American Journal of Neuroradiology 28:316-317, February 2007
© 2007 American Society of Neuroradiology
Case Report
BRAIN
Imaging Cerebral Amyloid Angiopathy with Susceptibility-Weighted Imaging
E.M. Haackea,
Z.S. DelPropostob,
S. Chaturvedic,
V. Sehgalb,
M. Tenzere,
J. Neelavallid and
D. Kidof
a Institute for Biomedical Research, Detroit, Mich
b Department of Radiology, Wayne State University, Detroit, Mich
c Department of Neurology, Wayne State University, Detroit, Mich
d Department of Biomedical Engineering, Wayne State University, Detroit, Mich
e School of Medicine, Wayne State University, Detroit, Mich
f Loma Linda University, Loma Linda, Calif
Address correspondence to E. Mark Haacke, PhD, 440 East Ferry St, Detroit, MI 48202; e-mail: nmrimaging{at}aol.com
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Abstract
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SUMMARY: Gradient-echo (GE) imaging is recognized as a means
to detect hemorrhagic changes in cerebral amyloid angiopathy
(CAA). However, almost 25% of patients with CAA do not show
microhemorrhages on T2* GE imaging. We applied a new imaging
method, susceptibility weighted imaging (SWI), to evaluate the
presence of microhemorrhages. In a suspected case of CAA, where
cognitive effects are also present, we show that SWI is much
more sensitive in detecting microhemorrhages than conventional
methods.
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Introduction
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Susceptibility-weighted imaging (SWI) is a new imaging method
that maximizes sensitivity to magnetic susceptibility effects
1,2 and is clinically useful for evaluating trauma and vascular
malformations.
3,4 However, the role of SWI in other neuropathology
has not been extensively evaluated. SWI is more sensitive than
conventional gradient-echo (GE) techniques for the detection
of blood products.
4 Because GE imaging is a well-recognized
method of detecting changes indicative of cerebral amyloid angiopathy
(CAA),
5–8 SWI should be successful as well. This is the
first reported evaluation of SWI in a patient with suspected
CAA showing marked increased sensitivity to the detection of
microhemorrhages compared with conventional GE sequences.
CAA is a vascular disease often associated with stroke, especially recurrent hemorrhagic stroke. However, its presentation is varied; depending upon severity, it may not be diagnosed until autopsy. It is not a rare entity; autopsy studies show moderate or severe CAA with an age-dependent prevalence of 8% (for ages 75–84) to 12% (for ages >84), and an even higher prevalence in patients with Alzheimer disease.9
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Case Report
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A 70-year-old man with a past medical history notable for diabetes,
hypertension, and ischemic heart disease was referred for evaluation
of recurrent cerebral hemorrhages. The patient had experienced
a left temporoparietal cerebral hemorrhage approximately 10
years before presentation. Six months before arrival at our
hospital, the patient presented with speech difficulty; subsequent
brain MR showed a 3.1
x 2.7-cm left temporooccipital lobe hemorrhage
with a small zone of surrounding edema. Two months before presentation,
the patient underwent coronary artery stent placement and was
placed on aspirin and clopidogrel. Within a week, he presented
with altered mental status, and a CT without contrast showed
a new 3.0
x 2.5-cm intraparenchymal hemorrhage in the left posterior
temporoparietal lobe. Because of recurrent hemorrhages in the
same location, diagnostic considerations included vascular malformation
and amyloid angiopathy. Before MR imaging, the patient underwent
cerebral angiography, which demonstrated no evidence of arteriovenous
malformation or any pathologic vascular condition. MR angiography
(MRA) showed similar negative findings. Brain MR demonstrated
encephalomalacia within the left temporoparietal lobe, consistent
with the patient’s history of prior repeated hemorrhages.
GE and SWI images showed low signal intensity within the left
temporoparietal lobe region, consistent with hemosiderin deposition.
