Transorbital Ultrasound for Morphological and Haemodynamical Assessment of Optic Nerve in Multiple Sclerosis

Background and aims: Changes of the optic nerve (ON) reflect the overall pathology in multiple sclerosis (MS). Transorbital ultrasonography (TOUS) is a promising tool for detecting ON changes after exposure to optic neuritis. We aimed to explore ON haemodynamic in addition to morphological changes in a sample of MS patients. Methods: Sixty-seven MS patients (Thompson diagnostic criteria) were included in this preliminary study: 53 women and 14 men aged 41.6 (11.3) and 40.1 (11.0) (p=ns) years. EDSS score was 0-2.5 in 47 (70.1%) and >2.5 in 20 (14.9%) subjects. ANCOVA was used to investigate the association between US morphological (ON diameter (OND) at 3 and 5 mm from papilla, ON sheath diameter (ONSD) at 3 mm from papilla and myelination index (MI) ratio), a history of optic neuritis, controlling for sex and EDSS. Results: Out of 134 eyes no history of optic neuritis was recorded in 89 (66.4%), while at least 1 episode was recorded for 45 (33.6%). A higher proportion of affected eyes among women (86.4%) than men (13.6%) was observed (p=ns). OND – at 5 mm from papilla especially - and ONSD at 3 mm were significantly reduced in ONs with optic neuritis. MI ratios were higher in affected vs unaffected eyes. Mean ON diameters were lower in patients with higher EDSS score, irrespective of history optic neuritis. Mean flow velocity was reduced in affected eyes for all principal arteries explored. Conclusion: TOUS and Doppler US examination can detect ON changes in MS, showing potential for prognostic marker.