Type:
Educational Exhibit
Keywords:
Performed at one institution, Not applicable, Pathology, Image verification, Haemorrhage, Surgery, Complications, Biopsy, MR, CT-Angiography, CT, Vascular, Neuroradiology brain, Haematologic, Neuro
Authors:
K. Sotomayor1, A. Bonilla2, M. NEGROTTO3, F. Bustamante1, C. Scelsi1, R. Figueroa1, S. Forseen1, B. Gilbert1, G. Palacios1; 1Augusta, GA/US, 2Lima/PE, 3Montevideo/UY
DOI:
10.26044/ecr2020/C-05803
Background
INTRODUCTION
Cerebral amyloid angiopathy (CAA) is a small vessel disease characterized by deposition of β-amyloid protein within the cerebral arterioles.[1,2] It is unrelated to systemic amyloidosis, being mostly associated with increasing age, Alzheimer's disease, dementia, or post-radiation treatment changes, among others. CAA is an important cause of intracerebral hemorrhage in the elderly. [3,4]
EPIDEMIOLOGY AND MANIFESTATIONS
Cerebral amyloid deposition occurs in three morphologic varieties, CAA, mass-like and inflammatory.[3,7] CAA is associated with cerebral microhemorrhages in approximately 63 to 73% of cases.[2] These bleeds are typically located at the cortical–subcortical junction, predominantly in the temporal and parietal lobes. In contrast, hypertensive or atherosclerotic microangiopathy shows microhemorrhages in a deep or infratentorial location. Amyloid angiopathy may present with leukoencephalopathy-like changes and reversible white-matter edema (inflammatory form of CAA).[1,3-5]
PATHOLOGY FINDINGS
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. [6-7] Pathologic specimens show fibrinoid degeneration and microaneurysms; amyloid stains with Congo red dye exhibit yellow-green birefringence when exposed to polarized light. As the β-amyloid protein builds up within the elastic lamina of vessel walls, vessels lose elasticity and become fragile. Fragile vessels are more easily damaged, and tiny hemorrhages (cerebral microbleeds) occur in and around the arteriole vessel wall. Microbleed-induced damage can cause a further loss of vessel wall elasticity, thinning of the vessel wall, or vessel wall dilation.[8,9]
CLINICAL MANIFESTATIONS
- With regard to morbidity and mortality, the most concerning clinical effect of CAA is spontaneous intracranial hemorrhage, which can be recurrent.[1,5]
- 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.
- 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.[4,6,8]
- 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.[3,8]
TECHNIQUE AND IMAGING FINDINGS
- CAA is a vascular disease that is insensitive to detection by MR angiography, conventional angiography, and digital subtraction angiography. Spectroscopic findings of low-grade gliomas may include decreased creatine and increased choline with an abnormal NAA/Cr ratio. There may also be an abnormal lactate peak with gliomas. By contrast, tumefactive CAA show a normal NAA/Cr ratio (1) and no increase in Cho/Cr ratio in keeping with the normal metabolic state of the underlying brain tissue. In addition, there is no evidence of restricted diffusion. Amyloidomas are a form of amyloid deposition that is distinct from tumefactive CAA both histopathologically and radiographically. [10,11,12].
- Neither CT nor conventional MR can detect microhemorrhages; however, susceptibility weighted imaging (SWI) sequences identified many more microhemorrhages than conventional T2*-weighted magnitude techniques and may lead to earlier diagnosis of patients with CAA.[13,14]
- SWI is a 3D, velocity-compensated, sequence that combines both magnitude information (used in conventional MR images, including T2*) with phase information to accentuate the visibility of susceptible foci (such as small veins and hemorrhage). [15,16] 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*. [17] The signal intensity loss is proportional to the amount of hemosiderin present. SWI,with its unique sensitivity to blood products and hemorrhage is well-suited to detect imaging changes consistent with CAA.
- 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. [16,17,18]