Background & Aims: Botulinum toxin is an effective treatment in idiopathic chronic anal fissure, but the long-term outcome after healing is not well documented. We analyzed the long-term outcome of patients in whom an anal fissure had healed after botulinum toxin injection and the factors contributing to recurrence. Methods: Fifty-seven patients who had completely healed 6 months after injection of botulinum toxin were reassessed every 6 months. The follow-up was 42 months in all patients.
Clinical and manometric differences between the permanently healed and the relapsed group were statistically analyzed. Results: Four patients were lost to follow-up. A fissure recurrence was shown in 22 patients (41.5%). Statistical differences between the permanently healed and the relapsed group were detected when analyzing the anterior location of the fissure (6% vs. 45%), a longer duration of the disease (38% vs. 68%), the need for reinjection (26% vs. 59%), a higher total dose injected to achieve definitive healing (13% vs. 45%), and the percentage decrease of maximum squeeze pressure after injection (−28% vs. −13%; P < 0.05). Conclusions: The late recurrence rate of chronic anal fissure is high when the effect of botulinum toxin disappears. The highest risk of recurrence is associated with anterior location of the anal fissure, prolonged illness, the need for reinjection and for high doses to achieve healing, and a lower decrease of maximum squeeze pressure after treatment.

This makes sense because I would not think that Botox would be a permanent solution to a sphincter problem just as Botox on the face is only temporary.
Thanks,
Cheryl