Consecutive superior oblique palsy after adjustable suture spacer surgery for Brown syndrome: incidence and predicting risk

Abstract

To determine the incidence of and to identify characteristics predicting significant superior oblique palsy (SOP) after adjustable superior oblique suture spacer surgery for treatment of Brown syndrome. The medical records of patients treated for unilateral Brown syndrome with adjustable suture spacers (2005-2016) were reviewed to identify possible association of age at surgery, spacer length, surgeon performing procedure, severity of Brown syndrome, preoperative hypotropia in primary position and affected side gaze, and reduction in Brown restriction on postoperative superior oblique function. "Good" postoperative superior oblique function was defined as absence of hypertropia and diplopia in primary position and no more than intermittent diplopia in downgaze comfortably fused with ≤4Δ base-down or head tilt of <10°. Presence of postoperative hypertropia in primary position with increase in downgaze met criteria for significant SOP. Postoperative Brown restriction of≤-2 indicated resolution of Brown syndrome. Median age at surgery was 59months, interquartile range (IQR) was 32-82months, and median spacer length was 6mm (range, 2-7mm) for 19 included patients. Preoperative median hypotropia was 9Δ (IQR, 0Δ-12Δ) in primary position and 18Δ (IQR, 5Δ-22Δ) in affected side gaze. Of 19 patients, 16 (84%) achieved sufficient resolution of Brown syndrome, but 6 (32%) developed significant SOP. Modest preoperative hypotropia in affected side gaze was the only predictor of significant SOP (likelihood ratio test=7.11; P=0.008). Logistic regression modeling enabled estimation of risk of significant SOP based on preoperative side gaze hypotropia. Suture spacer surgery can result in significant SOP. Risk may be predicted by magnitude of preoperative side gaze hypotropia.