Both the T2*-weighted GE (
Fig 1, left) and SWI image (
Fig 1,
right) show multiple low-signal intensity areas in a cortical-subcortical
distribution, consistent with hemosiderin deposition. However,
SWI shows the susceptible foci to be both more numerous and
with improved apparent contrast compared with the corresponding
conventional GE image. Using the same criteria for counting
the small rounded lesions, the SWI projected image shows 201
lesions, whereas the GE-projected image shows 74 lesions. Aggregate
imaging findings are consistent with old infarct and highly
suggestive of CAA.
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Fig 1. Axial gradient-echo T2*-weighted image (left; 800/26 ms [TR/TE], 5-mm section thickness, Nx = 256, Ny = 154) shows some low-signal-intensity foci associated with CAA. Corresponding SWI image (right; 85/35 ms [TR/TE],  = 20°, Nx = 512, Ny = 256, with a resolution of 0.5 mm x 0.5 mm x 2.0 mm, projected over 8 mm) shows many more associated low-signal-intensity foci.
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Discussion
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CAA is well known to manifest as amyloid protein deposits in
small arteries. Although CAA is unrelated to systemic amyloidosis,
it is associated with increasing age, dementia, Alzheimer disease,
dementia pugilistica, postradiation necrosis, and spongiform
encephalopathies. No CT- or MR-based imaging technique currently
exists to directly visualize or quantify amyloid deposits; diagnosis
can only be made by biopsy or autopsy. Pathologic specimens
show fibrinoid degeneration and microaneurysms; amyloid stains
with Congo red dye exhibit yellow-green birefringence when exposed
to polarized light. As the ß-amyloid protein builds
up within the elastic lamina of vessel walls, vessels lose elasticity
and become fragile.
6 Fragile vessels are more easily damaged,
and tiny hemorrhages (cerebral microbleeds) occur in and around
the arteriole vessel wall.
7 Microbleed-induced damage can cause
a further loss of vessel wall elasticity, thinning of the vessel
wall, or vessel wall dilation.
6 With regard to morbidity and
mortality, the most concerning clinical effect of CAA is spontaneous
intracranial hemorrhage, which can be recurrent. Cognitive impairment
is also a common feature of CAA; 40% of patients with CAA-related
intracranial hemorrhage have dementia, and more than 80% of
patients with Alzheimer disease have CAA.
9
Certain patterns of lobar hemorrhage, which can be detected on CT and conventional MR images, are suggestive of CAA. In addition, CAA should be suggested if lobar hemorrhage is identified with a superficial location and cortical involvement. Hemorrhages that involve the cortex and subcortical white matter within the frontal and parietal lobes are most common. Evidence of multiple hemorrhages confined to lobar regions may also be present, and subarachnoid extension of hematoma is more likely in CAA.10 CAA is a vascular disease that is insensitive to detection by MR angiography, conventional angiography, and digital subtraction angiography. Neither CT nor conventional MR can detect microhemorrhages. Although T2* GE sequences can detect microhemorrhages, 25% of patients ultimately diagnosed with CAA have no microhemorrhages on conventional T2* GE images.5–8
SWI is a 3D, velocity-compensated, GE sequence that combines both magnitude information (used in conventional MR images, including T2* GE) with phase information to accentuate the visibility of susceptible foci (such as small veins and hemorrhage). Microhemorrhages contain hemosiderin, which is paramagnetic relative to normal tissue and leads to large variations in local magnetic fields and a local reduction in T2*. The signal intensity loss is proportional to the amount of hemosiderin present. SWI, with its unique sensitivity to blood products and hemorrhage,2,3 is well-suited to detect imaging changes consistent with CAA as evidenced in Fig 1.
