Use of susceptibility-weighted imaging in assessing ischemic penumbra: A case report

Abstract

Rationale: The ischemic penumbra assessment is essential for the subsequent therapy and prediction of evolution in patients with acute ischemic infraction. Although controversial as a perfect equivalence to penumbra, perfusion-weighted imaging (PWI)-diffusion-weighted imaging (DWI) mismatch may predict the response to thrombolysis. Due to the reliance of PWI on contrast agents, noninvasive alternatives remain an unmet need.

Patient concerns: We reported a 65-year-old man complained of paroxysmal hemiplegia of his right limbs and anepia for 2 days, whereas the symptoms lasted for about 12 hours when he admitted to the hospital.

Diagnosis: We diagnosed it as acute ischemic stroke caused by the left middle cerebral artery stenosis.

Interventions: Susceptibility-weighted imaging (SWI), multimodal magnetic resonance imaging (MRI) work-up which includes conventional MRI sequences (T1WI, T2WI, and FLAIR), DWI, PWI.

Outcomes: His DWI-SWI mismatch was comparable to that of DWI-PWI at admission, suggesting that DWI-SWI could predict ischemic penumbra in patient with acute infarction. He refused the digital subtraction angiography examination or stenting, and he was treated with aspirin, atorvastain, and supportive treatment. The patient received a reexamination of the conventional MRI and SWI 11 days later. Expansion of the infarction in the affected MCA territory resulted from the penumbra indicated by the mismatch between DWI-SWI.

Lessons: SWI can be used as a noninvasive alternative to evaluate the ischemic penumbra. Besides, SWI can provide perfusion information comparable to PWI and SWI is sufficient to identify occlusive arteries.

Figure 1

Magnetic resonance imaging panels of the representative case. A–E were T1WI which showed no obvious abnormalities, while E–J and K–O were respectively the T2WI and the FLAIR image which revealed the hyper intense signals predominately involved in the regions of internal capsule, corona radiata, and centrum semiovale. P–T showed more extensive involvements (arrows) on DWI while U–Y the ADC maps consistent with DWI finding. ADC = apparent diffusion coefficient, DWI = diffusion-weighted imaging, FLAIR = fluid attenuated inversion recovery, T1WI = T1-weighted image.

Figure 2

Stenosed middle cerebral artery. MRA revealed a stenosis in the left MCA. MRA = magnetic resonance angiography.

Figure 3

Perfusion weighted imaging and susceptibility weighted imaging and follow-up imaging. A–E (arrows) indicated the more prolonged MTT on PWI of the affected MCA and F–J showed elevated CBV of the affected MCA. In addition, the K–O (arrows) revealed ACVS or PV on SWI in the affected MCA territory, which disappeared in the follow-up SWI, as revealed by P–T. The mismatch between DWI-PWI and DWI-SWI, indicating the ischemic penumbra, was comparable. The expansion of the infarction resulting from the penumbra in the affected MCA territory, as shown on FLAIR image during follow-up indicated by the mismatch between DWI-SWI which was comparable with that of DWI-PWI. ACVS = asymmetrical cortical vessel sign, CBV = cerebral blood volume, DWI = diffusion weighted imaging, FLAIR = fluid attenuated inversion recovery, MTT = mean transit time, PV = prominent vein, PWI = perfusion weighted imaging, SWI = susceptibility-weighted imaging.