Multimodality Review of Amyloid-related Diseases of the Central Nervous System

Amyloid-beta (A beta) is ubiquitous in the central nervous system (CNS), but pathologic accumulation of A beta results in four distinct neurologic disorders that affect middle-aged and elderly adults, with diverse clinical presentations ranging from chronic debilitating dementia to acute life-threatening intracranial hemorrhage. The characteristic imaging patterns of A beta-related CNS diseases reflect the pathophysiology of A beta deposition in the CNS. A beta is recognized as a key component in the neuronal damage that characterizes the pathophysiology of Alzheimer disease, the most common form of dementia. Targeted molecular imaging shows pathologic accumulation of A beta and tau protein, and fluorine 18 fluorodeoxyglucose positron emission tomography and anatomic imaging allow differentiation of typical patterns of neuronal dysfunction and loss in patients with Alzheimer disease from those seen in patients with other types of dementia. Cerebral amyloid angiopathy (CAA) is an important cause of cognitive impairment and spontaneous intracerebral hemorrhage in the elderly. Hemorrhage and white matter injury seen at imaging reflect vascular damage caused by the accumulation of A beta in vessel walls. The rare forms of inflammatory angiopathy attributed to Ab, A beta-related angiitis and CAA-related inflammation, cause debilitating neurologic symptoms that improve with corticosteroid therapy. Imaging shows marked subcortical and cortical inflammation due to perivascular inflammation, which is incited by vascular A beta accumulation. In the rarest of the four disorders, cerebral amyloidoma, the macroscopic accumulation of A beta mimics the imaging appearance of tumors. Knowledge of the imaging patterns and pathophysiology is essential for accurate diagnosis of Ab-related diseases of the CNS. (C) RSNA, 2016.