Original Investigation: Adjustable Nasal Transposition of Split Lateral Rectus Muscle for Third Nerve Palsy

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Abstract

IMPORTANCE

Third nerve palsy causes disfiguring, incomitant strabismus with limited options for correction.

OBJECTIVE

To evaluate the oculomotor outcomes, anatomical changes, and complications associated with adjustable nasal transposition of the split lateral rectus (LR) muscle, a novel technique for managing strabismus associated with third nerve palsy.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective medical record review appraising outcomes of 6 consecutive patients with third nerve palsy who underwent adjustable nasal transposition of the split LR muscle between 2010 and 2012 with follow-up of 5 to 25 months at a tertiary referral center.

INTERVENTION

Adjustable nasal transposition of the split LR muscle.

MAIN OUTCOMES AND MEASURES

The primary outcome was postoperative horizontal and vertical alignment. Secondary outcomes were (1) appraising the utility of adjustable positioning, (2) demonstrating the resultant anatomical changes using magnetic resonance imaging, and (3) identifying associated complications.

RESULTS

Four of 6 patients successfully underwent the procedure. Of these, 3 patients achieved orthotropia. Median preoperative horizontal deviation was 68 prism diopters of exotropia and median postoperative horizontal deviation was 0 prism diopters (P = .04). Two patients had preoperative vertical misalignment that resolved with surgery. All 4 patients underwent intraoperative adjustment of LR positioning. Imaging demonstrated nasal redirection of each half of the LR muscle around the posterior globe, avoiding contact with the optic nerve; the apex of the split sat posterior to the globe. One patient had transient choroidal effusion and undercorrection. Imaging revealed, in this case, the apex of the split in contact with the globe at an anterolateral location, suggesting an inadequate posterior extent of the split. In 2 patients, the surgical procedure was not completed because of an inability to nasally transpose a previously operated-on LR muscle.

CONCLUSIONS AND RELEVANCE

Adjustable nasal transposition of the split LR muscle can achieve excellent oculomotor alignment in some cases of third nerve palsy. The adjustable modification allows optimization of horizontal and vertical alignment. Imaging confirms that the split LR muscle tethers the globe, rotating it toward primary position. Case selection is critical because severe LR contracture, extensive scarring from prior strabismus surgery, or inadequate splitting of the LR muscle may reduce the likelihood of success and increase the risk of sight-threatening complications. Considering this uncertainty, more experience is necessary before widespread adoption of this technique should be considered.

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