PO:37:254 | Absence of ciliary artery occlusion does not exclude arteritic anterior ischemic optic neuropathy (A-AION): diagnostic and pathophysiologic implications

Ruggiero Mascolo Mascolo¹, Stefano Erba², Alba Xhepa², Martina Martelli¹, Gabriella Marinaro¹, Giulia Dieguez¹, Giacomo Iacomelli¹, Chiara Facoetti¹, Michel Chevallard³, Bruno Lucchino³, Mariaeva Romano³, Andrea Locatelli³, Giuliana La Paglia³, Donatella Ventura³, Giovanna Randisi³, Alessandra Mutti³, Alessandro Invernizzi², Stefano De Angelis², Giovanni Staurenghi², Antonio Brucato⁴, Enrico Tombetti⁴ | ¹Dipartimento di Medicina Interna, ASST Fatebenefratelli-Sacco, Università degli studi di Milano, Italy; ²U.O. Oculistica, ASST Fatebenefratelli-Sacco Milano, Italy; ³U.O. Reumatologia, ASST Fatebenefratelli-Sacco Milano, Italy; ⁴Dipartimento di Scienze cliniche e biomediche, ASST Fatebenefratelli-Sacco, Università degli studi di Milano, Italy

Introduction. Giant Cell Arteritis (GCA) is the most common vasculitis among the elderly. Ocular involvement in GCA represents a medical emergency due to the high risk of progression to complete blindness and bilateral involvement, which high-dose corticosteroids can prevent. Ocular damage involves the choroidal (i.e. Anterior Ischemic Optic Neuropathy-AION) and retinal (i.e. Central Retinal Artery Occlusion-CRAO) circulations. Traditionally, arteritic-AION (A-AION) is the most common ocular involvement in GCA, but “non-arteritic”-AION (NA-AION) occurs six times more frequently than A-AION in the general population without GCA. Despite the vasculitic ciliary artery occlusion in A-AION, NA-AION develops following transient hypoperfusion, causing fibre swelling and compartmental syndrome. Nevertheless, recent reports suggest the absence of artery occlusion in a few AION cases. We aimed to assess the clinical, laboratory, and prognostic differences among phenotypes associated with arterial occlusion (typical A-AION, CRAO), those not associated with occlusion (atypical A-AION).

Methods. Monocentric cohort study on the incident GCA patients with AION, CRAO and amaurosis at ASST Fatebenefratelli-Sacco in Milan from January 2019 to May 2025. AION and CRAO were recognised according to fundus and OCT features. A-AION subjects without evidence of ciliary artery occlusion were defined by the absence of any of the following: chalky white optic disk at fundus and delayed choroidal perfusion at indocyanine green angiography.

Results. Among 137 eyes from 98 ocular GCA patients, 77 (56%) eyes in 57 (58%) patients were linked to occlusive phenotypes, while 11 (8%) eyes in 8 (8%) patients exhibited an atypical non-occlusive phenotype. Sex and age were similar between occlusive and non-occlusive phenotypes (p=0.715 and 0.163, respectively). Amaurosis and/or diplopia preceded in 2/11 eyes without arterial occlusion (18%) and in 22/77 (29%) with arterial occlusion (p=0.001). Despite proven vasculitis (by total body MR/PET, echo or temporal artery biopsy), the sensitivity of temporal artery biopsy tended to be lower in the absence of occlusion (29% vs. 73%, p=0.135). Moreover, subjects without arterial occlusion had lower plasma levels of C-reactive protein [4.9 (2.0 to 6.8) vs. 35.6 (9.62 to 77.3) mg/L, p=0.009], but erythrocyte sedimentation rate, fibrinogen and leukocyte and platelet counts were similar in both groups. Fundoscopy showed signs of risk of developing a compartmental syndrome in the optic nerve head (ie, a small/crowded optic disk) in all subjects with a non-occlusive phenotype.

Conclusions. Ciliary artery occlusion explains 85-90% of ocular involvement in GCA. In the remaining cases, ophthalmologic features are indistinguishable from NA-AION, and GCA was revealed by elevation of inflammatory markers and imaging/biopsy and/or clinical symptoms. In the case of suspected GCA without ciliary artery occlusion, imaging of large-vessel vasculitis is suggested, as temporal artery biopsy might be less sensitive than in typical cases.