Surgical Management of Masquerading Superior Oblique Palsy.

Abstract

To compare the surgical outcomes between superior oblique (SO) palsy (SOP) and masquerading SO palsy (mSOP). Comparative interventional case series. Medical records of patients with SOP and mSOP were reviewed from 1991 to 2024. Palsy cases had maximum SO cross section in the hypertropic eye no more than 80% of that in the fellow eye, whereas mSOP cases had bilaterally symmetric SO muscles on magnetic resonance imaging. Types of surgery and effect on hypertropia were compared between groups. A total of 39 patients aged 38±20 (standard deviation) years had SOP and 18 aged 36±17 years had mSOP. Maximum palsied SO cross section was 10.6±3.8 mm², significantly smaller than 18.9±4.0 mm² of the contralateral fellow (P < .0001), but was bilaterally symmetric in mSOP. Mean preoperative central gaze hypertropia was similar at 14.7±9.8Δ in SOP and 11.0±6.9Δ in mSOP (P = .2). The commonest surgery was ipsilateral inferior oblique (IO) weakening combined with contralateral inferior rectus (IR) recession, followed by ipsilateral IO weakening alone and contralateral IR recession alone. After 41±65 months' follow-up in SOP and 22±41 months in mSOP, central gaze hypertropia decreased from 14.7±9.8Δ to 1.7±4.1Δ in SOP, and from 11.0±6.9Δ to -2.9±5.4Δ in mSOP (both P < .0001). Surgical effect was similar at 13.2±10.3Δ in SOP and 14.1±10.0Δ in mSOP. Reoperation rate was low and similar in both groups. Clinical characteristics and surgical effect are similar in mSOP and SOP. Conventional surgeries are comparably effective in both. This suggests that mechanism beyond SO muscle function drive head tilt-dependent cylcovertical strabismus.