Inferior rectus transposition as a secondary surgery in patients with acquired abducens nerve palsy

Abstract

We report the outcomes in 2 patients with acquired abducens nerve palsy with residual esotropia following superior rectus transposition and medial rectus recession who subsequently underwent inferior rectus transposition as a second procedure. Both patients showed improved abduction and reduced esotropia, with no induced cyclotorsion or vertical deviation. Inferior rectus transposition as a secondary procedure in these 2 patients with abducens nerve palsy appeared to augment the effect of prior superior rectus transposition and medial rectus recession.

Case Reports

Case 1

A 22-year-old man presented with a residual esotropia after treatment of a left abducens nerve palsy with a superior rectus transposition (SRT) and medial rectus recession (MRc). Two years earlier he had been diagnosed with a clival meningioma during a work-up for a post-traumatic headache. After surgical excision of the meningioma, he developed complete paralysis of the left abducens nerve and partial paralysis of the left facial nerve. Ocular motility testing revealed −4 abduction and 55^Δ esotropia in primary position, 35^Δ in right gaze, and >50^Δ in left gaze. The patient underwent left SRT with loop myopexy and left MRc of 10 mm. He was then referred to the Byers Eye Institute with persistent horizontal and vertical diplopia. His best-corrected visual acuity was 20/20 in both eyes. Ocular motility testing revealed 25^Δ left esotropia in primary position, orthotropia in right gaze, 8^Δ left hypotropia in upgaze, 12^Δ left esotropia and 8^Δ left hypotropia in downgaze, and 35^Δ left esotropia and 14^Δ left hypotropia and −4 abduction deficit in left gaze. He reported intorsion with the double Maddox rod test. One year after his initial strabismus surgery, a left inferior rectus transposition (IRT) with loop myopexy was performed. One-month postoperatively he had a 6^Δ intermittent esotropia in primary position, upgaze and downgaze, orthophoria in right gaze, 30^Δ left esotropia in left gaze, 2^Δ intermittent esotropia at near and −3.5 abduction deficit in his left eye (Figure 1). He reported no torsion with the double Maddox rod test.

FIG 1.

One-month postoperative ocular motility in patient 1 following inferior rectus transposition with loop myopexy. One year earlier the patient had undergone a left superior rectus transposition with loop myopexy and left medial rectus recession to correct an acquired abducens nerve palsy.

Case 2

A 23-year-old man with an acquired left abducens nerve palsy was referred to the Byers Eye Institute for consultation. Three years previously, he had developed intermittent horizonal diplopia. Neuroimaging revealed a grade 2 chondrosarcoma that was removed surgically. After neurosurgery, he developed constant horizontal diplopia. His best-corrected visual acuity was 20/20 in each eye. Ocular motility testing revealed a left esotropia of 35^Δ in primary position and down gaze, 20^Δ in right gaze and upgaze, >50^Δ in left gaze and 25^Δ at near. He had a −5 left abduction deficit. He preferred to adopt a left face turn. The patient underwent left SRT with loop myopexy and left MRc of 6 mm. One month postoperatively he had 14^Δ left esotropia in primary position and downgaze, 8^Δ in upgaze, 40^Δ in left gaze and 8^Δ at near. He was orthophoric in right gaze. The abduction deficit in the left eye had improved to −4. He reported no torsion with the double Maddox rod test.

Five months later, IRT without loop myopexy was performed as a second surgical procedure. One-month postoperatively, he had left esotropia of 6^Δ in primary position and upgaze, 16^δ in downgaze, 20^Δ in left gaze, and 2^Δ intermittent exotropia in right gaze and at near and −3 abduction in the left eye (Figure 2). He reported no torsion with the double Maddox rod test. However, mild narrowing of the palpebral fissure in the left eye was observed postoperatively.

FIG 2.

One-month postoperative ocular motility in patient 2 following inferior rectus transposition in the left eye. Five months earlier he had undergone a left superior rectus transposition with loop myopexy and a left medial rectus recession of 6 mm.

Discussion

Various surgical procedures have been used to treat patients with total abducens nerve palsies, including full or partial superior and inferior rectus transposition with or without medial rectus recession. The medial rectus muscle is generally not recessed at the same time as full transposition of both vertical rectus muscles because of the increased risk of anterior segment ischemia associated with this procedure.^1–4 Full transposition of the superior rectus muscle coupled with medial rectus recession has also been described. It has a similar efficacy as full transposition of both vertical rectus muscles.^2,5 Recently, Velez and colleagues⁶ have described full transposition of the inferior rectus muscle with or without medial rectus recession. Its efficacy in restoring ocular alignment in primary position has been reported to be similar to that of superior rectus transposition and medial rectus recession, and it can correct a concurrent vertical deviation.^2,6

To our knowledge, our case series is the first to report IRT as a second procedure in patients following SRT/MRc. In both cases abduction and ocular alignment in primary position improved. After IRT, the esotropia in primary position improved from 25^Δ to 6^Δ in the first patient and 14^Δ to 6 ^Δ in the second patient. The abduction deficit also improved in both patients. Loop myopexy was used in patient 1 to augment the effect of the procedure. A loop myopexy in patient 2 might have improved the outcome. A preexisting hypotropia was also corrected in patient 1. While Velez and colleagues⁶ used IRT as a primary surgery, we used IRT as a second procedure following SRT/MRc. IRT may have balanced the vector forces induced by SRT thereby correcting the vertical deviation. Neither patient developed torsional misalignment postoperatively. Due to the anatomical bond between the inferior rectus and the inferior tarsal muscle, IRT may cause slight narrowing of the palpebral fissure,⁷ as noted with patient 2. IRT improved ocular alignment in both of our patients with residual abducens nerve palsy following prior SRT/MRc.