Purpose: To evaluate the effect of botulinum toxin-A as an alternate to surgery in acute complete sixth nerve palsy and to shorten the recovery period.
Methods: Thirty patients with acute complete sixth nerve palsy received 1-10 units of botulinum toxin-A (Dysport) injection in the medial rectus muscle within one month from the onset of palsy. Toxin was injected directly into the muscle belly under local (25 cases) or general (5 cases) anesthesia. At the 1st, 7th, 30th, 90th, and 180th day followup, binocular field of vision, abduction and any residual deviation were measured.
Results: Patients aged between 9mo to 70yrs. 24 (80%) patients had significant improvement in abduction after 3 months and 6 (20%) had <10° abduction. Among treatment failures, 2 were traumatic and 2 were tumoral. Binocular diplopia free field was >75° in 22 (73%). 22 (73%) had no residual esotropia and other 8 patients (27%) had 10-50° residual esotropia which required surgery. No cases of exotropia or globe perforation were encountered.
Conclusion: Injection of botulinum toxin-A is a simple and safe way of treating acute complete sixth nerve palsy eliminating the need for invasive surgical manipulation in majority of cases. It can eliminate diplopia during acute stage of palsy in the cases of spontaneous recovery.