Botulinum Toxin Injection for Treatment of Acute Traumatic Superior Oblique Muscle Palsy

PURPOSE: To evaluate the outcomes of botulinum toxin injection into the inferior oblique (IO) muscle for management of unilateral acute traumatic superior oblique (SO) palsy. METHODS: In this prospective case series, 10-20 units of botulinum toxin A (Dysport, Ipsen, Biopharm Ltd., Wrexham, UK) was injected into the ipsilateral IO muscle of 13 consecutive patients with unilateral acute traumatic SO palsy. All patients received injections within four weeks of the incident. RESULTS: Mean age was 29 ± 15 years and 12 (92%) subjects were male. Mean amount of hypertropia (in primary position) was decreased from 10.0 ± 3.9(Δ) at baseline to 4.6 ± 8.9(Δ), one month after the injection, and to 1.5 ± 2.7(Δ) at final follow-up (P = 0.001). IO overaction improved from 2.7 ± 0.6 to 1.0 ± 1.2 and 0.6 ± 0.9 (P ≤ 0.001), and subjective torsion from 5.3 ± 3.9 to 3.2 ± 3.4 and 1.6 ± 2.5 degrees (P ≤ 0.001), at the same time intervals respectively. One month after the injection as well as at final follow-up, 10 (77%) patients were diplopia-free in primary and reading positions. Subgroup analysis showed that patients who recovered had less baseline hypertropia as compared to those who failed (8.3(Δ) vs. 15.7(Δ), respectively; P = 0.01). All patients with a favorable outcome had baseline hypertropia of 10(Δ) or less. CONCLUSION: A single injection of BTA into the IO muscle can rapidly and safely resolve symptomatic diplopia in patients with acute traumatic SO palsy, while waiting for spontaneous recovery.