Adduction on Attempted Abduction: The Opposite of Synergistic Divergence

Congenital fibrosis of the extraocular muscles (CFEOM) is a congenital ocular motility disorder that manifests as restrictive ophthalmoplegia with ptosis.¹ Synergistic divergence (SD) is a deficit of adduction associated with simultaneous bilateral abduction on attempted gaze into the field of action of the affected medial rectus muscle.² There has been no pathologic report of SD; however, magnetic resonance imaging showed that in 2 patients with CFEOM and SD, the oculomotor nerve was hypoplastic bilaterally and the abducens nerve was absent on the side exhibiting SD.³ To our knowledge, bilateral deficit of abduction associated with simultaneous bilateral adduction on attempted gaze into the field of action of the lateral rectus muscles, the counterpart of SD, has not been previously reported.

A 39-year-old man was referred for the evaluation of ophthalmoplegia and ptosis since birth. He underwent a bilateral frontalis sling operation at age 29 years. Otherwise, medical and family histories were noncontributory.

His corrected visual acuities were 20/60 OU. He had a chin-up posture, and both eyes were fixed in downgaze. He had 10 prism diopters (Δ) of esophoria in the primary position, which increased to an esotropia of more than 50Δ in right gaze, left gaze, and upgaze. He was unable to voluntarily elevate either eye to the primary position, and Bell's phenomenon was absent. Ductions were completely limited in both eyes, except for some residual adduction. During attempted right gaze, left gaze, and upgaze, both eyes adducted. He showed a limited retraction of the globe on attempted adduction, but he did not show upshoots or downshoots of either eye on adduction (Figure 1A). Both eyelids showed ptosis with a palpebral fissure of 2 mm. Both eyelid positions did not show any changes with gaze. Levator function was evaluated at 0 mm in both eyes. Neither eyelid showed movement accompanying mouth movement. Both lenses and fundi were normal. Both pupils reacted briskly to light without a relative afferent pupillary defect and did not contract with eye movement.

On thin-section magnetic resonance imaging, bilateral abducens nerves were absent, and bilateral oculomotor nerves were hypoplastic (Figure 1B-F). The superior rectus muscles of both eyes had severe atrophy, and the medial rectus muscles had mild atrophy (Figure 1G).¹ The inferior and lateral rectus muscles of both eyes were of normal size. In 30 normal controls, the abducens and oculomotor nerves were identified bilaterally in all of them (Figure 2).

Our study included 1 patient with CFEOM and the counterpart of SD, namely, adduction on attempted abduction. Magnetic resonance imaging showed bilateral hypoplasia of the oculomotor nerve and bilateral absence of the abducens nerve. Based on the pathologic findings of CFEOM¹ and Duane retraction syndrome,⁴ the absence of an abducens nerve may represent a specific finding of Duane retraction syndrome and bilateral hypoplasia of the oculomotor nerve, CFEOM. Because this finding was exactly the same as in those with synergistic divergence,³ we presume that this case is a rare variant of SD that could also be categorized as a neuropathologic disease with an aberrant innervation. This case shows that aberrant innervation supports a primary developmental abnormality of the cranial nerves in CFEOM.

In conclusion, our study demonstrates the rare existence of the counterpart of SD. The radiologic findings of bilateral hypoplasia of the oculomotor nerve and the absence of the abducens nerve were the same as those of SD.

Correspondence: Dr Hwang, Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam, Gyeonggi-do 463-707, Korea (hjm@snu.ac.kr).

Financial Disclosure: None.