Stroke: Acute infarction - radiology video tutorial (CT, MRI, angiography)

Aug 26, 2023

Stroke: Acute infarction - radiology video tutorial (CT, MRI, angiography)

“Stroke Series” video 3 of 7: Acute ischaemic stroke. Presented by Neuroradiologist Dr Frank Gaillard.

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Content

6.76 -> hello again this is frank gaillard from radiopaedia.org and today we're going

9.94 -> to be discussing the imaging off acute ischemic stroke.

14.139 -> in most instances

15.57 -> cerebral ischaemia

17.08 -> results from a thromboembolism

19.519 -> either from the heart

22.029 -> or from other carotids.

24.06 -> rarelt it is also due to paradoxical emboli through the

28.269 -> patent foramen ovale.

30 -> or from aortic atherosclerotic disease disease;

33.75 -> this is seen most commonly in the setting of

36.35 -> either angiography

38.88 -> cardiac surgery.

40.59 -> in-situ thrombosis within the cerebral circulation

44.29 -> is seen either superimposed on the pre-existing arteriosclerotic disease or in

50.43 -> the setting of arterial dissection.

52.57 -> imaging of acute stroke is performed either with CT or MRI.

57.14 -> the majority of imaging of acute strokes is performed with CT although MRI

62.32 -> is in fact more sensitive.

64.41 -> the reason for this is mainly to do with availability of MRI

68.47 -> and the ability to get a patient in and out of the CT scanner rapidly

72.89 -> without the concern for MRI compatible resuscitation equipment.

76.97 -> the mainstay of the imaging of acute ischemic stroke is with a non contrast

80.52 -> CT brian

81.31 -> although increasingly in the setting off ischemic strokes this is being

84.84 -> supplemented with CT angiography

87.77 -> and CT perfusion.

89.88 -> let's focus on the hypercube findings in ischemic stroke.

93.97 -> this can be divided into two main sections one is direct visualization of

98.299 -> the clot or embolism

100.54 -> and this can be seen immediately,

103.03 -> or early parenchymal changes which can be seen as early as within one hour of

107.65 -> onset of symptoms.

109.29 -> the hyperdence artery is a well-known sign on non contrast CT scan

114.46 -> and represents direct visualisation of the clot within the lumen of the

118.34 -> occluded artery.

119.59 -> it relies on the fact that clot it

122.85 -> hyperdense when compared to normal flowing blood however this depends on

127.66 -> what the age of the thromboembolism.

130.559 -> flowing blood

131.519 -> typically has a density of approximately 40 HU,

135.59 -> although this varies depending on the haematocrit and state of hydration.

139.639 -> acute thrombus is not significant denser than this however with time

144.18 -> it becomes progressively more hyperdense

147.03 -> reaching densities of up to a 100 HU.

150.339 -> fortunately the majority of ischaemic strokes are due to thromoemblism

153.839 -> which is caused by clot forming either in the carotid or within

157.989 -> the heart.

159.469 -> as such the clot that eventually embolises and occludes intracranial

163.069 -> circulation

164.629 -> has been present for some time

166.659 -> and is significantly hyperdense.

169.379 -> in this case we can see the right M1 segment of the middle cerebral artery

174.15 -> is much denser than any of the other arteries seen.

177.949 -> in this second case

179.479 -> thromboembolism has occurred to the top of the basilar artery which is much

184.219 -> more dense than the internal carotid arteries at the same level.

188.209 -> we can confirm direct visualization off the clot by performing CT angiography

193.749 -> which allows the segment which appears hyperdense on non contrast imaging to

198.059 -> appear as hypo enhancement or a filling defect on CT angiography. The same

203.489 -> direct visualisation can be seen on catheter angiography.

207.299 -> in this case the M1 segment is occluded and we can see collateral flow across

212.579 -> from the anterior cerebral circulation

215.649 -> to supply part at least of the middle cerebral artery territory.

220.029 -> the two regions that are affected most profoundly in acute occlusion of the

224.599 -> supraclinoid internal carotid artery, usually the M1 branch,

228.829 -> are the basal ganglia

230.24 -> particularly the caudate head and the lentiform nucleus,

233.759 -> and the insular cortex.

236.109 -> the basal ganglia are supplied by lenticulostriate perforating arteries which are

240.449 -> end arteries

241.649 -> and as such no collateral circulation is available to them.

245.379 -> the insular cortex, although capable of receiving collateral circulation, is the

249.499 -> most distant part of the cortex from the anterior cerebral artery and posterior cerebral

253.519 -> artery.

254.289 -> when ischemic

255.34 -> gray matter becomes hypodense and the gray white matter differentiation

259.979 -> becomes lost. this can be seen as early as within one hour of occlusion

264.9 -> and in up to seventy percent of patients it is seen within three hours.

268.69 -> the rest of the cortex because of the collateral circulation tends to be more

273.75 -> delayed in demonstrating changes on CT.

277.519 -> in this case we can see a hyperdense middle cerebral artery with vague

282.039 -> hypodensity of the surrounding cortex of the temple pole.

285.92 -> this is a little more pronounced on the slice more superior where there is blurring

290.07 -> of the lentifform nucleus and loss of the grey white differentiation of the

294.71 -> insular cortex. this is difficult to appreciate on standard windowing of

298.63 -> non contrast CT

300.57 -> but can be made more conspicuous by narrowing the window. here we can see

304.25 -> loss of the grey white matter differentiation particularly affecting insular cortex.

308.819 -> this is nonetheless subtle but is worth seeking as in many cases the

313.02 -> hyperdense artery will not be visible

315.3 -> and this may be the only sign available to confirm the presence of an acute

319.79 -> infarct.

320.849 -> in this case CT perfusion was performed which demonstrates

324.569 -> prolongation of Tmax and mean transit time but no significant

329.5 -> difference in cerebral blood volume or cerebral blood flow.

333.249 -> the region of ischemic penumbra

335.21 -> which is the area which has not infarcted, and is potentially salvageable by

339.46 -> reperfusion, on CT profusion is taken to be the mismatch between cerebral

344.02 -> blood flow and prolongation of Tmax; in this case shaded in green.

349.57 -> this patient went on to have an attempted clot retrieval which

352.949 -> unfortunately was unsuccessful.

355.3 -> A scan performed a few days later confirms evolution of the middle

359.36 -> cerebral artery territory infarct.

361.999 -> MRI is extremely sensitive to acute ischemia

365.069 -> with changes seen on diffusion weighted imaging and apparent diffusion

368.85 -> coefficient maps within a few minutes of onset.

372.37 -> these appear as bright areas on diffusion and dark areas on ADC maps.

377.699 -> as mentioned before, MRI is usually not used

380.549 -> in the very acute setting as it imposes to greater delay in

385.549 -> attempting to treat the patient either with intravenous thrombolysis, or intra

390.289 -> arterial thrombolysis or mechanical thrombectomy.

393.979 -> in summary the imaging of acute cerebral ischemia revolves around either

398.979 -> detecting the clot

401.229 -> or detecting early parenchymal changes.

403.83 -> this is most commonly done with CT

406.3 -> but can also be performed with MRI if available.

410.3 -> more information and many additional cases are available of course on

414.409 -> radiopaedia.org.

415.789 -> make sure you check out the other episodes in this series on imaging of

419.669 -> stroke.

421.269 -> see you next time

Source: https://www.youtube.com/watch?v=H4xErylBd1g