Ultrasound findings of the optic nerve and its arterial venous system in multiple sclerosis patients with and without optic neuritis vs. healthy controls
Vittoria M. Sarraa,
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).
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 3 mm 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.
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.
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.
It must be a Friday, because I'm not sure what this means. I'll reread in the morning.... Why would the CRV PI in non optic neuritis eyes of MS patients be increased, and what is a CRV PI? Central retinal vein pulsatility index. Pulsatility.... That there was no significant variation for CRA (central retinal artery) supply means that it is not because of less flow coming into the eye. But there is this difference in the pulsatility of the flow leaving the eye via the central retinal vein, which drains into a vein that ultimately drains into the internal jugular vein. The blockage in the internal jugular vein leads to pulsatility upstream in the central retinal vein, or at least that's one explanation.