Mobius syndrome redefined: a syndrome of rhombencephalic maldevelopment.

Objective: To investigate the variable clinical picture of Mobius syndrome (MIM no. 157900) and to further understand the pathogenesis of the disorder. Methods: A standardized questionnaire was submitted to 37 Dutch patients with Mobius syndrome. All underwent standardized neurologic examination with special attention to cranial nerve functions, motor skills, and facial and limb anomalies. Results: Of 37 patients with facial paresis, 97% had bilateral and 3% had unilateral ocular abduction weakness. Further analysis showed isolated abducens nerve palsy in 9%, a conjugated horizontal gaze paresis in 48%, features of Duane retraction syndrome in 34%, and congenital fibrosis of the extraocular muscles in 9%. Other signs included lingual involvement (77%), dysfunction of palate and pharynx (56%), general motor disability (88%), poor coordination (83%), and respiratory abnormalities (19%). Conclusion: Mobius syndrome is more than a cranial nerve or nuclear developmental disorder. It is a syndrome of rhombencephalic maldevelopment involving predominantly motor nuclei and axons, as well as traversing long tracts. The authors also noted gaze palsies, Duane retraction syndrome, feeding and respiratory problems, and poor motor development, suggesting a regional developmental disorder.