Cerebral intraparenchymal hyperattenuation post thrombolysis

Last revised by Frank Gaillard on 8 Feb 2024

Cerebral intraparenchymal hyperattenuations have been increasingly recognized on CT scans following mechanical thrombectomy for the treatment of thromboembolic ischemic stroke 1-3. They can also be seen following intravenous thrombolysis (without catheter angiography) 4.

The distribution of cerebral intraparenchymal hyperattenuation correlates with the eventual volume of infarction – in other words, the pre-procedural infarct core plus any portions of penumbra which despite treatment will go on to infarct 1

As such, intraparenchymal hyperattenuations immediately following mechanical thrombectomy or thrombolysis, observed either on conventional multi-detector CT or flat-panel CT, can provide prognostic information as to the eventual volume of infarction 1


The term is deliberately vague to encompass both contrast staining and petechial hemorrhagic change as distinguishing between the two is not always easy. An alternative term sometimes used is postinterventional cerebral hyperdensity 2.

Radiographic features

Distinguishing between contrast staining and petechial hemorrhagic transformation is not easy, particularly when obtained on current flat-panel CT

Contrast staining

Contrast staining typically appears as areas of hyperdensity mostly confined to grey matter (cortex and deep grey matter) and represent areas of blood-brain barrier breakdown secondary to ischemia with microvascular extravasation of contrast into the extracellular space 1. Typically such staining clears within the first 19-24 hours after the procedure 2

Dual-energy CT is also able to distinguish hyperdensity due to contrast versus hyperdensity due to hemorrhage 3

Petechial hemorrhagic transformation

Petechial hemorrhagic transformation of an ischemic infarct (as opposed to macroscopic solid cerebral hemorrhages also sometimes encountered) can have a very similar appearance. Follow-up CT performed at least 19-24 hours following intervention is the most specific way to differentiate, with persistent hyperdensity consistent with hemorrhage whereas contrast staining will reduce in density over time 2.

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