Long-term outcomes after surgical management of chronic sixth nerve palsy

Background: In a multicenter prospective data collection study of chronic sixth cranial nerve palsy, we previously reported that the initial successful outcome rate was 39% after a single surgical intervention and 25% after surgery combined with botulinum toxin (Botox), using strict success criteria. We now report the longer term outcome of these patients. Methods: A previously described cohort of 31 patients in 18 centers who underwent strabismus surgery for a sixth nerve palsy of greater that 6 months duration was studied prospectively. Twenty-three had strabismus surgery alone and 8 surgery with Botox. Fourteen (45%) were complete palsies and 17 (55%) were incomplete. Seven (23%) were bilateral and 24 (77%) were unilateral. Outcome was classified at time of last follow-up, which was 5 weeks to 24 months postoperatively. Success was defined as no diplopia in primary position at distance fixation. Partial success was defined as no more than 10 PD esotropia despite diplopia. Results: Overall, 16 (52%) of the patients were classified as successes, 7 (23%) as partial successes, and 8 (25%) as failures. Three (43%) of the partial successes were using prism. Eight (35%) of the patients classified as successes or partial successes required 2 surgical procedures. Of all patients (10, 32%) who had a second surgery, only 2 (20%) remained failures. Conclusions: Despite our reported poor initial surgical success rate in chronic sixth nerve palsy, additional strabismus surgery, longer follow-up, and the use of prism or face turn for small residual deviations yields an overall surgical success rate of 75%. More than 1 surgical procedure and prism are often necessary in the management of chronic sixth nerve palsy.