SWI imaging, in this case, detected far more microhemorrhages than the conventional T2* GE technique. Conventional T2* techniques underestimate microhemorrhages compared with autopsy, and only 75% of patients with amyloid and lobar hemorrhages show microhemorrhages on T2*-weighted sequences. SWI is a much more sensitive technique than conventional T2* imaging, making it an important method of improving initial diagnosis. Increased sensitivity may allow assessment of the rate of microhemorrhage development or regression, allowing more precise analysis of the natural history of the disease, or assessing response to therapy. Early recognition can be advantageous to patients on anticoagulant or aspirin therapy in that they are at increased risk for subsequent and possibly fatal hemorrhage (reported to be as high as 38%, with a 44% mortality rate).11 In our case, antithrombotic agents were discontinued because the risk of hemorrhage was determined to be greater for this patient than the risk of thromboembolic disease. Strict blood pressure control may also be of utility in patients with CAA-related hemorrhage.
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Conclusions
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Imaging the brain with SWI requires only 5 to 7 minutes, and
can easily be included in routine neuroimaging protocols. SWI
identified many more microhemorrhages than conventional T2*-weighted
GE magnitude techniques and may lead to earlier diagnosis of
patients with CAA. Improved detection of microhemorrhage may
become increasingly important in the diagnosis, management,
and monitoring of the therapeutic response of patients with
CAA, especially as new therapeutic options, such as low-molecular-weight
proteins that reduce amyloid fibril formation, become available.
12
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Footnotes
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This work was supported in part by grants from the National
Institutes of Health HL62983 and AG20948, Siemens Medical Solutions,
and the State of Michigan Grant 085P5200251.
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References
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- Reichenbach JR, Venkatesan R, Schillinger DJ, et al. Small vessels in the human brain: MR venography with deoxyhemoglobin as an intrinsic contrast agent. Radiology204; 1997:272–77[Abstract/Free Full Text]
- Reichenbach JR, Jonetz-Mentzel L, Fitzek C, et al. High-resolution blood oxygen-level dependent MR venography (HRBV): a new technique. Neuroradiology43; 2001:364–69[Medline]
- Sehgal V, DelProposto Z, Haacke EM et al. Clinical applications of neuroimaging with susceptibility-weighted imaging. J Magn Reson Imaging22; 2005:439–50[Medline]
- Tong KA, Ashwal S, Holshouser S, et al. Improved detection of hemorrhagic shearing lesions in children with post-traumatic diffuse axonal injury: initial results. Radiology227; 2003:332–39[Abstract/Free Full Text]
- Greenberg SM, O’Donnell HC, Schaefer PW, et al. MR imaging detection of new hemorrhages: potential marker of progression in cerebral amyloid angiopathy. Neurology53; 1999:1135–38[Abstract/Free Full Text]
- Walker DA, Broderick DF, Kotsenas AL, et al. Routine use of gradient-echo MR imaging to screen for cerebral amyloid angiopathy in elderly patients. AJR Am J Roentgenol182; 2004:1547–50[Abstract/Free Full Text]
- Greenberg SM, Eng JA, Ning M, et al. Hemorrhage burden predicts recurrent intracerebral hemorrhage after lobar hemorrhage. Stroke35; 2004:1415–20[Abstract/Free Full Text]
- Greenberg SM. Cerebral amyloid angiopathy: prospects for clinical diagnosis and treatment. Neurology;51; 1998:690–94[Abstract/Free Full Text]
- Ellis RJ, Olichney JM, Thal LJ, et al. Cerebral amyloid angiopathy in the brains of patients with Alzheimer disease: the CERAD experience, Part XV. Neurology46; 1996:1592–96[Abstract/Free Full Text]
- Ohtani R, Kazui S, Tomimoto H, et al. Clinical and radiographic features of lobar cerebral hemorrhage: hypertensive versus nonhypertensive cases. Intern Med42; 2003:576–80[Medline]
- Passero S, Burgalassi L, D’Andrea P, et al. Recurrence of bleeding in patients with primary intracerebral hemorrhage. Stroke26; 1995:1189–92[Abstract/Free Full Text]
- Greenberg SM, Schneider AT, Pettigrew CL et al. Phase II study of Cerebril, a candidate treatment for intracerebral hemorrhage related to cerebral amyloid angiopathy [abstract]. Neurology62; 2004:A102
Received November 17, 2005;
accepted after revision January 16, 2006.
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Abstract
Introduction