Pos0691 Optic Perineuritis in Giant Cell Arteritis: Can Measurement of Optic Nerve Sheath Be Used as a Disease Activity Biomarker?

Background: Neuroimaging is not generally necessary in GCA, but in patients with atypical presentation and visual symptoms, it has been shown that it can play an important role in its diagnosis. Neuroimaging in GCA may reveal optic nerve sheath enhancement, which is a cardinal finding of optic perineuritis. Objectives: To assess whether optic nerve sheath diameter ONSD and optic nerve sheath thickness ONST measurements can be used as Disease Activity Biomarker in Giant Cell Arteritis. Methods: This was cross sectional, retrospective study. Patients: GCA patients diagnosed according to the 2022 EULAR/ACR classification criteria. Methodology: Consecutive untreated patients diagnosed to have GCA were invited to participate in this study. The diagnosis was confirmed by US examination. All the patients were asked to complete a copy of the GCA-specific Patient Reported Outcome Measures (GCA-PROMs) questionnaire [1]. GCA patients presenting with acute visual symptoms were compared to a control group including GCA patients without acute visual manifestations. In the active group, assessments were carried out at baseline before starting glucocorticoids therapy and at 3-months after commencing the treatment. US was carried out for temporal/axillary arteries (both sides) and optic nerve (both eyes). Ocular US: All measurements were carried out with the use of linear transducer, at a frequency of 7.5–18 MHz. The ultrasound presets were established via the "small parts" mode. This setting produces a default field of 4–5 cm depth. For the mechanical index and thermal index for ophthalmic US, values less than 0.23 for the mechanical index (MI) and less than 1.0 for the thermal index (TI) were used. For all patients, the US beam was focused on the retrobulbar area and the gain was adjusted to obtain the optimal contrast between the optic nerve and the periorbital fat. US measurement of the optic nerve was carried out at 3mm distal to the posterior aspect of the ocular globe. Two measurements (in mm) were recorded: 1. Optic nerve sheath diameter (ONSD, includes optic nerve and its sheath) and, 2. Optic nerve diameter (OND). Optic nerve sheath thickness (ONST) was calculated by subtracting OND from ONSD. Same measures were recorded in the control group. Disease activity was scored and recorded using GCA-disease activity score (GCA-DAS) [2]. Results: 31 patients were included in this work. Mean age 68.4 + 6.2. Twenty-one were females and 10 males. The control group included 42 GCA patients (28 females and 14 males) who did not have any acute visual manifestations, mean age: 67.1 + 5.9. At baseline, in the active group, ONST measurement was 3.26 + 1.06 mm in the affected eye and 2.74 + 1.16 in the contralateral eye. ONST in the control group was 1.03 + 0.27 mm (p< 0.01). There was significant difference on comparing the optic nerve diameter in the active group to the control group. After 3-months, the active group patients who achieved remission status, ONST measurement was 1.25 + 0.52 in the eye, which was affected, the contralateral eye 1.11 + 0.47, whereas in the control group it was 1.05 + 0.43. There was no significant difference (p> 0.05) on comparing optic nerve diameter at 3-months after therapy in the active group who achieved remission in comparison to the control group. Conclusion: US can help target the diagnosis in patients presenting with optic neuropathy of unknown cause. ONST measured on US has shown responsiveness to therapy and can be used as a biomarker in GCA. REFERENCES: [1] El Miedany Y et al. Development of GCA PROMs. Semin Arthritis Rheum 2023; 63:152285. [2] El Miedany Y et al. Giant cell arteritis clinical disease activity measures: recommendations for use in clinical practice. Ann Rheum Dis 2023; 82:634. Acknowledgements: NIL. Disclosure of Interests: None declared.