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Imaging of Acute Cerebral Ischemia¹

¹ From the Morgan H. Russell Department of Radiology, Division of Neuroradiology, the Johns Hopkins Hospital, 600 N Wolfe St, Baltimore, MD 21287. Received April 16, 1998; revision requested June 24; final revision received January 13, 1999; accepted March 16. Address reprint requests to N.J.B. (e-mail: nbeauch@welchlink.welch.jhu.edu).

View larger version (156K): [in a new window]   Figure 1a. Left-sided hemiparesis in a 45-year-old man. (a) Axial CT scan of the head obtained 6 hours after onset of symptoms. Curved arrow denotes medial demarcation of the posterior limb of the right internal capsule. Note that the lateral margin of the right internal capsule is poorly defined due to decreased attenuation in the structure that makes up the lateral border—the lentiform nucleus. Compare this to the normal left internal capsule and left lentiform nucleus (straight arrow). (b) Axial CT scan of the head obtained superior to a. There is global decrease in gray matter-white matter differentiation in the right cerebral hemisphere that corresponds to the MCA distribution. (c) Axial CT scan of the head was obtained on hospital day 3 and demonstrates an area of increased attenuation (straight arrows) that corresponds to hemorrhage into a region of infarction. The nonhemorrhagic areas of infarction are seen as hypoattenuating (curved arrow).

View larger version (133K): [in a new window]   Figure 1b. Left-sided hemiparesis in a 45-year-old man. (a) Axial CT scan of the head obtained 6 hours after onset of symptoms. Curved arrow denotes medial demarcation of the posterior limb of the right internal capsule. Note that the lateral margin of the right internal capsule is poorly defined due to decreased attenuation in the structure that makes up the lateral border—the lentiform nucleus. Compare this to the normal left internal capsule and left lentiform nucleus (straight arrow). (b) Axial CT scan of the head obtained superior to a. There is global decrease in gray matter-white matter differentiation in the right cerebral hemisphere that corresponds to the MCA distribution. (c) Axial CT scan of the head was obtained on hospital day 3 and demonstrates an area of increased attenuation (straight arrows) that corresponds to hemorrhage into a region of infarction. The nonhemorrhagic areas of infarction are seen as hypoattenuating (curved arrow).

View larger version (153K): [in a new window]   Figure 1c. Left-sided hemiparesis in a 45-year-old man. (a) Axial CT scan of the head obtained 6 hours after onset of symptoms. Curved arrow denotes medial demarcation of the posterior limb of the right internal capsule. Note that the lateral margin of the right internal capsule is poorly defined due to decreased attenuation in the structure that makes up the lateral border—the lentiform nucleus. Compare this to the normal left internal capsule and left lentiform nucleus (straight arrow). (b) Axial CT scan of the head obtained superior to a. There is global decrease in gray matter-white matter differentiation in the right cerebral hemisphere that corresponds to the MCA distribution. (c) Axial CT scan of the head was obtained on hospital day 3 and demonstrates an area of increased attenuation (straight arrows) that corresponds to hemorrhage into a region of infarction. The nonhemorrhagic areas of infarction are seen as hypoattenuating (curved arrow).

View larger version (153K): [in a new window]   Figure 2. Acute onset of aphasia and right hemiparesis in a 27-year-old man. Axial CT scan of the head obtained 3 hours after onset of symptoms demonstrates a "hyperdense MCA sign" (curved arrow). Note that the vessel is of higher attenuation than that of the contralateral MCA.

View larger version (116K): [in a new window]   Figure 3a. Left hemiparesis upon awakening in a 56-year-old man. (a) Axial CT scan of the head obtained 2 hours after the patient awakened demonstrates subtle loss of demarcation of the posterior aspect of the insular ribbon (large straight arrow) and sulcal effacement (curved arrow). Compare the loss of the sulci on the right (curved arrow) to the normal sulci on the left (small straight arrow). Interpretation at the time of scanning did not detect these findings. (b) Axial CT scan of the head obtained 3 days after presentation demonstrates progression to infarction (straight arrows) and some petechial hemorrhage seen as areas of increased attenuation (curved arrow).

