Table 2. Classification of ICH attributed to CAA (modified Boston criteria).

CAA score	Postmortem examinationa	Pathologic tissue (evacuated hematoma or cortical biopsy)	Lobar, cortical, or subcortical hemorrhage	Age ≥ 55y	Other diagnostic lesion (A1, A2a) Other cause of hemorrhage or siderosis (A2b, A3)b
A1	+	+/-	+	+	-
A2A with supporting pathology	-	+	+	+	-
A2B	-	-	+c or d	+	-
A3	-	-	+e or f	+	-

A1: CAA definite

A2A: CAA probable with supporting pathology

A2B: CAA probable

A3: CAA possible

a. Full postmortem examination demonstrating: 1) Lobar, cortical, or corticosubcortical hemorrhage; 2) Severe CAA with vasculopathy; and 3) Absence of other diagnostic lesion

b. Other causes of intracerebral hemorrhage: excessive warfarin (INR>3); antecedent head trauma or ischemic stroke; CNS tumour, vascular malformation, or vasculitis; and blood dyscrasia or coagulopathy. (INR>3 or other nonspecific laboratory abnormalities permitted for diagnosis of possible CAA.) [8]

c. Multiple hemorrhages restricted to lobar, cortical, or corticosubcortical regions (cerebellar hemorrhage allowed)

d. Single lobar, cortical, or corticosubcortical hemorrhage and focal (restricted to 3 or fewer sulci) or disseminated (affecting at least 4 sulci) superficial siderosis

e. Single lobar, cortical, or corticosubcortical hemorrhage

f. Focal (restricted to 3 or fewer sulci) or disseminated (affecting at least 4 sulci) superficial siderosis [9].