One- vs Two-Muscle Surgery for Unilateral Fourth Nerve Palsy
David L. Nash; David A. Leske; Erick D. Bothun; Brian G. Mohney; Michael C. Brodsky; Jonathan M. Holmes
Introduction: Classic teaching regarding surgery for unilateral fourth nerve palsy is one muscle for 15pd or less in primary and two muscles for greater than 15pd, but surgeons still disagree on one versus two muscles for 14-25pd deviations. We compared outcomes of one- versus two-muscle surgery.
Methods: We reviewed medical records of 97 patients, age 5 to 86 years, who underwent either one- or two-muscle surgery for unilateral fourth nerve palsy with 14-25pd hypertropia in primary position. 6-week motor success was defined as orthophoria or 1-4pd undercorrection at both distance and near (by prism alternate cover test), overcorrection as any reversal of hypertropia, and undercorrection as >4pd. Diplopia-free success was defined as none or rare diplopia in distance straight ahead and reading.
Results: 42 patients underwent one-muscle, and 55 two-muscle surgery. Motor success was similar (55% vs 62%), but there were more undercorrections with one-muscle surgery (43% vs 20%, p=0.02), and more overcorrections with two-muscle surgery (2% vs 18%, p=0.02). Regarding symptoms, there were similar rates of diplopia-free success between one- and two-muscle surgery (76% vs 60%, p=0.1). 73% of overcorrections were associated with diplopia, compared with only 38% of undercorrections (p<0.01).
Discussion: Although there were more undercorrections with one-muscle surgery than overcorrections with 2-muscle surgery, the undercorrections were less symptomatic, leading to similar overall motor and diplopia-free success rates.
Conclusion: For hypertropia of 14-25pd in primary position due to unilateral fourth nerve palsy, there appears to be no clear advantage of two-muscle surgery over one-muscle surgery.