To analyze prospectively the prevalence of subclinical oculomotor disorders (OMDs) in different phenotypes of Multiple Sclerosis (MS) and to study correlations with brain MRI T2 data.

OMDs are common in MS, but type and severity according to the stage of MS (especially in Radiologically Isolated Syndrome (RIS) and in Clinically Isolated Syndrome (CIS)), and their links with cerebral lesions topography are poorly known.

This study, conducted in the Côte d’Azur University MS Center and in the Rainier III Gerontologic Center, has compared eyes movements in patients with RIS (n=12), CIS (n=10), Relapsing-Remitting MS (RRMS, n=11), Secondary Progressive MS (SPMS, n=10), Primary Progressive MS (PPMS, n=10) and matched controls (n=23). Eyes movements were recorded with the EyeBrain Tracker®. Fixations, horizontal and vertical reflex saccades, horizontal and vertical smooth pursuit and anti-saccades were assessed.

OMDs are observed in 83% of RIS and 80% of CIS and in 100% of MS, especially internuclear ophthalmoplegia (INO) which is not observed in controls. Compared to all MS phenotypes, nystagmus, slowing of horizontal peak velocity and hypermetric saccades are not observed in RIS and CIS.

INO is not related to MRI data (number of T2 lesions or posterior fossa lesions). OMDs are not linked to lesion load either in volume or location, excepted for slowing of saccades linked to posterior fossa T2 lesions.

OMDs are frequent in RIS and CIS, particularly INO which can be observed without posterior fossa lesions detected on MRI. Identification of some specific OMDs, related to posterior fossa lesions, seems to be important for defining MS status. Video oculography can be useful to confirm early demyelinating process, even without characteristic lesions on MRI.