View larger version (124K): [in a new window]   Figure 3b. Left hemiparesis upon awakening in a 56-year-old man. (a) Axial CT scan of the head obtained 2 hours after the patient awakened demonstrates subtle loss of demarcation of the posterior aspect of the insular ribbon (large straight arrow) and sulcal effacement (curved arrow). Compare the loss of the sulci on the right (curved arrow) to the normal sulci on the left (small straight arrow). Interpretation at the time of scanning did not detect these findings. (b) Axial CT scan of the head obtained 3 days after presentation demonstrates progression to infarction (straight arrows) and some petechial hemorrhage seen as areas of increased attenuation (curved arrow).

View larger version (146K): [in a new window]   Figure 4a. Left hemianopsia in a 67-year-old woman. MR imaging was performed 12 hours after onset of symptoms. (a) Axial T2-weighted MR image (3,000/100 [repetition time msec/echo time msec], 5-mm section thickness, 256 x 192 matrix) demonstrates a subtle area of hyperintensity (arrow) in the right occipital lobe. Proximity to the adjacent CSF obscures this area of infarction. (b) Axial intermediate-weighted image (3,000/25, 5-mm section thickness, 256 x 192 matrix) demonstrates the area of hyperintensity (arrow) with increased conspicuity because the CSF signal was isointense to gray matter. (c) Axial FLAIR MR image (10,002/104/2,200 [repetition time msec/echo time msec/inversion time msec], 5-mm section thickness, 256 x 192 matrix) demonstrates the area of hyperintensity (arrow) with optimal conspicuity due to nulling of signal from CSF.

View larger version (165K): [in a new window]   Figure 4b. Left hemianopsia in a 67-year-old woman. MR imaging was performed 12 hours after onset of symptoms. (a) Axial T2-weighted MR image (3,000/100 [repetition time msec/echo time msec], 5-mm section thickness, 256 x 192 matrix) demonstrates a subtle area of hyperintensity (arrow) in the right occipital lobe. Proximity to the adjacent CSF obscures this area of infarction. (b) Axial intermediate-weighted image (3,000/25, 5-mm section thickness, 256 x 192 matrix) demonstrates the area of hyperintensity (arrow) with increased conspicuity because the CSF signal was isointense to gray matter. (c) Axial FLAIR MR image (10,002/104/2,200 [repetition time msec/echo time msec/inversion time msec], 5-mm section thickness, 256 x 192 matrix) demonstrates the area of hyperintensity (arrow) with optimal conspicuity due to nulling of signal from CSF.

View larger version (163K): [in a new window]   Figure 4c. Left hemianopsia in a 67-year-old woman. MR imaging was performed 12 hours after onset of symptoms. (a) Axial T2-weighted MR image (3,000/100 [repetition time msec/echo time msec], 5-mm section thickness, 256 x 192 matrix) demonstrates a subtle area of hyperintensity (arrow) in the right occipital lobe. Proximity to the adjacent CSF obscures this area of infarction. (b) Axial intermediate-weighted image (3,000/25, 5-mm section thickness, 256 x 192 matrix) demonstrates the area of hyperintensity (arrow) with increased conspicuity because the CSF signal was isointense to gray matter. (c) Axial FLAIR MR image (10,002/104/2,200 [repetition time msec/echo time msec/inversion time msec], 5-mm section thickness, 256 x 192 matrix) demonstrates the area of hyperintensity (arrow) with optimal conspicuity due to nulling of signal from CSF.

