Ultrasound findings of the optic nerve and its arterial venous system in multiple sclerosis patients with and without optic neuritis vs. healthy controls.

Background: Optic Neuritis (ONe) is common in Multiple Sclerosis (MS). The aim of this study was to evaluate the Optic Nerve (ONr) and its vascularisation in MS patients with and without previous ONe and in Healthy Controls (HC). Methods: We performed high-resolution echo-color ultrasound examination in 50 subjects (29 MS patients and 21 HC). By a suprabulbar approach we measured the ONr diameter at 3mm from the retinal plane and at another unfixed point. We assessed the flow velocities of Ophthalmic Artery (OA), Central Retinal Artery (CRA) and Central Retinal Vein (CRV) measuring the Peak Systolic Velocity (PSV) and the End Diastolic Velocity (EDV) for the arteries and the Maximal Velocity (MaxV), Minimal Velocity (MinV) and mean Velocity (mV) for the veins. The Pulsatility Index (PI) and the Resistive Index (RI) were also calculated. Results: No significant variation for OA supply was found as well as no significant variation for CRA supply, while significant higher PI in the CRV of non-ONe MS eyes vs. both HC and ONe MS eyes was measured. We found that ONr diameter was decreased significantly from HC to non-ONe MS eyes and ONe MS eyes. Conclusions: Ultrasound examination of ONr and its vascularisation is feasible and can demonstrate ON atrophy. The increase of CRV PI in unaffected eyes of MS patients is intriguing and seems not associated to ONr atrophy. Larger studies are needed to confirm these results.