2020–2021 BCSC Basic and Clinical Science Course™
6 Pediatric Ophthalmology and Strabismus
Part I: Strabismus
Chapter 12: Special Motility Disorders
Congenital Cranial Dysinnervation Disorders
Möbius syndrome (or “sequence”; see Chapter 15 discussion of sequence) is a rare condition characterized by the association of both sixth and seventh nerve palsies, the latter causing masklike facies. Patients may also manifest gaze palsies that can be attributed to abnormalities in the paramedian pontine reticular formation or the sixth cranial nerve nucleus. Many patients also have limb, chest, and tongue defects. Some geneticists believe that Möbius syndrome is one of a family of syndromes in which hypoplastic limb anomalies may be associated with orofacial and cranial nerve defects. Poland syndrome (absent pectoralis muscle) is another variant.
Patients with Möbius syndrome exhibit 1 of 3 patterns of ocular motility involvement, which are likely related to the severity and timing of the in utero insult:
orthotropia in primary position with marked deficits in abduction and adduction (40% of cases) (Fig 12-4)
esotropia with cross-fixation and sparing of convergence (50% of cases)
large exotropia with absence of convergence (10% of cases)
Some patients appear to have palpebral fissure changes on adduction or vertical EOM involvement. Those with exotropia and vertical limitation may harbor TUBB3 mutations.
Carta A, Mora P, Neri A, Favilla S, Sadun AA. Ophthalmologic and systemic features in Möbius syndrome: an Italian case series. Ophthalmology. 2011;118(8):1518–1523.
MacKinnon S, Oystreck DT, Andrews C, Chan WM, Hunter DG, Engle EC. Diagnostic distinctions and genetic analysis of patients diagnosed with moebius syndrome. Ophthalmology. 2014;121(7):1461–1468.
Figure 12-4 Möbius syndrome. A, Straight eyes in primary position. B, The patient cannot smile because of bilateral seventh nerve palsy. C, Bilaterally absent adduction and severely limited abduction. D, Vertical movements are not affected.
(Courtesy of Edward L. Raab, MD.)
Medial rectus muscle recession has been advocated for patients with large-angle esotropia, but caution should be exercised in the presence of a significant limitation of adduction. Some surgeons have endeavored to improve abduction by performing vertical rectus muscle transposition procedures after medial rectus muscle restriction has been relieved.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.