Abstract
Purpose :
Synergistic convergence and divergence are rare clinical features usually with aberrant ocular innervation. Most aberrant ocular innervation diseases are clearly diagnosed as congenital cranial dysinnervation disorders(CCDDs), which commonly present dysinnervation in orbital level and seldom in brainstem level. We performed a retrospective, observational clinical study to learn about high-resolution magnetic resonance image (MRI) findings in patients with synergistic convergence and divengence.
Methods :
Six patients underwent MR examination including brain，brainstem，cavernous sinus and orbit. A human orbit was celloidin embedding and serially sectioned at 0.1mm of thickness for HE stains, the histologic sections were made as reference to identify the nerve branches in MR images.
Results :
Two patients were diagnosed as congenital fibrosis of extraocular muscles with the MRI showed thin liner bilateral oculomotor nerve suggesting hypoplasia. Images of a 7-month-old girl (the third patient) demonstrated that bilateral oculomotor nerves fuse in the interpeduncular cistern , which was also the only innervation dysgenesis found outside orbit (picture 1). The fourth patient was diagnosed as intermittent exotropia, when attempted up gaze with synergistic convergence and divengence when attempted down gaze, contiguous quasicoronal MRI of the orbits showed the branch of CN3 to the inferior rectus could barely be identified bilaterally but an enlarged branch to the medial rectus bilalerally. The fifth patient was a 5-year-old boy with right eye exotropia, during attempted left gaze, the right eye abducted, while during attempted right gaze, both eyes abducted. MRI showed the absence of medial rectus branch of the right oculomotor nerve, and an aberrant branch from the the right oculomotor nerve to the lateral rectus.
Conclusions :
Synergistic convergence and divergence are usually caused by aberrant innervation, high-resolution MRI can help us get better understanding and interpretation of such irregular eye movements.
This is a 2020 Imaging in the Eye Conference abstract.