Superior Oblique Atrophy on Magnetic Resonance Imaging with Clinical Features in Unilateral Superior Oblique Palsy

Purpose: To investigate the correlation of superior oblique (SO) atrophy of magnetic resonance imaging (MRI) with clinical features including surgical success in unilateral SO palsy. Methods: This study was a retrospective review of the records of 38 patients who had undergone inferior oblique (IO) myectomy due to SO palsy between January 2017 and March 2019 at our hospital. The patients with more than a 40% decrease of cross-section areas using preoperative orbital MRI were categorized into the atrophic group (16 patients). We compared surgical outcomes between the atrophic and non-atrophic groups. Results: Preoperative IO over-action and vertical deviation showed no significant difference, but the excyclotorsion in paralytic eyes were more frequent in the atrophic group and the surgical success (62.5% vs. 95.5%), and the degree in improvement of vertical deviation (7.17 +/- 5.19 prism diopters [PD] vs. 11.05 +/- 5.59 PD) was significantly lower in the atrophic group. The degree of SO atrophy showed a weak correlation with the degree of improvement of hypertropia or diopter differences of bilateral head tilting. Conclusions: SO atrophy, detected using preoperative MRI of unilateral SO palsy patients did not show a definite correlation with clinical features except for excyclotorsion in paralytic eyes but did show a clinically significant correlation with surgical outcomes. Preoperative MRI can therefore be used for predicting surgical outcomes of IO myectomy in unilateral SO palsy patients.