Inflammatory cerebral amyloid angiopathy (ICAA)
General description
Inflammatory cerebral amyloid angiopathy (ICAA) is a rare subtype of cerebral amyloid deposition disease, closely related to the more common non-inflammatory cerebral amyloid angiopathy (CAA). It typically presents with acute to subacute symptoms, including progressive cognitive impairment, seizures, headaches, altered consciousness, motor deficits, aphasia, and hallucinations. Symptom fluctuations are also common.
Pathologically, ICAA is classified into two subtypes: cerebral amyloid angiopathy-related inflammation (CAA-ri) and amyloid β-related angiitis (ABRA). CAA-ri is characterized by perivascular lymphocytic infiltrates, while ABRA shows transmural granulomatous inflammation. These two subtypes represent part of a spectrum of central nervous system (CNS) vasculopathies, intermediate between CAA and primary CNS vasculitis.
CAA-ri and ABRA are thought to result from an inflammatory response directed against amyloid-β (Aβ) deposition in the leptomeninges and cerebral parenchyma. This inflammatory response often manifests as vasogenic edema on imaging, particularly in T2-weighted or FLAIR MRI sequences.
While the term "inflammatory cerebral amyloid angiopathy" can serve as an umbrella term encompassing both CAA-ri and ABRA, the terminology varies. Some authors use the terms interchangeably, while others distinguish between the two. In certain cases, discussions focus exclusively on either CAA-ri or ABRA without referencing the other.
White matter lesion
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CerebrumCerebral white matterSubcortical white matter
Imaging findings in ICAA typically demonstrate asymmetric white matter lesions characterized by hyperintense areas on T2-weighted and FLAIR imaging, which may appear as patchy or confluent abnormalities. Confluent white matter lesions are consistently observed in all cases, often extending into the subcortical U-fibers.
Leptomeningeal enhancement
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LeptomenixCerebral leptomenix
Leptomeningeal contrast enhancement can be observed on T1WI and FLAIR sequences, and it is seen in approximately half of the patients in both CAA-related inflammation (CAA-ri) and amyloid β-related angiitis (ABRA).
Cerebral microbleeds
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CerebrumCerebral cortex
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CerebrumCerebral white matterSubcortical white matter
Detection of cerebral microbleeds is better achieved using susceptibility-weighted imaging (SWI) compared to T2*-weighted imaging. Microbleeds typically appear as punctate or linear hypointense areas, predominantly located in the cortical or subcortical regions.