Investig Magn Reson Imaging.  2018 Jun;22(2):131-134. 10.13104/imri.2018.22.2.131.

Hypointensity on Susceptibility-Weighted Images Prior to Signal Change on Diffusion-Weighted Images in a Hyperacute Ischemic Infarction: a Case Study

• Kim D
• Lee H
• Jung JM
• Lee YH
• Seo HS

• KMID: 2415893
• DOI: http://doi.org/10.13104/imri.2018.22.2.131

Abstract

Susceptibility-weighted imaging (SWI) is well known for detecting the presence of hemorrhagic transformation, microbleeds and the susceptibility of vessel signs in acute ischemic stroke. But in some cases, it can provide the tissue perfusion state as well. We describe a case of a patient with hyperacute ischemic infarction that had a slightly hypodense, patchy lesion at the left thalamus on the initial SWI, with a left proximal posterior cerebral artery occlusion on a magnetic resonance (MR) angiography and delayed time-to-peak on an MR perfusion performed two hours after symptom onset. No obvious abnormal signals at any intensity were found on the initial diffusion-weighted imaging (DWI). On a follow-up MR image (MRI), an acute ischemic infarction was seen on DWI, which is the same location as the lesion on SWI. The hypointensity on the initial SWI reflects the susceptibility artifact caused by an increased deoxyhemoglobin in the affected tissue and vessels, which reflects the hypoperfusion state due to decreasing arterial flow. It precedes the signal change on DWI that reflects a cytotoxic edema. This case highlights that, in some hyperacute stages of ischemic stroke, hypointensity on an SWI may be a finding before the hyperintensity is seen on a DWI.

Keyword

Stroke, acute; Ischemia; Magnetic resonance imaging

MeSH Terms

Angiography
Artifacts
Edema
Follow-Up Studies
Humans
Infarction*
Ischemia
Magnetic Resonance Imaging
Perfusion
Posterior Cerebral Artery
Stroke
Thalamus

Figure

• 

  Fig. 1 Initial CT and MRI two hours after the onset of ischemic infarction. Susceptibility-weighted imaging showed a slight hypointensity at the left thalamus (a) with left posterior cerebral artery occlusion (b), and delayed time-to-peak (c). However, no obvious abnormal signal changes were shown on diffusion-weighted imaging (d), and T2-FLAIR (fluid attenuated inversion recovery) (d). On the brain CT, there was no evidence of brain hemorrhage (f).

• 

  Fig. 2 Follow-up MRI after two days. Acute ischemic infarction at the left thalamus showed hyperintensity on diffusion-weighted imaging (a), and T2-FLAIR (fluid attenuated inversion recovery) (b). Additionally, petechial hemorrhagic transformation in the infarcted area was noted on T2* gradient echo sequences (c).

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