May 31, 2019 Conference
Dr. David G. Hunter, Boston Children's Hospital
Introduction: Congenital fibrosis of the extraocular muscles (CFEOM) is a rare genetic syndrome characterized by non-progressive ophthalmoplegia and ptosis. Mutations in axonal proteins have been identified in CFEOM and correlate with abnormal embryonic development of the oculomotor nucleus and its innervated muscles. Patients often require strabismus surgery to prevent functional limitations from anomalous compensatory head postures. We noticed abnormal superior oblique (SO) muscles intraoperatively in several children with CFEOM and wished to investigate this further.
Methods: Retrospective chart review of patients evaluated for CFEOM at a teaching hospital between January 2010 and July 2018.
Results: Of 24 patients identified (ages 1 month-62 years), 10 (42%) had genetically-confirmed CFEOM. Twenty-two underwent strabismus surgery, 14 (64%) involving the SO muscle. Of these, 13 (93%) had a documented SO abnormality, including absent, thin, or anomalously inserted tendons in 9 (most commonly attached nasal to the superior rectus muscle), and tight muscles in 4.
Discussion: Almost all CFEOM patients who underwent SO surgery had abnormal SO muscles, a finding mentioned (though not well-characterized) in two previous reports to our knowledge. The high incidence of tendon misplacement may be under-appreciated given that tenotomies are often performed in the superonasal fornix, away from the tendon's insertion on the globe.
Conclusion: CFEOM patients often have tight SO muscles or anomalously placed tendon insertions, suggesting that abnormal SO innervation is another feature of the disease process in these patients. Surgeons should expect to find such variants and should therefore plan to exclusively approach the SO tendon using a superonasal rather than superotemporal approach.