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Today, we're going to talk about global ischemia.

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Global ischemia is ischemia

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affecting the whole brain.

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The most common causes are cardiac arrest

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or severe systemic hypotension.

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You can also get it from carbon monoxide poisoning,

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because, remember, carbon monoxide

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replaces oxygen on the hemoglobin molecule.

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The structures that are preferentially affected

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are the structures that have the highest

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metabolic demands.

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So, remember, cortex, deep gray nuclei,

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cerebellum is less common,

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and then a pure white matter pattern

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is present at times.

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And we're going to talk about

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that with delayed hypoxia.

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But these are images of a 29 year old female

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who had cardiac arrest following

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the heroin overdose.

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And what you see is kind of a super scan.

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There's too much differentiation

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between gray and white matter.

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There's diffuse hyperintensity on the diffusion

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weighted images throughout the cortex,

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and the deep gray nuclei,

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including the lentiform nuclei,

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the caudate nuclei, and then also the thalami.

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And these areas are all dark or have restricted

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diffusion on the ADC maps.

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They're also bright on the FLAIR images,

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the coal cortex and the basal ganglia.

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And you can see that the lentiform nuclei and

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globus pallidi are a little bit brighter.

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And that's probably because

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they were affected first.

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Now, carbon monoxide poisoning,

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when it's severe, it can show you the whole brain,

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like I just showed you in the last images.

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But if you have less severe carbon monoxide

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poisoning and you image early,

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it affects the globus pallidi first.

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So, this patient has restricted diffusion

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characterized by hyperintensity in

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the globus pallidi on DWI images,

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hypointensity on ADC images,

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and hyperintensity on FLAIR images.

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So that's early,

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relatively minor carbon monoxide poisoning.

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There's a white matter pattern that's

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caused by delayed hypoxia.

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So, 2-3% of patients have this

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after global hypoxic insult.

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And what they have is they have an acute

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neurologic deficit or decline two to three

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weeks after the initial hypoxic insult.

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And they'll have diffuse

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confluent areas of restricted diffusion and FLAIR

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hyperintensity throughout the cerebral white matter.

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So, these are images of a 69-year-old female

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who had respiratory depression after surgery,

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was altered, then she got better,

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then she got progressively worse

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a couple of weeks later.

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And you can see the white matter is diffusely

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hyperintense on the FLAIR images,

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the periventricular and subcortical white matter.

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And it's all bright on the DWI images.

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Again, just including all the white matter,

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including the superficial and deep white matter,

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including the corpus callosum here,

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and all the subcortical white matter.

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And it's marked by dark signal in the ADC images,

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indicating restricted diffusion.

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So, this is delayed hypoxia preferentially

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affecting the white matter.