View larger version (130K): [in a new window]   Figure 5a. Acute onset of right hemiparesis and aphasia in a 52-year-old man. CT scan was obtained 4 hours after onset of symptoms and demonstrated a left frontoparietal intraparenchymal hematoma. MR images were obtained 7 hours after onset of symptoms. (a) Axial CT scan of the head demonstrates a central area of increased attenuation (curved arrow) compatible with a hemorrhage. Peripherally, there is surrounding edema manifested as decreased attenuation (straight arrows). (b) Axial intermediate-weighted MR image (3,000/25, 5-mm section thickness, 256 x 192 matrix) demonstrates diffuse hyperintensity in the left frontoparietal lobe (straight arrow). There is a more focal area posteriorly that is heterogeneous (curved arrow). (c) Axial GRE image (3,000/25, 23° flip angle, 5-mm section thickness, 256 x 192 matrix) demonstrates marked hypointensity (curved arrow) compatible with a hematoma. This demonstrates the increased sensitivity of GRE images for the detection of intraparenchymal hemorrhage.

View larger version (115K): [in a new window]   Figure 5b. Acute onset of right hemiparesis and aphasia in a 52-year-old man. CT scan was obtained 4 hours after onset of symptoms and demonstrated a left frontoparietal intraparenchymal hematoma. MR images were obtained 7 hours after onset of symptoms. (a) Axial CT scan of the head demonstrates a central area of increased attenuation (curved arrow) compatible with a hemorrhage. Peripherally, there is surrounding edema manifested as decreased attenuation (straight arrows). (b) Axial intermediate-weighted MR image (3,000/25, 5-mm section thickness, 256 x 192 matrix) demonstrates diffuse hyperintensity in the left frontoparietal lobe (straight arrow). There is a more focal area posteriorly that is heterogeneous (curved arrow). (c) Axial GRE image (3,000/25, 23° flip angle, 5-mm section thickness, 256 x 192 matrix) demonstrates marked hypointensity (curved arrow) compatible with a hematoma. This demonstrates the increased sensitivity of GRE images for the detection of intraparenchymal hemorrhage.

View larger version (136K): [in a new window]   Figure 5c. Acute onset of right hemiparesis and aphasia in a 52-year-old man. CT scan was obtained 4 hours after onset of symptoms and demonstrated a left frontoparietal intraparenchymal hematoma. MR images were obtained 7 hours after onset of symptoms. (a) Axial CT scan of the head demonstrates a central area of increased attenuation (curved arrow) compatible with a hemorrhage. Peripherally, there is surrounding edema manifested as decreased attenuation (straight arrows). (b) Axial intermediate-weighted MR image (3,000/25, 5-mm section thickness, 256 x 192 matrix) demonstrates diffuse hyperintensity in the left frontoparietal lobe (straight arrow). There is a more focal area posteriorly that is heterogeneous (curved arrow). (c) Axial GRE image (3,000/25, 23° flip angle, 5-mm section thickness, 256 x 192 matrix) demonstrates marked hypointensity (curved arrow) compatible with a hematoma. This demonstrates the increased sensitivity of GRE images for the detection of intraparenchymal hemorrhage.

View larger version (155K): [in a new window]   Figure 6a. Acute onset of left-sided hemiparesis in a 43-year-old woman with hypertension. CT was performed 4 hours after onset of symptoms. MR imaging was performed 12 hours after onset of symptoms. (a) Axial CT scan of the head was interpreted as normal. Note that the insular ribbons (straight arrows), the gray matter-white matter differentiation (arrowhead), and the internal capsules (curved arrows) are normal. (b) Axial FLAIR MR image(10,002/104/2,200, 5-mm section thickness, 256 x 192 matrix) demonstrates no evidence of a right hemispheric infarction. (c) Three-dimensional time-of-flight MR angiogram (53/4.1, 1.1- mm section thickness, 512 x 192 matrix) demonstrates occlusion (arrow) of the right MCA, potentially amenable to thrombolysis.

View larger version (158K): [in a new window]   Figure 6b. Acute onset of left-sided hemiparesis in a 43-year-old woman with hypertension. CT was performed 4 hours after onset of symptoms. MR imaging was performed 12 hours after onset of symptoms. (a) Axial CT scan of the head was interpreted as normal. Note that the insular ribbons (straight arrows), the gray matter-white matter differentiation (arrowhead), and the internal capsules (curved arrows) are normal. (b) Axial FLAIR MR image(10,002/104/2,200, 5-mm section thickness, 256 x 192 matrix) demonstrates no evidence of a right hemispheric infarction. (c) Three-dimensional time-of-flight MR angiogram (53/4.1, 1.1- mm section thickness, 512 x 192 matrix) demonstrates occlusion (arrow) of the right MCA, potentially amenable to thrombolysis.

