Diagnostic Value of eVOG

Plain-language summary

Eye movement is a complex neurological function controlled by many structures located in the central nervous system. The eyeball is mobile within the orbit and its movements are carried out using 6 muscles innervated by 3 oculomotor nerves allowing to perform reflex or voluntary eye movements in all elementary directions. So-called internuclear structures allow the two eyeballs to perform combined movements. The attack of these structures during an acute or chronic neurological disease will most often cause oculomotor paralysis in one or more directions of gaze which will be perceived by the patient as double vision. So-called supranuclear structures make it possible to generate different types of eye movements: saccades, which are extremely rapid eye movements of very short duration, eye pursuit, which is a slow movement whose purpose is to follow a moving visual target and finally, certain neural circuits are intended to stabilize the gaze. Many neurological diseases can be accompanied by oculomotor abnormalities affecting saccades or ocular pursuit. These include neurodegenerative diseases characterized by diffuse neurological damage. Involvement of gaze stabilization structures is also frequently found in certain neurological diseases affecting the posterior fossa. The clinical examination of oculomotricity focuses mainly on the analysis of ocular mobility in the different directions of space by asking the subject to fix an object (for example a pen) or the index of the examiner in moving in different directions in space. During a classic clinical examination, it is then possible to detect anomalies such as oculomotor paralysis or nystagmus, it is however very difficult to assess the speed or the precision of the saccades, as well as the quality of the pursuit ocular. As a result, the development of techniques to accurately record eye movements has emerged as a need in order to help in the diagnosis of certain visual disorders and certain neurodegenerative diseases. Video oculography (VOG) is a technique for precisely recording and analyzing the movements of the eyeballs. The use of VOG in neurology has long been dominated by helping to diagnose certain neurodegenerative diseases and in particular certain atypical Parkinson's syndromes. The value of VOG has also been demonstrated in certain pathologies characterized by atrophy of the brainstem or cerebellum, of hereditary or acquired origin. Some studies have also assessed its contribution to the diagnosis and management of certain dementias and certain psychiatric diseases such as schizophrenia. More recently, the interest of VOG has also emerged in the management of patients with a demyelinating disease of the multiple sclerosis spectrum. The VOG has a number of limitations to its large-scale use, first of all, it is an examination requiring specific, relatively expensive equipment. On the other hand, the examination requires know-how, both for the passing of the tests but also for the processing and analysis of the data. The eVOG (mobile VideoOculoGraphy) application has been developed to record oculomotor movements during different paradigms: horizontal saccades, vertical saccades, antisaccades, horizontal pursuit, vertical pursuit thanks to a tablet fixed on a support allowing keep in a stable and fixed position. The eVOG app was compared to a conventional VOG platform in a first study. The objective was to compare the measurements obtained by the eVOG application to the measurements collected by the standard method in a sample of patients with multiple sclerosis. This study showed that the detection of different anomalies by eVOG is correlated with classic VOG. In view of these encouraging preliminary results, a prospective study could be set up with the objective of evaluating the value of digital VOG in the diagnostic process in patients referred to a tertiary center for white matter signal abnormalities on MRI. the hypothesis is that subclinical oculomotor disorders will be found more frequently in the group of patients with MS spectrum disease due to the presence in this pathology of diffuse inflammatory and degenerative damage to brain tissue, unlike the others inflammatory or non-inflammatory pathologies.

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