Uses of Botulinum Toxin in Headache and Facial Pain Disorders: An Update.

Botulinum toxin is a neurotoxin that is used in the treatments for several medical conditions, such as dystonia, spasticity, hemifacial spasm, overactive bladder, and hyperhidrosis. This toxin can potentially treat several pain disorders through botulinum toxin's ability to inhibit the release of pro-nociceptive neurotransmitters into the synaptic cleft and its possible action on the central nervous system. This narrative review addresses the use of botulinum toxin in treating primary and secondary headaches and facial pain disorders. The highest level of evidence supporting its use varies among the headache and facial pain disorders: chronic migraine (multicenter, double-blind, placebo-controlled studies), trigeminal neuralgia (double-blind, placebo-controlled studies), post-traumatic headache (double-blind, placebo-controlled study), cluster headache (open-label clinical trials), nummular headache (open-label clinical trial), headache attributed to craniocervical dystonia (prospective cohort study), new daily persistent headache (retrospective cohort study), hemicrania continua, and SUNCT and SUNA (case reports). The site of toxin application and the doses used vary among the studies and depending on headache type. Botulinum toxin has been shown to be safe in different studies, with generally mild adverse reactions.