia and decreased cerebral blood flow causing ischaemia, resulting in a combination of hypoxic and ischaemic injury. The clinical manifestation of this insult is hypoxic ischaemic encephalopathy, or anoxic ischaemic encephalopathy (AIE). HIE results from a series of pathophysiological events with a variety of causes occurring before, during or after birth, or during childhood or adulthood.
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Non-contrast enhanced CT scan of a child who presented following a house fire. Here is a large area of focal decreased attenuation in the left frontal region, due to the hypoxic ischaemic insult.
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Anoxia, Fig.1 | |