Session: Free papers Session III - Incomitant Strabismus

Orthoptic outcomes in Moebius syndrome

Maxence RATEAUX^1,2, Cyril GITIAUX^3,4, Dominique BREMOND-GIGNAC^1,5, Matthieu ROBERT^1,2

¹Ophthalmological department, University Hospital Necker-Enfants malades, APHP, Paris, France
²Centre Borelli, Université Paris Cité, ENS-Saclay, CNRS, INSERM, SSA , Paris, France
³Department of Paediatric Neurophysiology, Necker-Enfants Malades Hospital, Paris University, APHP , Paris, France
⁴INSERM U955-Team 10, Department of Neurosciences, Mondor Biomedical Research Institute, Paris-Est University, Créteil, France
⁵INSERM UMRS 1138, Team 17, From Physiopathology of Ocular Diseases to Clinical Development, Université Sorbonne Paris Cité, Centre de Recherche des Cordeliers, Paris, France

Introduction:

Moebius syndrome (MS) manifests as lateral gaze paralysis and non-progressive facial weakness due to congenital lesions affecting the VI and VII cranial nuclei. In the literature, however, oculomotor abnormalities are often referred to as “bilateral sixth nerve palsy”, and adduction is said to be possibly preserved. Quantifying ocular deviation is challenging due to gaze paralysis, hindering any cover test application. This series aims to better characterize MS’s oculomotors features.

Method:

Files of patients clinically diagnosed with MS 01/11/2018 and 01/11/2023 were retrospectively included. A comprehensive orthoptic exam, including quantification of ocular deviation using Krimsky method, monocular and binocular ocular motility assessment, oculocephalic reflex, evaluation of visual acuity and sensory aspects, was conducted. Ophthalmological evaluation also included a slit-lamp exam, fundus examination, and cycloplegic refraction.

Result:

54 patients (32M; 22F), aged 6 months to 24 years (median=7.5; SD=5.5), were included. 53 had complete horizontal gaze palsy with a negative oculocephalic reflex. One patient had unilateral MS with left-sided gaze palsy. Among 47 testable patients, adduction occurred due to convergence recruitment; in no case was adduction in lateral gaze possible. 34 patients (63%) had strabismus: 30 esotropias (including 6 micro-esotropias) (ranging from 2∆ to 60∆ (median=30∆)), 2 exotropias, and 2 hypertropias. Among the 20 orthotropic patients, 9 (45%) had normal stereopsis.

Conclusion: Adduction, when possible in MS, seems to only result from convergence recruitment, while oculocephalic reflexes always remain absent. This points to a nuclear involvement – bilateral sixth nuclear palsy – and should further prevent any faulty mention of “sixth nerve palsy”. In patients without strabismus, preserved convergence allows good stereopsis, the only mean to ascertain phoria in these cases.