Background/Purpose: Recently, optic nerve sheath (ONS) enhancement using contrast-enhanced magnetic resonance imaging of the brain and orbits was observed in most patients with biopsy-proven GCA. In addition, we recently showed that ONS diameter (ONSD) and ONS thickness (ONST) measured by ultrasound are increased in patients with new-onset, active GCA. The objective of this study is to assess whether ONSD and ONST measurements improve when clinical remission is achieved in patients with GCA.

Methods: A prospective inception cohort study was conducted at the vasculitis clinic of Sacre-Coeur Hospital, in Montreal, Canada, from June 2022 to January 2023. Patients who had an optic nerve (ON) ultrasound at GCA diagnosis as part of a previous cross-sectional study were approached. Participants in clinical remission after 3 months of therapy were included if (1) ON ultrasound had successfully been performed at the time of GCA diagnosis, (2) GCA was confirmed on color doppler ultrasound (CDUS) of temporal/axillary arteries, (3) they satisfied the 2022 ACR/EULAR classification criteria for GCA.

At month 3, a standardized clinical assessment, bloodwork, CDUS of temporal/axillary arteries and ON ultrasound were performed. ON ultrasound was performed by the same investigator at diagnosis and month 3, unblinded to clinical information. Ultrasound measurements were performed for both eyes, 3mm distal to the posterior aspect of the ocular globe. Optic nerve sheath diameter (ONSD, includes ON and its sheath) and optic nerve diameter (OND) were measured. Optic nerve sheath thickness (ONST) was obtained by subtracting OND from ONSD.

Descriptive statistics for baseline characteristics and paired sample t-test were performed to assess the mean difference in OND, ONSD, and ONST between diagnosis and month 3. One-Way ANOVA was used to explore the association between clinically persistent vision defect at month 3 and ON ultrasound measurements.

Results: Nine patients with a diagnosis of GCA were included in our study. The median age at disease onset was 79 years (interquartile range (IQR) of 79 – 82 years) and 7 patients were males. All patients were in clinical remission at month 3. GCA characteristics and therapy at diagnosis and month 3 are presented in table 1.

There was strong evidence that the mean ONSD and ONST measured in millimeters were lower at month 3 (clinical remission) than at diagnosis (active GCA) for both eyes (table 2, figure 1). Furthermore, in 7/9 patients, ONSD decreased below 4.5mm (considered normal in healthy adults). As anticipated, OND measurements did not vary between diagnosis and month 3. There was no evidence of an association between persistent vision defect at month 3 and mean difference in ONSD and ONST measurements.

Conclusion: In patients with active, new-onset GCA, we demonstrated that ONSD and ONST measured on ultrasound improved with therapy. Thus, ONSD and ONST may be dynamic biomarkers in GCA and allow detection of disease relapse. These findings and hypothesis will be addressed in a larger, longer prospective trial (ClinicalTrials.gov id: NCT05749094).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/optic-nerve-sheath-measurement-as-a-disease-activity-biomarker-in-giant-cell-arteritis/