Amyloid-related imaging abnormalities

ARIA-E refers to cerebral edema, involving the breakdown of the tight endothelial junctions of the blood-brain barrier and subsequent accumulation of fluid. In a double-blind trial of the humanised monoclonal antibody solanezumab (n = 2042), sixteen patients (11 taking the drug, 5 taking a placebo), or 0.78% developed ARIA-E. A further 7 patients developed ARIA-E during an open-label extension of the trial. The effect of ARIA-E depends on the severity and location of the edema. Symptoms may include headache, changes in mental state, confusion, vomiting, nausea, tremor and gait disturbances. == ARIA-H ==

ARIA-H refers to cerebral microhaemorrhages (mH), small haemorrhages on the brain, often accompanied by hemosiderosis. == Mechanism of action ==

)Middle: ARIA-H with multiple microbleeds (T2* weighted)Right: ARIA-H with superficial siderosis (T2* weighted)|400x400px Two non-exclusive mechanisms have been postulated. Firstly, in the context of aging and neurodegeneration, the integrity of the blood-brain barrier (BBB) can become compromised, resulting in increased permeability. Notably, amyloid plaques have been hypothesized to counteract this BBB leakage. However, upon the administration of antibodies, these plaques are targeted and subsequently eliminated, potentially uncovering the occurrence of micro-hemorrhage Secondly, an alternate perspective posits that the introduction of antibodies into the bloodstream triggers an immune-inflammatory response as part of the treatment regimen. This orchestrated immune reaction might inadvertently precipitate micro-hemorrhages. == ARIA MRI Classification Criteria ==