View larger version (75K): [in a new window]   Figure 6c. Acute onset of left-sided hemiparesis in a 43-year-old woman with hypertension. CT was performed 4 hours after onset of symptoms. MR imaging was performed 12 hours after onset of symptoms. (a) Axial CT scan of the head was interpreted as normal. Note that the insular ribbons (straight arrows), the gray matter-white matter differentiation (arrowhead), and the internal capsules (curved arrows) are normal. (b) Axial FLAIR MR image(10,002/104/2,200, 5-mm section thickness, 256 x 192 matrix) demonstrates no evidence of a right hemispheric infarction. (c) Three-dimensional time-of-flight MR angiogram (53/4.1, 1.1- mm section thickness, 512 x 192 matrix) demonstrates occlusion (arrow) of the right MCA, potentially amenable to thrombolysis.

View larger version (122K): [in a new window]   Figure 7a. Acute onset of left-sided hemiparesis in a 72-year-old man. MR images were obtained 4 hours after ictus. (a) Axial T2-weighted image (3,000/100, 5-mm section thickness, 256 x 192 matrix) demonstrates no evidence of abnormality. (b) Axial, single-shot echo-planar diffusion-weighted image (5,000/126, 5-mm section thickness, 128 x 128) demonstrates two areas of hyperintensity (arrows) in the right MCA distribution. This finding is compatible with an acute infarct. (c) Axial, pure diffusion Dav MR image (5,000/126, 5-mm section thickness, 128 x 128 matrix) demonstrates decreased signal intensity (arrows) in the right MCA distribution. The areas of decreased ADC (hypointensity) correspond to an acute infarct.

View larger version (116K): [in a new window]   Figure 7b. Acute onset of left-sided hemiparesis in a 72-year-old man. MR images were obtained 4 hours after ictus. (a) Axial T2-weighted image (3,000/100, 5-mm section thickness, 256 x 192 matrix) demonstrates no evidence of abnormality. (b) Axial, single-shot echo-planar diffusion-weighted image (5,000/126, 5-mm section thickness, 128 x 128) demonstrates two areas of hyperintensity (arrows) in the right MCA distribution. This finding is compatible with an acute infarct. (c) Axial, pure diffusion Dav MR image (5,000/126, 5-mm section thickness, 128 x 128 matrix) demonstrates decreased signal intensity (arrows) in the right MCA distribution. The areas of decreased ADC (hypointensity) correspond to an acute infarct.

View larger version (112K): [in a new window]   Figure 7c. Acute onset of left-sided hemiparesis in a 72-year-old man. MR images were obtained 4 hours after ictus. (a) Axial T2-weighted image (3,000/100, 5-mm section thickness, 256 x 192 matrix) demonstrates no evidence of abnormality. (b) Axial, single-shot echo-planar diffusion-weighted image (5,000/126, 5-mm section thickness, 128 x 128) demonstrates two areas of hyperintensity (arrows) in the right MCA distribution. This finding is compatible with an acute infarct. (c) Axial, pure diffusion Dav MR image (5,000/126, 5-mm section thickness, 128 x 128 matrix) demonstrates decreased signal intensity (arrows) in the right MCA distribution. The areas of decreased ADC (hypointensity) correspond to an acute infarct.

View larger version (19K): [in a new window]   Figure 8. Simulated gamma-variate functions at constant blood volume for three different relative blood flows. The shaded gamma variant function depicts the values of interest including time to peak (b) and peak height (c). The bolus delay (a) is also depicted. The shaded area is proportional to regional cerebral blood volume.

