Sex: female
Age: 51 years
History
Hypertrophic cardiomyopathy and history of atrial fibrillation.
Laboratory data
Normal ECG on admission.
Physical findings
Right hemiplegia, disorientation, aphasia, gaze paresis and right facial paresis.
Case text
The patient presented with acute onset of transitory right hemiplegia, aphasia, disorientation, gaze paresis and right facial palsy. The patient was referred to radiology to evaluate possible vascular or tumoral lesions.
Image 1
CT Scan of the brain (5 hours after onset of symptoms).
1- Axial, 10mm thick section.
Image 2-5
Diffusion- weighted MRI of the brain, 6 hours after onset of symptoms.
2- Axial, T2- weighted (4000/ 105) image.
3 through 5- Axial, diffusion- weighted (5000/ 100), multi-slice spin-echo EPI images.
Image 6-10
Perfusion- weighted MRI of the brain, 6 hours after onset of symptoms.
Axial, perfusion- weighted (1500/ 45), dynamic gradient-echo EPI after gadolinium-enhancement.
6 and 7- Maps of relative blood flow (rCBF).
8- Mean transit time (MTT).
9 and 10- Relative cerebral blood volume (rCBV).
Image 11
MRI of the brain, 24 hours after onset of symptoms.
11- Axial, T2- weighted (4000/ 105) image.
Image 12-14
MRI of the brain, 22 days after admission.
12 through 14- Axial, T2- weighted (4000/ 105) images.
Image 1
1. Are there any abnormal findings?
Yes, there is effacement of the left fronto-parietal sulci.
2. What is your diagnosis?
These findings are compatible with infarct in the left middle cerebral artery territory.
3. What other imaging techniques could provide with more information?
Diffusion- (DWI) and perfusion- (PWI) weighted MRI.
Image 2-5
4. Are there any signs of embolism or thrombosis in the left middle cerebral artery?
Yes, there is absence of flow void in the distal M1 segment of the middle cerebral artery on the T2- weighted image.
5. Are there any signs of acute infarct on the diffusion- weighted images?
Yes, the left basal ganglia and internal capsule display areas of hyperintense signal.
Image 6-10
6. Do you detect any areas with abnormal cerebral blood flow in the brain?
Yes, there is severe hypoperfusion of the left middle cerebral artery territory when compared to the controlateral side.
7. Do you detect areas with prolonged MTT?
Yes, in the left middle cerebral artery territory a prolonged MTT is observed.
8. What does the "mismatch" between the large hypoperfused area and the hyperintense lesion at the Diffusion- weighted image represent?
This represents the territory surrounding the infarct zone which is functionally affected yet viable. It is called the penumbra zone.
9. Why is the rCBV almost normal in the left cortex?
Because there is good cortical collateral blood supply coming from the anterior and posterior cerebral arteries.
Image 11
10. Is there evidence of spontaneous reperfusion 24 hours after the first symptoms?
Yes, a flow void has reappeared in the distal M1 segment of the left middle cerebral artery.
Image 12-14
11. What is the lesion observed after 22 days?
A small left subcortical infarct is found in the corona radiata, the putamen ant he posterior limb of the internal capsule.
Final diagnosis
Thrombo- embolic infarction in the territory of the middle cerebral artery.
Differential diagnosis
None
Discussion
Diffusion- weighted imaging (DWI) demonstrates early ischaemic changes in the human brain. perfusion- weighted imaging (PWI) demonstrates hemodynamic changes in acute focal ischaemia. Therefore, a combination of the two modalities gives more information about viability of the ischaemic tissue than either modality alone.
DWI and PWI of this patient suggested that she had suffered from acute embolism of the left M1 segment of the middle cerebral artery (MCA). The initial DWI demonstrated the infarction core in the subcortical structures (basal ganglia, internal capsule) that was already irreversibly damaged within 6 hrs. The CBV was markedly reduced within the infarction core but almost normal in the adjacent cortex. This probably indicates a good cortical collateral supply coming from the anterior and posterior cerebral arteries in the initial critical phase. However, the patient experienced severe functional deterioration in the hyperacute stage, probably due to the hypoperfused penumbra zone. This was demonstrated by the reduced CBF and the prolonged MTT in the MCA territory. Within 24 h the penumbra zone recovered due to spontaneous reperfusion of the MCA and the patient rapidly improved.
DWI and PWI are new MR modalities that may come to be used to select patients who could potentially benefit from thrombolytic and/ or neuroprotective therapy in the future.