[Botulinum toxin A in treatment of the sixth cranial nerve palsy]

To study the methods and the effects of botulinum toxin A (BTXA) in the treatment of paralytic esotropia (PE) due to the sixth cranial nerve palsy.

BTXA was injected into the extra-ocular muscles of 89 patients with PE. The number of injections was 1 to 5, in average 1.5. Of them, 27 patients received injections combining with surgeries at the same time, and 16 received surgeries after injections for 3 to 28 months. The procedures include recession-resection (or combining with myectomy), Jenson procedure, or vertical muscle transposition.

Of the patients having received injections alone, 35 restored orthotropia and binocular single vision after 1 to 4 injections. Eleven patients restored to orthotropia after the injection and surgery at the second stage, and the mean correction of the strabismus degree was 42.7( triangle up ) +/- 32.2( triangle up ). Fourteen cases in the simultaneous surgical and injection group restored orthotropia after the surgery, and the mean correction of the strabismus degree was 90.0( triangle up ) +/- 40.1( triangle up ). Of them, 14 restored binocular single fusion and their range of visual fixation expanded to 20 degrees - 70 degrees.

BTXA injected into extra-ocular muscles is an ideal therapy for the treatment of PE. Injection of BTXA during the first 6 months after the onset as a preoperative therapy may alleviate medial rectus restriction and promote the recovery of the lateral rectus functions. Some patients may restore orthotropia by injection alone. Patients under-corrected at six months after onset can be treated with surgery. Injection combined with surgery at the same time may preserve the function of medial rectus, avoid performing operation on more than two rectus, prevent the risk of anterior segment ischemia in surgery of multiple muscles and expand the field of binocular single vision as large as possible.