ARIAs are not random: A posterior and border-zone vascular vulnerability model.

ARIA often shows posterior and watershed predominance, indicating region-specific vascular vulnerability beyond amyloid burden alone. Reduced autoregulatory reserve in posterior territories may predispose to blood-brain-barrier disruption during anti-amyloid therapy. Watershed regions are hemodynamically fragile, lowering the threshold for vasogenic edema or microhemorrhage after amyloid mobilization. ARIA may represent a PRES-like neurovascular decompensation within an amyloid-compromised vascular bed.