Early and late botulinum toxin treatment of acute sixth nerve palsy

Ten patients with sixth nerve palsy were treated with botulinum toxin injection to the antagonist nonparetic medial rectus. All patients were followed for a minimum of 14 months after the last injection. Six patients were treated within eight weeks of the onset of the palsy. Within a few days five of the six gained fusion, without the necessity of a marked head turn and none complained of confusing reversal of diplopia. The same five recovered full function. Four patients with no medial rectus contracture on forced duction testing were treated six months or longer after the onset of the palsy and none recovered full function. One of the four patients was permanently over-corrected despite persistent weakness of the lateral rectus. This preliminary report suggests that early botulinum toxin injection of patients with recent onset (acute) sixth nerve palsy is beneficial. Since some patients may recover spontaneously a randomised double-blind study is necessary to more precisely determine the effectiveness of this form of therapy. Botulinum toxin does not appear to be effective in facilitating recovery in those cases with poor lateral rectus function six months or longer after the onset of the palsy, even when there is no contracture of the medial rectus.