What causes hemorrhage in cerebral amyloid angiopathy (CAA)?

Updated: Dec 19, 2018
  • Author: Ravi S Menon, MD; Chief Editor: Helmi L Lutsep, MD  more...
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Amyloid damages the media and adventitia of cortical and leptomeningeal vessels, leading to thickening of the basal membrane, stenosis of the vessel lumen, and fragmentation of the internal elastic lamina. These processes result in fibrinoid necrosis and microaneurysm formation, predisposing to hemorrhage.

CAA-related brain changes include lobar cerebral and cerebellar hemorrhage, leukoencephalopathy, small cortical ischemic infarcts, and plaque deposition. Leukoencephalopathy may be related to chronic hypoperfusion of deep WM (meningo-cortical segments of long perforators).

Neuropathologically, mild CAA primarily affects a relatively smaller proportion of the leptomeningeal and superficial cortical vessels, in contrast to the diffuse, significant deposition of amyloid in small arteries and arterioles seen in severe CAA. Medium-sized leptomeningeal arteries are affected with amyloid deposition in the outer portion of tunica media to tunica adventitia.

Frequently, complete erosion occurs, with only endothelium surrounding the deposit, predisposing to hemorrhage. Electron microscopy demonstrates fibrils of amyloid in the outer basement membrane in the initial stage of CAA. As the disease progresses, significant amyloid accumulation leads to tunica media degeneration, capillary and arteriolar infiltration, and formation of dystrophic neuritic plaques.

The risk of intracranial bleeding following head trauma and neurosurgical procedures is increased in patients with CAA. Some evidence suggests that CAA has a role in a substantial proportion of anticoagulant- and thrombolytic-related hemorrhages.

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