Prognostic Factors for Successful Surgical Outcomes in Trochlear Nerve Palsy: A Retrospective Study and Literature Review

Worapot Srimanan Division of Ophthalmology, Phramongkutklao Hospital, Bangkok, ThailandCorrespondence: Worapot Srimanan, Ophthalmology Division, Phramongkutklao Hospital, 315 Ratchawithi Road, Thung Phayathai Subdistrict, Ratchathewi, Bangkok, Thailand, Tel +662-763-9300, Fax +662-354-9309, Email [email protected]: Trochlear nerve palsy is a common cause of double vision, particularly vertical diplopia. Surgery might be necessary if the condition does not improve independently. The success of the surgery can vary based on the method employed, and clear factors to predict its effectiveness are not evident. This study evaluates surgical techniques, success rates, and prognostic factors for trochlear nerve palsy at a tertiary hospital.Patients and Methods: A retrospective chart review was conducted on patients undergoing strabismus surgery for trochlear nerve palsy at Phramongkutklao Hospital between April 2012 and July 2024. Collected data included demographics, visual acuity, stereopsis, etiology, preoperative angles, surgical methods, and postoperative outcomes. A literature review regarding surgical success and prognostic factors was also conducted.Results: Seventy-two cases were included, with 79.2% involving decompensated congenital trochlear nerve palsy. The overall surgical success rate was 76.39%, and inferior oblique myectomy was the most common and effective procedure (44.4% of cases). Based on multivariate logistic regression analysis, a preoperative hypertropia of ≤ 15 prism diopters was the significant factor for predicting successful outcomes in this study (OR 5.13, 95% CI 1.19– 22.18).Conclusion: Inferior oblique muscle surgery effectively addresses small-angle deviations in trochlear nerve palsy. A < 15 prism diopters vertical deviation strongly predicted positive surgical outcomes in this study. Further studies are needed to compare surgical techniques and explore additional prognostic factors to optimize long-term outcomes and improve patient care.Plain Language Summary: Trochlear nerve palsy can lead to double vision, and surgery is required if there is no spontaneous improvement. The success of surgical procedures varies based on technique, and there are limited known predictors for which patients may achieve optimal results. When the condition does not resolve independently, surgery is necessary to rectify eye misalignment. This study explored various surgical methods, their success rates, and the factors affecting favorable outcomes from trochlear nerve palsy surgery.A review of medical records for 72 patients who underwent surgery for trochlear nerve palsy at Phramongkutklao Hospital between 2012 and 2024 showed that congenital causes were the most prevalent, accounting for 79.2% of cases. The findings indicated that 76.39% of the surgeries were successful, with inferior oblique myectomy being the most effective and frequently performed procedure. The primary predictor for a successful surgery was having a preoperative eye misalignment, specifically hypertropia, of ≤ 15 prism diopters.Notably, inferior oblique surgery successfully addresses small-angle deviations, with preoperative hypertropia remarkably predicting the surgical success. Further studies are necessary to compare surgical methods and explore other factors that may enhance long-term outcomes.Keywords: fourth nerve, paresis, prognosis, long-term, surgery, strabismus, neuro-ophthalmology