THE EFFICACY OF BOTULINUM NEUROTOXIN-A FOR THE TREATMENT OF COMPLETE AND PARTIALLY RECOVERED CHRONIC 6TH NERVE PALSY

Esotropia from chronic sixth nerve palsy or paresis usually requires s urgery. Chemodenervation of the antagonist medial rectus muscle, while popular for the treatment of acute sixth nerve palsies and pareses, h as not been used extensively for chronic cases. In this study, 22 pati ents with sixth nerve palsies or partially recovered palsies of greate r than 5 months duration were treated with chemodenervation, The etiol ogies of the sixth nerve palsies were trauma (n=7), tumor (n=4), infec tion/inflammation (n=3), nerve compression from aneurysm or increased intracranial pressure (n=4), congenital (n=1), ischemia (n=2), and idi opathic (n=1). The mean preinjection deviation was 41 prism diopters. A total of 38 injections were administered (mean, 1.7 per patient). Ea ch patient received an injection of 2.5 to 7.5 units (mean, 4.1) of bo tulinum neurotoxin A to the ipsilateral medial rectus muscle. Treatmen t success was assessed 6 months after the last injection. A course of chemodenervation significantly improved the alignment of 9 of the 22 p atients (41%). The mean postinjection deviation was 8 Delta. Seven pat ients (32%) had single binocular vision in primary position restored. These patients had a mean horizontal binocular field of 70 degrees (ra nge, 40 degrees to 100 degrees). Thirteen patients (59%) had only mode st improvement and required surgery. The data suggest that injection o f botulinum neurotoxin A is a useful treatment for some patients with chronic sixth nerve weakness. A course of chemodenervation therapy com pares less favorably with transposition surgery with concomitant neuro toxin injection for the treatment of these difficult problems.