Distinguish clinicoradiographic features of primary CNS vasculitis (PCNSV), amyloid-beta-related angiitis (ABRA), and cerebral amyloid angiopathy-related inflammation (CAAri).

PCNSV, ABRA, and CAAri are rare inflammatory vasculopathies presenting with similar clinical manifestations, yet comparative studies distinguishing them are limited. In a biopsy-confirmed cohort of these entities, we compare relapse risk and clinicoradiographic features.

We retrospectively identified PCNSV, ABRA, and CAAri cases at Mass General Brigham. Patients with non-supportive pathology were excluded. CAA cases met Boston 2.0 criteria. Relapse required worsening symptoms and new MRI lesion(s). Time-to-event analyses used Fine-Gray models with death as competing risk, reported as subdistribution hazard ratios (sHR). Multivariate logistic regressions were used to distinguish predictors of PCNSV vs amyloid-related vasculopathy (ARV).

Thirty-five PCNSV, 17 ABRA, and 24 CAAri patients were followed for a mean of 7.0, 4.4, and 3.9 years, respectively. Relapse occurred in 17/35 PCNSV, 4/17 ABRA, and 3/24 CAAri; overall p=0.02. Competing-risk model referenced to PCNSV, CAAri had a significantly lower sHR (0.33, CI [0.12-0.90], p=0.03) and ABRA trended lower (sHR 0.42, p=0.095). Most PCNSV relapses occurred within 2 years; ARV relapses by 4 years. Across groups, frequencies differed for sulcal T2/FLAIR hyperintensity (p=0.003), cortical T2/FLAIR hyperintensity (p=0.002), cortical microhemorrhage/siderosis (p<0.001), and enlarged perivascular spaces (p<0.001). Multivariable, age-adjusted model (PCNSV vs ARV) showed high discrimination (AUC 0.94); younger age (odds ratio (OR) per year 0.88, p=0.01), subcortical microhemorrhage/siderosis (OR 66.8, CI 4.0-790], p=0.02), and absence of cortical microhemorrhage/siderosis (OR 0.008, CI [0.0-0.14], p=0.008) independently distinguished PCNSV from ARV. Microhemorrhages rapidly accrued within 6 weeks in 2 PCNSV, 2 ABRA, and 0 CAA-ri.