Sex: female
Age: 88 years
History
History of stroke in the left fronto-temporal region.
Laboratory data
None.
Physical findings
Aphasic and right hemiparesis
Case text
The patient presented with a sudden onset of aphasia and right hemiparesis 3 hours prior to radiological investigations.
Image 1-4
MRI of the brain, 3 hours after onset of symptoms.
1- Axial, diffusion- weighted (DWI) images.
2- Axial, apparent diffusion coefficient (ADC) images.
3- Axial, FLAIR images.
4- Axial, contrast- enhanced, T1- weighted images.
Image 5-7
MR Angiogram (MRA) and perfusion- weighted MRI, 3 hours after onset of symptoms.
5- 3D, TOF angiogram on the circle of Willis.
Axial, perfusion- weighted (PWI) after contrast-enhancement:
6- Relative cerebral blood volume (rCBV) maps.
7- time to peak (TtoP) maps.
Image 8-11
MRI of the brain, 7 days after onset of symptoms.
8- Axial DWI.
9- Axial, apparent diffusion coefficient (ADC) images.
10- Axial, FLAIR images.
11- Axial, contrast- enhanced, T1- weighted images.
Image 12-14
MR Angiogram (MRA) and perfusion- weighted MRI and MRI, 3 hours after onset of symptoms.
12- 3D, TOF angiogram on the circle of Willis.
13- Axial, relative cerebral blood volume (rCBV) maps from PWI after contast-enhancement.
14- Axial, FLAIR image.
Image 1-7
1. What are the abnormalities observed?
On the DWI images a hyperintense area with low ADC in the left frontal and temporal lobe is observed. This lesion is compatible with an area of acute ischemic damage. FLAIR images show an old infarct on the left frontal region, but do not demonstrate the acute lesion. Enhanced T1 images demonstrate vascular enhancement in a region corresponding to the acute ischemic area. This represents slow collateral arterial flow. The rCBV and the TtoP maps show an area of altered hemodynamics in the left frontal, temporal, and parietal lobes in the presence of preserved cerebral blood volume and increased bolus transit time.
2. By comparing the FLAIR T2 images and the DWI images, can you say anything about the timing of the lesions?
The observation of a hyperintense area on DWI with low ADC which is not objectivized on the FLAIR sequences speaks in favour of an acute ischemic infarct presumably occurring within 8 to 12 hours prior to the investigations.
3. Can you see any abnormality on the MRA images?
The MRA images show reduced flow in the left middle cerebral artery with poor representation of the peripheral branches. Asymmetry of flow within the internal carotid arteries is also observed in favour of the left.
4. What is the diagnosis in the first study?
Acute left fronto-temporal infarction.
Image 9-14
5. What are the main changes in the follow-up study?
The DW images and the ADC maps demonstrate that the area of infarction is larger than the one observed in the initial study. It now includes a small region located in the posterior left parietal lobe close to the lateral ventricle. On the initial study, this area corresponded to an area of altered hemodynamics only.
6. Did you have sufficient information from the first study to predict the final outcome? And if so from which images?
The final area of infarction was already suggested by the area of increased vascular transit time surrounding the hyperintense lesion observed on DWI images.
Final diagnosis
Acute ischemia in the left middle cerebral artery territory .
Differential diagnosis
None.
Discussion
Cerebrovascular ischemic disease is the third death cause and one of the major morbidity causes in the United States and in Europe. Therapy to improve outcome with the use of neuroprotective or thrombolytic drugs is still under investigation in several clinical trials. The development of effective stroke therapies is based primarily on the concept of salvaging ischemic tissue that is not irreversibly injured. Such salvageable ischemic tissue must be distinguished from non salvageable ischemic tissue that has evolved to a status in which functional recovery is no longer possible. Although several authors have attempted to relate the metabolic and hemodynamic changes associated to irreversible injury to changes in DWI and in PWI, neither of the two imaging strategies has so far proved to be the only predictor of the final outcome. The combined use of these two techniques, however is extremely valuable in detecting the presence of cerebral ischemia in an hyperacute phase and in delineating the territory only reversibly injured but at risk of infarction.
In the present case, imagery included conventional MRI sequences and PWI and DWI sequences. The perfusion study was processed to generate maps of the relative cerebral blood volume (rCBV) and of the time to peak (TtoP ). The TtoP map can be used as a rough estimate of the transit time of the contrast agent in the brain, and has recently been indicated as a valuable predictor of the tissue at risk. The DWI images were acquired with gradients in three directions and used to generate isotropic ADC maps.
The FLAIR images obtained at the time of the first study showed changes related to the previous stroke. On the DWI images a new ischemic lesion was observed, which was not yet evident on the conventional study. This area, however, was smaller than the area of altered hemodynamics as seen on the perfusion maps. The final infarction involved tissue severely injured at the time of the first study as seen on DWI and extended beyond this area to tissue which, although yet damaged, showed altered hemodynamics.
Diffusion and perfusion MRI (DWI and PWI) can monitor the evolution of tissue injury from acute ischaemia to chronic infarction, and provide a means for monitoring the metabolic and hemodynamic changes in the acute stage. The combination of DWI and PWI provides information upon tissue at risk of infarction and can help predict stroke outcome.