View larger version (111K): [in a new window]   Figure 9a. Right hemiparesis in a 37-year-old man. MR imaging was performed 8 hours after ictus. (a) Axial diffusion-weighted image (5,000/126, 5-mm section thickness, 128 x 128) demonstrates a focal area of hyperintensity (arrow) in the left corona radiata and centrum semiovale. This lesion is too focal to explain the patient's symptom complex. (b) Axial echo-planar perfusion MR image (5,000/50, 5-mm section thickness, 128 x 128 matrix) is scaled such that hyperintensity corresponds to delayed time to peak. Note that the area of delayed arrival time (arrows) is larger than the diffusion abnormality. The area of demonstrated abnormality better corresponds to the patient's deficits. This appearance corresponds to the theoretic model of the penumbra.

View larger version (108K): [in a new window]   Figure 9b. Right hemiparesis in a 37-year-old man. MR imaging was performed 8 hours after ictus. (a) Axial diffusion-weighted image (5,000/126, 5-mm section thickness, 128 x 128) demonstrates a focal area of hyperintensity (arrow) in the left corona radiata and centrum semiovale. This lesion is too focal to explain the patient's symptom complex. (b) Axial echo-planar perfusion MR image (5,000/50, 5-mm section thickness, 128 x 128 matrix) is scaled such that hyperintensity corresponds to delayed time to peak. Note that the area of delayed arrival time (arrows) is larger than the diffusion abnormality. The area of demonstrated abnormality better corresponds to the patient's deficits. This appearance corresponds to the theoretic model of the penumbra.

View larger version (44K): [in a new window]   Figure 10a. Dense left-sided hemiparesis, severe dysarthria, and a central seventh nerve palsy in a 56-year-old man. Conventional T2-weighted MR image obtained 24 hours after ictus (image labeled T2 in b) demonstrated no areas of hyperintensity. MR angiogram (not shown) demonstrated an occlusion or high-grade stenosis of the right MCA. Multisection two-dimensional proton spectroscopic axial images (2,300/272, 15-mm section thickness, 32 x 32 matrix) (not shown) were also obtained at this time. Cho = choline, Cr = creatine and phosphocreatine, Lac = lactate, PPM = parts per million. (a) Spectra obtained from four regions in the brain show areas of NAA and lactate abnormality on the right (zones labeled 1 and 2). Conversely, the spectra obtained from the left cerebral hemisphere (zones labeled 3 and 4) are normal. Note the absence of a lactate peak in the left hemisphere. (b) Metabolite axial MR images (2,300/272, 15-mm section thickness, 32 x 32 matrix) demonstrate an area of NAA decrease (straight arrow) with surrounding lactate elevation (curved arrow). In the area of NAA decrease and highest lactate levels, there was progression to infarction. This appearance corresponds to the theoretic model of the penumbra.

View larger version (54K): [in a new window]   Figure 10b. Dense left-sided hemiparesis, severe dysarthria, and a central seventh nerve palsy in a 56-year-old man. Conventional T2-weighted MR image obtained 24 hours after ictus (image labeled T2 in b) demonstrated no areas of hyperintensity. MR angiogram (not shown) demonstrated an occlusion or high-grade stenosis of the right MCA. Multisection two-dimensional proton spectroscopic axial images (2,300/272, 15-mm section thickness, 32 x 32 matrix) (not shown) were also obtained at this time. Cho = choline, Cr = creatine and phosphocreatine, Lac = lactate, PPM = parts per million. (a) Spectra obtained from four regions in the brain show areas of NAA and lactate abnormality on the right (zones labeled 1 and 2). Conversely, the spectra obtained from the left cerebral hemisphere (zones labeled 3 and 4) are normal. Note the absence of a lactate peak in the left hemisphere. (b) Metabolite axial MR images (2,300/272, 15-mm section thickness, 32 x 32 matrix) demonstrate an area of NAA decrease (straight arrow) with surrounding lactate elevation (curved arrow). In the area of NAA decrease and highest lactate levels, there was progression to infarction. This appearance corresponds to the theoretic model of the penumbra.